Ultrafast switching dynamics of Mach-Zehnder interferometerswitches

We present results of cross-gain and cross-phase modulation experiments on InGaAsP-based semiconductor optical amplifiers and Mach-Zehnder interferometer (MZI) switches. For 150-fs input pulses, we observe strong spectral and pulse shape distortions of the signal pulse, especially in the pulse overlap regime. These pulse deteriorations are induced by subpicosecond gain and refractive index nonlinearities. In consequence, the ON-OFF ratio of the MZI switch is drastically reduced for subpicosecond switching windows. In the copropagation arrangement, the switching window with maximum transmission is shown to be limited to about 1.5 ps     

All-optical modulation and demultiplexing systems with significanttiming jitter tolerance through incorporation of pulse-shaping fiberBragg gratings

In this letter, we demonstrate the use of a superstructured fiber Bragg grating to preshape optical pulses to obtain optimal operation of nonlinear all-optical switches. Specifically, we demonstrate the conversion of 2.5-ps soliton pulses into 20-ps rectangular pulses at the input to both fiber and semiconductor optical amplifier-based switches, and show that rectangular switching windows can be achieved thereby providing a 5-10-fold reduction in timing jitter sensitivity. Error free penalty free optical time-division-multiplexing switching was readily achieved over a ±7-ps timing mismatch range for the square pulse driven fiber nonlinear optical loop mirror switch versus a ±1-ps range for the switch driven directly with 2.5-ps laser pulses     

PLC-based optical add/drop switch with automatic level control

A novel switch configuration for an optical add/drop multiplexer is proposed. By utilizing a certain Mach-Zehnder interferometer both as a component of a double-gate switch and as a level equalizer, we reduced the number of Mach-Zehnder interferometers from five in a conventional switch configuration to three. The add/drop switch simultaneously provides high-isolation switching and polarization-independent automatic level control. The use of planar lightwave circuit (PLC) technology enables this switch to be fabricated with three thermooptic switches (TOSWs) and a monitor tap. High isolation of more than 44 dB and automatic level control accuracy of better than 0.3 dB are achieved. Bit error rate (BER) measurements confirmed switch's usability in the optical add/drop multiplexer     

Hybrid optical switch using passive polymer waveguides andsemiconductor optical amplifiers

Optical switching can be performed by using optical amplifiers combined with a passive waveguiding network. Recently, most of the effort in optical amplifier switch modules have been focused on monolithic switches in which the entire device is fabricated on an InP substrate together with the semiconductor optical amplifiers (SOA's). In this paper, we investigate the use of SOA's with passive polymer waveguides to make hybrid switches of varying sizes. The optical amplifiers serve dual purposes, gating the signal and amplifying the signal. Amplification is needed in order to offset the losses associated with the passive waveguide elements as well as the losses from component misalignments in the switch module. Our analysis finds the largest switch module size that can be made with the architecture used. We also calculate the maximum number of switch modules which can be cascaded in order to retain a bit-error rate (BER) under 10^-9     

Silicon-integrated high-speed mode and polarization switch-and-selector

On-chip optical communications are growingly aiming at multimode operation together with mode-division multiplex-ing to further increase the transmission capacity.Optical switches,which are capable of optical signals switching at the nodes,play a key role in optical networks.We demonstrate a 2×2 electro-optic Mach-Zehnder interferometer-based mode-and polar-ization-selective switch fabricated by standard complementary metal-oxide-semiconductor process.An electro optic tuner based on a PN-doped junction in one of the Mach-Zehnder interferometer arms enables dynamic switching in 11 ns.For all the channels,the overall insertion losses and inter-modal crosstalk values are below 9.03 and-15.86 dB at 1550 nm,respect-ively.     

