Investigating the Miller matrix in optical fiber, this paper derives, for the first time, the expression ofthe vector of PMD (polarization mode dispersion), expression of the Stocks vector of Principal State of Polarization (PSP), and expression of the high-order vector of PMD, which are determined by the parameters of fiber. Then the relationship between vectors of local and whole PMD and the principle of PMD compensation are also discussed. Introducing the vector of compensating PMD and calculating the vector of compensating PMD of a piece of uniform non-circle birefringence wave-guide, we prove theoretically that it is impossible to compensate PMD by use of a piece of uniform non-circle birefringence wave-guide, such as one piece of polarization maintaining fiber. A novel PMD compensation scheme based on PMD vector and adjustment algorithm are given. All conclusions are very helpful to PMD compensation.

A new instrument to measure stokes vectors using an electro-drived polarization controller and a polarizer based on "TDM" is demonstrated. Using this instrument as well as data fitting and interleaving technique higher-order PMD is detailed.

We propose and demonstrate a simple decision-threshold tracking technique that can minimize the PMD-induced power penalties. Using this technique, we could reduce the power penalty of RZ signal to 0.2 dB even when the DGD were as large as 40 ps.

In this paper, the dispersion compensation of 4 X 10Gb/s 800km G.652 fiber by chirped optical fiber Bragg grating(FBG) was originally implemented. The ripple coefficient of reflectivity and time delay of FBGs are less than 0.9dB and 3Ops. When BER is 10-10 and the bit error is zero, the power penalty ofeach channel is less than 1.67dB.

We have shown the polarization mode dispersion (PMID) of chirped fiber Bragg gratings (FBG) written on different photosensitive optical fibers. PMD of FBGs on special photosensitive fibers and hydrogenated single mode fiber (SMF) was studied and compared. Experiment results showed that the chirped FBG written on hydrogenated SMF has very low differential group delay (DGD), and it adapt in long-haul optically amplified lightwave systems. The PMD of chirped FBG is determined by the birefringence of the fiber and the dispersion of the chirped FBGs. The birefringence of FBG involved intrinsic and extrinsic or photo-induced birefringence. At the end of this paper, we presented the PMID of the dispersion compensation system using CFBG as dispersion compensator.

The focus of this paper will be Oplink’s high-reliable fused coupler program. It is based on an Oplink proprietary fusion system design and offers a unique technology. The fusion temperature is extremely high so that the whole cladding glasses of the fibers are strongly fused together. The optical performance benefits provide superior stability over time and withstand extreme environmental condition changes. Additionally, the insertion losses and polarization dependent losses (PDL) can be achieved at extremely low values with almost no changes over time. The high reliability test shows results (beyond Telcordia requirements GR-1221-CORE) of up to 8000 hours in the damping heat test and the high temperature storage (at 100 °C). In addition, we will present the data results from other stringent tests. The FIT number is also estimated based on the test data. This unique fusion system design technology can be applied to a wide range of fused fiber products such as tap couplers and fused wavelength division multiplexers. In applications, it can be potentially implemented for fused products used in undersea submarine systems.

Optical communications and sensing systems have required optical fibers to meet the demanding applications day by day, such as high bit rates, dense wavelength division multiplexing (DWDM) and long distance, so that there could be always renewed interest in fiber designs to lift fundamental limitations of silica optical fibers. One kind of fiber, which is different from the conventional fiber, is silica photonic crystal fiber (PCF) that has an array of microscopic air-holes running along its length. For PCF, there are two distinct classes as the guidance; one is using a type of total internal refection which is referred to the terms microstructured fiber, holey fiber, effective-index fiber, and hole-assisted fiber, and the other is employing photonic band-gap which is referred to photonic band-gap, Bragg fiber, and omni-directional waveguide. In this paper, we will address recent advances in PCFs. While the potential applications are also addressed, the emphasis will be on PCFs for applications in optical communications and sensing systems.

The cylindrical waveguide (optical fiber ) with a metal outer clad were analysed. The propagation constant of core mode and clad mode were derived from vector method and then solved by numerical method. And some characteristics of the mode in metal clad fiber were studied. We also analysied the effect of metal clad to the long-period fiber grating.

The imaging properties and phase relations of MMI devices with two-dimensional (2-D) confinement have been discussed in this paper. The self-imaging effect in 2-D MMI can be regarded as the superposition coupling of two orthogonal and independent one dimension self-imaging effect. Because of the coupling of two orthogonal and independent self-imaging effects and asymmetry structure in three-dimensional waveguide, it is obvious that the imaging characteristic of 2-D confinement MMI devices is provided with asymmetry characteristic. The formalism of 2-D confinement MMI phase relation is presented. The law of the imaging and phase relations depends on the waveguide structure and the propagation distances.

We demonstrate the combined effects of SPM, GVD, and PMD-induced eye-diagram penalties by means of numerical simulations for 40Gbit/s NRZ and RZ modulation formats. Considering all orders of PMD, we choose a fixed state of input polarization (SOIP) and do the simulation 1000 times for each input average power, and then get the Q-penalty of eye-diagram by exponential extrapolation method for cumulative probability 10-5. When input average power is less than 0dBm, SPM effect is very weak and GVD is compensated completely, only PMD takes effect in this power area. The Q-penalties are constants for NRZ and RZ with different PMD values. As input average power increasing, SPM takes effect gradually. First order PMID can suspend the SPM affection, and the higher PMD value, the more postponement is observed. The Q-penalty contributed by higher order PMID has close relation with spectrum width of signal. For NRZ signal with chirp=-0.7, the interactions between SPM and chirp can decrease spectrum width of signal; the Q-penalty contributed by higher order PMD will decrease correspondingly. For RZ with duty 0.3, the changing of the root mean square (RMS) spectrum width induced by the interactions of SPM and chirp is not obviously in this case, the Q-penalties of SPM+GVD+PMD increase consistently. When SPM effect is too strong (For example: for NRZ, average power larger than 10dBm; for RZ with duty 0.3, average power larger than 6dBm.), the interactions of SPM+GVD+PMD will cause the seriously degradation of system performance for any duty cycle and PMID value. Under our simulation conditions, the narrower pulse-width, the less Q-penalty until duty cycle decreases to 0. 1.

