Wavelength Division Multiplexing (WDM) optical ring network is becoming more and more attractive due to its high capacity and survivability against fiber breaks. At the same time wavelength routing simplifies the node structure by using optical add/drop multiplexer (OADM) and optical cross-connect (OXC) in the network. In the two-fiber unidirectional optical path-protection switching ring (TUPSR) network, two separate OADM equipments are required to add/drop channels from the two fiber-ring simultaneously. Due to this high price, the cost benefit introduced by the WDM systems is reduced. In this paper, a novel OADM structure is proposed and demonstrated for two-fiber unidirectional optical path protection switching ring network. The OADM is designed with only one arrayed- waveguide grating (AWG) multiplexer in a loop-back configuration. Being used in bidirectional mode, the proposed OADM can add and drop any channel to and from both fiber-rings of the TUPSR simultaneously with only one module. As a result it is cost effective. Experimental results show that the degradation observed in the receiver sensitivity is very limit when the proposed OADM module is used in the two-fiber unidirectional optical protection switching ring network to add/drop multiple channels. The restoration time is less than 7 ms, which satisfies the requirement of ITU-T recommendations. Performance of the TUPSR against the two- fiber unidirectional optical line protection switching ring (TULSR) is also analyzed. It can be derived that the TUPSR has better performance compared to the TULSR not only on the transparent-ring circumference but also on the reliability and the simplicity of control.

In the presence of the increasing demand, it is urgent for the wavelength division multiplexing (WDM) optical transport network not only to boost the transmission capacity but also to enhance the survivability. In this paper, A M:N protection scheme for WDM optical transport networks is proposed and demonstrated. The M protection channels are used to transmit low priority traffic in normal condition, and can be switched automatically to replace a working channel when failure occurs to that working channel. Compared with the 1 + 1 protection system, the proposed scheme achieves better performance with lower costs. An optical add/drop multiplexer (OADM) is also proposed with the protection scheme. Any channel in M or in N can be dropped in the OADM according to the demand of the network management center. When failures occurred to a working channel that should be dropped in the OADM, and when the traffic on the failed working channel has already been switched to a protection channel at the previous node, the protection channel is dropped in the OADM automatically instead of the failed working channel. Then the corresponded adding signal is still added to the working channel, i.e., the protection channel is set free and can be used to carry low priority traffic again to the next node. Experimental result shows that the protection takes place within 7 ms, which satisfies the requirement of the ITU-T recommendations.

Optical add/drop multiplexer (OADM) and optical cross-connect (OXC) are key network elements in wavelength division multiplexing (WDM) optical transport networks. Homodyne crosstalk, due to the non-ideal performance of the demultiplexers/multiplexers and the switches, is introduced in OADMs and OXCs and causes system performance degradation. In this paper, we propose a low crosstalk structure for integrative OADM/OXC that implements the function of OADM and OXC simultaneously. For joined adding and dropping, we place a set of 2 X 2 switches between the demultiplexers and the cross-connect array instead of using larger dimensional cross- connect array. We also theoretical compared the impact of the homodyne crosstalk in the proposed structure and in the conventional integrative OADM/OXC. Simulation result shows that the power penalty caused by homodyne crosstalk can be decreased significantly in the proposed structure. Since the add/drop and cross-connect state of the integrative OADM/OXC changes from time to time for reconfiguration and restoration and the polarization state of the signals varies constantly due to the thermal and mechanical fluctuations, we statistically analyzed the power penalty distribution. It can be obtained that the power penalty in the proposed structure distributes in a smaller range. This is very helpful to the planning and design of the optical transport networks.

The measurement of frequency responsibility is very difficult to carry out by swept-frequency method but instead of optical spectrum analyzer approach when the modulating frequency is higher than 50 GHz. We will present the measurement of modulation index in both of theoretical derivation and experimental demonstration in this paper.

The microwave propagation characteristics of a coplanar waveguide (CPW) electrode on Ti:LiNbO₃ optical modulator are studied and a loss formula based on experimental data fitting is proposed. The loss requirement on a 160 GHz LiNbO₃ modulator is also studied.

In this paper, routing and wavelength assignment (RWA) algorithms whose optimum object is the minimum number of wavelength required (MNWR) in WDM All Optical Network were studied. Since the number of wavelength required (NWR) obtained by the existing two RWA algorithms is associated with the numbering order of the nodes in the network, a statistical method was proposed to modify the RWA algorithms. With statistical method, a smaller NWR can be acquired. And, it is the first time that the statistical method was proposed to compare the RWA algorithms. Two RWA algorithms can be compared by contrasting the distribution of the NWRs obtained by each RWA algorithm.

In this talk, we review recent achievements on compound semiconductor based optoelectronic devices in State Key Lab on Integrated Optoelectronics, Tsinghua University. The presentation will cover research work on electroabsorption (EA) modulator integrated distributed feedback (DFB) lasers for wavelength-division multiplexing (WDM) systems and the growth of InP based materials by all-solid-source molecular beam epitaxy (SSMBE) system.

In this paper dispersion compensation of two WDM channels using two cascaded Chirped fiber gratings (CFGs) fabricated by double exposure method as reported. The power penalty of dispersion compensation of two channels are both less than 1 dB.

Principles, characteristics and experiments of different schemes on clock recovery and demultiplexing in OTDM communication are presented.

A hybrid electro-optic oscillator is demonstrated to extract frame clock from injected OTDM signal, the operation principal lies in the harmonic injection locking property of the device.