A photonic front-end processor in a WDM ATM multicast switch

Dense wavelength-division multiplexing (DWDM) technology has provided tremendous transmission capacity in optical fiber communications. However, switching and routing capacity is still far behind transmission capacity. This is because most of today's packet switches and routers are implemented using electronic technologies. Optical packet switches are the potential candidate to boost switching capacity to be comparable with transmission capacity. In this paper, we present a photonic asynchronous transfer mode (ATM) front-end processor that has been implemented and is to be used in an optically transparent WDM ATM multicast (3M) switch. We have successfully demonstrate the front-end processor in two different experiments. One performs cell delineation based on ITU standards and overwrites VCI/VPI optically at 2.5 Gb/s. The other performs cell synchronization, where cells from different input ports running at 2.5 Gb/s are phase-aligned in the optical domain before they are routed in the switch fabric. The resolution of alignment is achieved to the extent of 100 ps (or 1/4 bit). An integrated 1×2 Y-junction semiconductor optical amplifier (SOA) switch has been developed to facilitate the cell synchronizer     

半导体光波导开关列阵

光波导开关是光网络的基础器件。半导体中的电光效应、能带填充效应、多量子阱的量子限制Stark效应以及等离子体色散效应等都可分别被利用来制作成光波导开关。本文综合介绍基于上述效应的光波导开关的发展动态。     

Semiconductor space switches based on multimode interferencecouplers

It is shown theoretically that selective perturbation by electrorefractive effect of the even-order modes in III-V semiconductor multimode interference couplers gives rise to high-performance optical switching. The calculated performance of the proposed switch is 3.4 GHz/Vmm, compared to 0.85 GHz/Vmm for an equivalent Mach-Zehnder interferometer (MZI) switch. The effects of electroabsorption and dimension variations are analyzed to demonstrate the feasibility of the proposed device     

Broadband hitless bypass switch for integrated photonic circuits

A new microphotonic hitless switch is proposed. By enabling continuous, uninterrupted transition to a bypass path, it permits tuning of wavelength add-drop filters without disturbing intermediate channels. The scheme comprises two symmetrically actuated, 2 /spl times/ 2 /spl Delta//spl beta/-type optical switches, antisymmetrically cascaded in a balanced Mach-Zehnder configuration, and a /spl pi/ differential phase shift in the interferometer arms. By symmetry, it provides for wavelength-independent hitless operation before, during and after switch reconfiguration, permitting slow switching independent of bit rate. Compact implementations using high-index-contrast microelectromechanical-system (MEMS)-actuated switches are proposed.     

Comparison of gain clamped and conventional semiconductor optical amplifiers for fast all-optical switching

This paper reports computer simulation results to compare a Mach-Zehnder interferometer (MZI) when the two arms of it operate with gain-clamped and conventional semiconductor optical amplifiers (gcSOA and convSOA, respectively) for fast all-optical switching. The comparison is for demultiplexing optical pulses from 160 Gb/s to the base rate of 10 Gb/s or 40 Gb/s. The gain dynamics of the gcSOA is presented, the switching windows at the drop port of the MZI for both cases that were referred before and finally an evaluation of them is discussed.     

All-optical XOR in a semiconductor optical amplifier-assisted fiberSagnac gate

All-optical Boolean XOR is demonstrated on a high-speed serial bit stream with a three-optical input fiber Sagnac interferometer switch, which uses a semiconductor optical amplifier. Full duty cycle bit switching has been demonstrated up to 5 GHz with contrast ratio as high as 14.6 dB     

Optical Static RAM Cell

We demonstrate an optical static random access memory cell that provides read and write functionality at 5 Gb/s. The circuit comprises a hybridly integrated semiconductor optical amplifier-Mach-Zehnder interferometer (SOA-MZI) flip-flop serving as the memory unit and two additional SOA-based cross-gain modulation switches for controlling access to the memory cell.     