Numerical results show that only apodization compensation is necessary for apodized binary sampled Bragg grating, while sampling compensation is not necessary. A novel apodization compensation preconditioning approach is proposed. This process doesn't require the removal ofthe phase mask. We fabricate a 5 channels sampled Bragg grating with 0.25nm's bandwidth and —980ps/nm's dispersion. Dispersion compensation using the fabricated grating for standard single mode fiber 10Gb/s-80km transmission is demonstraded.

In this paper, we discuss three GVD compensation schemes, including the post-compensation, pre-compensation and hybrid-compensation schemes with considering combined impacts of GVD, Kerr effect and PMD. By means of the split-step Fourier method, we numerically solve the nonlinear coupling equations of two orthogonal polarization modes. With respect to the statistical character of PMD in the optical fiber, we employ the parameters of average eye-opening penalty to evaluate the combined impacts induced by GVD, Kerr effect and PMID. The numerical results are obtained on the base of 1000 times computation with average DGD less than 35% bit duration. Simulations show that, for the 10Gbit/s NRZ system, the GVD pre-compensation scheme performs best with more than 1dB of average eye-opening penalty better than the other two schemes when input power is greater than lOdBm. However, for the 4OGbitJs NRZ system, when input power P0 > 5.0dBm , the GVD post-compensation scheme performs best with more than 1dB average eye-opening penalty better than the other two schemes. This is different than the previous conclusion that GVD hybrid-compensation scheme has best performance without considering the impact of PIVID. We also define the parameter of eye-opening penalty at outage probability 10-5 to reflect the impact of DGD at the trailing of the Maxwellian distribution. The results also verify that GVD pre-compensation performs best in the lOGbitJs system and post-compensation performs best in the 40Gbit/s system. In both lOGbitJs and 40Gbit/s systems, either average eyeopening penalty or eye-opening penalty at outage probability iO indicates that the system performance with the best GVD compensation scheme can be improved with the increased input power up to 10dBm, and the performance will be worse if input power is greater than 13dBm. We analyze this behavior and conclude that PMD can be suppressed by the increased Kerr effect within a certain power range.

With a new apodisation method and special package material, we have made high-quality chirped fiber Bragg gratings (CFBGs) with the fluctuating error of reflectivity less than 1dB, the delay ripple less than +/-15ps and the temperature coefficient being as low as 0.5‰onm/°C. Using such self-made high-quality CFBGs, we present, for the first time, the experiment results of dispersion compensation of 2x10Gb/s 1000km WDM system with less than 1 dB power penalty for each channel.

This paper describes four different types of PLC Fourier-filter interleaver designs and compares their optical performance. All of these interleave filters consist of multiple unbalanced Mach-Zender interferometer stages, but use different directional coupler designs. They use a new optical design with good optical performance, including cross talk > 32 dB, 0.5dB passband width > 68% of channel spacing, and ripple within 40% of channel spacing window of < 0.25dB. A new filter approach is introduced which uses only standard symmetric couplers in a coupling-ratio dispersion compensating configuration and provides better optical performance in terms of crosstalk, passband width, ripple and insertion loss and better tolerance to fabrication errors as compared to interleave filter circuits that utilize MMI couplers, Fourier-filter couplers, or standard couplers in a conventional configuration.

Results of theoretical and experimental investigation of optical parameters of slab guide resonators used in industrial lasers of the middle IR rang with radio - frequency pumping and output power from 200 W up to 4.5 kW are given. The measurements were carried out with the help of the automated system on the basis of scanning interferometer of the middle IR range supplied by high precision positioning system. Significant (two, three times and more) variation of optical losses in the resonator under small (down to several micrometers) change of its geometry has been found out experimentally. Replacement of a material or use of dielectric covering of the electrode surfaces has been followed not only the change of an average level of optical losses due to complex index of refraction, but also rather complex variation of their dependence on geometry of the resonator. It was shown experimentally that absolute value and character of dependence of optical losses on resonator geometry can change drastically with variation of the roughness of electrode surface. For example nearly smooth surfaces (with a the deepness of the roughness of some nm) are not optimum for minimal optical losses. The best results can be obtained for a structure of a surface of electrodes representing periodic or random structure (depending on electrode material or its dielectric covering ) with depth of around a radiation wavelength.

An arrayed-waveguide grating multiplexer is demonstrated, which is successfully designed and fabricated . A wavelength channel spacing was 1 .6nm, a crosstalk of less than —20dB and the insertion loss was 7-12dB around 1.55?m. The polarization-dependent wavelength shift was very small without special compensation methods.

Periodical perturbations along an optical fiber can cause power coupling between the core mode and cladding modes for the applications of spectral filtering and derivative operations. Such perturbations can be generated through periodical loading on fiber. By applying loading onto fiber with two face-to-face, identical periodical groove structures, it was found that the long-period grating effects were dependent on the relative phase of the two periodical corrugations. Particularly, when the relative phase was zero (crest-to-crest), spectral filtering effects disappeared completely. The comparisons of such results between the cases of jacketed and un-jacketed fibers led to the conclusion that geometric deformation, instead of direct pressure-induced effect, was the dominating mechanism for generating spectral filtering functions in the double-sided loading configuration. The same conclusion can be applied to the single-sided loading device.