Integrated-Optic Arrayed Waveguide Grating (AWG) N X N multiplexers are a new focus in All Optical Networks (AON) for their unique N input and N output geometry and have been used in a variety of applications. All AWGs fabricated so far have shown loss-imbalance among FDM channels due to non-uniform diffraction efficiency. It is fatal in AON because it will accumulate after each AWG. Uniform diffraction efficiency obtained in ideal design limit is one ideal solution, but it is nearly impossible to achieve the ideal limit with present fabrication technology. This paper applies a new method -- shifted connection -- on equalizing loss-imbalance of AWG- based OADM. The basic idea is simple and the result is of great significance. We theoretically analyze the effect of 8 various shifted configurations and predict each effectiveness. We find the relationship between the loss-imbalance and shift (delta) is a quadratic equation. We extend the method to cascaded AWGs. Also we deduce the limit of the equalization, which is independent of m and AWG's loss-imbalance parameter (alpha) , (beta) . Experiment results accord with theory very well and show that we successfully reduce a worst case loss- imbalance (9.5 dB) to a best case loss-imbalance (3 dB) in a single AWG-based OADM. We find that equalization configuration with foldback path is superior to loopback path configurations, when no more than N/2 wavelengths are used. The method is very simple and effective in equalizing AWG's loss-imbalance and the idea can be applied to other equalizations in AON.

A fiber loop mirror constructed from two polarization- maintaining dispersion-shifted fibers with different zero- dispersion wavelengths is theoretically investigated. Our results show that this fiber loop can be used for both four- wave mixing without optical filtering and all-optical switching.

This paper introduces a new structure of WDM local area network. Each node uses WDMA (Wavelength Division Multiplexing Access) to access the network. The switching router of WDM LANs proposed before often use PSC (Passive Star Coupler), but now has been replaced by AWG (Arrayed Waveguide Grating), while each user equipped one tunable transmitter and one tunable receiver is reserved. As we all know, in WDM LAN, destination collision is inevitable when two or more then two nodes want to communicate with the same destination node and this degrades the network performance. So, in all related papers, transmission and receiving procedure must be pre- scheduled in order to preventing from destination collision. However, if there is a configuration, which has the possibility of permitting more than one to access the same destination simultaneously, access scheduling can be more efficient and system performance can be improved. Obviously, adding receiver number or transmitter number is impractical, thus, the only solution is to introduce buffer at the router output side. This is a distinctive difference of the network router we proposed from others. We believe this design can improve the network performance and simulation and numerical results have confirmed that.

The paper demonstrates a 4 X 4 optical cross-connect architecture including a micro-mechanical switch module and a wavelength conversion module. Three channel of 622 Mbit/s signals and a channel of 2.5 Gbit/s signal are generated and cross-connected. The 2.5 Gbit/s signal has been converted for a wavelength down-shift of 19.4 nm. After 28.4 km non-zero dispersion shift fiber propagation, the bit error rate is below 10^-12.

In this paper, a design method by using comb-like dispersion profiled fiber (CDPF) to achieve pulse compressing has been given, and corresponding numerical model was also presented. Based on this model, the effect of nonlinear phase shift on pulse width and waveform from CDPF compressor was studied under the condition of different pulse peak power. The numerical results reveal that the incident pulse peak power and nonlinear phase shift should be satisfy certain conditions, to get the suited CDPF compressor for the ultrahigh speed OTDM system using.

In this paper proposed a novel approach integrated recent advances in MPLS traffic engineering with wavelength switching/routing technologies to achieve optical interconnect for IP-centric Data Networks. In it, digital wrapper replaces SDH/SONET function block, so the IP layer can be placed directly over the optical layer. By outlined how the MPLS Traffic Engineering could be used on the wavelength switching network and how to design new network node to achieve optical interconnect. Furthermore, have shown an approach to dynamically interconnect routers via wavelength, including a bypass routing in the node, new wavelengths may easily be introduced to the network at a reasonable cost and to better support various classes of traffic.

Two novel kinds of reconfigurable multi-path OADM structures based on MZI with FBGs are proposed in this paper. These novel OADM is determined by adding/dropping different wavelengths making use of optical switches and tunable FBGs. There are very low incoherent crosstalk and no any coherent crosstalk in these novel OADMs in theory. So very large scaling of the network which is composed of the novel OADMs is demonstrated in the paper.

In this paper, we give two multicast technologies. The one based on wavelength routing named light-tree; the other based on Multi-protocol Label Switching (MPLS) using Optical Label Switching (OLS). We discussed two services model guarantee QoS in MPLS/OLS.

Burst mode transmission and receiving is one of key techniques in an ATM-PON system and a well-performed optical transceiver is very important in OLT. In this paper some problems in burst mode receiving, such as timing recovery and noise suppressing are discussed first. Then the low cost and low crosstalk design methods of the transceiver are studied. Such a low cost transceiver can satisfy both the class B/C specifications in ITU-T G.983.1.

DWDM optical transport network is the hotspot of the optical communications, the protection and restoration of the multiple wavelength optical transport network is the key technique in the DWDM optical transport network. In this paper, at first we introduce the concept of separate optical layer- the concept of separate optical layer has been demonstrated in some important experimental optical networks- and some advantages of the multiple wavelength optical transport networks, we also compare the DWDM optical transport networks with the SDH networks, put forward some analogies of them. The second, we analyzes the protection and restoration of the multiple wavelength optical networks, we analyze multiple fiber ring networks in detail, we analyze the span protection, line protection and path protection, discuss the advantage and the shortcoming of these different protection mode.

