Self-routing optical crossbar switch

A self-routing optical crossbar switch in which wavelengths of tag light represent the information of destination address by using an optically addressable spatial light modulator as the 3-D crossbar switch along with a wavelength filter for tag light. A BSO (Bi₁₂SiO ₂₀) spatial light modulator was used to perform a 1×2 self-routing switching experiment with two different wavelengths of tag light. The implementation to scale-up the throughput of the switch is also presented     

8×8 optoelectronic crossbar switch

An optoelectronic crossbar switch has been fabricated and tested at 100-175 Mbit/s. The optoelectronic switching is achieved using bias switched detectors     

High-speed CMOS switch designs for free-space optoelectronic MIN's

We present the theory, experimental results, and analytical modeling of high-speed complementary metal-oxide-semiconductor (CMOS) switches, with a two-dimensional (2-D) layout, suitable for the implementation of packet-switched free-space optoelectronic multistage interconnection networks (MIN's). These switches are fully connected, bidirectional, and scaleable. The design is based on the implementation of a half-switch, which is a two-to-one multiplexer, using a 2-D layout. It introduces a novel self-routing concept, with contention detection and packet drop-and-resend capabilities. It uses three-valued logic, with 2.5 V being the third value for a 5 V power supply. Simulations show that for a 0.8-μm CMOS technology the switches can operate at speeds up to 250 Mb/s. Scaled-down versions of the switches have been successfully implemented in 2.0 μm CMOS. The analytical modeling of these switches show that large scale free-space optoelectronic MIN's using this concept could offer close to Terabit/sec throughput capabilities for very reasonable power and area figures. For example, a 4096 channel system could offer 256 Gb/s aggregate throughput for a total silicon area of about 18 cm² and a total power consumption (optics plus electronics) of about 90 W     

A simple 8×8 optoelectronic crossbar switch

The authors demonstrate the operation of an 8×8 optoelectronic crossbar switch consisting of integrated arrays of eight 1×8 GaAs metal-semiconductor-metal (MSM photodiodes connected in a current summing network to the input of Si bipolar transimpedance amplifiers. The MSM devices are also connected to TTL transistor-transistor logic) driven CMOS analog multiplexers which, in the `off' state, switch the detectors into an open-circuit mode. This particular combination of detectors and switching network gives a very high interchannel isolation, reduced circuit complexity, and low input noise. Data rates of 200 Mbit's and switch reconfiguration times of -100 ns are achieved. System noise is calculated and measured, and the advantages of using fully integrated GaAs crossbar switch arrays are quantitatively discussed     

Semiconductor optoelectronic devices for free-space optical communications

LIGHT emitting devices based AlGaAs lasers are very useful radiation sources in free-space opticalcommunications systems. Following a brief review of the properties of individual injection lasers, more complex devices are described. These include (or are relevant to) monolithic integration configurations of the lasers with their electronic driving circuitry, power combining methods of semiconductor lasers, and electronic methods of steering the radiation patterns of semiconductor lasers and laser arrays. Fabrication of such devices is one of the major prerequisites for realizing fully the potential advantages of free-space optical communications.     

Multimode 2 × 2 optical crossbar switch

A monolithic electro-optical 2 × 2 crossbar has been developed. The multimode network consists of channel waveguides and four crosspoint switches integrated in a LiTaO3 plate. Matrix switching loss was 11 dB and crosstalk was ?16 dB for TM-polarised 0.07-n.a. light.     