Novel optical add / drop multiplexers (OADMs) using slanted fiber Bragg gratings (S-FBGs) are proposed. The S-FBGs couple the guided-mode to radiation modes, and they also couple specific radiation modes to the guided mode. A set of the S-FBGs located nearby with each other has functions of OADMs. The proposed OADM requires no optical circulators which are components of usual multiplexers using FBGs. Low-cost and small size optical filters may be constructed. Calculations results successfully show the possibilities of OADMs.

this paper, the strain and temperature responses of long-period Bragg grating written on Panda fiber are presented. Both the strain and temperature responses show a good linear characteristics at a strain range of 0-2500 ?? and a temperature range of 50-100 °C . The temperature-tuning characteristics of the LPG by using a thin film metal coating on the nude surface of the fiber as a heater are also demonstrated. In the range of 0- 150 mA the response curve of the LPG have good linearity with the square of the current, while the loss change is less than 0.3dB.

A method is presented for the short period and large chirped fiber grating fabrication. The relation of grating reflectivity with chirp parameter is discussed and various reflectivity gratings have been achieved under different UV exposal conditions. At last, a broad bandwidth filter with a free filter zone is obtained.

All-optical networks provide unique opportunities for polymer waveguide devices because of their excellent mechanical, thermo-optic, and electro-optic properties. Polymer materials and components have been viewed as a viable solution for metropolitan and local area networks where high volume and low cost components are needed. In this paper, we present our recent progress on the design and development of photoresist-like highly fluorinated maleimide copolymers including waveguide fabrication and optical testing. We have developed and synthesized a series of thermally stable, (Tg>150 oC, Td>300 oC) highly fluorinated (>50%) maleimide copolymers by radical co-polymerization of halogenated maleimides with various halogenated co-monomers. A theoretical correlation between optical loss and different co-polymer structures has been quantitatively established from C-H overtone analysis. We studied this correlation through design and manipulation of the copolymer structure by changing the primary properties such as molecular weight, copolymer composition, copolymer sequence distribution, and variations of the side chain including photochemically functional side units. Detailed analysis has been obtained using various characterization methods such as (H, C13, F19) NMR, UV-NIR, FTIR, GPC and so forth. The copolymers exhibit excellent solubility in ketone solvents and high quality thin films can be prepared by spin coating. The polymer films were found to have a refractive index range of 1.42-1.67 and optical loss in the range of 0.2 to 0.4 dB/cm at 1550nm depending on the composition as extrapolated from UV-NIR spectra. When glycidyl methacrylate is incorporated into the polymer backbone, the material behaves like a negative photoresist with the addition of cationic photoinitiator. The final crosslinked waveguides show excellent optical and thermal properties. The photolithographic processing of the highly fluorinated copolymer material was examined in detail using insitu FTIR. The influence of various polymer structural parameters on the photosensitivity and photo contrast of the polymer has been evaluated in detail. The same polymeric material has been tested using hot micro-embossing and Ebeam lithography to fabricate channel waveguides and other microstructures. The versatility of this unique photocrosslinkable thermoplastic material for various passive and active optical components is discussed in detail.

In this paper, the design and characteristics of 1x2 digital optical switch using SOI are described for the first time. Its operation is based on the thermo-optic effect of SOI with an asymmetric Y-branch structure and the measured crosstalk was about 22 dB at the wavelength of 1550 nm

Conventional electro-optic modulators have been always fabricated based on channel waveguide with complicated electrodes. In this paper, we propose a new type of modulator based on proton-exchanged planar lithium niobate waveguide. After proton exchange and annealing, the refractive index of planar lithium niobate waveguide is gradually changed with the depth. Two-prism coupling method is used to determine the effective index of the planar waveguide by measuring the coupling angle of m-lines. When the transverse electric field is applied along the Z axis of the X-cut proton-exchanged planar lithium niobate waveguide, the index distribution of the waveguide will be changed due to the electro-optic effect, and the coupling angle of the m-lines will be also changed accordingly. Based on this principle, a new type of amplitude modulator is proposed theoretically. The relationship between the driven voltage and position of two electrodes are theoretically investigated. The change of refractive index of the waveguide caused by the applied transverse electric field as a function of waveguide depth is also studied. Compared with other type of amplitude modulators, it shows some advantages such as low fabrication cost and the low driven voltage.

A detailed theoretical and experimental analysis of the thermal effects on the transmission spectra of long-period fiber gratings is presented. We show that the temperature sensitivity of the resonance wavelength of the grating is proportional to a modal dispersion factor of the fiber and the difference of the thermo-optic coefficients of the core and the cladding of the fiber. To facilitate our study, we derive a simple, accurate analytical formula for the calculation of the modal dispersion factor. Our formula shows explicitly that the temperature sensitivity of the resonance wavelength can be greatly enhanced by maximizing this factor with a suitable cladding mode. We also show explicitly that the temperature sensitivity of the strength of the grating is mainly determined by the coupling coefficient of the grating and the temperature sensitivity of the resonance wavelength. A good agreement between our theoretical and experimental results is obtained. Our results are useful for the design and the packaging of devices and sensors based on long-period fiber gratings.

Long-period fiber gratings (LPFGs) are usually used as the spectrally selective loss filter in optical fiber communication networks and sensor systems. In this paper, we investigate the characteristics of a tunable filter based on metal-coated long-period fiber grating. By applying different current to the metal coat, the resonance wavelengths can be tuned, with the spectrum shape changing little. The experimental results and theoretical analysis indicate that the metal-coated LPFGs may find interesting applications such as tunable and adjustable filters.

Insertion loss characteristics of sampled fiber Bragg gratings were investigated theoretically and experimentally. The experiment results show that the LPG effect greatly influences the characteristics of insertion loss at the Bragg reflection wavelength when the LPG effect caused loss peak is coincide with the Bragg wavelength. This phenomenon will be obvious in the case of high duty-cycle of sampled fiber Bragg grating, for example, more than 1:9. Bending the SFBG will move the LPG-like loss peak and will then change the loss of SFBG reflection band. In experiment a reduction from 6.08dB to 2.56dB was obtained under a bend radius 17mm in a typical SFBG with duty-cycle 1:9.

