Design and performance of an optical path cross-connect systembased on wavelength path concept

This paper describes the system design and performance of an optical path cross-connect (OPXC) system based on wavelength path concept. The (OPXC) is designed to offer 16 sets of input and output fiber ports with each fiber transporting eight multiwavelength signals for optical paths. Each optical path has a capacity of 2.5 Gb/s. Consequently, the total system throughput is 8×16×2.5=320 Gb/s and the OPXC features high modularity and expandability for switch components. By exploiting planar lightwave circuit (PLC) technologies, four sets of (8×16) delivery-and-coupling-type optical switches (DC-switches) are developed for the 320 Gb/s throughput OPXC system. The DC-switch offers the average insertion-loss of 12.6 dB and ON/OFF ratio of 42.1 dB. The PLC arrayed-waveguide gratings are confirmed to successfully demultiplex the eight directly modulated signals, multiplexed at a spacing of 1 nm, with a crosstalk of under -25 dB. Eight wavelength-division multiplexing signals, directly modulated at 2.5 Gb/s, are confirmed to be transported over 330 km via a cross-connection node in the test-bed system that simulates five-node network. The experimental performances demonstrated In this paper ensures full scale implementation of the proposed optical path cross-connect system with 320 Gb/s throughput and high integrity     

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.     

Compact versatile thermooptical space switch based on beam steeringby a waveguide array

We present the implementation of an optical space switching concept based on thermooptic beam steering in an arrayed waveguide grating. Individual addressing of heaters on the array waveguides enables flexible switching of input signals to output waveguide channels. The switch can be used either as a 1-to-8 switch or as multiple parallel 1-to-4, 1-to-3, or 1-to-2 switches. For the implementation we used high-refractive-index SiON-SiO₂ planar waveguide technology, which allows the realization of compact devices using small bending radii. We achieved isolations of the “off'” channels with respect to the “on” channel of up to 29 dB for a 1-to-3 switch or better than 22 dB for all “off” waveguides for a 1-to-8 switch     

Four-channel polarization-insensitive optically transparent wavelength converter

Multichannel wavelength converters may be important components in the cross-connects in future wavelength-division multiplexed (WDM) transport networks. We demonstrate a multichannel, polarization-insensitive, optically transparent wavelength converter, based on four-wave mixing in two semiconductor optical amplifiers in a polarization-diversity arrangement. Bit-error-rate (BER) measurements with four input 2.5-Gb/s WDM channels, spaced by 2 nm, show penalties for wavelength conversion less than 2.6 dB at 10/sup -9/ BER. Changes in the state of polarization of the input signals cause the output power to change by less than 1.2 dB, and the corresponding power penalties change by less than 0.9 dB.     

Passive optical equalization of wavelength converters based onfour-wave mixing in semiconductor optical amplifiers

We demonstrate equalization of the frequency-shift dependent conversion efficiency of four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs). The wavelength converter provides fixed input tunable output wavelength conversion for ten wavelength-division-multiplexing (WDM) channels with 100-GHz spacing. Equalization is achieved by using a fiber Bragg grating (FBG) at the output of the fixed input tunable output wavelength converter. This method provides constant conversion efficiency to within ±1.5 dB over all WDM channels and can be easily adapted to other types of wavelength conversion     

Multichannel operation of an integrated acoustooptic wavelengthrouting switch for WDM systems

Polarization independent acousto-optic tunable filters (PIAOTF's) can operate as transparent wavelength-selective crossconnects to route signals in wavelength division multiplexed optical networks. In this paper, a new low power PIAOTF is characterized as a switch in multiwavelength operation, using four equally spaced lightwave signals with wavelengths between 1546 nm and 1558 nm. Interchannel interference due to sidelobe excitation is lower than -11 dB for single wavelength switching and is equal to -6 dB in the extreme case of simultaneous switching of all wavelength channels. Sources of interport and interchannel crosstalk for single and multiple wavelength switching are identified     

Quality improvement of the dual-wavelength signals in DLOB via power equalization

The data packet buffeting can be implemented in dual loop optical buffer （DLOB） through cross-phase modulation （XPM） between the control signal and the data packets. However, the output equality of dual wavelength signals will degrade due to the unbalanced gain and phase shift. This problem can be resolved by power oqualizafion using the saturation characteristics of SOA. The data packets with 2.5 Gb/s can be buffered in DLOB for 16 cycles corresponding to 16.5 μs.The extinction ratio of the output packet is 8 dB while the S/N is 8.1 dB.     