The principle of dispersion compensation in transmission using uniform fiber Bragg gratings is described. Its compensation efficiency is analyzed numerically and the experimental results are reported. We broadened the pulse-width of the initial signals from 114.5 ps to 191.2 ps and 257.8 ps after 11.1 km and 22.2 km fiber transmission, respectively and then re-compressed them to 125.8 ps and 147.2 ps, respectively using one unchirped fiber grating with some tuning techniques.

A new passive component, plastic fiber Bragg grating (PFBG), is proposed based on our researches on fiber grating tunability and plastic fibers. We analyzed its characteristics. It shows that this kind of component can be tuned hundreds of nanometers. It can be used to demultiplex any channel in all-wave fiber WDM in the future. We also discussed the problems in application of the plastic fiber gratings.

In this paper, one novel scheme for evaluating EDFA gain spectrum is introduced. In this scheme, one can determine the EDFA gain spectrum by adjusting one tunable F-P filter (TF) and one tunable attenuator (TA) embedded in the loop-locked configuration (LLC).

Resonant-cavity-enhanced (RCE) photodetectors have been demonstrated to be able to improve the bandwidth-efficiency product. We report one top-illumination and one bottom- illumination SiGe/Si multiple quantum-well (MQW) RCE photodetectors fabricated on a separation-by-implanted-oxygen (SIMOX) wafer operating near 1300 nm. The buried oxide layer in SIMOX is used as a mirror to form a vertical cavity with the silicon dioxide/silicon Bragg reflector deposited on the top surface. A peak responsivity with a reverse bias of 5 V is measured 10.2 mA/W at 1285 nm, and a full-width at half maximum of 25 nm for the top-illumination RCE photodetector, and 19 mA/W at 1305 nm, and a full-width at half maximum of 14 nm for the bottom-illumination one. The external quantum efficiency of the bottom-illumination RCE photodetector is up to 2.9% at 1305 nm with a reverse bias of 25 V. The responsivity of the bottom-illumination RCE photodetector is improved by two-fold compared with that of the top- illumination one.

We report on optoelectronic multiple chip modules, consisting of vertical cavity surface emitting laser (VCSEL), photodetector and 1.2 micrometer CMOS electronic circuit. The hybrid integrated components operate at a date rate of 155 Mb/s, which could be used in optical interconnects for multiple computers.

Wafer bonding is regardless of lattice mismatch in the integration of dissimilar semiconductor materials. This technology differs from the heteroepitaxy mainly in the mechanism of generating dislocations at the interface. A model of dislocations at the bonded interface is proposed in this paper. Edge-like dislocations, which most efficiently relax the strain, are predominant at the bonded interface. But the thermal stress associated with large thermal expansion misfit may drive dislocations away from the bonded interface upon cooling.

In this paper we proposed a single ridge waveguide electroabsorption modulated distributed feedback laser (EML) for long-haul high-speed optical fiber communication system. This EML was successfully fabricated by two step metal organic vapor phase epitaxy (MOVPE) including selective area growth (SAG) and helium partially implantation. No obvious changes of the threshold current (< 0.2 mA), extinction ratio (< 0.1 dB), output power (< 0.2 dBm) and isolation resistance were achieved in the preliminary aging test. With 2.5 Gb/s NRZ modulation, no power penalty was observed after the optical signal was transmitted through 280 Km normal single mode fiber.

Silicon-on insulator (SOI) is an attractive platform for the fabrication of optoelectronic integrated circuit. Thin cladding layers (< 1.0 micrometer) can be used in SOI waveguide due to the large index step between Si and SiO₂, making them compatible with the VLSI technology. Here we demonstrate the fabrication of 1 X 4 and 2 X 2 multimode interference (MMI) coupler based on SOI technology. Performances of the devices are analyzed. The minimum excess loss of the devices is about 1.8 dB. The devices show uniform power distribution.

A novel crosslinkable polyurethane is used as the core layer of the electro-optic (E-O) modulator. The refractive index and dispersion of this material have been detected by analyzing the F-P oscillation in transmission spectra. Calculated results from the effective index method are given to design the Mach-Zehnder and straight 5-layer ridge waveguide device (including the metal electrodes). With light at 1.31 micrometers being fiber coupled into waveguide, the mode properties of these devices have been demonstrated in a micron control system. The guided mode is accordant with the theoretical analysis.

Propose coupling equation between counter-propagating signal and control pulse in nonlinear optical loop mirror (NOLM). Study the nonlinear phase shift deference between the co- propagating and the counter-propagating signal in transmission process. Analyze the switching characteristics of Gaussian and non-return zero (NRZ) pulse. Get the first best de- multiplexing lengths, switch windows, output waveform and so on, which are important in practical usage.

In this paper, some study results to apply fiber link to a computer cluster are presented. The research is based on a ring network topology for a cluster system, which is connected by gigabit/s virtual parallel optical fiber link (VPOFLink) and its driver is for Linux Operating System, the transmission protocol of VPOFLink is compliant with Ethernet standard. We have studied the effect of different types of motherboard on transmission rate of the VPOFLink, and have analyzed the influence of optical interconnection network topology and computer networks protocol on the performance of this optical interconnection computer cluster. The round-trip transmission bandwidth of the VPOFLink have been tested, and the factors that limit transmission bandwidth, such as modes of forwarding data packets in the optical interconnection ring networks, and the size of the link buffer etc., are investigated.