The advent of the technology of Dense Wavelength Division Multiplexing (DWDM) in Optical Fiber Networks (OFNs) has resulted in the necessity of developing advanced Optical Add/Drop Multiplexers (OADMs) on the basis of submicron Bragg gratings. The OADMs for dense multichannel OFNs with bit rates 10 – 40 Gbits/s per channel and channel spacing 200, 100 and 50 GHz must possess rectangular-shaped reflection/transmission spectra and linear phase characteristic within the stop/passband. These features can not be achieved with uniform periodic Bragg gratings and therefore nonuniform gratings with space-modulated coupling coefficient should be used. We present the recent advances in the design and fabrication of narrowband wavelength-selective optical filters for DWDM applications on the basis of single-mode fibers with side-polishing and periodic relief Bragg gratings with apodized coupling coefficient. The peculiarities of propagation, interaction and diffraction of electromagnetic waves in nonuniform Bragg grating structures are considered. Narrowband reflection filters based on side-polished fibers and submicron relief gratings on SiO2 and SiO materials are designed and fabricated. The filters have stopband width 0.4 – 0.8 nm and peak reflectivity R > 98% in the 1.55 ?m wavelength communication region. Narrowband flat-top reflection filters for DWDM applications based on side-polished fibers and periodic relief Bragg gratings are designed. The schemes for multichannel integration of Bragg grating filters into OFNs are presented.

We design and analyze a novel low-loss symmetric Y-branch in Lithium Niobate by heavily annealed proton exchange (APE). In this design, a wide transitional waveguide is used between the input and two S-shape output waveguides, making the field match with the mode in the two output waveguides by intentionally generating second-order mode and radiation. By this method, optical power can be coupled into the two output waveguides with high efficiency. simultaneously , the minimum gap between the two output waveguides is 2.7 microns, thus the stem region of this Y-branch has no sharp taper and the fabrication of the device is easy. The Y-branch is optimized by the method of three-dimensional FD-BPM, after optimization, losses can be less than 0.05dB.

According to Analytic Transfer Matrix (ATM) Method, it is possible to precisely determine the modal characteristics of a planar optical waveguide with arbitrary index profiles. In this paper, we present an Inversed Analytic Transfer Matrix (IATM) method to predict the refractive index profiles from measurement of mode indices, which has been proved to be valid even when solving some problems that inversed WKB method would find difficult.

A new method of detecting a minute change in refractive index of an analyte is illustrated in this article. Compared with the sensors based on surface plasmon resonance (SPR), we proposed this new structure of sensor based on the theory of guided wave resonance (GWR). In this proposed double metal-cladding waveguide structure, the sample to be probed serves as its guiding layer, and two metal films act as its cladding layer. Both theoretical simulation and experimental results have shown that the sensitivity enhancement factor of GWR over SPR is more than 1 order higher to the magnitude.

In this paper, we report, for the first time to our knowledge, a new decreasing Q-switched pulse width method. We can reduce the pulse width of the MZI Q-switched by moving the pulse of ECL (whose pulse width is narrower than the MZI Q-switched pulse) into the MZI Q-switched pulse. And in our experiment, the pulse width of the MZI Q-switched is 4? s, the ultimate pulse width is O.8? s. So the ultimate pulse width is one fifth of the MZI Q-switched.

A Tabu Search (TS) algorithm, to our knowledge, for the first time, is introduced into the optimized design of Fiber Bragg gratings (FBGs). By combining the Transfer Matrix Method (TMM) for calculating the reflection spectrum and the TS algorithm, we obtained a new method for synthesis the FBGs with advanced characteristics. A new appodization profile is proposed as an example to demonstrate the effectiveness of the method that is general to be useful for inverse problems in FBGs application.

As one of the most important properties in fiber Bragg gratings (FBGs), the reflected spectra of FBG have been attractive research subjects. However, the issue of non-reciprocity of reflected spectra in the grating has not be addressed. We observed the phenomenon of non-reciprocity in uniform FBGs in our experiment and in this paper make a preliminary analysis and calculation of the reflected sprectrum non-reciprocity in a uniform FBG

Based on the theory of mode analysis, we present here a new method to calculate the absorption efficiency for the double-clad optical fibers. The ratio of the number of the absorbable modes to total number of guided modes is taken as absorption efficiency. Taking the radius of caustic surface as a threshold value, we can estimate whether or not an individual mode is absorbable. Results show that for a symmetric circular DCF, there is a large fraction of power which can never be absorbed and its absorption efficiency is low. Increasing the radius of RE-doped core can raise the absorption efficiency, but the single mode operation will be destroyed. For an offset core DCF, the high absorption efficiency can be achieved by increasing the offset distance. Also there exists an offset limit, beyond this the absorption efficiency reaches saturation. The result is that we can improve the absorption efficiency by increasing offset distance instead of the radius of fiber core. This conclusion is in principle consistent with precious 2-D ray optics methods.

We used the UV exposure system, and two FBGs(Fibre Bragg Gratings) centered at 1546. mm Bragg wavelengths were fabricated out in H2-loaded fiber successfully by a fixed 1069.O3nm phase mask and 248nm KrF excimer laser, and it can be used as dispersion compensator in 40G OTDM system, and the dispersion and Polarization mode dispersion(PMD) in 120km G652 SMF was successfully compensated by two chirp FBGs in a 40Gb/s OTDM transmission system.

