Design,fabrication and characterization of high-speed asymmetric Fabry-Perot modulators for optical interconnect applications

Free-space smart-pixel optical interconnect architectures promise to relieve the interconnect bottleneck in high-speed parallel computers and switching systems. One of the most promising output devices that has been advanced for use in these systems is the asymmetric Fabry-Perot modulator, or AFPM, which offers high on-off contrast, low insertion loss, and low operating voltage swing, among other advantages. In this paper we summarize our work on optimizing the AFPM for high-speed operation, including analysis of the material structure design considerations, fabrication of small (16×20 m) devices, and high-speed electrical and optical characterization of the finished modulators. We conclude that at relatively high incident optical intensities the modulators' speed appears to be limited by transit effects to about 18 GHz, but that at lower optical intensities their frequency response outstrips that of our 20 GHz measurement apparatus — that is, these AFPMs are still capable of large signal modulation (20 dB contrast, 1.5 dB insertion loss) at low AC voltage swings (±3 V) for operating frequencies up to 20 GHz. We presume that further investigation will prove them to be RC-limited in this low-intensity regime to speeds of about 35 GHz.     

Flexible integration of optical switch with optical power splitting and attenuating functions for optical fiber-based networking applications

A flexible integration of optical switch with optical power splitting and attenuating functions has been proposed to optimally serve optical fiber-based networking applications. In this switch, an etched binary-slope sidewall reflector is electrostatically actuated in and out of the plane to manipulate optical signals between input and output optical fibers. The fabrication process is a simple combination of a bulk-silicon micromachining process and silicon-to-glass anodic bonding where fiber alignment grooves, reflectors and actuators are fabricated on the same silicon substrate. Ball-lensed fibers are assembled with the device to achieve high coupling efficiency. Performances of the fabricated devices are measured and discussed. The switching time is less than 9 ms at 31 V. The excess loss of the device is less than 3 dB and the controllable attenuation range is up to 38 dB at 139 V, respectively. Moreover, polarization-dependent loss is less than 0.7 dB in the whole attenuation and splitting range.     

Tunable optical switch for DWDM systems

Characteristics of optical gratings on Si/SiGe heterostructures for switchable optical band-pass filters will be discussed. The grooves of the gratings have an angle of 45° to the propagation of light. The bandwidth can be as low as 0.2 nm. By reducing the refractive index of the SiGe layer due to injected free carriers it is possible to move the transmission band to lower wavelengths. In dense wavelength division multiplexing (DWDM) systems transmission channels can be selected by tuning the current. Therefore, the structure can be used as an electronic adjustable switch.     

Advanced multifunctional optical switch for multimode optical fiber networks

In this work, an advanced multifunctional optical switch based on multimode fibers is proposed. It can work as a 3 × 1 optical multiplexer/combiner, a 2 × 2 optical switch, a variable optical attenuator and a variable optical power splitter. All these functionalities can be developed in the same device without any hardware modification, only by using the proper ports and control electronics.The proposed switch has been developed for being used in the visible and near infrared wavelength range: 450–650 nm for optical fiber automobile applications, 650–850 nm for home broadband applications; and 850–1300 nm for multimode fiber access networks. Up to three different types of twisted nematic liquid crystal cells have been designed and fabricated for fulfilling these different wavelength ranges as part of the proposed device.The multifunctional switch has been implemented and experimentally tested. Crosstalk usually better than ? 15 dB at 532 nm, 660 nm and 850 nm, in any state has been measured. Switching is achieved at voltage levels of 4 Vrms. Fiber to fiber insertion losses when operating as a 2 × 2 optical switch, range from 10 to 15 dB within 200 nm wavelength range; with a non-optimized optics for collimation and coupling.     