In this paper, a communication protocol has been designed for the two-layer scalable optical interconnection network (TSOINet) designed in Tianjin University. The communication protocol has been designed based on TCP/IP (transmission control protocol/internet protocol) protocol. But it is more efficient than TCP/IP for data transmission in TSOINet. An auxiliary channel has been introduced in TSOINet for transmission of the communication status messages among the sub-layer rings. Many network management functions, such as flow control, hand shaking, etc., can be achieved via the auxiliary channel, so the communication overheads can be decreased. The performance of the communication protocol has been evaluated compared to TCP/IP protocol for data transmission in TSOINet.

In this paper we report the generation of narrow line-width laser from a laser diode (LD) by using a fiber Bragg grating (FBG). When slipping an FBG onto the pigtail of the LD, the spectral line width becomes narrower (only including a single longitudinal mode). And the spectral bandwidth is below 0.2 nm. The corresponding intensity with a side-mode-suppression ratio (SMSR) of about 22 dB is observed. In addition, tuning the reflection wavelengths of the FBG, we can get a serial of single mode laser with wavelength spacing 0.94 nm (the tuning range about 10 nm). The spectral widths of lasers at different wavelengths are almost the same.

The objective of this paper is to give an overview of the different studies we have performed at the research level regarding the design and implementation of a photonic wavelength division multiplexing layer providing transparent transport services to client layer. Such a network requires a number of enabling factors to be accessed in order to become a reality. Among these factors are the availability of high- capacity WDM transmission systems and efficient optical routing nodes based on mature technology, etc. In this paper, based on several key build blocks we developed such as fiber lasers, flattened EDFA's, and WADM's, an all-fiber WDM system was demonstrated. A cost effective alternative to OSA was proposed.

The paper reports the theoretical and experimental research of Yb-doped double-clad fiber laser. In the experiment, we use F- P cavity structure. We obtained an output power of 233 mW at a slope efficiency of 79.6% with respect to input fiber power. The total optical-to-optical conversion efficiency is 30.3%. And the output wavelength is 1.078 micrometers .

The experimental results on a high-power Yb-doped double- cladding fiber broadband superfluorescent source pumped by a 976 nm broad-stripe laser diode are reported. The maximum superfluorescent output power is 54.11 mW, while the slope efficiency is 19.3%, central wavelength of superfluorescent spectrum is 1082 nm with a 17.2 nm 3 dB bandwidth.

In this paper, a self-Q-switched Er-doped fiber (EDF) laser is reported, which employs stimulated Brillouin scattering (SBS) in single-mode (SM) fiber as a passively Q-switched mechanism. The stable nanosecond magnitude optical pulses were obtained. Pulses with peak power 800 mW, pulse width 2.2 ns and repetition rate about 64.5 MHz could be achieved, when the pumped power was 88.0 mW. A few factors that affect the pulse characters are studied.

A cladding pumped self-Q-switched Yb³⁺ fiber laser is described in this paper. By exploiting fiber nonlinearity -- stimulated Brillouin scattering (SBS) in the fiber laser cavity, we demonstrated a series of stable pulses with the full width at half maximum (FWHM) about 2 ns and repetition frequency about 29.4 MHz.

In this paper, we improve the rate equations of the Single Quantum Well Laser Diodes (SWQ-LD's) by introducing photon phase equation and three terms of Langivin noise for carriers and photons. Modeling of SQW-LD by means of Matlab Simulink is present. Small signal modulation response, relative intensity noise (RIN) and phase noise are studied. Various simulation results are given.

In addressing the integration of IP and WDM networks, we propose a joint operation approach. Through reconfiguration or real-time setup of lightpaths, joint operation focuses on optimizing network performance or guaranteeing it to a defined level under current network configuration and dynamic data traffic pattern at the network operational stage. Our model features a separation of control plane and data plane. The data plane Formulations have been studied in building the model, and the initial findings help in understanding the behavior of data plane and designing the routing and signaling protocols within control plane.

A new type of electro-optic polymer modulator based on guided modes of the Attenuated Total Reflection (ATR) spectrum is described and fabricated. Using a prism to couple a laser beam into a poled polymer thin film, it is found in its ATR spectrum that the fall-offs of the absorbance peaks corresponding to the guided modes can be considered linear. The angular positions of these fall-offs are sensitive to the dielectric coefficient of the poled polymer. If the operating interior angle of the modulator is properly chosen at the midst of these fall-offs, the intensity of the reflected light can be directly modulated by the applied electric field due to the electric-field-induced dielectric coefficient change in the poled polymer film. Compared with the conventional Electro-optical (EO) modulator based on waveguide technology, the insertion loss of the device can be greatly reduced; Compared with the EO modulator based on surface plasmon resonance, the driven voltage can be lessen because that guided wave resonance is much sharper than the surface plasmon resonance.

Recently much attention has been paid to the electro-optic modulators with reflection geometry. A new type of electro- optic modulator, which consists of prism-metal-polymer-buffer- metal geometry and works based on Attenuated Total Reflection spectrum, has been developed in our group. In this paper, we propose a double-channel electro-optic polymer modulator, in which two pairs of electrodes are fabricated in ATR configuration. When two light beams are arranged to incident at the prism base with an appropriate angle corresponding to a special mode of the polymer waveguide. The intensity of the two reflected light beams can be directly modulated by the applied voltages due to Pockels effect of the poled-polymer film simultaneously. In the case of applying two different electrical signals to the two different pairs of electrodes, double-channel polymer modulator carrying different information can be fulfilled in a single-prism configuration.