32 chirped FBGs (fiber Bragg gratings)-based dispersion compensators and EDFA (Er-Doped Fiber Amplifier) gain-equalizators is demonstrated. Dispersion compensation of 600km G652 fiber and limiting amplification of 16 wavelength signals with low power penalty of<2dB can be obtained at a 10GHz/s optical communication system.

It is first time to study on Gauss pulse transmission over ultra-high PMD fiber. Gauss pulse is broken into a series of deformed pulse when it transmits over ultra-high PMD fiber. He has explained that the walk-off deformed pulses cause by ultra-high PMD. Transmitted experiment has been done using fiber with PMD coefficient 237.95ps/km1/2. The simulated result is consistent with experiment.

Using the experiment results of RH. Stolen's, we got the polynomial formula of the SRS Stokes spectrum by sampling and digital fitting. Based on the formula, the Raman gain and noise figure properties of multi-wavelength pumping broadband Raman amplifier are obtained with considering the inter-amplifying between multi pumps. After numerical analyze, we got the properties of the gain and the noise figure of different Raman amplifiers in different fibers G652, G653, G655 and LEAF.

In this paper we show how to adjust a standard first-order compensator, consisting of an adaptive polarization controller, describe a method for single-order PMD compensation, whereby an adaptive polarization controller mitigates 1st-order DGD. With this scheme we compensate the differential group delay (DGD), study how to reduce the frequency dependent rotation of the output state of polarization (OSOP), and how to jointly reduce second-order DGD treated by Dynamic AWG chirp. We also fabricated a new optical PMD compensator on a lightwave circuit, where an Adaptive feedback loop polarization controller and a polarization-dependent delay line are installed. We confirmed its operational principle in a 40-Gbps-transmission system.

The authors present a simulation analysis of Gauss pulse broadening due to polarization mode dispersion and polarization dependent losses in long single-mode fibers. It is found that probability density function of pulse broadening is a combined Rayleigh and Gauss distribution function.

We used UV laser to write Bragg gratings on the polarization maintaining fiber (PMF). Because of the high-birefringence of the fiber, the Bragg wavelength of the grating on the two polarization axes was different. So that it could introduce great polarization mode dispersion (PMD). When the input was adapted to the axis of the grating, it can serve as the polarization compensation. We measured the polarization of the grating at the end of the article.

For the first time, the polarization mode dispersion(PMD) of fiber Bragg grating(FBG) was measured and compensated. And the FBGs are used for dispersion compensation of 4 X 10Gb/s 400km G.652 fiber. When BER is 10-10 and the bit error is zero, the best power penalty of transmission channel is negative.

In this paper we propose a novel structure to enhance pump conversion efficiency and noise characteristics of L-band EDFAs. By adding only a input-reflect fiber Bragg grating and reflecting fractional backward ASE power as a secondary forward pump to further amplify the signal light, larger than 20dB small signal gain improvement and 1dB NF decrease can be achieved. We also investigate the influences of different wavelength FBGs. Experimental results agree well with numerical simulations.

This module combined the techniques of MEMS, near-field optics, fly head, and multiple beam. It organized the optical component and waveguide into a substrate. It integrated the multiple beam optical module for near-field high density recording, used the optics characteristic of the diffractive optical element, (DOE), generate multiple beams equally on the module, and reduce the spot size by using the near field optics. Simultaneously, quite a bit of information is recorded on the tracks of high density optical discs.

Presently, polarization mode dispersion(PMD) of cabled optical fiber has been regarded to be a more and more important parameter. But the effect of cabling to PMD wasn’t clear to people yet. So in this paper, we try to study the change of PMD during cabling of optical fiber. Based on elementary principles and testing standard of PMD, we introduced a method to test PMD more accurately in optical fiber which is in different status. Then we applied this test method to research change of PMD in naked and cabled optical fibers provided by different company, and got a conclusion that the PMD of optical fibers will lessen after being cabled. We researched variation of PMD in the stranded loose-tube cable and the center loose-tube cable consist of G.652 and G.655 optical fibers during cabling, and found two working procedure can have a obvious effect on PMD of optical fiber. Then we got some useful conclusion. Moreover, we proposed to sort PMD of optical fiber into three parts: Original PMD, Induced PMD and Stressremaining PMD. So we can understand more clearly origin and variation of PMD in optical fiber affected by many cause.

Random or periodic corrugation of the waveguide laser electrode surface may strongly influence on the waveguide mode shape, losses, and the laser beam quality. Such waveguide wall gratings can be used for phase and polarization correction of the light field. The development of the laser with such field correction elements is usually considered as a slab waveguide problem. Corrugated surface reflecting properties must be taken into account by such model. The light scattering by corrugated surface segment was investigated. The problem is formulated as electromagnetic wave diffraction on a corrugated surface segment with a periodic or statistical irregularity for the wave propagated along the electrode. The classical theory of diffraction is used. The problem for the segment of the surface is formulated as an electrodynamics problem with impedance boundary conditions. Numerical calculation of the angular dependence of the light reflection from the corrugated surface is performed. It is shown that there is an optimal groove depth giving maximum reflection at given surface structure period.

This paper presents an experimental study of the photosensitivity of various types of photosensitive optical fiber. A new interferometric technique based on low-finesse fiber Bragg grating Fabry-Perot interferometers allowed the determination of the evolution of the refractive index during exposure to ultra-violet radiation from a KrF excimer laser. It was demonstrated experimentally that enhanced photosensitivity of standard SMF-28 fiber retains after complete outdiffusion of hydrogen. The dependencies of effective refractive index change versus fluence are presented for different photosensitive fibers and hydrogen-loaded fiber.

This paper presents the results of measurements of the time-dependent concentration of hydrogen in optical fiber during isothermal and isobaric hydrogen loading to increase its photosensitivity. A low-finesse fiber Bragg grating Fabry-Perot interferometer allows the determination of the evolution of the hydrogen concentration in situ. The estimated resolution of the measurements is better than 10 parts-per-million for a 10 millimetre long interferometer.