Delay time in GaAs high-power photoconductive switches

The delay time defined as the time interval between the beginning of optical illumination and the onset of switching in photocurrent in gallium arsenide (GaAs) high-power photoconductivity switches is studied on the basis of electroabsorption caused by absorption edge shifting due to bandgap narrowing. The influences of the initial open-state field, the laser wavelength and the temperature are given. The results show it is the reflection and the transmission of the switch semiconductor slab indicated by the absorption fraction express the absorption rate of the illumination energy by the switch     

Implementation of an All-Optical Time-Slot-Interchanger Architecture

We demonstrate a wavelength-converter-based optical time-slot-interchanger. It consists of three cascaded programmable delay stages and employs the first hybrid integrated, on a chip, quadruple array of semiconductor optical amplifier Mach-Zehnder interferometer switches. It exhibits error-free operation with 10-Gb/s nonreturn-to-zero packets and a power penalty of 1.8 dB.     

High-speed InGaAlAs-InAlAs MQW directional coupler waveguide switchmodules integrated with a spotsize converter having a lateral taper,thin-film core, and ridge

Fully packaged 2×2 and 4×4 semiconductor optical switch modules are successfully developed by integrating spotsize converters (SSCs) consisting of lateral tapers, thin-film cores, and ridges in InGaAlAs-InAlAs multiple quantum-well (MQW) directional coupler waveguide switches in the 1.55-μm wavelength region. Good reproducibility is obtained for the perfect coupling length of the directional coupler by appropriately designing the ridge width and gap of strip-loaded optical waveguides and by making use of the Cl₂ reactive-ion-beam-etching and successive wet-etching. Since the switching time is sufficiently short (<70 ps, which is limited by the driver speed) for the 4×4 switch module, no bits are lost during a 10-Gb/s switching experiment at a wavelength of 1.55 μm     

All-optical switching at multi-100-Gb/s data rates with Mach-Zehnder interferometer switches

We present experimental and theoretical results on ultrafast nonlinear dynamics in InGaAsP semiconductor optical amplifiers (SOAs). Carrier heating, spectral hole burning, and two-photon absorption are analyzed by heterodyne pump-probe experiments which deliver basic model parameters like gain-phase coupling parameters of the material. The impact on the device performance induced by these physical effects is verified by cross-gain/cross-phase experiments on InGaAsP-based SOAs and Mach-Zehnder interferometer switches. In the co-propagation arrangement, the switching window with maximum transmission is shown to be 1.5 ps which translates into demultiplexing capabilities beyond 600 Gb/s. Calculations based on a distributed rate equation model show that, for high-speed applications, the switching window can be limited by pulse saturation and by subpicosecond nonlinear effects.     

用于线圈发射器的三电极间隙开关系统

电磁线圈发射器工作需要能承受很高工作电压和很大工作电流的闭合开关,这些开关目前主要有半导体开关和间隙类开关。其中间隙类开关具有电感低、耐压高、寿命长、可靠性高等特点而被广泛使用。在理论分析的基础上设计了一套用于线圈发射器的三电极间隙开关系统,它包括光控部分、触发系统、开关器件3部分。光控信号控制触发系统产生陡化的脉冲高电压,脉冲高压接入三电极的触发极控制主电极导通。控制信号与触发部分采用光纤连接,隔离了高压对低压的干扰。控制电路用金属罩屏蔽,能够有效地在复杂电磁环境下运行。试验检验得到开关性能：延迟时间为1．2μs,抖动时间约300ns。开关系统满足了电磁线圈发射的需要。     

Switch energies of electronic and optical switches: a simplecomparative study

A comparison of the switch energies of electrically controlled optical absorption switches and electronic switches is performed. It is shown that in the investigated case with quantum box based absorption switches, the switch energies of the optical switches are generally orders of magnitude larger than those of the electronic switches for very high frequencies. Consequences on integration of optical devices as well as on the potential for photonic switching and processing are briefly discussed     

Improvement of switching time in a thermocapillarity optical switch

The switching time of existing thermocapillarity optical switches is about two orders of magnitude larger than that of other optical switches, such as a thermooptics switch and a free-space switch using microelectromechanical system technology. This paper reports a thermocapillarity switch whose switching time is comparable to that of the thermooptics and free-space switches. The greatly improved switching time is achieved by lowering the absolute viscosity of the refractive-index matching liquid and improving the switch design