Mitigation of signal quality degradation induced by PMD using synchronous modulation

In-line synchronous modulation as a way of mitigating the signal quality degradation induced by polar ization mode dispersion(PMD)was experimentally studied using 10-Gb/s return to zero signal.Bit error rate of the degraded signal and the synchronously modulated signal under the differential group delay(DGD)values of 10,20,34,and 70 ps was measured and compared.The experimental results showed that in-line synchronous modulation is useful to mitigate the signal quality degeneration induced by PMD.1-dB power penalty reduction was obtained even when the PMD was as high as 70％ of the bit interval.The limitation of method is also discussed.     

PMD mitigation using 3R regeneration based on EAM with wavelength conversion

Polarization mode dispersion (PMD) mitigation is performed using an optical 3R (re-amplification, reshaping, re-timing) regenerator based on electro-absorption modulator (EAM) with wavelength conversion. System performance without and with 3R regeneration was separately studied by eye analysis and bit-error rate (BER) measurements. The signal quality was significantly improved by 3R regeneration under serious first order PMD (up to 40% of the bit interval) combined with second order PMD (up to about 520 ps2). The PMD mitigation margin of the proposed method is also investigated by measuring the sensitivity at BER 10-10. Further studies indicate that 3R regenerators have the potential to combat with the effects of PMD combined with polarization dependent loss (PDL) and polarization hole-burning (PHB).     

基于半导体光放大器结合延迟干涉仪的全光波长转换

研究了基于半导体光放大器(SOA)结合延迟干涉仪(DI)结构的伞光波长转换.分析了SOA-DI结构的工作原理和DI参数的作用,进行了10 Gb/s和40 Gb/s归零码全光波长转换实验研究.实验结果表明,基于SOA中交叉增益调制(XGM)效应实现的波长转换为反相转换,输出信号消光比较低.当工作速率较高时波长转换信号质量明显恶化.而SOA-DI结构可实现同相波长转换并可改善波长转换信号的消光比,从而改善单个SOA实现波长转换的性能并提高系统的工作速率,该结构还具有结构简单、可光子集成等优点.     

光收发机IQ损伤宽范围联合估计新型DSP方案

大波特率、高阶调制格式信号的广泛应用使相干光通信系统对收发机中存在的硬件损伤更加敏感,因此迫切需要相应的损伤估计方法.提出了一种新的基于数字信号处理的收发机损伤联合估计方案,该方案可同时监测因光发射机和光接收机硬件不完美引起的光信号同相/正交(IQ)分量幅度、相位不平衡和时钟偏移.该方案首先使用Godard定时误差检测...     

Demonstration of a 16×10-Gb/s OTDM system

A 16×10-Gb/s optical time-division-multiplexing (OTDM) system was demonstrated experimentally with a well-designed ultrashort pulse source based on an electro-absorption modulator (EAM) and nonlinear fiber compressor. The obtained 10-GHz stable and pedestal-free pulse train has 2-ps width, high extinction ratio, and low timing jitter. An ultrafast demultiplexer based on a nonlinear optical loop mirror (NOLM) including a commercially available highly nonlinear fiber (HNLF) is employed to demultiplex data signal from 160 to 10 Gb/s. A back-to-back error-free demultiplexing experiment is carried out to verify the system performance.     

PMD compensation based on a new type dynamic first-order PMD compensator

A dynamic first-order polarization mode dispersion (PMD) compensator based on garnet and yttrium vanadate crystal has been proposed and implemented. Consisting of a differential group delay (DGD) generator and a Faraday rotator (FR), this PMD compensator has only two degrees of freedom. Feedback control and compensation algorithm are both very simple. Experimental results reveal the compensator behaviors to be excellent for PMD compensation in 40-Gb/s optical time domain multiplexing (OTDM) system.     

A Stable Ultrashort Pulse Generator Based on EAM and Well-Designed Compressor for Applications in 160 Gbit/s OTDM Networks

A stable 10 GHz ultrashort pulse generator consisted of an electroabsorption modulator （EAM） and a welldesigned fibre-based pulse compressor is proposed and demonstrated experimentally. The obtained short pulse has high extinction ratio, no pedestal, low timing jitter, and FWHM of only 2.4ps. The excellent performance of multiplexing from 10 GHz to 160 GHz confirms the potential of the generator for applications in 160 Gbit/s optical time-division-multiplexing （OTDM） systems.     

Demonstration of an 8×10-Gb/s OTDM system

An 8×10 Gb/s optical time-division-multiplexing (OTDM) system was demonstrated with an electroab-sorption modulator (EAM) based short pulse generator followed by a two-stage nonlinear compression scheme which generated stable 10-GHz, 2-ps full-width at half-maximum (FWHM) pulse train, an optoelectronic oscillator (OEO) that extracted 10-GHz clock with a timing jitter of 300 fs from 80-Gb/s OTDM signal and a self cascaded EAM which produced a switching window of about 10 ps. A back-to-back error free demultiplexing experiment with a power penalty of 3.25 dB was carried out to verify the system performance.     

Performance of free-space optical communication systems using circle polarization shift keying with spatial diversity receivers

A closed-form bit-error rate （BER） expression is derived for free-space optical （FSO） communication systems with circle polarization shift keying and spatial diversity receivers in the gamma-gamma （GG） distribution fading channel. This model can predict the performance without the need of lengthy simulation runs. The performance can be analyzed by some system parameters such as atmospheric conditions, link length, communication wavelength, receiver aperture size, and number of spatial diversity receivers. Numerical results demonstrate the influence of the above parameters on the FSO systems and show quantitatively the differences in behavior among various different parameters.     

40 Gb/s信号的全光3R再生

研制出以注入锁模光纤激光器进行时钟恢复、电吸收调制器（EAM）作光判决门进行信号再整形的新型全光3R再生器,成功地运行于40Gb／s。理论和实验证明锁模环形激光器腔内放置的可调谐光滤波器的透射谱形状对时钟的脉宽有显著影响,超高斯透射谱的光滤波器利于获得窄时钟光脉冲,腔内放置这样的滤波器使恢复的时钟光脉冲谱宽达0．44nm、脉宽6ps、时间抖动小于1ps。最佳选择用作光判决的开关门的参量,改善了开关门的传输函数,使其接近阶跃函数,并使得开关窗宽度达到最佳。对于被剩余色散恶化的40Gb／s归零码信号进行了3R再牛,再生后达到了无误码。