Optoelectromechanical switch array with passively aligned free-space optical components

An all-optical switch array with micro mirrors driven by electrostatic micro motors has been developed in a LIGA-technique. The system has been designed for single mode application at the telecommunication wavelength of 1.55 /spl mu/m. All fixed optical components are passively aligned inside a LIGA-structured micro optical bench. The signals are detoured inside the optical bench by means of micro mirrors, which are attached to micro wobble motors. In order to avoid angular displacements of the deflected light beams double mirrors are used. First, prototypes with 2 input and output ports have been realized. Two of these 2 /spl times/ 2 switch matrices have been integrated on a 10 /spl times/ 10 mm/sup 2/ ceramic substrate with six micro motors of 1.7 mm diameter. Switching times down to 30 ms have been achieved. The crosstalk between different channels is 90 dB. The insertion loss with passive alignment of the optical elements yielded 3 dB with a repeatability better than /spl plusmn/0.3 dB.     

Rearrangeable multichannel free-space optical switch using polarisation multiplexing technique

A rearrangeable free-space optical multichannel switch using the polarisation multiplexing technique is examined. The switch consists of LCTV polarisation switches and routing elements. It is shown that the switch is suitable for network reconfiguration in parallel processing systems. A 32-channel prototype optical switch was constructed, and excellent switching performance and stable insertion loss were confirmed.<>     

基于色散的ATM自由空间光交换结构

根据波导型光交换的一些弱点，提出了一类克服以上缺点的基于色散异步转移模式（ＡＴＭ）的自由空间光交换结构，并对该结构进行了一些讨论。     

Performance of 4*4 optical crossbar switch utilising acousto-optic deflector

A multicasting photonic space switch reconfigurable in 50 ns is demonstrated utilising commercially available acousto-optic Bragg cells at lambda =0.83 mu m. Insertion loss of 15 dB, extinction ratio of 33 dB, crosstalk of -24 dB and polarisation difference of 0.8 dB are reported.<>     

Integrated optical/optoelectronic switch for parallel opticalinterconnects

A monolithic optical/optoelectronic switch for a reconfigurable, parallel optical interconnect is described. By integrating a vertical-cavity surface-emitting laser with a three-terminal GaAs-AlGaAs heterojunction phototransistor, the functions of an optical transceiver and an optical space switch are combined. Switching experiments demonstrate optical/optoelectronic switching and data conversion at 200 Mbit/s     

The optical crossbar switch for signal routeing on board communication satellites

A switch matrix operating on baseband or microwave signals is a critical element of communications satellites employing multiple beam antennas and on-board switching. Optical switching by spatial light modulators (SLMs) offers a means of implementing large and highly flexible switch arrays capable of routeing signals at baseband or microwave frequencies. This approach offers potential mass, power and size advantages compared to alternative technologies. The paper reviews the essential features of optical crossbar switch architectures based on SLMs and discusses options for the lasers, SLMs, interface optics and photodetectors. Proof-of-concept demonstrators for optical crossbar switches operating on both baseband and microwave signals are described. Finally, an outline design for a compact switch module is described and the critical component developments needed to realize this are identified.     

基于自由空间耦合技术光开关的实验研究

本文提出了一种基于自由空间耦合技术的新型光开关器件.该光开关是利用聚合物薄膜的电光效应,通过控制导模的耦合效率来进一步控制反射光强来实现光的通断,理论与实验表明:该器件具有响应速度快、消光比大、损耗小、稳定性高,与传统棱镜耦合方式的光开关器件相比其具有结构和制备工艺更加简单和成本低廉等诸多优点.     

Electrical and optical properties of the three-terminaldouble-heterostructure optoelectronic switch

A theory is developed for the three-terminal version of the double-heterojunction optoelectronic switch (DOES), in which the third terminal, the injector, makes ohmic contact to the active layer of the device. The injector permits the biasing of the active-layer-substrate junction, the effect of which is to reduce the threshold voltage at which switching from the electrical and optical OFF-state to the ON-state occurs. Reverse baising the junction initiates switching from the ON- to the OFF-state. The current and optical output as a function of voltage with the injector current as a parametric variable are plotted in terms of the physical and geometrical properties of the device     

Characteristics of a photoconductive detector as an optoelectronic switch

Measurements of the wavelength, signal frequency, and position sensitivities of GaAs field effect transistors used as photoconductive detectors are presented. Switching of the optical sensitivity by means of both the drain and gate voltages are demonstrated. The former method can provide the basis for employing such photoconductive detectors as optoelectronic wide-band switches. The observed properties of the field effect transistor (FET) devices studied shows that the design of photoconductive optoelectronic switches will involve compromises between sensitivity and isolation in choosing the operating wavelength, and among frequency response, power consumption, and physical size in choosing the physical layout of the device.     

