Low crosstalk 4 × 4 TiLiNbO3optical switch with permanently attached polarization maintaining fiber array

Several low crosstalk 4 × 4 crossbar optical switch arrays have been fabricated for use atlambda = 1.3 mum. Each array consists of 16 independently functioning directional coupler switches. We describe the typical device performance characteristics. The average insertion loss is 5.2 dB. Crosstalk levels routinely measured < -35 dB. The voltage required to operate the device is ≈ 13 V. The inputs to one of the device arrays were permanently attached to four laser transmitters using lensed polarization maintaining fiber at the laser end and an array of polarization maintaining fibers at the device end.     

A novel 1×4 coupler-multiplexer permutation switch for WDMapplications

A novel 1×4 coupler multiplexer permutation switch (CMPS) is proposed for applications in wavelength-division-multiplexing (WDM) optical networks. The structure of the CMPS integrates the multiplexing and switching functions into a single compact device. It consists of a single-mode/multimode-waveguide grating-assisted, backward-coupler multiplexer followed by a 1×4 digital optical switch (DOS). The specific design uses an InP-based 1×4 CMPS with InGaAsP-InP multiple-quantum-well (MQW) DOS. The calculated values of crosstalk for the coupler multiplexer and the DOS are <-25 dB and -23 dB, respectively, giving an overall crosstalk <-21 dB for channel bandwidths of 10-13 GHz. The device channels are unequally spaced, which reduces unwanted four-wave mixing (FWM), but are fitted to the ITU standard wavelength grid     

A low-voltage 8×8 Ti:LiNbO3 switch with adilated-Benes architecture

An 8×8 switch array with a dilated-Benes architecture that greatly relaxes the crosspoint extinction ratio requirements needed to achieve low overall switch array crosstalk is discussed. This, combined with the low uniform switching voltages (9.2+0.2 V) of the 48 directional coupler crosspoints, facilitates high-speed low-crosstalk operation. The crosspoints can be switched in about 1 ns. The switch array is fully packaged with permanently attached single-mode fiber pigtails. The high data transfer rate inherent in lithium niobate switches in general, combined with the low crosstalk and high switching speed of this switch array, is a good match to the requirements of time-multiplexing switching     

Y-cut LiNbO3 directional coupler with a self-alignedelectrode

A 2×2 Y-cut LiNbO₃ directional coupler switch using a self-aligned uniform Δβ electrode is fabricated by the proton diffusion method. Our design method makes it possible to form the electrode without the delicate alignment of the electrode pattern mask and optical waveguide. The switching voltage is also reduced due to the enhanced electro-optic efficiency by using the self-aligned electrode. To achieve the initial cross state of the uniform Δβ switch that is essential for low crosstalk, we control the proton diffusion time successively after the proton exchange. The measured crosstalk level of the directional coupler switch is -23 dB~-29 dB and its voltage-length product is as small as 9.6 Vmm     

低串扰载流子注入型光开关的设计

针对载流子注入马赫-曾德尔干涉型光开关,提出使用输出比可调的3dB耦合器,补偿相移臂上通过载流子注入实现π相位调制所产生的吸收损耗,从而降低光开关的串扰。使用传输矩阵方法计算分析了载流子注入所伴随的吸收损耗对光开关串扰的影响,同时计算了可调3dB耦合器对光开关串扰性能的改进。计算结果表明,可调3dB耦合器的引入可以有效补偿相移臂的吸收损耗,对改善光开关的串扰性能有着明显的作用。     

2×2多模干涉光开关的设计与制作

以多模干涉耦合器为主体,通过载流子注入效应所引起的折射率改变来调整二重像之间的相位差,当折射率下降所引起的相位改变达到π相位时完成开关功能。在AlGaAs/GaAs/AlGaAs外延材料上,利用两步湿法腐蚀工艺,实际制作了2×2光开关并进行了测试。测试结果表明,工作在1.55μm波段,当注入电流达到160mA时,完成了开关功能。     