A kind of new optical interconnection element -- holographic Bragg grating with a red sensitive photopolymer is reported in this paper. Grating-splitting boards with equal intensity are designed and fabricated on a red sensitive photopolymer by Lloyd's interferometer of the special design, and they are successfully demonstrated in application of optical butterfly interconnection network.

In this paper a new means of coupling of high-power diode laser arrays and fiber are introduced. This means promises highly efficient optical coupling between the laser arrays and fibers, and a simplified assembly process. The relative height between the laser arrays and fiber is controlled by adjusting the width of the v-groove. Excellent uniformity of optical coupling and temperature stability have been obtained.

By using light as a carrier, the information of voice and data is sent to a receiver through atmosphere, so this system with computer via some interfaces can be applied to link computers into network. This system has shown many advantages on volume weight flexibility, convenience, security and anti- interference. In this paper, firstly, the principle of a laser communication system is introduced, then the performance of LOC, GaAs, AlGaAs semiconductor lasers are presented; moreover, the basis of choosing photo-detector, the characteristic and usage of silicon avalanche photo-detectors, and the threshold detection and false-alarm ratio of the system are presented in detail.

We report the fabricated process of Rb/Ba ion-exchanged KTiOPO₄ waveguide with and without periodically segment and the measured results of lattice constant change in the waveguides. The experimental results show that the change of lattice constant of the waveguide is 0.42% to approximately 0.25%, which decrease with increase the Ba ion density. The ideal mol% ratio of Rb to Ba were obtain for making waveguide.

In this paper, we present a scheme of controlling chaos in an Er-doped fiber dual-ring laser with one polarized mode by using the linear feedback method. Numerical results show that under some stiffness of feedback the controlled system has negative maximum Lyapunov exponents (MLE) and separate spectra, which demonstrate that controlling the chaotic system into the stable states could be realized by adjusting the feedback stiffness.

Based on the earlier theoretical work on the bifurcation and chaos of laser oscillation output in a ring cavity, we present in this paper a study of pattern dynamics in the spatially extended laser system. In numerical simulation, we find the homogeneous stationary states, traveling wave solutions and the formation of kink-antikink patterns in space with their periodic doubling bifurcation in time. Finally, we demonstrate that the oscillation output in the transverse section can evolve into spatiotemporal chaos state with the change of the system parameters.

This article describes Omni-directional laser digital communication system, discuses the whole design idea of the system and the basic work principle, and describes in detail the hardware configuration and some pivotal technology solution in software.

This paper describes a high-speed atmosphere laser communication system working in digital communication mode. It has many advantages: working for long distances, full duplex communication mode, transfer information with safety, confidentiality and anti-electromagnetic interference etc. It can be used singly, or be used to be the supplement part of the short-wave radio station and the satellite earth station information transfer system to construct high-speed laser communication network.

This paper goes deeply into the characteristics of polarization and optical activity. Using these phenomena, it presents a new fiber-optic switch. The switch is characteristic in simple structure and polarization- independence. Meanwhile, the output light has no difference in phase and the switch has low optical insertion loss and interchannel crosstalk. Moreover, it has fast response speed and can be small in size and so on. Further, the add-drop filter of any wavelength can be realized through the combination of the fiber-optic switch with wavelength division multiplexer and demultiplexer. The paper analyzes the performance of 2 in - 2 out fiber-optic switching network. The results show that the insertion loss and the interchannel crosstalk are small.

A N X N integrated planar optical waveguide acousto-optical switch design is presented based on waveguide geodesic lenses and acousto-optical deflector. This kind of switches gets over the difficulties occurred in integrated switches based on strip waveguide. It can be integrated in a chip, and the channel numbers N can be up to 218. As an example, a 2 X 2 integrated planar optical waveguide acousto-optical switch has been fabricated and tested. Experiment result shows only one mode is transmitted in the Ti:LiNbO₃ waveguide; the chip insertion loss is 0.8 dB; the central acoustic frequency is 150 MHz; the 3 dB bandwidth of IDT is 56 MHz; the chip acoustic frequency resolution is 6 MHz and the chip extinction ratio is larger than 20 dB.

In this paper, our main goal was to simulate vertical cavity surface emitting lasers (VCSEL) characteristics, including the threshold current, transient phenomena, and modulation operation. The simulation results of transient response and the phase diagram of the carrier and photon are given. We have got the relation of spontaneous emission factor, current and aperture size on threshold, turn-on delay, relaxation oscillations frequency, and output power. Furthermore, it is found that the threshold current, light current curves, transient phenomena, and modulation operation of a VCSEL are determined by size-dependent.

In this paper, a scheme of all-optical wavelength conversion based on fiber semiconductor ring lasers has been suggested. The analyses on this wavelength converter have also been given by using rate equations. Some properties such as extinction ratio and the conversion wavelength range are discussed.

Improved approach to BOA device of low extinction ration and half-wave voltage has been proposed. The relations between extinction ration, half-wave voltage and electrode have been discussed detailedly with transfer matrix methods. The following conclusions has been made: the electrode width can be optimized to get the lowest half-wave voltage; To gain low extinction ration less than -40 dB, the offset of electrode position should be less than 0.3 micron. A BOA device with the extinction ration less than -40 dB can be fabricated by a technics named Self-adjustable Technics.

