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).