Design of wavelength adjustable lasers with photonic crystal based Fabry-Perot etalon for applications in optical network units of wavelength-division-multiplexed passive optical network systems

We propose a novel wavelength adjustable laser (WAL) with a photonic crystal based Fabry-Perot (FP) etalon. This laser will be a promising light source for optical network units (ONUs) of conventional wavelength-division-multiplexed passive optical network (WDM-PON) systems for up-stream transmission. It has the merits of a relatively simple fabrication and operation, wide process tolerance, low-cost, high side-mode suppression ratio, and wavelength-tunable characteristics. The optimization of the device structure and the implementation methods for this type of laser are discussed. Although the WALs in WDM-PON systems are not colorless, each laser can cover several wavelengths. Thus, the required number of different ONUs can be reduced. This approach may be necessary for 10 Gbps upstream transmission in next-generation optical access networks because the 10 Gbps data rate is difficult to achieve by using current colorless schemes.     

Signal-processing algorithm for white-light optical fiber extrinsic Fabry-Perot interferometric sensors

We present a novel signal-processing algorithm for single-mode optical fiber extrinsic Fabry-Perot interferometric sensors that can achieve both high-resolution, absolute measurement of the cavity length and a large dynamic measurement range simultaneously. The algorithm is based on an accurate model of the characteristics of a fiber-optic sensor that takes into account the phase shift that is due to the coupling of light reflected at the second surface to the lead-in fiber end.     

Dispersive optical bistability in a Fabry-Perot cavity

This is a numerical analysis of the steady-state Maxwell-Bloch equations in a Fabry-Perot cavity with standing waves, atomic detuning and cavity mistuning; the atoms are homogeneously broadened. In the Mean-Field Approximation (MFA) limit, the resulting output-input characteristics agree exactly with the analytical predictions for a ring cavity. This leads to the derivation of a state equation for the Fabry-Perot cavity in the MFA limit identical to that for a ring cavity. Agreement with the MFA within 4% are obtained when αL < 3, the mirror reflectivity is above 90%, and the cavity mistuning below 4% of its free spectral range. Simulations beyond the scope of the MFA are also made and the case of purely dispersive optical bistability is also considered.     

Two-step enantio-selective optical switch

We present an optical "enantio-selective switch" that, in two steps, turns a ("racemic") mixture of left-handed and right-handed chiral molecules into the enantiomerically pure state of interest. The optical switch is composed of an "enantio-discriminator" and an "enantio-converter" acting in tandem. The method is robust, insensitive to decay processes, and does not require molecular preorientation. We demonstrate the method on the purification of a racemate of (transiently chiral) D2S2 molecules, performed on the nanosecond time scale.     

基于MEMS光开关的机群系统光互连网络

基于MEMS光开关设计了星型环型混合拓扑的光互连网络,为其开发了具有硬件路由功能的光互连网络控制卡(ONIC),以LAN为控制网络实现了对MEMS光开光的动态配置。提出了影响网络系统整体性能的关键因素,分析并测试了光互连网络的通信性能。环网稳定带宽达51Mb/s,峰值数据传输率可达1Gb/s,且数据量在3Mb以上时,网络整体性能明显提高。     

The C-number treatment for one-photon absorptive optical bistability in Fabry-Perot cavity

The problem of optical bistability in a standing wave cavity in the steady state leads to a pair of coupled, nonlinear, ordinary differential equations for the forward and backward waves. Here an approach different from the truncation of hierarchy and spatial average is applied to obtain this pair of equations. The results are compared with those obtained from the other approaches.     

Rigid reed-type routing switch for multimode optical fibers

Abstract

A mechanical switch developed earlier for routing light in multimode optical fibers has been improved by reducing its cubic volume, insertion loss, switching time, and required switching power. Using an immersion fluid, an insertion loss below 0.5 dB was realized. The switching time is shorter than 13 msec, and the required switching power less than 16 mW.     

