Optoelectronic matrix switch using heterojunction switching photodiodes

Heterojunction switching photodiodes (InGaAs/InP) were used to construct a 3×3 matrix switch. Isolation and cross-talk losses were better than 63 dB over a frequency range of 10 Hz to 400 MHz and 400 Mbit/s digital signals were switched with switching times shorter than 30 ns.     

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.     

A double-barrier-emitter triangular-barrier optoelectronic switch

In this study, a triangular-barrier and a double-barrier structure are combined to form a double-barrier-emitter triangular-barrier optoelectronic switch (DTOS). In the structure center of the triangular barrier, a p-type delta-doped quantum well is inserted to enhance the hole confinement. Owing to the resonant tunneling through the double-barrier structure and avalanche multiplication in the reverse-biased junction, N-shaped and S-shaped negative-differential-resistance (NDR) phenomena occur in the current-voltage (I--V) characteristics under normal and reverse operation modes, respectively. The NDR characteristics show variations from dark to illumination conditions. Temperature effects on the NDRs of the DTOS are also obvious. The illumination and temperature influences on the device characteristics are investigated in this paper.     

8端口ATM工作组交换机设计与性能分析

本文概述了基于FPGA的8端口155Mbit/s(25Mbit/s)ATM工作组交换机的设计,对其关键部分如输入输出端口处理,交换结构等进行了阐述,并对其性能进行了分析,试验运行表明各项指标均满足设计要求。     

Design and performance analysis of an asynchronous non-blocking switch with window policy

In this paper, we propose an architecture of an asynchronous non-blocking switch. The switch structure is relatively simple, but it has an advantage in that the window scheme can easily be implemented. Many switch structures synchronized with time slots have been proposed, but they are not efficient when implementing a window scheme. The asynchronous switch proposed in this paper with its implementation of a window scheme can increase its maximum throughput up to 1 in the case of minimum changeover time and large packet size. We also investigate the delay characteristics of the asynchronous switch. In the analysis of delay characteristics, we make some approximations. However, the results of the analysis are in good agreement with simulation results. In addition, the maximum throughput of the switch with finite window size is investigated.     

Si/SiGe digital optoelectronic switch

The physical parameters and functional characteristics of a Si/SiGe digital optoelectronic switch are reported. The device is found to have bistable electrical states: a high-impedance (40 kΩ) OFF state connected to a low-impedance (100 Ω) ON state by a regime of negative differential resistance. The switching voltage and holding voltage are measured to be 2.6 and 1.3 V, respectively, and the switching current and holding current are measured to be 500 μA and 1 mA, respectively. These DC characteristics are found to be similar to those measured in double heterostructure optoelectronic switching devices manifested in the AlGaAs/GaAs materials system. The DC characteristics of this Si/SiGe digital optoelectronic switch are also found to be sensitive to optical input and temperature     

InP/InGaAsP double-heterostructure optoelectronic switch

The double-heterostructure optoelectronic switch (DOES), fabricated in the InP/InGaAsP material system, is demonstrated. The functional characteristics and operational parameters exhibit a lower switching voltage (≈1.8 V) and a higher on-state holding current (≈20 mA) than found in either the Si/SiGe- or GaAs/AlGaAs-based DOES of comparable structures and doping levels. In the on-state, optical emission is observed in a manner analogous to a light emitting diode. However, enhanced optical emission is observed when the device is biased in the regime of negative differential resistance     

Operation of an optoelectronic crossbar switch containing a terabit-per-second free-space optical interconnect

The experimental operation of a terabit-per-second scale optoelectronic connection to a silicon very-large-scale-integrated circuit is described. A demonstrator system, in the form of an optoelectronic crossbar switch, has been constructed as a technology test bed. The assembly and testing of the components making up the system, including a flip-chipped InGaAs-GaAs optical interface chip, are reported. Using optical inputs to the electronic switching chip, single-channel routing of data through the system at the design rate of 250 Mb/s (without internal fan-out) was achieved. With 4000 optical inputs, this corresponds to a potential aggregate data input of a terabit per second into the single 14.6 /spl times/ 15.6 mm CMOS chip. In addition 50-Mb/s data rates were switched utilizing the full internal optical fan-out included in the system to complete the required connectivity. This simultaneous input of data across the chip corresponds to an aggregate data input of 0.2 Tb/s. The experimental system also utilized optical distribution of clock signals across the CMOS chip.     

