Forward error correction concatenated code in DWDM systems

The three concatenated coding schemes of the inner-outer type, the parallel type and the consecutive type to improve the current forward error correction (FEC)coding technologies are proposed for dense wavelengthdivision multiplexing (DWDM) systems, after introducing the development trend of DWDM optical communication systems. The concatenated code is theoretically analyzed.The theoretical analyses and simulation results show that inner-outer concatenated code has a greater redundancy and the decoding of parallel concatenated code is too complex. However, consecutive concatenated code is superior coding scheme with advantages such as better error correction performance, moderate redundancy and easy implementation, therefore it could be better used in high-speed and long-haul DWDM systems.     

多信道IM—DD密集波分复用光纤传输系统中的交叉相位调制效应

本文研究了交叉相位调制（XPM）对DWDM数字基带主干传输网性的影响,建立了表征XPM效应对任意调制信号在色散信道中传输的指标损伤的等效系统函数模型,并据此推导出了不同系统参数条件下（基带信号速率,波长信道间隔,复用信道数）计算XPM导致和系统光功率代价的计算公式,通过数值模拟计算证明了在基带信号速率高（＞2.5Gbit/s),波长信道间隔窄（－1nm),复用信道数多（＞8）的条件下XPM效应将成为限制系统性能的主要非线性因素。     

介质光波导中非线性薛定谔方程的一种近似解法及其应用

为了对长距离无中继光传输系统中距离和容量极限进行估计 ,提出了一种非线性薛定谔方程的近似分段解法 ,该方法可同时考虑自相位调制、群速度色散、SRS和SBS的影响。它将整个传输距离分为两段 ,在第一段只考虑自相位调制作用 ,而第二段只考虑色散的作用 ,频率啁啾是联系两段的纽带 ,从而得出距离带宽与入纤初啁啾的解析关系式 ,将图解法得出的最佳初啁啾带入就可得到距离带宽的简单关系式。对 2 .5Gbps系统采用此法得出最大无中继距离 ,采用分步傅里叶算法验证了这一结果的正确性。     

适用于高速长途DWDM系统的色散管理线路

对于高速长途密集波分复用（DWDM）传输，必需采用各种各样的色散补偿、色散管理技术，其中，交替使用正负色散光纤构成色散管理线路（DML）是可行的解决方案之一，在国际上已经取得显著进展，正成为人们关注的焦点，国内在这方面的研究报道还少见.文章以高速长途DWDM系统对传输线路的性能要求为基础，综述了有代表性的3种不同类型的DML的特点和最新进展。     

可调谐激光器技术及其在DWDM系统的应用

大容量、长距离DWDM传输系统及动态波长交换DWDM光网络对保护方式、波长分配、波长备份成本的要求,使可调谐激光器变得十分重要。讨论了常用可调谐激光器的技术原理和水平,概要说明了可调谐激光器的市场前景,介绍了可调谐激光器在DWDM系统中的部分应用。     

基于重叠光栅和啁啾光栅的双波长光纤激光器

研究光寻址电位传感器(LAPS)的器件噪声特性 。通过对LAPS半导体场效应器件的结构分析,建 立LAPS的理论模型,并进一步分析LAPS器件噪声信号的来源、种类及特性。以 pH缓冲液中H离子 浓度为检测对象,搭建基于NI采集卡和Labview环境的LAPS测试系统,对影响LAPS信号噪声 特性的光源 波长、光源调制频率、光源强度和Si衬底厚度等因素进行了仿真和实验研究。结果表明,增 大光源波长和光源强度 是提高输出信号幅值和信噪比(SNR)的最有效方法。     

XPM对非线性光纤环镜微波光子开关的影响

为了研究交叉相位调制(XPM)对非线性光纤环镜微波光子开关的影响.基于耦合非线性薜定谔方程,彩分步傅里叶法建立考虑XPM在内的数值分析平台,获得了MOLM微波光子开关中XPM对微波调制光载波信号和NOLM功率舆函数的影响.数值计算表明:XPM导致调制波波形畸变,信号能量从主瓣泄露;并且随着调制带宽的增大,旁瓣泄露愈加严重.同时由于XPM效应的非互易性,NOLM功率传输函数扭变,在耦合器分光比f∈(0,0.5)区间减少而在f∈(0,0.5)区间增大.     