Without accurate models of the modulation behavior of multi quantum wells (MQW) lasers, it would be impossible to construct simulation circuits that include the models, the driver circuits and so on. A study of equivalent circuit model of MQW lasers derived from three-level rate equations has been carried out. It can explain the carrier distribution, which can not be explained by traditional two-level model. Then the simulation of modulation behavior has been implemented in SPICE. Results of various modulation properties from the simulator have been discussed. Especially, the scheme was implemented in a hierarchic way, which means a much easier management. And this hierarchic way help to realize photonic design automation (PDA).

Improved approach to low-loss and high-uniformity MMI devices is proposed in this paper. The propagation constant error of guided modes in the MMI region is analyzed. An optimized index contrast is selected to decrease the propagation constant errors of those modes near cutoff. 1 X N MMI splitters designed by this means are analyzed by exact mode analysis. Results show that the loss and uniformity of this new structure are notably improved, especially when N is large. The loss of 0.0892 and uniformity of 0.0826 are acquired when N equals 32.

This paper presents polarization-insensitive multimode interference (MMI) N X N Mach-Zehnder interferometer (MZI) optical switch. First we analyze the working principle of each component of the MMI-MZI optical switch. Then using the discrete spectral index method (DSIM) to optimize the access single-mode rib waveguide of the device, we design and fabricate a 4 X 4 MMI - MZI optical switch with simple digital driven circuitry, acceptable voltage (approximately 12 V) and low crosstalk (approximately -20 dB).

This paper reviews recent progress and the future prospects for ultrahigh speed optical modulator. In particular, details are provided on GaAs/AlGaAs traveling-wave modulators using doped epitaxial layers.

The design and deposition of the optical thin film, which have high-transmittance nearby 1550 nm wavelength for the desire of such components in the modern optical fiber communication, is systematically studied in this paper. Using the optimum-seek method of Monte Carlo experiment and POWELL least square method, we built optimization program. Based on anti- reflecting film structure, the optimum design of the BK7 glass and the GaAs is gotten. Several methods to deposit such irregular film structure are searched. The results indicate that using the double wavelength method or the various over- shoot quantities methods can accurately monitor the optical thickness of each layer. The optical thin-film components with high-transmittance nearby 1550 nm wavelength are gotten.

The film structure of a multiple-cavity narrow-band interference filer is always used as DEMUX in WDM optical fiber communication system. To ensure the repeat of the film coating results, the optical thickness of every layer in this film structure is designed to be the integer multiple of the quarter of the monitor wavelength. But such design, which is only composed of regular layers, cannot meet the desire. Therefore, a design method, in which the film structure of a few irregular layers is added to the multiple-layer standard film structure, is introduced in this paper. Thus, the design desire can be basically satisfied. In the design, the optical thickness of the irregular layers is obtained by the optimal method with computer. An estimate function of the optimizing is made in this paper. A program is built in MATLAB programming language. By using the program, the thickness of the irregular compensates film on whatever multiple-layer regular film structure can be optimized.

A 4 X 4 optical switch performing bi-directional crossbar switching on optical communication signals at 1550 nm is presented and experimented. This switch is expanded from several elementary 1 X 2 optical switches. The switch is made of bulk passive components. Operation is totally polarization independent. The proposed free-space architecture has the features of high compactness, reliability and fast response time compared with common switching solutions.

In this paper, the crosstalk influence between signal channels of 4 X 48 free-space parallel optical interconnect network system based on VCSEL/CMOS optoelectronic chip and 2-D optical fiber data link is studied. The crosstalk analysis shows that the crosstalk between signal channels may be reduced by introducing a small displacement at vertical direction. This optical interconnection system can realize 12-bit wide bi- directional data transfer between four computers through a 4 X 48 high density 2-D optical fiber data link. The influence of the crosstalk would be reduced in this optical interconnect system.

IP traffic on the Internet and enterprise networks has been growing exponentially in the last several years, and much attention is being focused on the use of IP multicast for real-time multimedia applications. The current soft and general-purpose CPU-based routers face great stress since they have great latency and low forwarding speeds. Based on the ASICs, layer 2 switching provides high-speed packet forwarding. Integrating high-speed of Layer 2 switching with the flexibility of Layer 3 routing, Layer 3 switching (IP switching) has been put forward in order to avoid the performance bottleneck associated with Layer 3 forwarding. In this paper, we present a prototype system of a scalable IP switching based on scalable ATM switching fabric and optical interconnect. The IP switching system mainly consists of the input/output interface unit, scalable ATM switching fabric and IP control component. Optical interconnects between the input fan-out stage and the interconnect stage, also the interconnect stage and the output concentration stage provide high-speed data paths. And the interconnect stage is composed of 16 X 16 CMOS-SEED ATM switching modules. With 64 ports of OC-12 interface, the maximum throughput of the prototype system is about 20 million packets per second (MPPS) for 256 bytes average packet length, and the packet loss ratio is less than 10e-9. Benefiting from the scalable architecture and the optical interconnect, this IP switching system can easily scale to very large network size.

High performance, low polarization sensitivity semiconductor optical amplifier based on mixed strained multiquantum wells active material has been realized. Fiber to fiber gain as large as 20 dB with polarization sensitivity less than 1.0 dB are achieved for a component of 450 micrometer-long cavity with carefully designed AR coating on both facets.

