双泵浦偏振无关SOA波长转换器

提出一种圆偏振泵浦光注入SOA的NDFWM波长转换方法,此方法不仅可消除偏振相关性,而且能在较宽的波长范围提高波长转换的效率.     

Four-channel integrated-optic wavelength demultiplexer with weakpolarization dependence

A planar four-channel wavelength demultiplexer with weak polarization dependence is proposed and demonstrated. This demultiplexer is based on an optical-phased array. An experimental device with dimensions 4.5×3.2 mm² was designed and fabricated, using conventional (high-quality) optical lithography. The demultiplexer operates in the wavelength range 776.5-781.2 nm, with a channel spacing of 1.55 nm. Insertion loss was 0.6 dB for the central channels and 1.2 dB for the outer channels for transverse-electric (TE) polarization, excluding 1.3-dB waveguide propagation loss. Crosstalk values measured 15.4-29.7 dB for the TE and 13.4-22.2 dB for the transverse-magnetic (TM) polarization     

Four-channel wavelength division multiplexers and bandpass filtersbased on elliptical Bragg reflectors

Four-channel multiplexers and four-wavelength bandpass filters based on elliptical Bragg reflectors (EBRs) are discussed. The channel spacing is 50 Å near 1.56 μm. The EBRs are narrowband elliptical mirrors that can refocus light from an input waveguide to any one of a number of output waveguides. Spectrally, they perform similarly to Bragg reflectors. The devices were fabricated on silicon using silica-based waveguide technology. The elliptical gratings with 0.53-μm periods were patterned using deep UV spatial frequency doubling photolithography. Multiplexers with single filtering and double filtering were demonstrated. With single filtering, the fiber-to-fiber insertion loss was 3.0±0.5 dB, and the crosstalk was -20 dB; with double filtering, the insertion loss was 4.0±0.5 dB, and the crosstalk was -30 dB. About 2 dB of this loss was due to coupling between the fibers and the waveguide. The additive loss associated with the EBR, including propagation, Bragg reflection, and coupling between input and output waveguides, was about 1 dB     

A novel interferometric wavelength converter

The fiber Kerr effect employment in a wavelength conversion version, owing to low silica nonlinearity, has been prevented by the lack of an efficient interferometric architecture. A novel all-fiber wavelength converter is presented and characterized. The proposed scheme while taking advantage of the Kerr effect properties in standard communication optical fiber overcomes classical interferometric structure limitations, such as high environmental sensitivity and difficult operating management. A comparison with these architectures is discussed. Operation up to 3 Gb/s is demonstrated in the whole third communication window     

System design and optimization of optically amplified WDM-TDMhybrid polarization-insensitive fiber-optic Michelson interferometricsensor

We investigate the optically amplified time-division-multiplexed (TDM) polarization-insensitive fiber-optic Michelson interferometric sensor (PIFOMIS) system using erbium-doped fiber amplifier (EDFA). The EDFA was named preamplifier, in-line amplifier or postamplifier; by the position it was located. We find that the preamplifier EDFA has limited usefulness because of its unstable amplification of the optical pulse trains. Both post- and in-line cases can work successfully in the TDM-PIFOMIS system. The amplitudes of the optical pulse trains are stable after amplified by the in-line EDFA, this is a significantly advantage of the optically amplified TDM-PIFOMIS system. The MPDS of the unamplified TDM-PIPOMIS system with an extinction ratio (ER) of 33 dB of the output pulse of the optical guide wave (OGW) modulator was 2.4×10^-5 rad/(Hz)^1/2 at 1 kHz. For maintaining MPDS better than 3.4×10^-5 rad/(Hz)^1/2 at 1 kHz, the allowable worst ER for the post- and in-line amplified system are 20 and 17.8 dB, respectively, and the corresponding input signal peak power should be larger than -20 and -25 dBm. While employing such two post- and two in-line EDFAs in the TDM-PIFOMIS system, the allowable loss of the sensor array is 47 dB. We analyze the phase-induced intensity noise (PIIN) of the optically amplified TDM-PIFOMIS system in detail and propose methods to reduce the PIIN. The output optical pulse of an intensity modulator with high ER is a key issue to minimize the PIIN and sensor crosstalk in the system. In order to reduce the system PIIN, complexity and cost, we suggest an optimum optically amplified WDM (wavelength-division multiplexing)-TDM hybrid PIFOMIS system with four wavelengths and four eight-sensor subarrays     

Optically transparent digitally tunable wavelength filter

A new digital architecture combining a spatial light modulator written dynamic hologram and a fixed diffractive grating has been demonstrated to produce a tunable wavelength filter with a tuning resolution of 2.5 nm over a 160 nm range. Three modes of a broadband 1.45 μm laser diode have been isolated using the filter and selectively coupled into singlemode communications fibre     

