The development of optical fibers with two-dimensional patterns of air holes running down their length has reinvigorated research in the field of fiber optics. It has greatly - and fundamentally - broadened the range of specialty optical fibers, by demonstrating that optical fibers can be more 'special" than previously thought. Applications of such special fibers have not been hard to find. Fibers with air cores have made it possible to deliver energetic femtosecond-scale optical pulses, transform limited, as solitons, using single-mode fiber. Other fibers with anomalous dispersion at visible wavelengths have spawned a new generation of single-mode optical supercontinuum sources, spanning visible and near-infrared wavelengths and based on compact pump sources. A third example is in the field of fiber lasers, where the use of photonic crystal fiber concepts has led to a new hybrid laser technology, in which the very high numerical aperture available using air holes have enabled fibers so short they are more naturally held straight than bent. However, commercial success demands more than just a fiber and an application. The useful properties of the fibers need to be optimized for the specific application. This tutorial will describe some of the basic physics and technology behind these photonic crystal fibers (PCF's), illustrated with some of the impressive demonstrations of the past 18 months.

A highly negative dispersion photonic crystal fibre with less germanium doped core and central index dip is numerically investigated by fully vectorial finite element method. By adjusting the pitch, the depths and radius of the central index dip and the diameter of six small air holes in the third ring, Highly negative dispersion value (-1325.5ps/nm.km) and large mode effective area (71.4um²) DCPCF around the wavelength of 1.55μm is obtained.

A high concentration silica host Erbium Doped Fiber with Bismuth-Gallium-Aluminum co-doped was fabricated. The absorption coefficient of this fiber was up to 19dB/m at the wavelength of 980nm and 42dB/m at 1530nm. Ring structure lasers with different fiber lengths were presented. Their output characteristics were measured and analyzed.

The temporal characteristics of a fiber ring laser are reported. The laser has a simple configuration, which contains an Erbium-doped fiber amplifier (EDFA), a polarization controller (PC) and a coupler. The EDFA has a high saturation power of 27dBm to provide the gain in the cavity. The PC is used to control the polarization state of light. A 99/1 coupler is used to extract the laser output. There is no filter in the cavity to confine the spectrum of the laser. The simple laser configuration can operate in different temporal modes with different pump power. In the self mode locking state, the repetition rate is equal to the inverse of the round trip time of the cavity. The repetition rate of the laser can be increased by increasing the pump power of the EDFA. This self mode locking phenomena is due to the homogeneous gain medium in the cavity, rather than the nonlinear effect in the cavity. The nonlinear effect can suppress the self mode locking phenomena by inserting a short length highly nonlinear fiber in the laser cavity.

The erbium doped fiber, optical isolator and WDM coupler, which are three key optical components of commercial erbium-doped fiber amplifier (EDFA), are radiated to the radiation dose of 5krad by electron. The radiated erbium-doped fiber (EDF) make the output power of EDFA come down 0.5dB when the input power is between -12dBm and-5dBm. The NF climb up 1dB. However, the peak wavelength changes little. The radiation experiment results also show that the deterioration of the optical isolator and WDM coupler can be neglected at the dose of 5krad. In order to assure the accuracy of analysis, the recovery experiment has been done to correct the radiation effect on the EDFA. The results indicate that if optical communication systems have enough redundancy, the EDFA can be used on the low dose orbits without any radiation protection for inter-satellite optical communication.

The temperature dependence of fluorescence in erbium-doped silica fiber between ~-30 and ~150°C is discussed. 980nm pumping configuration is used in our experiment. 1450nm and 1531nm wavelengths are chosen to calculate the FIR (fluorescence intensity ratio) at the first time instead of the mostly used wavelengths 525nm and 550nm. It shows that as the temperature increases, the fluorescence intensity increases obviously at short wavelengths but changes a little at long wavelengths. The temperature coefficient can achieve ~0.023dB/°C, and its resolution is improved as the temperature decreases. Because there are many effects in our experiments, so it shows a deviation from the behavior of simulation.

Development of Er and ErYb doped fibers for high performance Er-doped fiber amplifiers (EDFA) and high power fiber lasers is reviewed. Fiber design optimization for applications including wide flat gain spectrum, and high power conversion efficiency are discussed. Major parameters such as fiber gain spectrum consistent and uniformity for volume production are presented. In addition, some of nonlinear effects in EDFA for modern optical communication network will be discussed.

By analyzed the two-step cascaded step-changed LPGs which have been already used as band filters for flattening the gain of EDFAs, an improved method of introducing three or more steps cascade has been advanced in order to optimize the transmission spectra of the filters. The calculation and simulation of the cascaded LPGs' transmission spectra are given. The simulation results show that the transmission spectral profile can be tailored into an adoptive shape and simultaneously the effective bandwidth would become wider by adjusting the two parameters, the length and the index perturbations of each segment in cascade. This method is demonstrated to be an effective way to flatten the gains profile of EDFAs.

The emergent of True-Bend-Insensitive-Fiber product is a major triumph for the fiber optics industry. By defining the requirements and understanding the trade-offs in optical performance, large-scale manufacturing compatibility, standards compliance, mechanical performance, compatibility with field equipments and installation procedures will be critical to identify the most cost effective alternative.

As deployment of fiber to the home (FTTH) within multiple dwelling units (MDUs) is growing, more technicians will be involved in the deployment of optical drop cables, and there is a desire to use craft and practice similar to what is used for copper cables. We introduce a solid bend insensitive fiber in this application that is backwards compatible to G.652D fiber, and has macrobending, splice loss and system performance to meet the very demanding conditions of these applications. A closer look at the demands of this environment has made it necessary to re-evaluate reliability in these critical applications. We apply the Power Law Model to predict reliability in these demanding applications, and provide experimental evaluation of the model through testing on optical fibers and cables. It will be shown that bends and tension need to be considered together when evaluating the reliability of the passive optical plant.

We propose that nanomaterials can be used for fibers. A novel nano-InP doped fiber has been fabricated by the method of modified chemical vapor deposition (MCVD).It has been measured that the doping concentration is 0.1%. The relationship between refractive index and the wavelength is obtained by fitting experimental data to Sellmeier equation. Dispersion of the fiber has been calculated in the wavelength range 1.2-1.6μm. As the wavelength varies from 1.2μm to 1.60μm, dispersion parameter D increases but is always negative. It has found that the dispersion of nano-InP doped fibers is strongly changed compared to standard single-mode fibers, due to the nano-InP dopant which lead to a higher refractive index difference.

Phase sampling and phase shift techniques are introduced in a uniform fiber Bragg grating (FBG) structure to achieve a multi-bandpass filter with ultranarrow transmission bandwidth. A pair of dual-bandpass transmission windows are opened at 1542.32, 1542.36, and 1542.66, 1542.71 nm, respectively. The channel spacing between the pair can be designed by the phase sampling period, as well as the wavelength spacing in the dual-bandpass can be controlled through the phase shift length. This new kind of bandpass structure can be applied in the ultranarrow filtering in multi-channel, multi-wavelength distributed feedback Bragg lasing, photonic generation of microwave signal etc.

We introduce our recent progresses in the design and fabrication of the high channel-count fiber Bragg grating (FBG). We theoretically and experimentally demonstrated the phase-only sampled FBG with channels up to 81, which could be used as the dispersion compensator, the simultaneous dispersion and dispersion-slope compensator, respectively. Moreover, we have presented a novel method for multi-channel FBG design, which enables us to design any kind of multi-channel FBGs where the amplitude or the spectral response of each channel could be either identical or non-identical. As an example, a novel design for a multi-channel FBG with asymmetrical triangular reflection spectrum has been demonstrated.

A fiber Bragg grating (FBG) temperature insensitive packaging scheme based on a flat diaphragm and an L shaped lever is presented. The curve where the L shaped lever contacts the diaphragm is a segment of an Archimedes spiral, which is used to reduce the temperature responsivity. Because the thermal expansion coefficient of the quartz-glass L shaped lever and the steel sensor shell is different, the temperature effect is compensated for by optimizing the dimension parameters. Theoretical analysis is presented, and the experimental results show that a low temperature responsivity of 2.8pm/°C are achieved.

The spectral self-imaging phenomenon is observed in binary phase-only sampled fiber Bragg gratings (SFBGs) using numerical simulations. Integer and fractional Talbot effects are obtained under conditions of Talbot effect. The characteristics of the Talbot spectrum in terms of channel spacing and the group delay from the phase-only sampled FBGs are discussed.

We present an analytical expression for sampled fiber Bragg gratings (SFBGs) with arbitrary chirps in sampling function or grating period or combination of both. The relationship among the wavelength of each channel, the chirp coefficient of the sampling and the grating period, and the total length of the grating is explicitly given. Specifically, the chirped sampling function is first expanded into a new function using Fourier theory; the equivalent local Bragg period is then obtained to derive the expression of the reflection peak wavelength. The overall wavelength position is obtained by summation of both contributions from sampling chirp and the grating chirp. The calculated results based on the analytical expression are examined with the conventional numerical results, which are found to be in excellent agreement.

Tilted fibre Bragg grating (TFBG) belongs to short-period gratings family; there is core mode and a lot of cladding modes in the transmission spectrum. According to the special structure and coupling characteristic of the TFBG, we propose a novel method of edge filter linear demodulation using tilted fiber Bragg gratings in a fiber sensor system. The results show that the widely linear range of katabatic edge (1505nm~1535nm) and an assurgent edge (1545nm~1565nm) can be used in edge filtering; the thermal characteristic of the core mode and cladding modes is similar to FBG's. Therefore, it can compensate dynamically the temperature shift of the FBG and the effect of temperature noise on the strain or other sensing signals is eliminated. The advantages of this simple system are an all-fiber design, quasi static and dynamic operation, high stability and lower cost.

A continuously tunable, coherence free microwave photonic filter is proposed and experimentally demonstrated. The filter is based on a high-birefringence linearly chirped fibre Bragg grating (Hi-Bi LCFBG) as the tuning component. The filter response tunability is realized through changing the differential group delay of the Hi-Bi LCFBG by applying gradient tension or adjusting the operating wavelength. Free spectral range tuning by 1.11 GHz with about 40 dB notch rejection is achieved.

We realize the correlated photon pair generation at 1.5μm by spontaneous four-wave mixing in high nonlinear microstructure fibre with a length of 25m, showing that high nonlinear microstructure fibres have great potential in bright, high efficiency and compact sources of correlated photon pairs at 1.5μm.