Different types of optoelectronic bistabilities inresonant-tunnelling triangular-barrier optoelectronic switch (R-TOPS)

Novel optoelectronic bistabilities in a resonant-tunnelling triangular-barrier optoelectronic switch (R-TOPS) are reported. Optically controlled S-shaped and N-shaped NDRs were observed simultaneously in a single device. Different types of optoelectronic bistabilities originated from S-shaped and N-shaped NDRs were obtained by changing the input light power     

Design and performance analysis of InP-based high-speed andhigh-sensitivity optoelectronic integrated receivers

A novel transimpedance optoelectronic receiver amplifier suitable for monolithic integration is proposed and analyzed by exploiting state-of-the-art high-speed MSM photodiodes and HBT's based on lattice-matched InGaAs-InAlAs heterostructures on InP substrates. The projected performance characteristics of this amplifier indicate a high transimpedance (≈3.6 kΩ), a large bandwidth (17 GHz), and an excellent optical detection sensitivity (-26.8 dBm) at 17 Gb/s for the standard bit-error-rate of 10^-9. The latter corresponds to an input noise spectral density, √(i_in²/B), of 2.29 pA/√(Hz) for the full bandwidth. The bandwidth of the amplifier can be increased to 30 GHz for a reduced transimpedance (0.82 kΩ) and a lower detection sensitivity, i.e., -21 dBm at 30 Gb/s. The amplifier also achieves a detected optical-to-electrical power gain of 21.5 dBm into a 50 Ω load termination. The design utilizes small emitter-area HBT's for the input cascoded-pair stage, followed by a two-step emitter-follower involving one small and one large emitter-area HBT's. The design strategy of using small emitter-area HBT's is matched by a low-capacitance novel series/parallel connected MSM photodiode. This combined approach has yielded this amplifier's combined high performance characteristics which exceed either achieved or projected performances of any receiver amplifier reported to-date. The paper also discusses the issues concerning IC implementation of the receiver, including the means of realizing a high-value feedback resistor     

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     

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     

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.     

Electrical switching speed of the double-heterostructure optoelectronic switch

The electrical switching speed of a new double-heterostructure optoelectronic switch (designated DOES) is measured in a relaxation oscillator circuit. A minimum value of capacitance was required to obtain oscillations. The turn-on speed was measured to be 100 ps. The turn-off speed was limited to the RC pull-up time.     

Multiwavelength performance of an apodized acousto-optic switch

Use of the acousto-optic switch as a wavelength-routing element in WDM networks is described. The need for deep isolation between wavelength channels has resulted in the search for efficient sidelobe suppression techniques such as tapering of the acousto-optic profile by imbedding an optical waveguide in one arm of an acoustic directional coupler. The theory of sidelobe-suppression in the optical transmission function of a SAW-coupler apodized acousto-optic filter is presented. A low-sidelobe SAW-coupler-apodized AO switch was fabricated and used in a 1.5 micron multi-wavelength WDM switching demonstration employing four 4 nm-spaced optical channels. Crosstalk was below -19 dB for single wavelength selection and below -15 dB for arbitrary routing patterns, a dramatic improvement over unapodized AO switches     

A reflex optoelectronic switching matrix

A novel method of rapidly composing any required signal delay or combination of delays from a set of precise fixed delay lines is described. Both simple delays and recirculating delay loops can be obtained. The construction of programmable ring resonators with both optical and electrical delay lines is demonstrated. Tunable comb filters with bandwidths up to 1 GHz were obtained. Since delays can be altered within nanoseconds, many applications in digital and analog signal processing can be realized.     

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     

An optoelectronic switch based on a triangular-barrier structure

A GaAs-InGaP triangular-barrier optoelectronic switch, grown by metalorganic chemical vapor deposition (MOCVD), is reported in the paper. Owing to the avalanche multiplication and hole confinement in the device operation, S-shaped negative-differential-resistance (NDR) performances are observed in the current-voltage (I-V) characteristics under both normal and reverse operation modes. The device also showed a flexible optical function related to the potential barrier height controllable by incident light. The dependency of the carrier transport mechanism on illumination, as well as the I-V characteristics at different temperatures, are investigated     

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     

New reflection-type optoelectronic microwave switch for CW applications

The operation of a new type of optoelectronic switch is described. Using the principle of an optically controlled reflection coefficient, the capacitive effects of conventional gap-discontinuity devices are eliminated and the insertion loss can be made extremely low. This switch offers the possibility in the millimetre wave range.<>