一种可调谐的宽带喇曼波长转换器

为了提高宽带波长转换技术的响应速度，采用高非线性光子晶体光纤，设计了一种受激喇曼散射的可调谐全光宽带波长转换器。基于光纤中喇曼效应，对光子晶体光纤喇曼增益谱采取高斯曲线进行拟合，建立了喇曼波长转换器的理论模型，并进行了仿真分析，讨论了光纤长度对转换效率的影响。结果表明，在符合通信系统的条件下，实现了100nm转换带宽，波段为1487nm~1587nm，Q因子随探测光波长变化与喇曼增益谱走势相同，其波长转换质量最优处在喇曼增益系数最大处。该研究对未来光网络的波长转换器波长分配以及光纤长度的配置研究具有参考意义。     

全光波长转换器及其研究进展

实现全光波长转换主要利用四种非线性效应，交叉增益调制（XGM）、交叉相位调制（XPM）、四波混频（FWM）和差频（DFG）效应。根据所用非线性器件不同，分别介绍了基于这四种效应的全光波长转换器的基本原理，系统结构、特点和发展现状，每种波长转换器都有其不足之处，针对这一现实，重点介绍了国内外最新的全光波长转换方案，这些方案在一定程度上改进了原有波长转换器的性能，促进了全光波长转换器的实用化进程。     

All-optical Mach-Zehnder wavelength converter with monolithicallyintegrated preamplifiers

An interferometric wavelength converter with preamplifiers for both the signal input and the continuous-wave probe input is presented. The dynamic range of the device is enhanced: penalty-free conversion is demonstrated at 2.5 Gb/s for input powers ranging from -6 to +4 dBm. Transmission of the converted signal over 480 km of standard fiber shows penalty improvement relative to the unconverted, information-limited signal     

基于四波混频效应的全光波长转换器

全光波长转换(AOWC)是波分复用(WDM)光网络的一项关键技术,可以通过几种非线性效应来实现,其中的四波混频效应(FWM)由于其对输入信号的变换具有严格透明性而受到人们的广泛关注。鉴于此,详细介绍了基于四波混频效应的各种波长转换方案的原理、性能及优缺点。     

NRZ-OOK-to-RZ-BPSK modulation-format conversion using SOA-MZI wavelength converter

A novel all-optical modulation-format conversion from nonreturn-to-zero on-off keying (NRZ-OOK) to return-to-zero binary phase-shift keying (RZ-BPSK) is proposed. A Mach-Zehnder interferometric (MZI) wavelength converter consisting of integrated semiconductor optical amplifiers (SOAs) is utilized to implement the proposed format conversion. Error-free operation at a bit rate of 10.7 Gb/s is experimentally demonstrated in order to show the feasibility of the proposed scheme. The received sensitivity of the converted signal is improved by 2.9 dB compared with a back-to-back NRZ-OOK signal at BER=10/sup -9/. In addition, a reasonable dispersion tolerance of the converted signal up to /spl plusmn/500 ps/nm is observed. The numerical simulation based upon the carrier-rate equation verifies the experimental results.     

Routing and wavelength assignment vs. wavelength converter placement in all-optical networks

Blocking has been the key performance index in the design of an all-optical network. Existing research demonstrates that an effective routing and wavelength assignment strategy and a proper wavelength converter placement algorithm are the two primary vehicles for improving the blocking performance. However, these two issues have largely been investigated separately in that the existing RWA algorithms have seldom considered the presence of wavelength conversion, while the wavelength converter placement algorithms have largely assumed that a static routing and random wavelength assignment algorithm is employed. The main objective of this article is to present some strong evidence that these two issues need to be considered jointly, and call for the reexamination of both RWA and wavelength converter placement.     

XGM波长变换器网络的路由波长分配算法研究

交叉增益调制(XGM,Cross-Gain Modulation),用于波长变换技术,可较简单地制成全光波长变换器。该文先用一个简单的近似模型分析了XGM波长变换器对路径阻塞率的影响,进而根据其本身固有的特点,设计了3种适合于XGM波长变换器网络的路由波长分配算法。通过在美国科学基金会骨干网络(NSFNET,National Science Foundation backbone network),和网孔型(Mesh-torus)网络中的仿真,从网络的阻塞率和公平性两个方面研究XGM波长变换器对网络性能的影响,同时比较了3种算法的性能。仿真结果表明,XGM波长变换器较无波长变换,可以在网络的阻塞率和公平性两个方面都得到较大的改善;3种算法中,FF/lowest算法在改善网络的阻塞率和公平性两个方面都是最优的。     