This paper presents a design for rectangular ring resonators based on low-index polymers operating at an 850 nm wavelength. Multimode interference couplers are used to enable signal splitting and combining and air trench assisted 90° mirrors are used as beam turning elements. 3D full-vector, 2D FDTD and parameter models are combined to simulate the ring resonator design. This design, suitable for spectral shaping, achieves a FSR of 0.29 nm, a FWHM of 0.066 nm and an on-off ratio of approximately 20 dB.

A pair of fiber Bragg grating (FBG) comb filters with different channel-spacings are designed and fabricated to measure strain. The reflection peaks of one comb filter shift when the strain changes. And the other comb filter is used as calibration standard. The two comb filters have different channel-spacings, 1.00 nm and 0.95 nm, which can be regard as the structure of vernier caliper. In our experiment, the strain resolution is about 41.7 με, with low demand of the demodulation devices. And it could be greatly improved further in terms of Gaussian fitting technology of the peaks' intensity.

Optical buffer is an important component in optical switching and optical signal processing. In this paper, we present a novel all-optical buffer based on nonlinear polarization rotation induced by injection current of semiconductor optical amplifier. With Mueller matrix, we theoretically investigate the change of polarization state induced by nonlinear polarization rotation in semiconductor optical amplifier. The operation of the proposed optical buffer at 2.5Gb/s is experimentally setup. The loading and reading operations with 1024bit with this optical buffer are demonstrated. Polarization maintenance is taken into account to give the optimum operation condition

In this paper we present measurement results of an ultracompact echelle-grating demultiplexer based on silicon-on-insulator nanowire platform, in which we introduced a total internal reflection design of the grating facets to improve the diffraction efficiency. An average increase of the diffraction efficiency with 3.7dB is observed for the 3 channels compared to a normal design.

A slot waveguide structure is used in the part of arrayed waveguides in AWG instead of silicon waveguides. It is filled with high negative thermo-optic coefficient polymer in the narrow slot. The arrayed slot structure can remarkably reduce the center wavelength shift when the temperature changes. In this study, we use the polymer WIR30-490 and ZP49 to be filled in the slot. The thermo-optic coefficients of WIR30-490 and ZP49 are negative, and have the same order of magnitude with silicon. In our simulations, by adjusting several variables of the slot structure, such as the width of the slot between the pair of silicon wires, the width of the silicon waveguide, and the height of the silicon waveguide, we can get the athermal condition of AWG for each polymer. Even if there is an acceptable error on fabrication, temperature-dependent center wavelength shift of AWG can still be reduced down to 1 pm/°C. It makes the fabrication of athermal silicon AWG possible.

We introduce a phenomenological model to describe polarization-sensitive SOAs which is composed of a partly linear polarizer, a retarder, and a polarization independent amplifier. It shows that any input optical vector of signal will first be partly linearly polarized, then rotate around S1-axis of the Poincaré sphere for θ, and finally be amplified equably. Then we investigate and experimentally demonstrate the relationship between polarization rotation (PR) and mode gains. We further obtain two necessary conditions for the valuable orthogonal polarization rotation (OPR), and then perform a power-equalized OPR by optical-electric synchronous control of the SOA. The polarization duration time is ~10 ns which is applicable to high-speed polarization state generation.

In this paper, the total output power features and the mode power characteristics of the extremely short external cavity semiconductor lasers (ESECSLs) have been investigated experimentally and theoretically, and a new type of variation of ESECSL's mode power is reported. The results show that with the variation of the external cavity length at the order of lasing wavelength, the total output power and the mode power of ESECSLs will hop periodically, and the different mode presents diverse power characteristics. Especially, some modes, locating at the material gain center of ESECSL, present unique double peak characteristics. Moreover, the primarily theoretical simulations and the physics explanation about these double peak characteristics have been given. The theoretical simulation results agree well with the experimental results. These new type characteristics of ESECSL's mode power may be useful in improving the sensitivity of all-optical sensors and developing the new type of optical data read-write head.

We propose and experimentally demonstrate a novel method for generating ultra-wideband (UWB) monocycle pulse by exploiting a turbo-switch which consists of two reflective semiconductor optical amplifiers (RSOAs). By adjusting the currents applied to both RSOAs, the monocycle pulse is realized due to the gain overshoot induced by the turbo-switch. The polarity inversed monocycle pairs and the UWB doublet pulse train are numerically realized by cascading turboswitches.

Perhaps the most common specialty optical fiber is HCS hard polymer clad silica fiber. It was invented almost 30 years ago for transmitting laser light to initiate explosives in mining industry and later adapted to be used in a variety of new applications, such as data communications. The most typical HCS fiber typically consists of a 200 μm pure silica glass core, a thin coating of low refractive index hard polymer as the cladding, and an ETFE buffer. This design enables the "crimp-and-cleave" technique of terminating and connectorizing fibers quickly and reliably. Its greater glass diameter also renders greater robustness allowing the fiber to endure greater forces during installation. Due to its larger core size and high numerical aperture (NA), the fiber can be used with a plastic connector and low cost LED transmitter that can greatly reduce the system cost. It can also be used at higher temperature and humidity conditions than standard optical fibers coated with telecommunications grade acrylate material. As applications evolve and require greater bandwidth and/or performance over a greater distance, the challenge now is to develop specialty optical fibers with significantly greater bandwidth-length product while maintaining all other characteristics critical to their ease of use and performance. As a response to the demand, two new fiber types have been designed and developed as higher bandwidth versions of the original HCS fiber. In this paper, we will discuss some of the main design requirements for the fibers, describe in detail the two designs, and present the results of fiber performance.

Linearity of the micro-resonator-based modulators for analogue modulation in terms of the spurious free dynamic range is quantified. Some design strategies and operation techniques are presented to improve the linearity of these devices.

By using small SU-8 polymer ridge waveguides, compact micro-racetrack resonator (MRR) add-drop filters are presented. This used small ridge waveguide has an air-cladded SU-8 polymer core (n~1.573) on a SiO2 buffer (n~1.445) so that the bending radius could be as small as ~102μm. Considering the resolution limitation of a regular UV-lithography process, the gap in the coupling region of the present MRR in our design is no less than 1.0 μm. In order to enhance the coupling between the access optical waveguide and the micro-racetrack, narrow optical waveguides are used in the coupling regions. Meanwhile, wide optical waveguides are used in the bending sections to have a small bending radius. And a single-side taper is used to connect these two sections with different widths so that the gap width is kept as small as 1.0 μm in the whole region. With a regular UV lithography process, the designed micro-racetrack resonator (MRR) add-drop filters are fabricated. The measured propagation loss for straight waveguides is about 0.1dB/mm and the measured spectral responses of the through/drop ports show a Q-factor of 8000.

A photosensitive terpolymeric composition suitable for practical waveguide devices is provided. The terpolymer was produced from pentafluorostyrene (PFS), perfluoro-n-octyl acrylate (PFOA), and glycidyl methacrylate (GMA). We present a fabrication process where the device structure utilizes the same class of material for the core and cladding layers and it was fabricated without a plasma etching process. We also present simulation results that show good agreement with measured data and which thus permit to optimize the device performance. Based on the developed material and process; a 16-channel arrayed waveguide grating (AWG) multiplexer with excellent performance has been realized. The channel spacing of the multiplexer is 0.8 nm and operating around the 1550 nm wavelength. Together the developed material and process combine to produce AWG with an average insertion loss of 5 dB, the best channel shows an insertion loss of 4.7 dB; the uniformity of 1 dB, a crosstalk of less than -28 dB and a polarization dependence loss (PDL) of ~ 0.2 dB. During temperature cycling, a slight thickness hysteresis and refractive index hysteresis were observed above the glass transition temperature and is ascribed to the fact that the terpolymer material may not completely recover its elasticity in the heating/cooling cycle.

Two kinds of liquid photopatternable inorganic-organic hybrid polymer materials polysiloxanes, named as PSQ-LL and PSQ-LH, are prepared by a sol-gel process at room temperature. The refractive indexes of waveguide materials can be tuned linearly from 1.4482 to 1.5212 at 1310nm and from 1.4478 to 1.5198 at 1550nm by blending PSQ-LL and PSQ-LH. These materials have low optical losses of 0.31dB/cm at 1310nm and 0.80dB/cm at 1550nm, and high thermal stability with 1% decomposition temperatures of 297°C (in air) and 340°C (in N₂) for PSQ-LH and 313°C (in air) and 370°C (in N₂) for PSQ-LL. Typical waveguide structures based on PSQ-Ls are fabricated by UV imprint technology.

Based on the mutual coupling coefficient what derived from the method of field distribution analysis, the expressions of coupling factor and coupling efficiency between two identical structure nonparallel straight rectangular waveguides are suggested, and computing instances are introduced for showing the crosstalk between adjacent rectangular waveguides in the star coupler of an AWG demultiplexer. Then, an approximation expression for computing the maximal crosstalk between adjacent arrayed waveguides of an AWG demultiplexer is recommended. As the crosstalk between adjacent arrayed waveguides of an AWG demultiplexer is in need of a limit, the expression for estimating the space between the end face centers of adjacent arrayed waveguides in an AWG demultiplexer is advanced also, and a computing instance is introduced for showing the crosstalk between adjacent arrayed waveguides in an AWG demultiplexer. Finally, based on the Gaussian approximation for the mode field distribution of optical waveguide, the theoretical model of the spectral response efficiency of an AWG demultiplexer is engaged, a computing instance is presented for showing the spectral response characteristic and crosstalk characteristic of an bilateral symmetry structure AWG demultiplexer. These works provides some help for ascertaining the basic parameters of an AWG demultiplexer.

A theoretical model for description of the cSFG/DFG is developed in this paper. The factors influence the poled period of PPLN is studied and the result shows that the poled period decreases while the temperature increases, and the poled period also changes while we choose different signal wavelengths. In our simulation, a pulsed light is injected into a PPLN waveguide as the signal, and then the performances of the wavelength conversion structures with two continuous waves and two pulsed lights are compared in detail by numerical simulation. The output of these two situations are educed while depletion, walk-off and nonlinear effect are all considered. The walk-off effects of output and conversion efficiency are studied in both cases. The results demonstrate that there is an obvious walk-off between input signal and output in the pulse pumped case, and in the CW case the converted wave width is boarder than that of input signal due to pulse dispersion. Factors that influence the conversion efficiency are also analyzed including the power of the pump light, the length of the PPLN waveguide and the experiment structure.