Heater optimization for polymer in silica optical switch

An optimization process of specialized heater electrode design for a Multimode Interference (MMI) based polymer in silica thermo-optical switch is described. The switch is designed based on the waveguide structure of photodefinable BenzoCyclobutene (BCB 4024-40) polymer core, sandwiched by a 6 μm thickness of silica (SiO₂) upper clad layer and BK7 glass as a substrate. The upper clad thickness has been chosen such that to avoid any attenuation due to lossy behavior of the metal electrode. The light path is controlled by embedded thermal heater on top of the waveguide at specified location. Starting from a straight rectangular heater at pre-designed location, a migration technique and optimization toward a trapezoidal heater structure has been proposed which utterly claimed a significant improvement in terms of tuning power by more than 15%.     

Rigid reed-type routing switch for multimode optical fibers

A mechanical switch developed earlier for routing light in multimode optical fibers has been improved by reducing its cubic volume, insertion loss, switching time, and required switching power. Using an immersion fluid, an insertion loss below 0.5 dB was realized. The switching time is shorter than 13 msec, and the required switching power less than 16 mW.     

激光点火系统用高功率光纤光开关

 仿真和实验研究了一种控制Nd:YAG脉冲激光能量通断的光纤直接连接型光开关。建立光纤耦合模型,分析了光纤对准误差中对耦合效率的影响,其中横向偏移的影响最显著。采用微机电系统V型槽固定光纤,微小型凸轮作为制动器,步进电机驱动凸轮旋转,微小型凸轮与移动光纤相切,带动光纤移动,实现两光纤的错开和对准。制造了这种高功率直接连接型光纤光开关原理样机,并进行了主要性能测试。测试结果表明,这种光开关能够满足激光点火系统的大容量、高隔离度的要求。     

Optical power equalization using Fabry-Perot semiconductor optical amplifier

A novel scheme of optical power equalization based on Fabry-Perot semiconductor optical amplifier (FPSOA) is proposed. Because of the gain characteristic of FP-SOA, real-time controlling mechanism according to input optical power is aborted in the scheme. The simulations show that 10-dB pulse peak power variation can be clamped in less than i dB. The influences of injecting current, pulse periods, and pulse width are discussed.     

Atom-loss-induced quantum optical bi-stability switch

We investigate the nonlinear dynamics of a system composed of a cigar-shaped Bose-Einstein condensate and an optical cavity with the two sides coupled dispersively.By adopting discrete-mode approximation for the condensate,taking atom loss as a necessary part of the model to analyze the evolution of the system,while using trial and error method to find out steady states of the system as a reference,numerical simulation demonstrates that with a constant pump,atom loss will trigger a quantum optical bi-stability switch,which predicts a new interesting phenomenon for experiments to verify.     

数字光开关网络中四功能交换开关光学Omega网络

本文提出了一种用于数字光开关网络中，四功能交换开关光学Ｏｍｅｇａ网络。文中详细地阐述了用液晶空间光调制方法实现光学四功能交换开关，和Ｏｍｅｇａ互连网络的原理，并给出了光学系统和实验结果。     

Injection locked Fabry-Perot laser diodes for WDM passive optical network spare function

In this paper, a protection scheme for transmitters in wavelength-division-multiplexing passive optical network (WDM-PON) has been proposed and demonstrated. If any downstream transmitter encounters problems at the central office (CO), the interrupted communication can be restored immediately by injecting a Fabry-Perot laser diode (FP-LD) with the upstream lightwave corresponding to the failure transmitter. Compared with the conventional methods, this proposed architecture provides a cost-effective and reliable protection scheme employing a common FP-LD. In the experiment, a 1:36 protection capability was implemented with a 2.5 Gbit/s downstream transmission capability.     

Steady-state formulation of optical bistability for a Doppler-broadened medium in a Fabry-Perot

A two-level model for absorptive and dispersive bistability in a Fabry-Perot is described. Doppler broadening and the effects of atomic motion through the standing wave field are included. Numerical results illustrating saturation of the Doppler line are presented and bistable transmission characteristics are obtained for systems with varying degrees of Doppler broadening.