一种新型基于子图的波长转换器配置算法

文章在已有的"子图+ADD(代数决策图)"波长转换器配置算法的基础上,将节点在路由上的平均中心距离作为权值对节点进行排序,提出了用优先配置中心节点的启发式思想对该算法进行优化,得到了新的算法,即"子图+CNF(中心节点优先分配)"算法。对本算法进行计算机仿真,结果显示新算法在保证结果准确的同时,有效降低了运算的时间复杂度。     

Performance analysis of the silicon waveguide-based wavelength converter

The conversion efficiency and noise figure (NF) of the silicon-on-insulator (SOI) waveguide-based wavelength converter are investigated with the coupled equations. The effects of the pump power, the nonlinear absorption and the waveguide length on the conversion efficiency and noise figure are discussed. The conversion efficiency decreases with the increasing pump power and the noise figure is degraded due to the two-photon absorption (TPA) and the TPA-induced free-carrier absorption (FCA) at the higher pump power. With the increasing of the free carrier lifetime, the conversion efficiency will decrease and the noise figure will increase accordingly. The optimal waveguide length depends on the pump power and the free carrier lifetime. In practical applications, the high conversion efficiency and low noise figure can be achieved by choosing suitable parameters of the silicon waveguide.     

Raman-enhanced regenerative ultrafast all-optical fiber XPM wavelength converter

The Raman gain enhancement of a regenerative ultrafast all-optical cross-phase modulation (XPM) wavelength converter (WC) is quantitatively investigated and experimentally demonstrated to operate error free at 40 and 80 Gb/s. The regenerative nature of the converter is shown by experimentally demonstrating a negative 2-dB power penalty at 80 Gb/s. It is also shown that the Raman gain greatly enhances the wavelength conversion efficiency at 80 Gb/s by 21 dB at a Raman pump power of 600 mW using 1 km of highly nonlinear fiber. An analytical theory based on nonlinear phase-shift enhancement of the fiber-effective length is presented and shows the relationship between a nonlinear enhancement and Raman gain as a function of pump power and fiber design parameters. Measured parameters are used in the analytical model, and a good fit between experiment and theory is shown for two different types of fiber: one dispersion-shifted and one highly nonlinear fiber. The ultrafast response time of Raman gain makes this technique applicable to fiber-based ultrafast WCs. In addition, the applicability to other nonlinear fiber wavelength conversion techniques is discussed.     

Wide-range all-optical wavelength conversion usingdual-wavelength-pumped fiber Raman converter

A wavelength conversion scheme based on a fiber Raman converter is proposed, in which an externally injected high power pump laser and the associated Stokes laser are used to assist the Raman conversion process of signal light coded with optical information. Because the Raman gain spectrum in fibers is extremely broad, a wavelength conversion device with wide-range tunability is feasible. We numerically demonstrate that wavelength conversion from 1.31 to 1.42 μm can be realized using a fiber Raman converter at up to 10 Gb/s with an efficiency of 18%. It is also demonstrated that wide range conversion from 1.31 to 1.55 μm for optical fiber communication is feasible at up to 5 Gb/s when the fiber Raman converters are cascaded twice     

Monolithically integrated 40-gb/s switchable wavelength converter

An all-optical switchable wavelength-converting module at 40 Gb/s line rate is demonstrated in a fully integrated InP chip. The device combines a semiconductor optical amplifier-based wavelength converter and a fast-tunable multifrequency laser. Sub-nanosecond switching among the eight channels of the integrated laser is shown, and error-free operation of the wavelength conversion process at 40 Gb/s for each wavelength is demonstrated. The applications of fast switching wavelength conversion for optical switching and packet routing are discussed.     

SOA-XGM全光波长变换器的特性分析

对基于半导体光放大器交叉增益调制实现的全光波长变换器的工作特性进行了分析，归纳了要取得较好的变换效果，应在输入信号光功率、波长、偏置电流、放大器腔体长度等方面作合理的选择，使输出信号的消光比、信噪比等指标符合要求。     

WDM网络中一种新型的波长转换器配置算法

在波分复用(WDM)光网络中,文章将经过各节点的最短路径的总长度作为权值对节点进行排序,利用优先配置最短路径总长度较长的节点的思想,对已有的"子图+ 代数决策图(ADD)"算法进行改进,得到了一种新的"子图+路径长度排序 (PLS)"算法.对两种算法进行了计算机仿真,结果显示新算法在保证结果准确的同时,较有效地降低了运算的时间复杂度.