A fully vectorial effective index method and multiple-cladding method (FVEIM&MCM) is developed for modeling photonic crystal fibers. Large negative dispersion photonic crystal fibers can be designed by changing the diameters of the first, second and third ring of air-holes.

By using the linear step effective index model (LSEIM), we analyze the chromatic dispersions (CDs) of high nonlinear photonic crystal fibers (PCFs). The linear expression of the air filling fraction as a function of the relative air-hole size is introduced for the cladding effective index. Then it is found that the LSEIM is an efficient method in high speed and high precision. And this method demonstrated by experimental data can be widely used in not only larger relative air-hole high nonlinear PCF, but also in the endlessly single mode PCF. Therefore, this research provides important theoretical basis for the development and application of high-precision phase matching PCF.

A broadband dispersion-compensating microstructure fiber is proposed. The designed fiber is shown to exhibit large normal dispersion up to -2000ps/nm/km at 1550nm and compensate conventional single mode fiber within 0.6% residual dispersion compensation ratio over a 100-nm wavelength range. Furthermore, the effective modal area is about 16μm² at 1550nm.

We demonstrate three kinds of optoelectronic devices used to all-optical signal processing, namely, semiconductor optical amplifier (SOA), periodically poled lithium niobate (PPLN), and microring resonator. Especially all these devices are competitive for all-optical wavelength conversion, logic gates, and format conversion, etc.

As the key of these all optical techniques which would be widely used in the future optical fiber communication, the stimulated Brillouin scattering (SBS) slow light draws a great of attention and shows several advantages over other slow light methods. With recent growth of nano-technology, researchers are hoping to improve the nonlinearity of the optical fiber by using the nano-technology. According to this current situation, a numerical model of the SBS slow light and three typical experiments are discussed. A novel optical fiber doped with nano material as InP is manufactured and introduced into the SBS slow light, serving as the nonlinear medium of SBS process. And the numerical simulations are performed to validate our method. The results show a considerable time delay of the optical light can be achieved through this novel optical fiber.

In this paper, a novel all optical buffer based on cascaded double-loop all optical buffer (DLOB) unites is proposed and demonstrated experimentally with the SNR analyze. This buffer is compact, simple, and inherently stable, the delay can be adjusted in the range of 0 to 250us. By injecting a synchronizing control pulse, the operation of reading and writing can be realized easily and the switch time is up to 20ps. The new optical buffer can be used in optical routers to solve the packets contention.

Conversion wavelength and power dependence of the time delay and output signal quality for an optical delay system consisting of dispersion compensation fiber (DCF) and highly nonlinear fibers (HNLFs) is investigated in this paper. The numerical results show that the time delay generally varies linearly with the conversion wavelength propagating through DCF and changes slightly with the power launched into HNLFs. But it has abrupt change at some values of conversion wavelength or input power level. Output signal quality of the overall system varies significantly with the conversion wavelength and input power level. The reasons behind these results are analyzed. Finally, the input power level is optimized to achieve linearly varying time delay and desirable output signal quality for an optical delay system.

We review fundamental waveguide optics at a fiber joint between dissimilar specialty fibers and its diffusion characteristics when the joint experiences thermal treatment. We then describe optical coupling techniques including thermal diffusion and fiber tapering in order to achieve minimum transmission loss through the fiber joint. We discuss the optical coupling property change due to diffusion and the effect of fiber taper ratio and taper length with application examples.

Rare earth and metal ion doped optical fiber preforms have been produced using a novel flash vaporization method for precursor delivery [1] into substrate tube. TEOS and solutions of organometallic compounds, containing lanthanide, Al, Bi, Fe or Co were used. Use of TEOS and organometallic precursors makes this process similar to aerosol and sol-gel processes, but glass is laid down in thin layers in MCVD fashion, strongly relying on thermophoretic forces. Preforms with fully consolidated core layers have been made and were in most cases drawn to fibers. Results of these fibers and preform glass composition are discussed.

In this paper, we describe the characteristics of advanced MMF, how it is specified, how it is manufactured, and update its application in IEEE P802.3ba 40G/100G SR4/10 standards development.

With the increasing application in the ultraviolet (UV) area, the fiber's UV transmission performance should be studied. In UV fibers, however, the presence of Germanium can result in ultraviolet radiation-induced color centers, which are point defects in the core's silica that generate absorption bands in the UV and visible spectrum that deteriorate the optical fiber transmission in that spectral region. The fiber's UV transmission performance would be influenced by the fiber core's doping content. Based on the advanced plasma chemical vapour deposition process, three types of different doping content fibers were fabricated. With test these fibers' transmission efficiency and stability, study the optimized doping process of the UV fiber.

We discuss silicon photonic wires and components based on this technology, such as filters based on ring resonators, interferometers or arrayed waveguide gratings. The devices are fabricated using standard CMOS technology, including 193nm lithography. We also discuss their application in a number of demonstrator devices within different application fields.

We demonstrate efficient nonlinear functions using silicon nanophotonic structures. In the ultrasmall core of the waveguides and cavities, nonlinear phenomena are significantly enhanced. Applying the two-photon absorption effect, we have confirmed all optical modulation, in which the modulation speed is improved to around 50 ps by eliminating free carriers. Applying the four-wave-mixing effect, we have achieved high-efficiency wavelength conversion. The conversion efficiency is -11 dB, and the efficiency will be further improved by eliminating free carriers. Using the four-wave- mixing effect, we have also realized a low-noise entangled photon pair source. The source does not need a refrigeration system for noise reduction, which is a great advantage for practical application.

A novel dispersion-compensation superstructure fiber Bragg grating (SFBG) based comb gain equalizer for fiber optical parametric amplifier (FOPA) is proposed. It is characterized by its eight-channel 100GHz DWDM-channel separations and 80 km dispersion compensation function. The object reflectivity spectra of gain equalizer are calculated in two parts independently. Inner channel part for every channel is designed according to the gain spectrum of fiber OPA. Inter-channel part is calculated with Gaussian hypergeometric function (-0.5dB bandwidth 0.1nm, -45dB bandwidth 0.3nm) to obtain slower rising and descending edges than the simply zeroed case. Then the SFBG is designed with layer-peeling inverse scattering technique. Simulation results show that this SFBG satisfies all requirements. Using this SFBG as comb gain equalizer, the gain of fiber OPA is flattened in every channel to within ±0.4dB among 8 ITU-T regulated channels, with 80 km dispersion compensated.

Four-wave mixing (FWM), including phase-insensitive amplification (PIA, no idler input) and phase-sensitive amplification (PSA, with idler input), has been exploited for a wide range of applications in all-optical signal processing, e.g. in-line amplification, wavelength conversion, optical-phase conjugation (OPC), amplitude limiter, phase regeneration, etc. In a lot of those applications, the input signal is pulse. In this paper, the FWM-based signal processing with pulsed signal input is analytically analyzed. A set of exact analytical expressions for the output amplitude and phase is derived, taking into account the pump depletion and the self- and cross-phase modulation (SPM and XPM) from pumps, signal and idler. For PIA, analytical analysis shows that the generated idler pulse is far away from the phase conjugation of the input signal, and that the output signal is not an amplified replica of the input signal. These phenomena are due to both the phase distortion caused by SPM/XPM from signal/idler, and the temporal envelope broadening resulting from pump depletion. Besides, in the frequency domain, the spectral inversion between signal/idler will be destroyed. The induced phase distortions of idler pulses in dual pumps case are found to be much smaller than those of single pump case. For PSA, neglecting the SPM/XPM from signal pulse, chirp-free output signal pulse will be obtained. However, the SPM/XPM from signal will cause frequency chirping to the output. For a pulse-sequence, through the SPM/XPM, amplitude-fluctuation will cause phase-jitter thus destroy the phase regeneration. We found that in some PSA configurations, the frequency chirping and phase-jitter mentioned above will be suppressed. Similar to PIA case, the output signal pulse of PSA may be broadened due to pump depletion. In both PIA and PSA applications, the implications of the phase and shape distortions in all-optical signal processing by FWM are discussed.

Microwave signal generation and processing such as frequency conversion are proposed and experimentally demonstrated based on stimulated Brillouin scattering (SBS) in single-mode fibers (SMFs). A simple scheme to generate microwave/millimeter-wave sources is realized by utilizing the optical heterodyne technique between an optical carrier and its Stokes light. Stable microwave sources with the frequencies of about 10.56 and 21.71 GHz are experimentally realized using the first- and second-order SBS frequency shifts based on standard SMFs. A microwave frequency up/down conversion method is presented without premodulation for bi-direction radio-over-fiber systems by using fiber SBS. The microwave signal of 1.5 GHz is experimentally up-converted to 9.06 and 12.06 GHz, and the microwave signal of 9 GHz is down-converted to 1.56 GHz, respectively.

The nonlinear optical loop mirror (NOLM) and the nonlinear amplifying loop mirror (NALM) based optical thresholding in the high speed OCDM system are analyzed, the input pulse peak power of the NOLM is optimized considering the thresholding decision function, pulse shaping and side-lobe suppressing of the NOLM based on high nonlinear fiber (HNLF) are numerically simulated, and theoretical investigation is compared with experimental result. The results show that the interference noise in the 40 Gbit/s OCDM system could be suppressed effectively by the optical thresholding techniques based on the NOLM and the NALM. We show that the NOLM and the NALM can act as a nonlinear processing element capable of reducing both the pedestal associated with conventional matched filtering and the width of the associated code recognition pulse.

A distributed-feedback (DFB) grating was written in twin-hole fibres with internal electrodes. Due to the intrinsic birefringence, the grating has two ultra-narrow peaks (~0.41 pm and ~0.27 pm) corresponding to x- and y-polarization. The separation between them can vary from 40 pm to 104 pm when the temperature increases from room temperature to 96°C. The dominant contributions of the Bragg wavelength shift as the increasing temperature are the change in refracitive index of the fibre and the expansion of the substrate (largest). Under the current pulses excitation, full on-off switching with response time ~2.5 ns has been achieved for x-polarization of the DFB grating.

In this paper two new types of 1x2 all fiber high-speed magneto-optic switches with thick film ferromagnetic bismuth-substituted rare-earth iron garnets are proposed and tested. Two types of magneto-optic switches are discussed by using two kinds of crystals. One is the ordinary switch which needs indurance magnetic field to maintain its state; And the other is latching type switch, the crystal remains in a given magnetic state for unlimited duration without energy supply. Circuits used to generate magnetic field are also discussed. The theoretical and experimental analysis of optical route, measurement of switching time and magnetic filed etc. are included. The extinction ratio of the switches are currently about 20 dB. It can be improved further by additional Faraday rotation created by another magneto-optic (MO) material in the light path. The switching time of MO material is under 100 ns, it can be ignored. Magnetic field should be able to change the voltage rapidly in order to obtain fast operating time of the optical switch. The inductance of the solenoid used for generating the required magnetic field is the bottleneck for rapid switching of the magnetic field in the MO material. The switching time of the two optical switch are discussed.