High-output-power polarization-insensitive semiconductor optical amplifier

A high-output-power 1550 nm polarization-insensitive semiconductor optical amplifier (SOA) was developed for use as a compact in-line optical amplifier. A very thin tensile-strained bulk structure was used for the active layer and active width-tapered spot-size converters (SSCs) were integrated on both input and output sides. The SOA module exhibited a high saturation output power of +17 dBm together with a low noise figure of 7 dB, large gain of 19 dB, and low polarization sensitivity of 0.2 dB for optical signals of 1550 nm wavelength. For the amplification of optical signals modulated at 10 Gb/s in the nonreturn-to-zero (NRZ) format, a good eye pattern without waveform distortion due to the pattern effect was obtained at an average output power of up to +12 dBm. Additionally, good amplification characteristics were demonstrated for the signal wavelength range corresponding to the C-band.     

A 10-Gb/s high-isolation, 16×16 crosspoint switch implementedwith AlGaAs/GaAs HBT's

A high-isolation, 16×16 crosspoint switch is reported, capable of aggregate data throughput of 160 Gb/s with low crosstalk and output jitter. Each of the 16 fully asynchronous channels can transmit data at rates up to 10 Gb/s with a worst case r.m.s. output jitter of 4 ps. Single channel operation output jitter below 2.8 ps r.m.s. has been demonstrated. The high-isolation circuitry allows for inter-channel crosstalk isolation of more than 40 dB with all channels operative. The circuit is based on AlGaAs/GaAs heterojunction bipolar transistor technology     

Tuning technique to optimize input power of a cross-phase modulation wavelength converter

This paper proposes a tuning technique to optimize the input power of a cross-phase modulation wavelength converter (XPM-WC). The focus is on an output signal whose wavelength is the same as the input signal. The optimum input power can be easily set by keeping the output signal (not converted signal) power constant. Input continuous-wave (CW) power should be increased or decreased with increasing or decreasing input signal power so that the output signal power stays fixed at the optimum level. Observing the eye pattern of the converted signal is unnecessary. Wavelength conversion from a fixed optical channel to a random one (30 channels with 100-GHz spacing) is successfully demonstrated by using this technique. A low-power penalty (<1dB) and a low-power fluctuation (<1dB) were confirmed in all optical channels. An XPM-WC unit containing a variable CW light source and its level controller were fabricated and simultaneous and automatic operation was confirmed.     

1.55μm SiGe 2×3光开关

利用多模干涉效应和自由载流子等离子体色散效应设计和模拟了基于1.55μm波长的2×3 SiGe光开关.该光开关由两个单模输入端口、一个多模干涉区和三个单模输出端口构成.在多模干涉区,设有两个折射率调制区,可以利用来把从两个输入端口输入的光信号分别从三个输出端口输出.束传播法分析结果表明,该光开关的传输损耗小于1.43dB,串扰在-18～-32.8dB之间.     

4×4 OEIC switch module using GaAs substrate

A compact 4×4 optical switch module consisting of a monolithic 4-channel OEIC receiver chip, a 4×4 GaAs IC chip, and a 4-channel OEIC transmitter chip has been developed for the first time. The module offers good performance, without an optical loss, a bandwidth of more than 600 MHz, and a crosstalk between neighboring channels of less than -20 dB. It has a good switching and distributive performance for high speed optical input signals of 560 Mbit/s. The switch module is attractive for use in high data-rate optical communication systems, particularly in local area networks, CATV systems, and intra-office links     

A 70-Mbit/s (RZ) 16×16 crosspoint switch for ternary-encodedsignals

An experimental 16×16 crosspoint switch that can switch ternary signals and handle data rates of up to 70 Mb/s return-to-zero (RZ) (equivalent to 140-Mb/s nonreturn-to-zero (NRZ)) per channel is described. Ternary signals, in particular, alternate mark inversion (AMI) encoded signals, are widely used in telephone interoffice digital-transmission systems. This chip could be used in an asynchronous cross-connection system at the DS3 (44.736-Mb/s) signal level. This crosspoint chip has 16 input and 16 output channels. Any input can be connected to any output or outputs without blocking. The architecture allows for paralleling many chips to increase the size of the crosspoint array and also for cascading them to provide multistage switching capability. The switch can be addressed in the same way as a memory chip, and the cross-connection map can be written to and read back from the device. The chip is fabricated using a standard 2-μm CMOS technology, and the die size is 20.16 mm² (177.2×176.4 mil), containing about 11000 transistors     

1092 Channel 2-D Array Demultiplexer for Ultralarge Data Bandwidth

We demonstrate 1 x 1092 channel wavelength demultiplexing with 50-GHz channel pitch and a 600-nm total bandwidth. Outputs from 1 x 40 channel arrayed waveguide gratings operating with multiple orders enter a free-space optical grating demultiplexer which separates the orders into a 2-D spot array, where the light can be coupled into discrete output fibers or operated on by a surface normal device (i.e., microelectromechanical system switch or detector array). Supercontinuum source input from 1140 to 1750 nm produced a 28 times 39 spot array at the output plane. The insertion loss for light is coupled into a single mode fiber ranged from 7 to 18 dB with less than 10-dB loss in channels between 1300 and 1750 nm. Bit-error-rate measurements show a negligible 0.1-dB power penalty at 10 GB/s.     