4*4 directional coupler switch matrix with an InGaAlAs/InAlAs multiquantum well structure

A 4*4 directional coupler switch matrix is developed which uses, for the first time, the quantum confined Stark effect of InGaAlAs/InAlAs multiquantum well structures. The rearrangeable nonblocking 4*4 network with six 2*2 switches is shown to be perfectly functional with switching voltages between 5 and 6 V and crosstalk below -17 dB in all the operation states.<>     

4 × 4 optical-gate matrix switch

An optical gate-based matrix switch is proposed and a switching function in a 4 × 4 experimental switch is demonstrated. The experimental switch is composed of fiber-type splitters, a lantham-modified lead zirconate-titanate solid solution (PLZT) optical-gate array, and fiber-type combiners. The switch has a broad bandwidth of 400 Mbit/s for nonreturn-to-zero (NRZ) optical signal transmission. A possible maximum matrix size is discussed theoretically based on optical power level and optical crosstalk.     

Holographic optical switching: the “ROSES” demonstrator

The design, assembly, and performance of a prototype 1×8 free-space switch demonstrator using reconfigurable holograms are reported. Central to the switch fabric is a ferroelectric liquid crystal (FLC) on silicon spatial light modulator (SLM) deposited with a 540×1 array of highly reflective and planar mirror strips. The input and output ports of the switch are fabricated as a linear array of silica planar waveguides connected to single-mode fibers, and the holographic beam-steerer operates without the need for adjustment or dynamic alignment. The waveguide array and the single Fourier transform lens for the 2f holographic replay system are housed in an opto-mechanical mount to provide stability. The switch operates at 1.55 μm wavelength and has a designed optical bandwidth of >60 nm. The first measured insertion loss and crosstalk figures are 16.9 dB and -19.1 dB, respectively. Improvements in SLM performance, the use of new addressing schemes and the introduction of better alignment techniques are expected to improve these figures considerably. The preliminary performance of a 3×3 optical crossconnect is also presented to show that this technology is scalable to N×N switching fabrics     

Linear crosstalk in 4×4 semiconductor optical amplifier gateswitch matrix

We report a comprehensive crosstalk investigation of a packaged InGaAsP/InP 4×4 semiconductor optical amplifier gate switch matrix, experimentally as well as theoretically. For a fully loaded switch with the same wavelength on all four inputs, all possible switching combinations are analyzed, thus yielding realistic crosstalk figures. Coherent and incoherent crosstalk phenomena are identified, and a switch crosstalk less than -40 dB has been measured     

Fluctuational crosstalk in Ti:LiNbO3 directional couplerswitches

It has been found that the fluctuations in the Ti concentration along waveguides of Ti:LiNbO₃ directional coupler switches degrade the switch extinction ratio and introduce an unwanted crosstalk between both channels. We discuss analytically the effect of effective optical index fluctuations on the transfer matrix of the optical switch. We demonstrate the sensitivity of the mismatch to the statistics of the fluctuations of the Ti concentration     

Multimode interference photonic switches (MIPS)

The switching characteristics of multimode interference photonic switches (MIPS) are analyzed by wide-angle finite difference beam propagation method (FD-BPM). As a result, it is found that the MIPS with a multimode interference (MMI) length of 599 μm can switch the output light polarization insensitively with a crosstalk of less than -20 dB for a wavelength range of 70 nm. These analyses show that the MIPS can also have a 3-dB coupler function. Experimentally, an InGaAsP/InP 1×2 MIPS with a thicker InP cladding layer was fabricated and exhibited switching operation with crosstalks of -8 dB and -10 dB at 0 and 20 mA current injections, respectively. For a 2×2 MIPS with a thinner InP cladding layer, better switching characteristics with a crosstalk of -13 dB and an extinction ratio of 17 dB were realized     

Tunable MQW-DBR laser with monolithically integrated GaInAsP/InP directional coupler switch