In the paper, a high speed magneto-optic switch based on the Faraday Effect is designed and analyzed. The novel magneto-optic switch presented in this paper will satisfy high speed transmission and exchange of optical-message through all-optic network. It consists of three important components as followed novel optical route, Faraday rotator configuration with ultrafast magnetic field and picosecond impulser. It may switch the optical route by controlling Faraday rotator which is supplied by picosecond impulser. By the development of the magneto-optic crystal, and ultrafast magnetic field, the designed magneto-optic switch featured as low insertion loss, low crosstalk, high switching speed and small bulky size gets ahead of traditional optic switches. As the first part of this paper, a design scheme of optical route in high speed magneto-optic switch and its experiment analysis will be discussed. Good avalanche effect of transistor FMMT415 is adopted to generate picosecond pulse signal and then to drive the high speed magnetic field. Shown by the experiment data, the rising time of the impulse about 1ns, the amplitude of the impulse about 100~500V are available on the Output end from the picosecond impulser, which can be used as driving current pulse of Faraday rotator. By using the relationship between the polarization plane rotate direction of polarization light and magnetic direction, the Faraday rotator is designed.

One kind of electro-optic polymer assisted Mach-Zehnder optical switch based on silicon slot structure is presented. By filling electro-optic material in the void slot of the arms, direct electro-optic modulation can be introduced. Theoretical model and detailed analysis is given in this paper.

This paper presents a novel micro-ring-resonator-assisted structure as an optical switch. This device couples two outputs of a 1x2 power splitter into a micro-ring resonator (MRR). The double-beam interference will occur in the MRR. If the phase difference between the beams and the coupling coefficients of MRR are set properly, the device can switch the light by applying phase shift on MRR. High extinction ratio or low crosstalk can be achieved, even if the modulation additional loss is large.

We present a novel fiber design using both stress rods and air holes for making wide band single polarization fibers as well as polarization maintaining fibers. The key factor that makes the fiber design possible is that the stress-induced birefringence from the stress rods and the form birefringence from air holes are added constructively, which increases the total birefringence and allows more flexible choice of fiber parameters. We established a finite element model that is capable to study both the stress-optic effect and the wave-guide effect. Through the detailed modeling, we systematically explore the role of each major parameter. Different aspects of the fiber properties related to the fundamental mode cutoff, fiber birefringence and effective area are revealed. As a result, fibers with very large single polarization bandwidth as well as larger effective area are identified.

Influence of stress area mismatched Panda erbium-doped polarization-maintaining fibre on the birefringence is analyzed and compared by finite element method and approximate analytical expression educed by the complex variable method of elasticity with superposition techniques.

Automatically controlled polarization controllers (PC) are the essential integral parts in an automatic compensator for polarization mode dispersion (PMD). It is suggested by Prof. M. Karsson et al. at Charlmers University of Technology, and afterward widely accepted that we need to adjust only two waveplate PC (two degrees of freedom, DOF) for each stage PMD compensator to complete PMD compensation. It is equivalent to say that only two of degrees of freedom for each PC are needed to complete the state of polarization (SOP) transformation from any input state into any other state covering the entire Poincare Sphere. In this paper will take two types of commercial available PC as examples to prove theoretically and experimentally that except for the reset-free problem it is necessary to adjust at least three instead of two waveplates in order to transform any input state into any other state covering the entire Poincare Sphere. Therefore we can achieve complete PMD compensation at least using 3 DOF instead 2 PC in each stage PMD compensator.

A matrix theory which is capable of describing the Cross-polarization modulation (XPolM) in semiconductor optical amplifier (SOA) is presented in this paper. Using the transfer matrix method, we prove that there exists Principal State of Polarization (PSP) vector and Polarization Dependent Gain (PDG) vector in SOA. The evolution of output SOP on the Poincare Sphere (PS) can be decomposed into two circles, which are induced by PDG and Polarization Dependent Phase Shift (PDPS), respectively. The expressions of PSP vector and PDG vector with regard to inner parameters of SOA are obtained. The pump-power induced evolution of output SOP is investigated experimentally. The experimental results accord well with this matrix theory.

Polarization-induced phase noise in Michelson interferometer with imperfect Faraday rotator mirrors was investigated. This kind of noise generates from the rotation angle errors of Faraday rotator mirrors and external polarization perturbation. The conversion factor κ, representing the magnitude conversion ability from polarization-noise to polarization induced phase-noise, have been theoretically evaluated and experimentally investigated.

In this letter, a novel optical sensor based on high birefringence fiber loop mirror with a single Fiber Bragg Grating, available for temperature insensitive measurement for strain, was proposed and demonstrated. Considering that the HBFLM (high birefringence fiber loop mirror) and the conditional Fiber Bragg Grating have different response to strain and temperature, respectively, we can detect both the peak wavelength shift of these two devices. So we can build a lineal matrix equation between the perturbation of the surrounding and the shift of the transmission spectrum. Compared with conditional sensors for simultaneous measurement, this kind of sensor has several advantages, including simple configuration, low cost and easy to be fabricated.

An optimized 1.66μm Q-switched fiber laser is demonstrated for Raman-based distributed temperature sensor. In a ring type Q-switched erbium-doped fiber laser, 850m TrueWave fiber is introduced to serve as both delay line fiber and Raman gain medium so that in addition to the wavelength shifted to 1.6μm, the pulse duration and the buildup time can be relatively extended. By properly controlling the fall edge of the acousto-optic switch, the pulse duration of 30-74ns with peak power of 1.3-3.3W is achieved. Based on this light source, a 2.4km Raman-based distributed temperature sensor is obtained with temperature resolution of 1°C and spatial resolution of 8m.

Two-mode highly birefringent optical fibers support two spatial modes. The two spatial modes can be used to set up two detectors. The birefringence would change with the variety of environment. Therefore, two-mode highly birefringent optical fibers can sense two parameters synchronously. A finite element method (FEM) was used to numerically calculate the distribution of pressure, distribution of temperature and the birefringence variety versus pressure and temperature in two-mode highly birefringent photonic crystal fibers. Based on the single parameter sensor, the muti-parameter sensor was analyzed. The results show that the muti-parameter sensor can measure pressure and temperature synchronously.

In general, an operational sonar system will require an anti-aliasing low-pass filter if any high frequency components are present in the sensor phase information. A mechanical filter must be used in the sensor since anti-aliasing filtering must be performed before sampling. Fiber-optic hydrophones with mechanical anti-aliasing filter, which consists of soft closed-cell sponge rubber, have been reported, but they have poor ability of resistance to hydrostatic pressure due to the softness of the rubber. Furthermore, the theoretical analysis and design of the hydrophone are difficult due to the uncertainty of the rubber's mechanical properties. To effectively eliminate the aliasing in a practical sonar system based on interferometric fiber-optic hydrophones, a novel mechanical anti-aliasing filtering fiber-optic hydrophone with a cylindrical Helmholtz resonator has been proposed. The low frequency lumped parameters model of the fiber-optic hydrophone is given based on the theories of electro-acoustic analogy, and the acoustic properties are analyzed using the standard circuit analysis methods. The acoustic sensitivity frequency response is measured in a standing-wave tube using a comparative measurement method. Experimental results show that this new type of fiber-optic hydrophones has good acoustic low-pass filtering performance. The low frequency response, as determined by the sensing mandrel and the fiber optical interferometer, is very flat and the average acoustic phase sensitivity is about -140 dB re 1rad/μPa with a fluctuation within ±1.0 dB. The response curve has a resonant frequency determined by the hydrophone structure. Apart from the resonant frequencies and the high frequency responses, the measured response curves are well in agreement with the simulation results, which show the correction of the model and the theories. It is expected that this new type of mechanical anti-aliasing fiber-optic hydrophone will have wide potential applications in modern sonar systems.

A New magnetic field measurement based on polarization effect of fiber grating was analyzed in theory and experiment. The simulations show the linear relationship between the peak value of PDL and magnetic field in certain range. Moreover, this method is temperature insensitive. The precision of this method is 2Gs using the optical vector analyzer in experiment and agree well with the theory.

Chemical composition gratings, used as strain sensing elements at high temperature environments, show a temperature dependence of their strain response. Temperature dependence of the strain response of CCGs over a range of temperatures from 24°C to 900°C has been measured. It is found that the wavelength shift of CCGs is linear with applied tensile strain at a constant temperature, and the strain sensitivity is 0.0011nm/με.

This paper describes the observation of a fiber fuse observed in the core of a high-power high-NA, all-glass, double-clad fiber. Fiber fuse is a phenomenon that results in a specific type of catastrophic destruction of an optical fiber-core from the point of initiation toward the light source. It is so named because its appearance is very similar to a burning fuse. In this paper, we examine the origin or the initiation source for the fiber fuse observed in the double-clad fiber. Furthermore, we propose a two-step thermal mechanism for the fiber-fuse generation in optical fiber.

The LD-clad-pumped CW and Q-switched pulse Tm³⁺-doped silica fiber amplifiers were general experimental investigations. The CW fiber amplifier provided up to 3W output with the slope efficiency nearly 30%, and the Q-switched pulse fiber amplifier output power was 2W with the slope efficiency 32.6%. The gain fiber was 27.5/400μm D-shaped Tm³⁺-doped silica double-cladding fiber, and the pump sources was a 792nm LD with a 400μm pigtail fiber output. The signal seed sources was a LD-pumped Tm³⁺:YAP lasing at 1.99μm. By the AO Q-switched method, The Tm³⁺:YAP laser had a nearly 120ns pulse duration and 1kHz repeat rates. The measured amplified spectrum only stretched a little relative to the input signal spectrum.

Based on an external cavity using Littrow configuration, a high-power, narrow-linewidth and broadband-tunable Yb³⁺-doped double-clad fiber (YDCF) laser was demonstrated. Numerical simulations were performed to optimize the design of the laser. A wide wavelength tuning range from 1046 nm to 1121 nm was achieved. The 3-dB linewidth of the laser was up to 0.5 nm. An output power of over 20W at 1089 nm with a slope efficiency of 60% was achieved.