In this paper, we present the details of a simple, sensitive, low cost and portable optical fiber sensor, based on evanescent wave absorption, for measuring chromium concentration in water ranging from 10ppb to 2000ppb. A plastic clad silica core (PCS) fiber with unclad middle region acts as the sensing element. The use of a super-bright green light emitting diode (LED) as light source reduces the size and cost of the system considerably. The use of a reference arm and ratio detector significantly reduces the effect of power supply fluctuations or ambient variations of the LED. The conventional methods used for the determination of chromium in water are spectrophotometric and colorimetric methods. Hence a comparative study between the present sensor and the spectrophotometric method has also been carried out. The response time of the sensor is also studied.

Based on unbalanced Mach-Zehnder interferometers, a novel electrooptical waveguide tunable filter is proposed and designed. By coupled-mode equations method and beam propagation method, the variation of the output light intensity versus applied voltage and frequency is analyzed for a single filter. Then several filters are combined to filtrate and route one of several frequencies, and a good result is obtained.

Very low-loss coupling between standard single-mode fibers (SMF) and high refractive-index waveguides is achieved using diffraction optical element (DOE) as mode converter. The DOE is a beam-shaping element designed based on diffraction optics theory. DOE shapes the mode field of SMF to that of the waveguide, or vice versa. The mode mismatch between them is eliminated. DOE is a pure phase element, which phase distribution optimized by G-S algorithm. The most attractive point of this mode converter is that the DOE can be designed to achieve any mode field distribution of any waveguide structure. This advantage makes DOE a strong and flexible mode converter. Though being a phase element, DOE has certain wavelength tolerance covering a sufficiently wide band, which makes it applicable in multi-wavelength integrated planar lightwave circuits (PLCs). DOE can be approximated by binary optical element (BOE), so that it can be fabricated using existing PLC fabrication step

We report that a non-unitary transfer matrix that we have developed is highly effective in analyzing the transfer characteristics of a racetrack resonator. While the unitary transfer matrix method shows a limited description, the nonunitary matrix method has been found to explain the behaviors of a racetrack resonator effectively, including the characteristics of t-dependent drop power and the length-dependent phase variations. The results show excellent agreement with the results from the finite difference time domain (FDTD)-based simulation study.

Planar lightwave circuits (PLC) utilizing glass related waveguide technologies are nowadays crucial components in optical communication system. In this paper, we present a standardized, silicon dioxide (SiO2) based waveguide structure prepared by plasma enhanced chemical vapor deposition (PECVD) for applications in telecommunication devices, such as wide-band optical power splitter. The index of waveguide layer can be controlled by the N2O:SiH4 ratio and process parameter. High density inductively coupled plasma (ICP) etching system was used to define the waveguide pattern. The fabricated waveguides show satisfactory optical characteristics including low waveguide loss, low chip-to-fiber coupling loss (< 0.5 dB/facet), and low polarization dependence loss (< 0.2 dB).

We report on the method of successfully controlling the multimode effect in an arrayed waveguide (AWG) gratingdevice, in which the propagation modes of the optical waves are determined by the waveguide structure. As the grating order (m) changes, the imaging profiles for the other modes also change and can be effectively controlled. We found optimized values of order m for a given InP-ridge-type waveguide that can minimize the channel crosstalk. We compared the results of our simulation study with the experimental results that we obtained from the AWG device that we designed and fabricated by controlling various grating orders of m.

This paper presents a theoretical investigation on the mode coupling and mode coupling induced attenuation in step-index plastic optical fiber under different launching condition. We solved numerically power flow equation of multimode optical fiber by explicit finite difference methods. In our calculation, we adopted mode coupling coefficient measured in Garito’s experiments , and supposed power distribution of incident beam have Gaussin form with respect to angle between beam and optical core axis. Under different incident angle and same beam width, we calculated power distribution at fiber output end when optical fiber length is 1,5,15, 20, 50m respectively. In shorter transmission distance, mode coupling isn’t evident, output power distribution is similar to input ones. With increasing of fiber length, power diffused gradually from high order modes to low order modes, and mode coupling finished in about 20m, where equilibrium mode distribution is achieved. In addition, we calculated mode-coupling induced attenuation of different width and launching angle Gaussin beam, with enhancing of beam width and launching angle , attenuation increased .

The refractive index and the film thickness were measured by the prism coupler, and GeO2 and P2O5 concentration were analyzed by EPMA (Electron Probe Micro Analysis) according to the torch inclination angle and the distance between torch and substrate. As the torch angle was steeper, the thickness and the GeO2 concentration were increased, and the P2O5 concentration was decreased for the angle greater than 45o.

The self-frequency shift effect has been examined in a harmonically mode-locked ring laser. With the insertion of a filter inside the cavity, we observed that this effect can be greatly suppressed and the range of gain for stable operation can be wider.

In photonic integrated circuits, coupling structures with polarization independence and low insertion loss between their access ports and optical fibers are increasingly becoming critical. Multimode interference (MMI) based couplers have these properties in addition to possessing good fabrication tolerance and stable splitting ratio. Symmetrical excitation of the multiple ports plays a significant factor that determines these structures for use in interferometric sensor applications. Studies on backre flected properties of these devices help in the analysis and understanding of their functions and are also addressed in the context of their suitability for sensor applications.

We demonstrate the development of tunable optical filters based on fiber bragg gratings (FBGs). A distributed on fiber resistive heater consisting of a thin metal film is deposited by means of an Electron Beam Evaporator onto the outer surface of an uniform FBG. The physics of heat flowand diffusion in these structures leads to resistive heating of the metal film that follow, to a remarkably good approximation, the local resistance of the coating. This generated heating induces changes in the fiber’s refraction index (thermo-optic effect), which together with the thermal expansion effect of fiber causes a shift in the Bragg wavelength thereby achieving the tunability. Experimental results show a dc tuning range of 4.284 nm (nickel as thin film) with a corresponding electrical power of 569 mW. A maximum efficiency of 8.133 nm/W (gold as thin film) was obtained for dc tuning.