FTTH/FTTC systems will be soon used in both a broadcast service and a wavelength-addressed point-to-point communication service. Optical wavelength routers will be the key devices in these systems. In this paper, we propose a new method for high-density optical routing using arrayed- waveguide gratings (AWGs), present the transmission properties of the wavelength router, and analyze the channel crosstalks and the insertion losses of the 16-channel wavelength router. The results show that the channel crosstalks are less than -18 dB, and the insertion losses are less than -6 dB. Its advantages include small volume with miniatured structure, low insertion loss, low coupling loss to fiber, and compatible with the microelectronics technology. It can be used to construct photonic integrated circuits with the waveguide laser diodes and photodetectors.

In this paper, a nonblocking OXC devices based on dense wavelength division multiplexing (DWDM) developed by us are presented. The structure of the OXC is introduced briefly. Some experimental results are shown and discussed.

Chirped fiber grating (CFG) is an important device that can be used to realize dispersion compensation of a fiber communication system and filter signals at the same time. Besides the ordinary way used to measure the spectrum properties of FBGs, an accurate method of measuring dispersion is crucial to specifying CFGs. This paper presents a simple system to suit the needs. The simple system is mainly composed of two facilities: a tunable laser and a lightwave component analyzer. In the system, a wavelength resolution of 1 pm and a phase resolution of 0.01⁰, i.e. about 0.1 ps for time delay are obtained. The system can also be used in the measurement of the optical spectrum of the fiber grating.

The nonlinear Schroedinger equation in erbium-doped fiber and the more generalized form of the propagation equation in the erbium-doped fiber amplifiers are obtained which have included the phase shift that the erbium ions induce. An analytical expression is given to the erbium ions induced phase shift and frequency chirp. It was found that the frequency chirp dose not change much with the wavelength except at the neighboring wavelengths (around 1.531 micrometer) where the absorption and the emission cross-sections of the erbium ions reach their maximum, and the frequency chirp has opposite sign on the two sides around 1.531 micrometer.

As the FTTH (Fiber To The Home) is getting its way into families step by step, the FLAN (Fiber Local Access Network) will become a hot topic in the near future. In FLAN, the wavelength selector is a key component. We need passive, cheaper and easier-operational optical components to build up FLAN. The device based on FBGs could be one of the best choices for wavelength selecting in the FLAN, which is seldom reported before. According to the analysis on the Topology of FLAN, (STAR+BUS) will be a better structure. Here an experimental scheme for FLAN with passive FBGs, Circulators and Couplers is proposed.

In this paper analysis the status and development trend of optical transceiver in the direction of small-form-factor, lower cost, higher speed. And discuss the key technology including small-form-factor optical connector and transmitter and receiver module, integrated electronic circuit of the transceivers, and introduce the design results of this kind transceiver in Photon Tech. Co., Ltd China.

This paper approaches the fundamental principle and design methods of digital communication system by using CO₂ laser to relay through free space, and analyses the principle of acoustic-optic modulator as the key technology in the system, and HgGdTe sensor, low noise amplifier and relay interface circuit. Large-scale programmable integrated device isp1032 is applied to realize the design of no-standard relay interface circuit. The trunking of full-duplex digital communication is realized between the electricity terminals.

The low power penalty wavelength conversion technology at 1.55 micrometer band operating at high bitrate is addressed in this paper by experimental research. The improved performance of the 10 Gb/s all-optical wavelength converters based on XGM and FWM in SOA's after taking certain measures is reported. Optical fiber transmission of 10 Gb/s converted NRZ signal over about 100 km G.652 single mode fiber is implemented successfully in both of XGM and FWM regimes.

Novel multi-active region semiconductor lasers with large coupled optical cavity and high quantum efficiency, and new mechanism tunneling-regenerated multi-active region light emitting diodes with high quantum efficiency and high brightness have been proposed and fabricated. The external and differential quantum efficiency are 2.9 and 3.0 W/A, and the output light power as high as approximately 5 W when the injecting current equals 2A for the four active region 980 nm strained InGaAs/GaAs QW lasers. The fundamental mode light output with perpendicular angle <EQ 17 degrees for this type of large coupled optical cavity laser has been achieved. The on-axis luminous intensity of the new mechanism 620 nm AlGaInP/AlInP LEDs with two active regions is more than 5 cd. It was theoretically and experimentally resulted in that the electro-luminescence efficiency and the on-axis luminous intensity are linearly increasing approximately with the number of the active regions.

Gaussian distributed index change, in which its d.c. component keeps constant, is achieved by using the double exposure technique with a uniform phase mask and Gaussian UV laser beam. The reflected spectral sidelobes of the grating can be suppressed to below -30 dB and the related channel bandwidth is as narrow as expected.

We propose a novel passive optical network which can dynamic control of transmission sequence at high speed and high crosstalk rejection. The experimental system using two wavelength dilated acousto-optic tunable filters has been demonstrated. The wavelength dilation, doubling the distance between channels, provides substantial improvement in both interchannel and intrachannel crosstalk at the condition of fast interchannel switching speed.

Broad band-rejection all fiber filters based on Long Period Fiber Gratings were fabricated by a novel method. Adopting the grating period (Lambda) equals 550 micrometer, and (Lambda) equals 610 micrometer, number of periods N equals 15 and different heating condition, the two kinds of devices are obtained with different band-rejection peak wavelengths at 1310 nm and 1550 nm, respectively. The isolation is more than 25 dB. The bandwidth at the 10 nm isolation point is over 20 nm. The insertion loss is less than 1.2 dB and backward reflection loss is less than -70 dB.