Power complexity of multiplexer-based optoelectronic crossbar switches

The integration of thousands of optical input/output (I/O) devices and large electronic crossbar switching elements onto a single optoelectronic integrated circuit (IC) can place stringent power demands on the CMOS substrates. Currently, there is no sufficiently general analytic methodology for power analysis and power reduction of large-scale crossbar switching systems. An analysis of the power complexity of single-chip optoelectronic switches is presented, assuming the classic broadcast-and-select crossbar architecture. The analysis yields the distribution of power dissipation and allows for design optimization. Both unpipelined and pipelined designs are analyzed, and a technique to reduce power dissipation significantly is proposed. The design of a 5.12 Tbit single-chip optoelectronic switch using 0.18-/spl mu/m CMOS technology is illustrated. The pipelined switch design occupies < 70 mm/sup 2/ of CMOS area, and consumes <80 W of power, which compares favorably to the power required in electrical crossbar switches of equivalent capacity.     

A rearrangeable multichannel free-space optical switch based onmultistage network configuration

A rearrangeable 128×128-channel optical switch based on a multistage network configuration is demonstrated. The properties of optical components required for achieving up to 1000×1000-channel switches are discussed, taking into account the diffraction limit and liquid crystal light modulator (LCLM) crosstalk. An examination of the insertion loss and crosstalk properties of the switch reveals an average loss and crosstalk of 7.9 and -21.2 dB, respectively, and worst-case loss and crosstalk of 11.0 and -12.8 dB, respectively. Such low-loss and low-crosstalk properties indicate that the proposed switch structure is suitable for a large-scale rearrangeable switch     

Performance of a packet switch with crossbar architecture

A packet having a crossbar architecture with M inputs and N outputs is considered. Following earlier work, the theoretical capacity of such a switch is found in terms of the throughput of a closed queueing network. A state-dependent server model that approximates the rate at which the switch is transferring packets as a function of the work backlog (the number of packets queued at the switch inputs) is then developed. In this way, the model reflects the fact that such a switch tends to function more efficiently as the work backlog increases. This model yields an accurate method for approximating the entire distribution of the work backlog, as well as mean queue lengths and waiting times     

Optically-cascaded, multistage switching operation of a multifunctional binary optical/optoelectronic switch

Optically cascadable and multifunctional binary optical switches consisting of AlGaAs-GaAs vertical cavity surface-emitting lasers (VCSELs), heterojunction bipolar transistors (HBTs), and p-i-n photodetectors (PINs) have been realized. Each switching element consists of a pair of PIN/HBT/VCSEL switches that can perform optical switching and routing at a data rate of 100 Mb/s, and optoelectronic signal conversion at a data rate of 100 Mb/s, while achieving a peak dc optical gain of 18 and an ac optical gain of 4. Optically-cascaded, multistage switching operation has been demonstrated using two linear arrays of HBT/PIN/VCSEL switches, with an overall cascaded dc optical gain of 50 and an ac gain of 8.     

Theoretical model for a microsctip optoelectronic switch

A theoretical model is given to represent the active part of either an optoelectronic switch, similar to those described by Auston el al., or an optoelectronic gate such as the one we developed. These devices consist mainly of a microstrip line, with a characteristic impedance of 50 ?, which is deposited on a high-resistivity semiconductor. The centre strip has a break, creating a gap which can be illuminated by an optical laser pulse. The latter generates an electron-hole plasma of high density at the surface of the semiconductor, allowing the transmission of a signal across the gap.