The authors report the successful monolithic integration of a GaInAsP/InP single-mode Delta kappa directional coupler switch with a 4-section tunable multiple-quantum-well distributed Bragg reflector laser. They obtain several mW of output power through the switch, with approximately 10 dB crosstalk either from the internal laser source or with external light injected through the parallel input port.<>     

光开关串扰及其对光控相控阵列系统的影响研究

建立了光开关时延波束形成网络中光开关串扰和光控相控阵列的模型,在此基础上,通过计算机数值仿真,研究了光开关串扰对光控阵列方向图,包括最大值指向偏移、旁瓣电平的影响以及对阵列接收的线性调频(LFM)雷达信号的脉冲压缩的影响。仿真结果表明光开关的串扰比应小于20dB。     

多波长光交叉连接节点的优化设计

在WDM光网络中，光交叉连接（OXC）节点的串扰是限制网络规模的关键因素，提高光开关的隔离度是降低OXC串扰的一条途径，文章比较了3种不同结构的光开关矩阵的串扰特性，在此基础上对OXC节点进行了优化设计，改进后的OXC节点的串扰性能大的改善，网络规模也因此而得到了极大地扩展。     

基于热光效应的1×4聚合物数字光开关

提出了基于热光型聚合物的集成有S弯曲光衰减器的1×4 Y分叉数字光开关.利用开关与光纤阵列耦合用的S弯曲,将其设计成可变光衰减器,这使得器件更紧凑,并获得低串扰和大分叉角.在小于200mW的驱动功耗下,器件串扰可低至-35dB.     

Hybrid polymer/silica vertical coupler switch with <-32 dBpolarisation-independent crosstalk

A modified hybrid polymer/silica 1×2 vertical coupler switch (VCS) with a polymer gap layer and a refractive index contrast of 0.008 has been designed, fabricated and characterised. The VCS exhibits low loss, low crosstalk, low switching power, and polarisation insensitivity. Using the 1×2 VCS as a building block, a 1×8 VCS matrix has been implemented     

Carrier-injected GaInAsP/InP directional coupler optical switchwith both tapered velocity and tapered coupling

For most applications, a quasi-digital switching response is desired. The authors report on the design and fabrication of a 2×2 `digital' optical switch in GaInAsP/InP based on a directional coupler with both tapered velocity and tapered coupling and designed to be in the cross state at the zero bias condition. Complete power transfer to the cross output port for both TE and TM polarizations has been realized in the passive couplers for a wide range of device lengths proving the theoretically predicted fabrication tolerances. In the very first controllable device, switching operation with a crosstalk of -7 dB has been achieved using carrier injection     

Dilated Networks for Photonic Switching

We present some novel architectures for rearrangeably nonblocking multistage photonic space switches implemented using arrays ofTi:LiNbO_{3}directional couplers. Multistage networks, studied mostly in the electronic domain, are obtained by minimizing the number of 2 × 2 elements needed to implement a switch. Unfortunately, straightforward extensions of these networks to the photonic domain show that the switch size has to be severely limited by the crosstalk in each of theTi:LiNbO_{3} 2 times 2switching elements. Our networks, on the other hand, have a controllable (including almost zero) amount of crosstalk, low optical path loss, and an asymptotically optimal number of directional coupler switches for a given switch size. In addition, the switch has a simple control algorithm and its performance for light loading appears very promising. The switch is easily decomposable into smaller arrays of no more than two types, making it easy to partition the switch into chips. At the cost of a slight increase in crosstalk, the switch can be made single fault tolerant in terms of its ability to connect any input to any output.     

A phased array optical scanning (PHAROS) device used as a 1-to-9way switch

An optical switch is demonstrated which uses a phased array of 30 closely spaced, individually addressed electrooptic AlGaAs-GaAs waveguides to focus and steer a light beam under electronic control in a planar output waveguide. A small and potentially very high speed 1-to-9 way optical switch, (with -15 dB of crosstalk) was made by placing an array of nine output waveguides at different positions in a focal plane 1 mm from the end of the electrooptic array