We propose to use a nearby metallic nano-particle to greatly enhance the transmission efficiency of a nano-slit aperture in a metallic film. The metallic nano-particle helps to form a T shape cavity which could effectively transform the propagating incident light into localized near-filed light. Harvest efficiency is enhanced by 20 times for a non-resonant 25 nm-width nano-slit.

High-speed Photonic Analog-to-Digital Convertor (ADC) has attracted intense interest of researchers for the past three decades, for it has the potential applications in areas that have extreme bandwidth requirements, such as radio astronomy, real-time measurements and so on. Photonic ADCs can be categorized into two major classes: optical assisted ADC and all-optical ADC. In optical assisted ADC, the sampling is performed in optical domain and the quantization is done in electrical domain. In all-optical ADC, the sampling, quantization and coding are done in optical domain. Optical assisted ADC combines the ultra-stable, ultra-low time jitter characterizations of mode-locked lasers and mature high-speed electronic circuits, therefore it is much easier to implement in practical systems. However, the ultra-short (less than tens of pico-seconds) post-sampling pulse sequence required by high resolution ADC places a challenge for the following electrical processing, because ultra-high-speed (>2GHz) "integrate-hold" circuits are hard to design and manufacture. In this paper, an optical hold module (OHM) is proposed, theoretically analyzed, numerically simulated and experimentally demonstrated, which can be used to replace ultra-high-speed "integrate-hold" circuits and has more merits than the latter. This optical hold module has potential applications in several other areas, such as fiber sensors, and so on.

A novel correlator based on 3x3 coupler with dual loops which perform XOR operation and feedback with power compensating is proposed. The validity of device is demonstrated by the simulation with realistic parameters at 10Gb/s and 40Gb/s. For this kind of correlator, the amplified spontaneous emission (ASE) noise accumulation is the crucial limitation. The relationship between the output signal-to-noise ratio (SNR) and bits to be compared is analyzed theoretically. The ASE noise is retrained and the output SNR is enhanced by introducing the assistant light advisably. Therefore, this device can perform the comparison of arbitrary length data. If the dual loops length is minimized by integrate, the devise is applicable for the higher speed data.

We demonstrate a novel optical flip-flop configuration which consists of one Fabry-Perot laser diode (FP-LD) and two Fiber-Bragg-Gratings (FBG).The all-optical flip-flop is realized based on the optical bistability of injection-locked single-mode of FP-LD. The essential part to obtain bistability in this system is that the output of FP-LD is fed back partly by two FBGs at certain wavelengths. The EDFA was used to adjust the power of feedback beam. The on or off state of the All-optical flip-flop is determined by the set or reset light externally at different wavelength. The all-optical flip-flop operated at the wavelength of 1537nm with on-off contrast ratio of 15 dB. The theory and experimental result are presented.

A mismatched optical coupler with waveguide weighted by the Blackman function is numerically investigated in the demand of short-length, C+L-band, low crosstalk, and process tolerance. Utilizing the full factorial design, the structure parameters of coupling waveguide are obtained by beam propagation method. In the condition of crosstalk of -33.5 dB, the mismatched optical coupler with proper selected waveguide structure parameters is found to have a coupling length of 2.80 mm in the transmission wavelength ranges of C+L-band (1.53~1.61 μm). Obviously, the selection and design of waveguide structure are very important to satisfy the qualities of a mismatched optical coupler for the demand of short-length, bandwidth, and low-crosstalk.

An octagonal photonic crystal fiber (O-PCF) structure with eight air-holes on the first ring is proposed based on a unit isosceles triangle. The mode effective index and chromatic dispersion of the O-PCF are numerically investigated by employing the finite element method. It is found that under the same value of air filling fraction (AFF), the octagonal photonic crystal fiber has smaller mode effective index and higher amplitude of dispersion. On the other hand, the dispersion of O-PCF can be easily controlled through adjusting appropriately the air-hole pitches and air-hole diameters.

We show that, using index guidance within an isotropic all SiO₂ structure of only 4 layers, it possible to design an optical fiber that supports just one mode of a single polarization: the azimuthally polarized TE₀₁ mode. In particular a ring guide of appropriate index of doped SiO₂, thickness and radius guides TE₀₁ as the fundamental mode. Then an outer layer can be used to cut off higher order modes. This design is in contrast to those that require Bragg guidance or anisotropic materials.

10-GHz optical injection mode-locking of a weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) with 10%-end-facet reflectivity based fiber ring with an intra-cavity power controlled wavelength shift and a reducing chirp linewidth at high intra-cavity coupling ratio condition is demonstrated. Both the strong dark-optical comb and strong feedback coupling contribute to the red shift of mode-locking spectrum. The wavelength shift from 1536 to 1542 nm of the WRC-FPLD based fiber ring associated with its pulsewidth and linewidth also reduced from 27 to 19 ps and from 10 to 6 nm, respectively, can be observed. The peak-to-peak frequency chirp reduced from 3.5 to 1.8 GHz was caused by the shrink of linewidth. The WRC-FPLD exhibits relatively weak cavity modes and a gain profile covering > 33.5 nm. The least common multiple of the WRC-FPLD and the fiber-ring mode-spacing is tunable by adjusting length of the fiber ring cavity to approach intracavity mode spacing of 1.6 nm. Up to 12 lasing modes naturally and a mode-locking pulsewidth up to 19 ps can be observed. With an additional intracavity bandpass filter, the operating wavelength can further extend from 1520 to 1553.5 nm. After channel filtering and linear dispersion compensating, the pulsewidth can be further compressed to 8 ps with corresponding chirp reducing from 9.7 to 4.3 GHz. Such a mode-spacing tunable pulsed fiber laser matching ITU-T DWDM channels can be employed as a novel optical carrier to integrate the OTDM function into the DWDM system with a channel spacing tunable from 50 to 200 GHz.

Fiber laser with two polarization-dependent output states is demonstrated. On one hand, nonlinear polarization rotation induced intensity-dependent loss of nonlinear optical loop mirror can balance mode competition of homogenous broadening gain medium, and thus allows for stable room-temperature multiwavelength generation. On the other hand, intensity-dependent transmission can act as an equivalent saturable absorber, which results in passively mode-locking of fiber laser. It may be a potential multifunction fiber laser.

A tunable single polarization Yb³⁺-doped fiber laser using 45° tilted fiber Bragg grating is demonstrated. It generates high degree of polarization (>99.86%) 1.06μm laser with 25 nm wavelength tuning range. This 45° tilted fiber Bragg grating was fabricated using a zero-order-nulled phase mask. It has a near constant polarization-dependent loss (PDL) across a wide wavelength range (1030 to 1080 nm).

A novel narrow linewidth, discretely tunable and stable fiber ring laser based on the matching of the transmission spectra of two fiber Bragg grating Fabry-Perot (FBG-FP) filters is proposed in this paper. We studied the characteristics of this sort of tunable fiber laser both theoretically and experimentally, and obtained eight discretely tunable lasing wavelengths from 1552.24 nm to 1552.912 nm with an average 96 pm spacing, by pulling one of the FBG-FPs. The output of the laser at the discrete wavelengths specified by the transmission maximum of the fixed FBG-FP is quite stable, and the fluctuation of the output power is less than 0.1dB.

An active mode-locked fiber ring laser based on XGM in SOAs is demonstrated with an external pulse sequence. The laser operates at a variable repetition rate from 1GHz to 15GHz, even up to 40GHz with an additional fiber-based multiplexer. By a wavelength tunable filter, a wide wavelength tunable span about 37nm is achieved continuously between 1528nm to 1565nm. Without any pulse compression device, the pulse sequence with low pulsewidth about 12ps and high output power about 9dBm can be obtained in different operation repetition rate. The output pulses show a time jitter low than 180fs in all operation repetition rate. A detailed analysis is done experimentally to investigate the relationship between parameters of the SOA-based fiber ring laser and pulsewidth of the generated mode-locked pulses.

A discretely tunable fiber ring laser based on a Sagnac interferometer incorporating a few-mode polarization maintaining fiber and semiconductor optical amplifier as the gain media is presented. Nine lasing wavelengths at a tuning step of 2.5 nm is achieved with side-mode suppression ratio over 20 dB.

Optical liquids can be used to engineer the dispersion characteristics of fibers by serving as the core or cladding. The short-/long-pass filters are so made and concatenated to achieve widely tunable Gaussian-shaped filters for bio-imaging.

A systemic design on multi-bandpass filters is developed based on a plurality of Fabry-Perot(FP) interferometers, which are composed of a cavity between mirrors. Certain number of passbands can be built by selecting the number of cavities, while the band-width and the band- interval can be adjusted by the total layers contained in mirrors. By changing the configuration of mirrors and cavities a huge group of multi-band-pass filter will be developed. Among many multi-bandpass filters given here several of them are tested. A double-passband filter is deposited on a super-thin substrate of thickness about 5 μm. One of its passbands situates 1550nm, three rejection bands situate 1310nm, 1490nm and 1640nm make this filter very useful for B-PON and GE-PON in the fiber communications. A triple-bandpass filter with four rejected bands is deposited on glass, its high transmittance in passbands and high isolation in rejection band make it a valuable filter for Add/Drop device. In another deposition its three passbands can transmit blue, green and red (B, G and R) lights but reject other lights which otherwise become noise to the B, G and R light signals. The good performances of the filters deposited above prove that multi-bandpass filter designed by this way is easy to do.

Instead of real phase shifts, equivalent phase shifts (EPS) are adopted to construct ultra narrow phase-shifted band-pass filer in sampled Bragg gratings (SBG). Two optimized distributions of multiple equivalent phase shifts, using 2 and 5 EPSs respectively, are given in this paper to realize flat-top and ripple-free transmission characteristics simultaneously. Also two demonstrations with 5 EPSs both on hydrogen-loaded and photosensitive fibers are presented and their spectrums are examined by an optical vector analyzer (OVA). Given only ordinary phase mask and sub-micrometer precision control, ultra-narrowband flat-top filters with expected performance can be achieved flexibly and cost-effectively.

We propose an all fiber tunable band pass filter based on dual acousto-optic mode coupling scheme. By applying two acoustic waves on a piece of etched single mode fiber, the feasibility of the filter is demonstrated experimentally. The tunable characteristics of the device are discussed theoretically.

Based on the coupled mode theory, the transfer matrix approach is presented to investigate the fiber grating external cavity semiconductor lasers (FGECSL). As a result, the P-I curve, the lasing wavelength and the side-mode-suppression-ratio (SMSR) have been investigated numerically in detail. With the length of the fiber grating increasing, the reflection spectrum of FGECSL changes obviously, the threshold current and threshold carrier density decreases, the mode distribution is irregular, and the output spectrum becomes complex. Moreover, the optical bistablility is also observed.