We report the position dependent tuning of fluorescence emission from Rhodamine 6G doped plastic waveguide using side illumination technique . The transmitted fluorescence as a function of the distance from the point of illumination is measured by translating the waveguide horizontally across a monochromatic light source. This technique has proved to be a useful method for characterizing the light propagation properties of dye-doped waveguides. An important finding of the present studies is the nonlinear behavior of the loss coefficient as a function of propagation distance through the waveguide. It is also found that this type of nonlinear nature depends on the dye concentration and thickness of the waveguide.

A novel structure of single-mode Y-branch waveguide with low branching loss is proposed. The waveguide is free from the critical fabrication requirements. The characteristics of it are analyzed in detail and the branching loss is calculated using FD-BPM.

A new explanation of the intensity-dependent subpulse structure formation in linearly polarized picosecond laser pulses in a single-mode optical fiber is proposed based on the coupled-mode equations of the two linearly polarization components considering the intrinsic birefringent and nonlinear birefringent effects, and the numerical results show a good agreement with the experimental results.

Our interests focus on the new theme of electro-optical modulator relevant to the development of domain-inverted LiNbO3 waveguide technology. By means of the theory of dielectric planar optical waveguide, we have not only computed and drew the corresponding characteristic figures of domain-inverted LiNbO3 waveguide electro-optical modulator with variable parameters, but also given the explanation of linear area involving input and output ports in theory. In addition, some improving and revising thoughts about buffer layer and electrooptic efficiency of such modulator is done. We have experimented a lot mainly including steps of the domain-inverse poling techniques to validate the feasibility of making the smart structure of modulator.

In this paper, the tensile tests of the indoor cable and the central tube fiber ribbon optic cable are discussed, as well as the phenomenon and the results in the tests are analyzed in detail with graphic charts. Finally, the author illustrates the test results of the secondary tensile and presents its influences in the cable configuration.

In this paper, we present a novel coupling method, direct coupling method, for double metal-cladding waveguide which is free from using the prism, grating or other coupling elements. The double metal-cladding waveguide used in our experiment is a metal-dielectric-metal three layer structure. Through ATR scanning technique, we demonstrate that light could be directly coupled into the waveguide successfully with this structure. The direct coupling method not only avoids the difficulty of grating fabrication process in grating coupling method, but also the coupling gap adjustment problem in prism coupling method. The application of this coupling method keeps advantages of the prism coupling technique in the optical parameters measurement for thin films. It also has some extra advantages. Since high order modes could be coupled into thick film waveguide while it is hard for prism coupling technique, the thickness of thick films (0. lmm—lmm) can be determined. Moreover, light can be coupled at any position on the surface of the waveguide, thus it can be used to detect almost the whole area of the film. Our experimental results agree well with the theoretical prediction.

In this paper we propose a novel design of prism-based device as a Fabry-Perot resonance mode sensor. In this setup, liquid or gaseous sample to be probed acts as a core of the F-P device, in which supporting oscillating field, rather than evanescent field. Owing to the strong concentration of the electromagnetic field in the sensing medium, which is about an order of magnitude higher than that in typical evanescent field sensors using SPR, the proposed device exhibits unusual optical properties. It is shown that the fundamental limitation of device sensitivity is set by beam divergence of the laser.

An approximate solution has been presented for the single-input nonlinear optical directional coupler under the most commonly used condition: operating near the critical power. By introducing the approximation in previous step, a simplified integral equation has been obtained. It can be integrated as simple functions instead of elliptic functions. Numerical examples of our results have been given and compared with the exact solution and the approximate solution derived by A. T. Pham et al. Our results are more accurate than that of A. T. Pham et al.

We propose a general routine, Genetic-Simulated Annealing method (GSA) for the optimal design of quasi-phase matched (QPM) non-uniform grating. Here this method is applied to the design of the flat broadened wavelength conversion bandwidth of 40-mm aperiodically poled lithium niobate (APLN) based on difference-frequency generation (DFG). The flat conversion bandwidth of APLN is broadened from the original 65nm in a 40-mm periodically poled lithium niobate (PPLN) to the pre-designated 130 nm in a 40-mm APLN, which conversion efficiency is 6.7 dB higher than that of 12.4-mm PPLN under the same conversion bandwidth.

A statistical optimum design method suitable for temperature-insensitive waveguide coupler is proposed. Using the method, l2Onm waveband fluorinated polyimide waveguide 3dB coupler is designed with the optimization of the temperature fluctuation. The design result is verified by the 3D-BPM simulation, and shows that the coupling ratio of (50±O.7)% in the waveband of 1490nm ~1610nm and temperature region of -10°C ~40°C is realized. The measuring method for refractive index dependence on temperature and dispersion characteristic of the fluorinated polyimide film is also reported.

Scalar finite-element-method optimization algorithm was used to calculate the effective index and mode field distribution in a LD-pumped SMF-coupled Er:Yb co-doped glass channel waveguide lasers. The channel waveguides were made by electric field assisted K+-Na+ ion-exchanged in commercially available laser glass, and it supports a single mode at 1540-nm laser wavelength and double mode at 980 nm pump wavelength. Applied the optimized parameters, we designed the waveguide lasers which can convert 200 mW continuous-wave power at 980-nm from a LD-pump laser into 18 mW of continuous-wave at 1540-nm coupled into the LPO1 mode of standard single-mode fiber.