This study propose and demonstrate a directly modulated NTSC AM-VSB 77-channel together with Internet access system by using switched-star architecture, FP laser diodes, single AM- VSB channel transmission, wavelength-division-multiplexing (WDM) and two-way communication techniques over the existed multimode fibers (MMF's) in the campus. Performances of carrier-to-noise ratio (CNR) of > 50 dB, composite second order (CSO) of > 71 dB and composite triple beat (CTB) of > 71 dB were obtained over 0.5 to approximately 2.0 km MMF's transmission. This proposed two-way communication system is simpler and lower cost than the conventional broadcasting fiber optical CATV system.

The mutual effects of stimulated Raman scattering and four- wave mixing (FWM) in phosphosilicate fibers is studied experimentally and theoretically. It is found that the output spectra depend on the launched condition strongly. When only one mode is excited in the fiber, the output spectrum is determined by the competition of stimulated Raman scattering between the SiO₂ and P₂O₅. The SiO₂ Raman line is dominative with lower pump power or using of short length fiber. While the pump power is increased or the long fiber is used, the P₂O₅ Raman line increased and the SiO₂ Raman line is suppressed. When two modes are excited in the fiber, the effects of four-wave mixing is dominative and the spectrum only consist of lines of FMW-assisted Raman scattering of SiO₂.

We present a theoretical analysis of second-order nonlinear difference frequency generation (DFG) in a generalized mirrorless quasi-phase-matching (QPM) frame, aimed at a comparison of counter-propagating difference frequency generation configuration (CDFG) to other DFG schemes, in view of all-optical processing and optical amplifying applications. The evolution of propagating fields within the material have been calculated in dependence of operating parameters. The increased complexity in the evolution of amplitude and phase for fields interacting in CDFG with respect to forward- propagating DFG(FDFG) is at the basis of a dramatic increase in optical amplification under particular settings of device parameters.

The technical issues involved in the construction of smart pixels are discussed from the viewpoint of their system applications to both image processing and optical interconnections. The smart pixels for image processing are aiming at sensing and processing images by one chip. The smart pixels for chip-to-chip interconnects are aiming at eliminating the pin-bottleneck among LSI chips.

This paper describes a novel compact detector-switched polymeric waveguide true-time-delay (TTD) module for application in a wideband (18 - 26 GHz) phased array antenna. The use of photolithographically defined ultra-low-loss polymeric waveguide delay lines provides an attractive solution for achieving the necessary delay time over tens of nsec with ultra fine resolution of less than 1 ps. The two- dimensionally distributed waveguide grating couplers tap the optically encoded microwave signal, propagating along the polymeric channel waveguide, to high-speed photodetectors. Each photodetector is independently switched on and off to select the appropriate delay time. The optically encoded microwave signals are obtained by using a semiconductor-laser- based optical heterodyne technique. Such a monolithic integrated module could reduce the cost associated with optoelectronic packaging and also reduce the system complexity. This paper provides a description of the ongoing research activities in the development and integration of advanced polymeric circuits and packaging as a key building block of the next generation wide-bandwidth phased-array antenna system.

Development in both systems and applications are driving semiconductor technology towards gigascale and terascale integration. The electrical interconnection networks are severely limiting this effort due to RC delay, clock skew, crosstalk, and electromigration. Many novel communication mechanisms have been proposed, but the optical interconnection remains as the most promising candidate. This paper is to review the optical interconnection in high-density data communications, from the point of view of semiconductor technology, and present the most recent developments and results.

Non-linear optical materials have wide uses in the optically control switching systems, and therefore in all-optical parallel computation these materials show a potential prospect. Here in this communication we propose an idea of expressing an analog optical signal by its respective digital counterpart. The analog optical signal may be successfully expressed here by the scheme in proper digital data in binary form. To develop the scheme it requires a system guided by tree architecture followed by a combination of non-linear and linear material. The input light beam whose analog intensity value is supposed to be expressed in binary data form should be a polarized light beam (preferably a laser beam) for properly activating the non-linear material. We now describe the whole scheme in detail.

The transmission characteristics of phase-shifted long-period gratings (LPGs) are simulated theoretically by a combination of coupled-mode theory and fundamental-matrix method. It is suggested that a phase-shifted LPG device cascaded with another normal LPG can be used to flatten the gain spectrum of an erbium-doped fiber amplifier (EDFA) with all three gain peaks. The results of simulations have shown that a broadband amplifier with peak-to-peak 0.7 dB gain variation over 36 nm can be practically realized. It proves that such a gain- flattening fiber filter is indeed plausible, and has a potential application in gain-flattening in dense wavelength- division multiplexed (DWDM) telecommunication systems.

A series of theoretical investigations of the quaternary InAlGaAs material system are carried out. The electronic band structures, the density-of-states, the optical gain spectra and the radiative current density have been investigated based on the Hamiltonian derived using the k.p method. We investigated the dependence of the optical gain and transparent current density on the well width, barrier height, and strain using a numerical approach with high accuracy. By varying the well width, mole fraction in the well material and the Al mole fraction in the barrier the effects of quantum confinement and compressive strain are examined. Furthermore, we demonstrate that a reduction of the well width offers improved modal gain over all radiative current densities. Two different material systems, InAlGaAs on InP and GaAs substrates, strained and unstrained, are examined, respectively. Our results suggest that a suitable combination of well width and barrier height should be selected in improving the TE mode optical gain in InAlGaAs single QW. A very low transparent threshold current density 35 A/cm² of (formula available in paper) strained quantum well laser is predicted. These theoretical results would be useful for design and further performance improvement of the quaternary InAlGaAs strained QW laser diodes.