Chirp compensation capability of a semiconductor laser amplifier

Performance improvement is reported resulting from incorporating a semiconductor laser amplifier (SLA) as a post-transmitter-amplifier in long-haul directly modulated optical systems operating in the 1.5 mu m region. This improvement arises from reduction of the chirp produced by the semiconductor laser as the signal passes through the SLA. Eye closure penalty improvements in excess of 5 dB are observed for an illustrative long-haul 4.8 Gbit/s system.<>     

折射率啁啾调制光纤光栅性能研究

从耦合模理论出发,详细推导出平均折射率调制啁啾系数、初始位置平均折射率调制系数和啁啾光纤Bragg光栅(FBG)周期啁啾系数之间的对应关系,并进行了数值模拟和实验研究。结果表明：通过对平均折射率调制系数进行啁啾控制,可以利用一块相位掩膜版制作出不同色散补偿量的FBG。     

利用光脉冲传输特性抑制偏振模色散

基于双折射光纤中光脉冲传输方程,详细分析了二阶色散、自相位调制以及交叉相位调制在光脉冲传输过程中引起的啁啾。分析结果显示:通过合理选取入射功率,二阶色散引起的啁啾与自相位调制引起的啁啾在脉冲中心附近可以相互抵消,从而使脉冲展宽最小;交叉相位调制产生的两偏振分量的啁啾引起的频移,可使两偏振分量间产生互束缚,利用这种现象可以抑制偏振模色散。     

ROF系统中基于SOA非线性效应的光子上变频技术研究

在光载射频（ROF）系统中,为了将承载信息的光基带信号上变频到微波／毫米波波段,本文基于半导体光放大器（SOA）中的交叉增益调制（xGM）和交叉相位调制（XPM）效应实现了光子上变频：即实现了1．25Gb／s基带信号到30GHz的毫米波信号的转换。文中分析了SOA驱动电流的变化（50～200mA）和信号光与本振光波长间...     

Dynamic linewidth of amplitude-modulated single-longitudinal-mode semiconductor lasers operating at 1.5 ?m wavelength

We have measured the frequency chirp characteristics of single-longitudinal-mode semiconductor lasers operating at 1.5 ?m wavelength and subject to large signal amplitude modulation in the 50 to 800 MHz range. Measurements on cleaved-coupled-cavity (C3) and GRIN-rod external cavity lasers show that the wavelength chirp is large enough to cause a penalty in ultra-high-bit-rate long-haul optical-fibre systems.     

半导体光放大器对超短光脉冲频谱特性的影响

为进一步理解半导体光放大器工作的物理本质，从速率方程出发，采用分段模型数值分析了超短光脉冲经SOA后的输出频谱和由SOA产生的附加啁啾特性。结果表明：SOA引起的附加啁啾是与SOA的偏置电流、初始信号脉冲的波长、脉冲形状、峰值功率以及脉冲宽度等因素有关；对应的输出脉冲的频谱形状也与上述因素密切相关。     

新一代大保实光纤及其主要性能指标

从理论上对色散和非线性效应的影响进行了简要分析，介绍了一种既能控制色散，又能有效抑制非线性效应，而且具有低PMD值的适合于大容量和超长中继距离的DWDM系统的非零色散位移单模光纤－大保实。     

Characteristics of 10-Gb/s Electroabsorption Modulator Integrated Distributed Feedback Lasers for Long-Haul Optical Transmission Systems

