A method of multi-channel receiving for high bit rate heterodyne direct-detection optical orthogonal frequency-division-multiplexing (OOFDM) system is proposed to reduce the sampling rate demand of analog-to-digital converter (ADC). The sampling rate of ADCs can be reduced to 1/N that of the original signal bandwidth in an N-channel receiving system. Aided by a succeeding digital signal processing (DSP) at the receiver, aliasing free signal can be recovered. A back-to-back experimental result is given for a 4-channel system, based on which, a down conversion process for heterodyne can be reduced. The signal rebuilding algorithm is given and analyzed in its complexity and noise tolerance.

A cost-effective method of multi-receiver optical orthogonal frequency-division multiplexing (OOFDM) system is proposed to reduce the requirement for the speed of the receiver and the size of fast Fourier transform (FFT). The sampling rate of analog-to-digital converters (ADCs) can be reduced to 1/N of the original signal bandwidth in an N-receiver system. Aided by signal predistortion at the transmitter, aliasing-free signal can be retrieved independently and directly at the low speed receivers. A back-to-back experimental result is given for a two-receiver system. The effect of the electrical filters added before the ADC is studied and the analysis for filters optimization is given.

利用光纤无源器件制作了光学90°混频器,实现了混频器90°相移的精确控制与监测,稳定时间达到12 h以上,利用此混频器研究并实现了数字相干光检测。对差分相移键控(DPSK)信号光和本振光进行混频,高速模数转换器(ADC)对混频后的基带信号采样,利用离线数字信号处理算法进行光载波相位估计和色散补偿,利用有限冲击响应(FIR)数字滤波器补偿了经过90 km光纤传输的8 Gb/s速率DPSK信号的色散失真,测量无误码。

提出并实现了用相干自混频方法监测马赫-曾德尔调制器(MZM)零偏置点漂移, 将同一光源所产生的部分未调制光和调制后的光进行混频, 利用混频光功率的最大最小值之比作为监测量监测。相比于监测信号光平均光功率的方法, 可使±5%偏置点漂移下的灵敏度从0.02 dB提高到0.3 dB。利用设计完成的硬件反馈控制系统进行了多次实验, 讨论了影响系统工作的各种因素及相应的解决办法, 结果表明该方法工作有效。

We have studied a function-lock strategy for all-optical logic gate (AOLG) utilizing the cross-polarization modulation (CPM) effect in a semiconductor optical amplifier (SOA). By monitoring the power of logic light, the strategy realized controllable methods to capture OR and NOR functions and switch between them. The strategy has been successfully applied in experiment with 10-Gb/s not-return-to-zero (NRZ) signals, which has a high success-rate above 95% and ensures the high extinction ratio of result light above 11.4 dB. Every step in the strategy has definite numeric evaluation, which provides the potential of automatic implementation.

为了改善基于半导体光放大器(SOA)中交叉偏振调制效应(CPM)的波长转换器的转换信号码型效应,对交叉偏振调制半导体光放大器波长转换器的工作原理进行了分析;通过讨论交叉偏振调制半导体光放大器波长转换脉冲的上升沿和下降沿的频率啁啾,结合滤波器的透过谱特性,提出了一种利用滤波器的波长正斜率边和波长负斜率边分别对正相转换信号和反相转换信号进行码型优化的方案,并进行了实验验证。在信号码率为10 Gb/s的交叉偏振调制半导体光放大器波长转换实验中,采用光带宽为0.3 nm的JDS滤波器优化转换信号的波形,基本消除了转换信号中长“1”码和长“0”码的码型效应,并将正相转换信号和反相转换信号的功率代价分别改善了3 dB以上。

设计并研制出了一种可灵活重构的多波长OADM,建立了OADM级联光信噪比的理论计算模型并进行了分析计算,给出了OADM的内部功率预算.最后对OADM设备进行了测试,所有性能指标都达到设计要求,目前已经通过工程验收,并正式在"中国高速信息示范网(CAINOnet)"中运行.

根据国际电信联盟(ITU-T)建议G.873定义的光传送网(OTN)中光路的假设参考模型(HRM),提出了光路经过多个光节点和光纤传输段后噪声积累的数学模型,推导了解析计算公式,并且按照节点隔离原理推导了计算噪声积累的简化公式以及工程等效模型。分析了光节点中增益(损耗)分配对噪声功率的影响,得出了光节点的优化设计原则。提出的光路噪声模型可以为光网络中光节点和光纤传输段的设计提供参考。

对基于半导体光放大器中交叉增益调制效应的波长转换后信号的啁啾特性进行了分析.研究了输入信号光和参考光的功率、波长、转换速率、信号光消光比以及半导体光放大器的偏置电流对转换后信号啁啾的影响.

增益调制型波长转换中,为得到转换后信号最大的消光比(ER),信号光波长应该比半导体光放大器(SOA)的小信号增益峰值波长长.采用分段模型,考虑了SOA中增益谱的不对称性以及增益峰值波长随载流子密度的漂移,深入研究了信号光功率,ER,参考光功率,波长以及SOA注入电流对选择信号光波长λpk,s以及消光比改善量的影响.模拟计算表明,信号光功率每增加3 dB,λpk,s就需向长波长移动约7 nm.信号光ER增加、参考光功率增加以及SOA注入电流的增加,λpk,s需向短波长移动.消光比改善量随信号光功率和电流的增加而显著增加,随信号ER的增加而降低,但是参考光功率和波长变化时影响不大.