Simultaneous fast wavelength switching and intensity modulationusing a tunable DBR laser

The use of a three-section distributed Bragg reflector (DBR) laser to switch wavelengths rapidly and simultaneously transmit data by intensity modulation is discussed. This combination simulates the operation of a tunable transmitter in a multiwavelength packet switch. In this type of switch, each output port is tuned to receive data on a unique, fixed wavelength; packets are routed from input ports to the appropriate output ports by wavelength addressing. In each transmission cycle, the input port transmitter tunes to the wavelength associated with the intended output port and subsequently broadcasts the data packet. Limitations on various system parameters, such as the number of allowed channels, the wavelength switching times, and packet lengths (residency times), as determined by thermally-induced wavelength drifts are also discussed. The advantages of using a single device for both fast wavelength switching and direct data modulation are significant: the elimination of external modulators improves both the simplicity of the implementation and the available power budget     

Regenerative all-optical wavelength multicast for next generation WDM network and system applications

We experimentally demonstrate regenerative all-optical wavelength multicast by simultaneous multi-wavelength conversion of 10 Gb/s non-return-to-zero signals to four ITU 100 GHz spaced channels with a receiver sensitivity improvement of 1.84 dB and less than 0.14 dB difference among all the multicast channels, using a single commercial monolithically integrated SOA-MZI. The multicast device also exhibited about 22 dB optical signal-to-noise ratio enhancement for all the converted channels compared to the original signal channel without wavelength conversion. Our experiment for the first time revealed the regeneration properties of a SOA-MZI device for WDM wavelength multicast purposes, and proved the excellent performance of a simple scheme for various future network and system applications, such as all-optical wavelength routing and grid networking.     

A novel all-optical switch: the wavelength recognizing switch

A new class of an all-optical switch-the wavelength recognizing switch is proposed and experimentally demonstrated. The device uses a control signal to sense the wavelength of the input packet and taps a portion of the data packet to the appropriate output port. The device is based on noncollinear four-wave mixing in a broad-area traveling-wave semiconductor optical amplifier. Measured switching efficiency is +8.2 dB with -28.8 dB of crosstalk. The recognition bandwidth is as narrow as 0.03 /spl Aring/ and the 3-dB switching bandwidth is 42 nm.     

8×8 symmetric nonblocking integrated acoustooptic spaceswitch module on LiNbO3

An 8×8 symmetric nonblocking integrated acoustooptic space switch module has been realized on a Y-cut LiNbO₃ substrate, 1.0×10.0×37.0 mm in size. The switch module consists of a new hybrid beam expanding-collimating lens, a large aperture focusing lens, and a pair of four-element tilted surface acoustic wave (SAW) transducer arrays in a titanium-in-diffused channel-planar-channel composite waveguide. Experimental results of point-to-point nonblocking switching at the optical wavelength of 0.6328 μm, including an average crosstalk of -12.2 dB, optical switching efficiency of 25% at 125 mW RF drive power, carrier frequency increment of 13.5 MHz for switching between adjacent output channels and reconfiguration time of 0.4 μs have been obtained     

16-channel optical FDM distribution/transmission experiment utilising Er/sup 3+/-doped fibre amplifier

A 16-channel optical FDM distribution/transmission experiment at around 1534 nm wavelength is demonstrated utilising an Er/sup 3+/-doped fibre amplifier. 16 intensity-modulated optical signals at 622 Mbit/s were amplified simultaneously at a gain of 15.2-18.5 dB. One of the amplified signals is selected using the waveguide frequency selection switch and directly detected with a receiver sensitivity of -38 dBm (P/sub e/=10/sup -9/).<>     

SOI基PLC型阵列波导光栅与可调光衰减器单片集成

制作了基于绝缘体上硅(Silicon on Insulator,SOI)材料的8×16通道的阵列波导光栅(Arrayed Waveguide Grating,AWG)与电吸收型可调光衰减器(Variable OpticalAttenuator,VOA)的单片集成器件,其信道间隔为200 GHz.该集成器件采用脊形波导结构,其截面尺寸为亚微米级,整体尺寸为2.9 mm×1 mm.该VMUX器件的片上损耗为9.324～10.048 dB,串扰为6.5～8.2 dB;在20 dB衰减下,单通道最大功耗为87.98 mW;最大信道偏振相关损耗(Polarization Dependent Loss,PDL)为0.461 dB,16通道的衰减一致性为0.245 dB.该器件能够实现良好的波分复用/解复用及信道功率均衡的功能.