Wavelength-spacing-tunable multiwavelength filters and lasers have been realized using a superimposed chirped-fiber Bragg grating based distributed Fabry-Perot interferometer incorporating with a beam-bending chirp tuning method. Continuously wavelength spacing tuning of 0.3-0.6 nm has been achieved.

The paper reviews the recent progress on CO₂-laser writing of long-period fiber gratings (LPFGs) in different kinds of fibers, including conventional single-mode fiber (SMF), boron-doped SMF, polarization-maintaining fiber, photonic crystal fiber, and polarization-maintaining photonic crystal fiber. In particular, we report the writing dynamics for the understanding of the physical mechanisms involved in the writing process and show that the CO₂-laser pulses can not only relax the internal stress in the fiber core but also induce a frozen-in stress in the cladding of the fiber under tension. The applications of CO₂-laser written LPFGs, especially for the realization of broadband optical couplers, are also discussed.

We present the experimental results of a novel single-ended reflecting surface plasma resonance (SPR) based long period fiber grating (LPFG) sensor. A long period fiber grating sensing device is properly designed and fabricated with a pulsed CO2 laser writing system. Different nm-thick thin metal films are deposited on the fiber cladding and the fiber end facet for the excitation of surface plasma waves (SPWs) and the reflection of the transmission spectrum of the LPFG with doubled interaction between metal-dielectric interfaces of the fiber to enhance the SPW of the all-fiber SPR-LPFG sensing system. Different thin metal films with different thicknesses are investigated. The effect of the excited SPW transmission along the fiber cladding-metal interface with silver and aluminum films is observed. It is found that different thicknesses of the metal overlay show different resonant behaviors in terms of resonance peak situation, bandwidth and energy loss. Within a certain range, thinner metal film shows narrower bandwidth and deeper peak loss.

Some experiments of optical performance monitoring (OPM) with uniform or nonuniform quasi-phase matching (QPM) gratings waveguides have already been demonstrated during the last few years. Theoretical analyses based on coupled-wave equations are carried out for nonuniform QPM gratings. The generation process of SHG in nonuniform QPM gratings is simulated and the outcome comparison between uniform and nonuniform QPM gratings, which demonstrate that nonuniform QPM gratings are more suitable for the OPM systems, is carried out in this paper. The value of grating chirp coefficient of the chirped PPLN has influence on the efficiency and band width of the output pulse. The relation between them is also discussed. These are new simulative attemptation to apply the nonuniform quasi-phase matching gratings into optical performance monitoring system.

We constructed a fiber Raman amplifier with an ordinary single-mode fiber in the U-band located on the 1.66μm for the first time. This paper studies the gain characteristics of FRA by using the pump sources with different property and different power. Experiments showed the system amplified steadily when pump power was tens of milliwatt. To the same pump sources, as pump power is increased, the gain of the signal improves obviously. In the case of identical pump powers, FRA' gain is also concerns with the pump source's type and the pump way. When the double-clad Er-Yb codoped fiber laser was used as the pump source, though our 1.66μm fiber Raman amplifier, the signal was amplified effectively and the maximal peak gain reached 5.11dB.

A spectral sliced multiwavelength laser source which utilizes supercontinuum generated in a high nonlinear dispersion flattened holey fiber(HNL-DF-HF) and spectral slicing in an arrayed waveguide grating has been demonstrated. All 32 channels exhibit almost constant pulsewidth, the channel separation is 100GHz, and crosstalk of the adjacent channels is more than 25dB.

We consider the continuous wave propagation in a highly dispersive and nonlinear medium wherein the wave propagation is governed by the generalized nonlinear Schrodinger equation. We demonstrate the novel flat-top modulational instability gain for a wide range of modulation frequencies in the anomalous dispersion regime of highly dispersive and nonlinear media. We find that the resulting MI gain is independent of input power. Besides, we compare the analytical results with those of numerical results.

An all-optical low-pass filter utilizing cross-gain modulation (XGM) in fiber optical parametric amplifier (OPA) has been proposed and experimentally demonstrated. In this proposed low-pass filter, the pump, signal and a continuous-wave probe were launched in the highly-nonlinear fiber (HNLF) to introduce OPA and thereby XGM effects. Pump, signals and idlers were then being separated and then filtered. With suitable time delay being introduced into different optical paths, the low-pass filter was implemented, which was verified with the experimental results of pseudo-random signal. The timing waveforms of the filtered signal were shown, followed by the transfer function of the low-pass filter's frequency response. They all showed a good agreement with the numerical results.

The exploitations of air holes in optical fiber design have been receiving growing research interest since the first photonic crystal fiber (PCF) was demonstrated. Many peculiar optical properties are achievable with the flexible control of the geometry of the air holes in the microstructured cladding. Different from the complex geometry of microstructured cladding in the holey PCF, hole-assisted lightguide fiber (HALF) is based on conventional optical fiber design and therefore guides light by total internal reflection. The existence of the assisting air holes in the cladding helps to tailor the optical properties of the fiber. In this work, the dispersion tailoring is demonstrated by varying the structural parameters and material properties of the fiber. Additional tunability is achieved by infiltrating substance with tunable refractive index into the assisting holes.

The paper firstly demonstrates a theoretical investigation of clock recovery from carrier-suppressed return-to-zero (CSRZ) modulation format data at 40Gbit/s by using SOA-based ring laser. And a completely numerical analysis about the clock characteristics at 40Gbit/s is done, which is an effective guide for experiment and necessary to optimize the system performance. Meanwhile, simulation results show high-quality clock recovery from 2⁷-1 PRBS CSRZ data at 40Gbit/s can be achieved by using higher power assist CW light into a SOA-based ring laser.

A simple novel ultrafast scheme of all-optical nonreturn-to-zero(NRZ) to return-to-zero(RZ) is proposed based on Sagnac interferometric structure. The operations of this scheme at 40Gbit/s 2⁷-1 PRBS sequences are simulated correctly with the output extinction ratio more than 19.1dB. Through built theoretical model and numerical analysis, the operating characteristics of the scheme are illustrated. Furthermore, the carrier recovery time of the SOA is no more a crucial parameter to restrict the operation speed of this scheme.

Copper-doped planar glass waveguides were prepared by the thermal ion-exchanged of commercial soda-lime glass wafers in molten mixture of CuSO₄ with sodium sulfates at temperature of about 600°C. The effective indices were measured by means of prism-coupled technique, and the guided modes were not monotonic increasing with the ionexchange times. The properties of photoluminescence (PL) spectra of the waveguides were studied. The broad emission bands centered at around 520 nm (at the excitation wavelength of 310 nm, at the room temperature) were measured on the samples, which were also strongly influenced by the ion-exchange times and the intensity of the PL emission is not monotonic increasing with the ion-exchange times as well.

A new tunable wavelength selector based on the fiber Bragg grating with cladding made of LiNbO₃ with optical axis running along the axis of fiber Bragg grating was investigated. The calculated results indicate that the reflected wavelength can be tunable from 1550.921 nm to 1548.9668 nm with variation of electric field running along the fiber axis from 10⁷ to 10⁸V/m, the reflectivity varies from 99.8252% to 99.9715%. The tunable wavelength range will be large with the electric field increases. These rules indicate that the new tunable wavelength selector based on the fiber Bragg grating with cladding which is made of uniaxial anisotropic electro-optic crystal material can be achieved through adjusting the electric field intensity while keeping the fiber grating length, periodicity and the other parameters as constants.

A dual-order Raman fiber laser (RFL) is numerically presented with suppressed low-frequency relative-intensity-noise transfer from pump sources to both the first- and second-order Stokes output. It is accomplished by generating the amplified spontaneous emission near second-order Stokes shift from the launched pump. Their powers can be tuned in a large dynamic range. Besides these, the low-power second-order Stokes output is also stabilized in the RFL setup. These special behaviors fit the proposed RFL for use as dual-order pump sources in Raman fiber amplifiers.

Combined DLP algorithm and sampled theory, super-narrow FBG filter for arbitrary shaping spectrum can be successfully synthesized, and the process of design and fabrication using one uniform mask are demonstrated. A novel method for a single stage illumination to fabricate dc-free apodized sampled FBG is proposed based on the chirp of sample period. Above design and fabrication method are testified by simulation and experiment results, and a super-narrowband triangle shaping FBG filter with 25pm 3dB bandwidth and side lobes suppression beyond 20dB is fabricated.

It is well known that the thermal expansion coefficient of the cladding layer can significantly influence the stress induced birefringence in arrayed waveguide gratings. For the first time, the so-called cladding layer is divided to two parts, i.e. upper cladding and interlayer. The effects of the thermal expansion coefficient, the Young's modulus and the Poisson's ratio of the interlayer, the upper cladding layer and the buffer layer on thermal stresses in buried channel silica-on-silicon optical waveguide cores are studied by use of finite element simulation. The results show that the interlayer between waveguide cores plays the most important role in determining thermal stresses of waveguide cores. The influences of the upper cladding layer and the buffer layer are small, though the former affects slightly larger than the later. By adjusting the thermal expansion coefficient of the interlayer instead of the cladding layer, it is faster to minimize the stress induced birefringence, and the thermal stresses around waveguide cores are almost symmetry. It is also shown that the thermal stress effects of the thermal expansion coefficient and the Poisson's ratio on the cladding layer can be considered as linear superposition of those on the interlayer and the upper cladding layer. However, this conclusion is unsuitable for Young's modulus because of big coupling effect when the thermal expansion coefficient of the interlayer is large.

We report on the fiber-based amplification of a commercially packaged, fiber-pigtailed-pulsed diode laser operating at wavelength of 1064nm (bandwidth 0.45nm). The cascaded Yb-doped fiber amplifier can operate safely by using cascaded Wavelength division multiplexing (WDM) in each single-mode amplification stage. The total isolation of cascaded WDM can protect the laser diodes from destroyed by feedback of optical power. At repetition rate of 50kHz, pulse duration of 20ns, and average power of 0.5mW, output power up to 1.05W And peak power up to 1.05kW are obtained, with a high signal to noise ratio of 20dB. The whole system is a good choice for a preamplifier of high-power short-pulse amplification. The aim of the experiment is to study the design of preamplifier for high-power short-pulse amplifier via cascaded fiber-based amplifier.