In this study, we review the characteristics of 10-Gb/s electroabsorption modulator integrated (EAMI) distributed feedback (DFB) lasers for long-haul optical transmission systems. The recent progress and issue of extinction ratio, chirp, and frequency response are described, which are important parameters to improve transmission performance. Except for the extinction ratio, frequency response and chirp characteristics are discussed further. The frequency response of packaged EAMI-DFB lasers has been improved using the novel impedance matching technique. The large signal chirp characteristics are calculated with varying bias voltage, facet reflectance, grating phase, and a coupling coefficient (κL) to predict the measured chirp characteristics. Finally, transmission performance (BER, eye margin, and eye opening penalty) is measured and estimated using the calculated chirp characteristics.     

Wavelength chirp in a high-κL quarter-wave-shiftedDFB laser: characterization and influence on system performance

Time-resolved and time-averaged chirp measurements of a quarter-wave shifted 1.53-μm DFB laser with a high-coupling coefficient are presented, showing a slow-steady shift towards shorter wavelengths lasting 1.5 ns after the laser is turned on. A simple method of screening for this phenomenon is presented. Transmission on a regular single-mode fiber reveals the effect of pattern-dependent pulse compression causing severe performance degradation in a long-haul NRZ (nonreturn-to-zero) system, but improving that of an RZ system     

40-gb/s EA modulators with wide temperature operation and negative chirp

Broad bandwidth external modulators are widely used in optical fiber networks to avoid the chirp associated with the direct modulation of laser diode sources. For transmission application beyond 10 Gb/s, electroabsorption modulators (EAMs) offer many advantages such as low drive voltage, low chirp characteristics, small size, and added functionality through integration with a distributed feedback laser. In this letter, we present static and dynamic characterization of an EAM demonstrating the possibility to have with the same device uncooled operation at 40 Gb/s and negative chirp at low negative bias. These features are attractive for cost reduction in short link applications and for long-haul transmission. All the measurements are performed at 40 Gb/s from room temperature up to 60/spl deg/C demonstrating a negative chirp behavior for the stand-alone modulator over the entire temperature range.     

Variation of frequency chirp with wavelength in an InGaAsP/InP multiple-quantum-well (MQW) waveguide electroabsorption modulator

Through measurements of the modulation index and the optical power spectra, the chirp parameter for an InGaAsP quantum-well electroabsorption waveguide modulator has been determined. The result shows that the frequency chirp parameter achieves a minimum value of 0.6 in the wavelength range 1509-1545 nm. This is significantly less than what is obtained from direct intensity modulation of injection lasers, making this a useful device in high-bit-rate, long-haul systems.<>     

Tunable silicon etalon for simultaneous spectral filtering andwavelength monitoring of a DWDM transmitter

A temperature-tunable Fabry-Perot filter made of silicon has been developed and applied for simultaneous spectral filtering and wavelength monitoring of a directly modulated DFB laser. This novel device decreases the dispersion penalty of a cost-effective dense wavelength-division-multiplexing (DWDM) transmitter in a long-haul transmission link. Moreover, it allows the operating wavelength of the transmitter to be accurately monitored in real time     

基于SOA的交叉相位调制生成UWB信号的研究

超宽带信号(UWB)的光学生成技术是光载超宽带通信系统(UWB-over-fiber)的关键技术,半导体光放大器(SOA)的非线性特征在全光信号处理中有着广泛的应用。提出基于SOA的交叉相位调制(XPM)效应的UWB的光学生成方法。该方法首先利用SOA的XPM实现高功率的高斯泵浦光和低功率的直流探测光的XPM,然后利用光学滤波器对探测光进行鉴频,实现相位调制到强度调制的转换,从而获得单周期UWB信号。提出了采用光带通滤波器和波分复用器对探测光进行鉴频的两种方法,获得中心频率分别为5.15GHz和5.05GHz,相对带宽分别为150%和149%的UWB信号,符合FCC标准。