An aluminum nitride thin film on sapphire substrate was prepared by metal-organic chemical-vapor deposition for optical waveguide study. In order to investigate thermo-optic dispersion properties of aluminum nitride waveguide, a new experimental arrangement is designed. The thermo-optic properties of thin film are obtained using a prism coupled waveguide devices, which has auto-temperature controlling system. The temperature range is 30 ° C — 85° C with the control accuracy of ± 1 ° C. The experiment was carried out by using different light source with wavelength of 441.6 nm, 514.5 nm, and 632.8nm. A set of curve of thermo-optic dispersion of aluminum nitride film is given.

An improved method to overcome the d*efect of interfacial-gel polymerization technique, named gradual-interfacial-gel polymerization was put forward. The effects of reaction conditions on formation of the UI polymer rod, i.e. reaction temperature and atmosphere pressure, were investigated. High performance large-sized graded-index polymer rod was prepared by this technique, in which diphenyl sulfide was used as higher refractive index molecules.

Grating based integrated waveguide demultiplexer is one of the most promising types of planar waveguide DWDM devices. In order to reduce reflection loss of the grating, the grating facets need metallic coating for high efficiency. The analysis of retro-diffraction efficiency for echelle grating with metallic coating is given in the present paper by using a Finite-Difference Time-Domain (FDTD) method. This numerical method is more accurate and reliable than other methods such as the ray approximation method. Numerical simulation is given for S-polarized lights and the numerical results show that the loss is about 1dB.

In the coming new general optical network, tunable filter is one of important optical devices, and can be used to compose dynamically optical add/drop multiplexer (OADM). Polarization independent integrated acousto-optic tunable filter (IAOTF) is one of devices which have most potential to perform the function[1][2]. Mode splitting and merging are realized by using two symmetrically directional couplers in the IAOTF. Mode polarization is converted by the acousto-optic mode converter when the condition of phase matching is met at the specifically light wavelength. The light wavelength passing the filter can be easily adjusted by changing the frequency of acoustic wave. The Ti diffused technology is adopted to fabricate the device on the X-cut Y propagation LiNbO3 slice. The relation of index difference in the X-cut Y propagation LiNbO3 waveguide with different diffusion conditions is computed in this paper. And the theory of coupling mode is utilized to analyze and design the directional coupler, in which TE/TM mode splitting can be realized. The designed structure is simulated by using BPM software. The extinction ratio of TE/TM mode can be reached 25. 1 dB and 24.9 dB respectively.

A flattened spectral response for an arrayed-waveguide grating (AWG) can be obtained by using a multimode interference (MMI) coupler. In the present paper, an analytical expression for the flattened spectral response is derived by using a Gaussian approximation. A simple formula relating the optimal MMI length and the normalized separation is given. The normalized separation describes the separation between the peaks of the two fold images in the MMI region. With the present formula, the optimal value for the MM! length can be obtained for a given normalized separation determined by a required 1dB passband width. By using the present optimal design method, a flattened spectral response for an AWG is obtained. The optimal design result obtained from the present analytical formula is verified by a beam propagation method.

The temperature related the spectrum shift is a serious problem of arrayed waveguide grating (AWG). This paper present a method for reducing the temperature-related spectrum shifts in AWG device. The waveguide of a three-layer hybrid material structure is used in this method. In the hybrid structure, polymer which has a negative coefficient of refractive index related to temperature and silica material which has a positive refractive index coefficient of temperature are employed. The hybrid structure waveguide has a negative coefficient of efficient refractive index related to temperature, which can compensate the phase change due to the length change when temperature changes. Finite difference method is used to analyze three layer athermal waveguide structure, and the maximum temperature related spectrum shift of O.026nm for the designed AWG, which is about one thirtieth of the normal silica/silicon AWG structure, is achieved.

Nano-porous polymer material is recently developed and is of very important practical value in optical field. In this paper, nano-porous polymer films which can be used in optical planar waveguide were studied. The refractive index of this kind film can be controlled and adjusted precisely. Through changing the volume fraction of PS in the film, the relationship between the effective refractive index and the pore volume ratio in the film was found with the scanning electron microscope and ellipsometry. The effective refractive index decreases with the increase of the pore volume ratio. The propagation characteristics of the fields in a nano-porous polymer planar waveguide were simulated with the Finite Difference Time Domain (FDTD) method and the result of the experiment was confirmed with the FDTD method too.

To realize practical wavelength division multiplexing (WDM) system, a high-performance AWG with an all-optical polarization state controller (AOPSC) is introduced. This device is polarization-independence based on asymmetric planar waveguide in the silicon-oxynitride material system with a high-refractive-index difference n =0.7 % and large a/b (here, a is the width and b is the thickness of the core layer waveguide). Only TE0 mode can exist in the device, the TM0 mode is cutoff. Finally, an eight-channel AWG using 100GHz channel spacing (the center wavelength is 1552.52nm) is designed. In order to get more realistic results, the BPM method was used to simulate the light propagation in the AWG. The simulation was calculated for both TE and TM. Using BPM method, and we found only TE0 can propagate through the device. No polarization dependence was measured in the wavelength response.

By establishing the relation of Talbot self-imaging effects in free space and in waveguide, we have rediscovered the self-imaging diffraction effect in waveguide with the view of Talbot effect in free-space. We have found that the diffraction theory of Talbot effect in free space do give us a set of simplified equations, that can't be obtained with the theory of multimode interference (MMI), beam propagation method, etc.. We show that simple equations for explanation of Talbot self-imaging effect in free space can be used to design the waveguide beam splitters and combiners. Thus, the heavy designing work with the previous multimode interference method can be released with the new simple equations. More importantly, new configurations of waveguide beam splitters and combiners can be designed with the simple equations. The importance of rediscovering waveguide beam splitter is that a complete new and clear physical picture can explain the complex self-imaging phenomena in waveguide, which should be highly interesting for practical applications.