The terahertz dielectric properties of GaAs were tested in the frequency range extending from 0.23 THz to 0.375 THz by using backward-wave oscillator (BWO). The terahertz refractive indices, the absorption spectra and the dielectric functions of various resistivity GaAs were measured and compared. The experimental results indicate that the absorption coefficient of the GaAs is decreased with the frequency increasing and its least absorption coefficient equals 3.87x10^-4 cm^-1. Our results demonstrate that the applicability of the backward-wave oscillator THz absorption spectroscopy to GaAs characteristic analysis by calculating the absorption spectra. This work establishes the basic spectra data for GaAs is very significative to design the high efficiency terahertz wave antenna.

In this paper, a compact optical modulator using negative refractive material slow-wave waveguide is proposed. The finite element method (FEM) has been employed to analysis the performances of the novel modulator. The results show that the size of the novel optical modulator has low power consumption, compact size, easy fabrication, and the cost. Its dimension is only 40μm-long. The size of the novel optical modulator is 100 times shorter than that of the conventional lithium niobate optical modulator. It has a potential application for future optical communication systems.

In this paper, a pressure sensor based on distributed Bragg reflector (DBR) fiber laser was reported. The laser was operated in single longitudinal mode. For the longitudinal-mode has two orthogonal polarizations, external press on the cavity would induce birefringence. It can be used to sense external pressure by measuring the beat frequency shift of polarization mode. After theoretical derivation and experimental verification, the sensing characteristics of the laser were shown in detail.

Optical en/decoder is one of the key components in Optical Code Division Multiple Access (OCDMA) systems. Therefore, the improvement of performance of en/decoder is very necessary for improving the whole performance of OCDMA system. Among all kinds of factors which affecting the performance of en/decoder, the compatibility between optical source and en/decoder is proved to be an inevitable item. In this paper, as to equivalent phase shift super-structured FBG (EPS-SSFBG), an advanced en/decoding technology, both optimum pulse width and proper central wavelength deviation between optical source and EPS-SSFBG based en/decoder are first investigated, which lead to a novel method of optimizing the compatibility between optical source and en/decoder. The simulation results show that there exists an optimum pulse width, not the narrowest one, fit for EPS-SSFBG based en/decoder, what's more, it is proved advisable that proper central wavelength deviation would be beneficial when pulse width is relatively wide. Simulation and experimental results prove the feasibility and effectivity of the proposed method.

A fiber laser hydrophone system for measuring tone-burst ultrasonic signals up to 40 MHz is developed. The hydrophone consists of a cladding-etched dual polarization distributed Bragg reflector (DBR) fiber laser. The sensing mechanism is based on the modulation of the fiber laser's birefringence induced by the ultrasonic pressure. The ultrasonic signal waveform is demodulated using an FM-DEM (frequency modulation-demodulation) circuit and measured with a digital oscilloscope. Incorporating the time delay measurement of ultrasonic signal, this fiber laser hydrophone system achieves a spatial resolution of 37.5 μm at 40 MHz.

We propose a simple method for achieving a desirable chirp in the grating based on refractive index direct current component (RIDCC) modulation. The method uses dual-scan technique with an UV beam to obtain an increase of refractive index direct current component in the grating along the grating length. The effect of RIDCC modulation on the group delay characteristic of fiber grating is analyzed and the relationship between the RIDCC modulation and group delay of grating is deduced. Also, the numerical simulation results are given by using coupled mode theory and they agree very well with theoretical values. By controlling the RIDCC modulation function and modulation coefficient, we can realize different group delay profile using the same phase mask. These gratings can be used to compensate dispersion and dispersion slope of transmission fiber in high-speed optical communication systems.

Simultaneous independent measurement of surrounding refractive index (SRI) and temperature using the tilted fiber Bragg grating is proposed and experimentally demonstrated. Core mode is sensitive only to the temperature while cladding modes are sensitive to the temperature and SRI, theirs temperature sensitivities are equal. The wavelength shifts of two kinds of modes with a change of temperature and SRI allow for simultaneous discrimination temperature and SRI effect. In addition, the sensitivity of TFBG to SRI is significantly enhanced by hydrofluoric etching clad; it can satisfy the custom-built sensitivity that the clad of TFBG was etched in different degrees as well. This sensor is potential for chemical-biochemical sensing application and measuring the concentration of the chemical solutions accurately.

An all-fiber LD-clad-pumped Tm-doped fiber laser was reported, and the CW maximal output power reached 24W at nearly 1.94µm. The homemade double-clad Tm³⁺-doped fiber had a demission of 25/250µm with the core NA 0.13 and inner-clad NA 0.46. A matched passive multi-mode FBG acted as the front cavity. The cavity was build-up by the high reflectivity FBG and fiber end Fresnel reflectivity. The all-fiber scheme was build-up by splicing the pigtail fiber, FBG fiber and Tm³⁺-doped fiber. Cooling by the water, the 56% high slope efficiency was achieved and threshold was 6.4W, respected to the launched pump power. When the output power was less-than 3W, the output laser was single-peak operating at 1936.4 nm with a very narrow linewidth (50 pm) laser output. Increasing the launched pump power, the output laser wavelength grew to 3~4 peaks. The multimode fiber Bragg grating (FBG) transmission spectrum was also measured with a matched 82cm Nufern Tm³⁺-doped fiber as fluorescent sources. With the dichroic and the FBG building up cavity, the output laser characteristics were also investigated. Because the multi-mode FBG reflectivity was not very high, both ends of the fiber laser had laser output power, and the ratio was nearly 10:1. As we know, it was the first time to report the multi-mode FBG all-fiber laser. Under this simple Tm³⁺-doped fiber laser scheme, we estimated that the maximal output power could reach several ten watts.

Fiber grating is sensitive to the stress, temperature and other entironmental factors. It has caused much attention and has been used widely. In this paper a new magnetic field measurement using different group delay (DGD) of fiber grating is proposed. When the magnetic field applied the refractive index difference of the two circularly polarized light in fiber grating will be changed because of the faraday effect. So the DGD of fiber grating is changed. Through the formula derivation in certain condition, the linear relationship between the peak value of DGD and magnetic field in measurement range is found. Through the simulations the effect of applied magnetic field, fiber length and index modulation coefficient on the peak value of DGD is shown. On the other hand, the linearity will tend to saturation when magnetic field exceed the measurement range. So we can determine the mesurement range given design parameters. In the experiments the DGD of FBG without and with magnetic field are performed. The peak value of DGD increases with the applied magnetic field linearly. The fit curve of experimental and simulated results is parallel approximately and the gap is because of the intrinsic DGD of fiber grating. Using the optical vector analyzer with precision of 10^-5ps we get the sensitivity of 0.001Gs in experiment. The simulations and experiments validate this method.

The very high dispersive dual-core photonic crystal fiber is analyzed by the full-vector finite element method. The dependence of the phase-matching wavelength (PMW) and the full width at half-maximum (FWHM) on the refractive index of the doped inner core, the diameter of air holes and the hole pitch is demonstrated. The dispersion value is as large as -1427 ps/(nm km) and the effective mode area of the fundamental mode, 82.06 um² are obtained.

End surface grating by direct inscribing an index modulation pattern on optical waveguide surface to control amplitude and direction of the diffracted light is fabricated. Direct inscribing an index modulation pattern by femto-laser is simple, agile and the pattern is steady and durable. We control power and direction of diffracting orders by inscribing different modulation patterns and the controllability may well offer opportunities for various kinds of applications such as beam splitter, beam deflector, and beam shape controller.

Dual-wavelength with orthogonal polarizations erbium-doped fiber ring laser at room temperature is proposed. One polarization-maintaining fiber Bragg grating (PMFBG) in a Sagnac loop interferometer is used as the wavelength-selective filter. Due to the polarization hole burning (PHB) enhanced by the PMFBG, the laser can operate in stable dual-wavelength operation with wavelength spacing of 0.336 nm at room temperature by adjusting a polarization controller (PC). The optical signal-to-noise ratio (OSNR) is over 52 dB. The amplitude variation in nearly one and half an hour is less than 0.6 dB for both wavelengths.

In order to achieve photonic band-gap effect as sensing mechanism and improve biocompatibility of relatively lower-cost silica-core phonic crystal fibers (SCPCF) and make use of photonic band-gap effect as sensing mechanism, polymer with similar biocompatibility as PMMA coating in SCPCF air-holes is proposed in this paper. In order to evaluate the polymer coating effect, a three-layer model of air hole is proposed. The wavelength shifts of photonic band-gap edges (PBEs) were evaluated by plane wave expansion (PWE) method, assuming refractive index of silica n_s, polymer n_p and air n_a are 1.45, 1.50 and 1.00 respectively. Blue shifting of bands are observed in the simulation and the bandwidth of each band-gap becomes narrower with the increasing of air ratio. The result shows that 1nm change of air hole is able to obtain a wavelength shift of 0.43nm. Assuming the wavelength shift of 0.01nm can be detected, a small air hole variation of 0.023nm can be measured.

Sol-gel entrapment technique is proposed for glucose oxidase immobilization in long period grating glucose sensor. The glucose oxidase is encapsulated in transparent sol-gel matrix to detect the presence of D-glucose molecules. A sensitivity of 39.8mM/nm was achieved for the fabricated glucose biosensors.

A ring-cavity Er/Yb co-doped fiber laser (EYDFL) was designed and the characteristics was studied in this paper. It used 1064nm Nd:YAG laser as its pump, and the gain medium is a 4.1m-long EYDF. The single longitudinal-mode operation is realized by introducing a fiber Bragg grating (FBG) as narrow wavelength-selective element, and a section of EDF not-pumped as saturable absorber. The fiber laser resonator has been optimized, and the stable laser output with single longitudinal-mode was got. In the simulation and experimental study, the difference of fiber laser output power using output coupler in different coupling ratio has been studied. The optimal coupling ratio testified in experiments was near 80 percents. The effects and influences of saturable absorber on characteristics of output laser mode are analyzed.

A novel and simple in-line fiber polarizer is presented. The proposed device is fabricated by tapering an anisotropic flat-cladding birefringent micro-fiber surrounding with low-dispersion optical-liquid cladding. We also presented a theoretical analysis for dispersive birefringence of flat-clad micro-fiber with liquid overlay. The proposed device can be useful as all-fiber polarizer for optical communications. Simulation results show the birefringence of the device can be enhanced when the aspect is larger. In the experimental measurement for polarization extinction ratio (PER) of the proposed device, a fiber-pigtailed 1549.25 nm DFB laser light was used as light source. The PER about 30 dB was demonstrated when the liquid with refractive index n_D = 1.45 was used.

We fabricate versatile holey fibers with 6-hole, 18-holes in order to improve their property in terms of bending insensitivity. The fabricated holey fibers are applied for connection and integration for compact optical devices.

A time-domain optical add-drop multiplexing (OADM) technology using microring resonators is reported. Design and simulation are presented. The microring resonator is predicted to be fabricated by using Pockler electro-optic materials. The microring resonators possess a multistage-cascaded structure to satisfy the requirement to generate switching windows. Cascaded coupled microring resonator can expand the single resonant point into a box-like resonant region and reduce the wings of resonant curve. While multistage resonators are used and a certain shift of the resonant region is arranged between the stages, the total resonant region can be expanded further. We achieve the shift of the resonant region between the two stages by selecting different ring radii. The resulted microring resonators possess a box-like characteristic with shape wings. The OADM includes two microring resonators (MMRs) driven by sine wave voltages, one is used to accomplish the add function the other is used to accomplish the drop function. The only operation differences between the two MMRs are the bias voltage and the phase of the driving signal. The OADM only requires electrical control signal and simple structure instead of high-quality optical control pulse and interferometer structure. FDTD simulation results show that the resonators can stratify the requirements to generate complementary switching windows for OADM operation.

In this study, we model and compare the performance for several different metal wire-grid polarizers over the visible spectrum using rigorous coupled wave analysis and determine that the best choice for the wire material is aluminum. However, a layer of Al₂0₃ forms rapidly on the aluminum wires even in high vacuum. The effect of metal oxide layers forming on the wires is also modeled. It is shown that the actual oxide layer forming on the wires has only a small effect on the performance of the polarizers. With the oxide layers coated on the wire, the transmission coefficient is nearly invariable, extinction ratio slightly decreases. Next, the polarization properties are considered with changes in the physical parameters, including period, metal height, duty cycle, and angle of incidence. The results show that aluminum wire-grid polarizer has high transmission coefficient and extinction ratio over visible spectrum, as well as uniform performance with wide variations in the angle of incidence. These features with their small form factor make it desirable for use in field-of-view and allow more compact component designs.

Compact samples of quarter wave plate have been fabricated respectively by cutting holey birefringent fiber and conventional birefringent fiber into different length of short sections. The temperature instability and wavelength sensitivity of these samples are analyzed and measured. The influence of fiber length and fiber prototype on the retardation variation is compared. The retardation deviation almost linearly increases with the fiber length of samples. Compared with the sample made of conventional birefringent fiber, the temperature stability of the sample made of holey birefringent fiber is greatly improved by one order, but the wavelength bandwidth needs to be further expanded by optimizing the holey cladding structure.

The influence of extension lead at both sides and input polarization state on polarization transform performance of increscent-spinning birefringent fibre is calculated and examined. In the extension lead, the output polarization state is fluctuating with period relevant with the max-spin-rate or the beat length of birefringent fiber. It is found, the optimal input polarization state for the best output linear polarization is not the ideal circular polarization but a elliptical polarization related with the maximum spin rate, the optimal input linear polarization orientation is not in line but has a slight divergence angle with the birefringent axes of fiber, and if the input linear polarization is not perfect linear polarization, the output circular polarization would be nonlinearly degraded. These results have advisable meaning for the design, test and evaluation of the quarter wave plate made by the increscent-spinning birefringent fibre.

A Fabry-Perot (FP) etalon constructed in a two-dimensional photonic crystal (2D PhC) utilizing self-collimation effect is proposed and investigated. The 2D PhC consists of a square lattice of air holes in silicon. It has square-shaped equal frequency contours (EFCs) in the frequency range of 0.275-0.295c/a for TE modes. The FP proposed consists of two PhC reflectors and one cavity between them. Light propagates in the photonic crystal employing self-collimation effect. The two reflectors have reflectivities of around 97.5% in the frequency range 0.275-0.295c/a. The FDTD calculation results show that the transmission spectrum of the FP etalon has a uniform peak spacing between 0.275c/a and 0.295c/a. The transmission spectrum shifts to the lower frequency as the refractive index of a fluid filling in the air holes in the FP cavity is increased. Therefore this etalon can work as an optical sensor for a gas and a liquid. The fluids whose refractive index vary within 1.0-1.5 can be sensed and detected. Its dimensions are only about tens of microns when the central operating wavelength is equal to 1550nm. So it can be applied as a micro-scale sensor.

Using the nonlinear polarization rotation technique and an Er³⁺/Yb³⁺ co-doped fiber amplifier, we have experimentally obtained high output power wavelength continuously tunable laser and high output power passively mode-locked pulse in an erbium-doped fiber ring laser.

Based on the nonlinear coupled-mode equations (NCMEs) of fibre Bragg grating (FBG), all-optically tuned delay is realized in two linearly apodized FBGs in simulation. The characteristics of tuneable delay under the control of input optical power are analyzed, and the sensitivity of delay time with optical power is discussed. Results show that the delay maximum can be obtained at the optimal points in connection with input power, operating wavelength and grating length.

A new method of fabricating Panda-type photosensitive polarization-maintaining erbium-doped fiber(PM-EDF) is proposed and demonstrated. A sample of PM-EDF is fabricated using this method and an exhaustive analysis is made about the characteristics of PM-EDF, the results shows that this method is practicable. Two fiber Bragg Gratings (FBGs) are written into PM-EDF directly as the lasers reflectors, a three-states-tuned fiber laser is then obtained using a polarization controller (PC).

A simple multi-wavelength erbium-doped fiber laser with narrow-line-width lasing output was proposed and demonstrated using fiber Bragg gratings and Arrayed-Waveguide Gratings (AWG). Wavelength competition was naturally prevented in this kind of laser by using AWG in the linear-cavity. As an example, a triple-wavelength erbium-doped fiber laser was experimentally investigated. Using the laser scheme, the proposed laser can laser three wavelengths simultaneously. The fiber laser retrieved the optical side-mode suppression ratio of over 50dB and the average output power of -10.714, -10.649 and -10.578dBm at 1554.710, 1555.516 and 1556.421nm, respectively. And the 3-dB bandwidth of each laser was less than 0.010nm. Moreover, the output power stability of the laser had also been measured and analyzed. Experiment results showed that the laser can be operated stably in narrow-line-width with single- and triple-wavelength output at room temperature.

In this paper, a tunable single-frequency fiber laser is designed. For narrow linewidth and single frequency operation, a length of 2.75m unpumped EDF as a saturable absorber is used. The FBG combined with the unpumped EDF provides narrow frequency selection. Counter propagating beams in the unpumped EDF form a standing wave that results in periodic spatial hole burning. This creates a narrower bandwidth absorption grating than the FBG. The output laser wavelength can be changed from 1530nm to 1570nm by the FBG. The 3dB spectrum width of output laser is 0.08nm and the side mode suppression ratio is 55dB. The maximum output power exceeds 12mW, and the stability is less than ±0.005dB. A nice single-frequency laser is observed. From the relationship of the pump power and output power, it is obvious that the optical bistability switchable phenomena is showed in output characteristics. The bistability switchable phenomena is caused by the saturable absorber in the ring cavity. A 10Gb/s codes rate is used in the fiber laser transmission experiment. The high speed optical signal is transmitted in long distance without regeneration. The eye diagrams of optical transmission are measured, the performance of long haul transmission with high speed modulation is perfect.

A low-loss broadband Y-branch for fiber-to-the-home applications is presented. Smaller waveguide height is utilized for the potential of better deposition of the upper-cladding. A multimode section allows broadband operation. Simulation results show good performance in the wavelength region from 1200nm to 1700nm for FTTH systems.

In this study, we propose a high-performance polarizer with Aluminum wire-grid structure that an antireflection layer (AR) is deposited between the metal wires and the transparent substrate. The polarization properties of the polarizer are analyzed in detail using rigorous coupled wave analysis (RCWA). The theoretical research shows that aluminum wire-grid polarizer has high transmission coefficient and extinction ratio in near infrared, as well as uniform performance with wide variations in the angle of incidence. For the fiber communication window of 1550nm, the transmittance and the extinction ratio are 95.4% and 35.3dB, respectively. Furthermore, a layer of Al₂0₃ forms rapidly on the aluminum wires even in high vacuum, the effect of the metal oxide layers on the polarization properties is modeled and analyzed. The results have shown that the polarizer with oxide layers coating on the wires still provides high performance. These features with their small form factor make it has potential for use in many integrated optical applications.

In this paper, a short polarization-maintaining Er:Yb co-doped fiber laser is experimented. A pair of FBGs are written in the Er:Yb co-doped sensitive fiber using UV beams. A 976nm pumping laser diode is used, and output wavelength is selected by two FBGs. The PM Er:Yb co-doped fiber is used to main the orthogonal polarizations SM lasing stability. The SM operation in each wavelength has been verified. On the basis of previous short cavity fiber, a simple DBR dual wavelength fiber laser array has been designed and experimented. Two sections of short Er:Yb co-doped fiber cavities are pumped by a 976nm LD simultaneously. The pump laser is splitted to pump each Er:Yb co-doped fiber. It used a WDM coupler at 1550nm to connect the output port of two DBR fiber laser, an isolator is spliced to the common arm of the WDM and used as the output port. The dual wavelength spacing is 0.31nm. The output power reaches 6mW with the optical signal to noise ratio of greater than 30dB. A 12.5Gb/s codes rate is used in the fiber laser transmission experiment. A nice optical eye diagram is recieved after long distance single-mode communications fiber transmission.

This paper presents a detailed study on Wavelength Division Multiplexing - Passive Optical Network (WDM-PON) light source of spectrum sliced multiwavelength fiber ring laser and simple optical Lyot filter. First, the principle of the Lyot birefringent filter for comb generation of the multiwavelength laser is theoretically analyzed. Then we incorporate the Lyot filter and a semiconductor optical amplifier (SOA) as the gain medium into a ring laser cavity. Finally, we experimentally demonstrate an SOA based multiwavelength fiber ring laser using Lyot birefringent filter. Multiwavelength operation up to 25 laser lines with the signal-to-noise ratio over 30dB and 0.8nm wavelength spacing was demonstrated. The power equalize is within 2 dB and the line width 0.108nm is close to the equipment resolution. This multiwavelength laser source has also been proved to have good stability after consistently 90 min time evolution. In general, this multiwavelength laser source has the advantage of simple structure, multiwavelength operation, high SNR and good stability.