Half baudrate electrical clock based demultiplexing scheme for OTDM-DQPSK signal using SOA and optical filter

A demultiplexing scheme based on semiconductor optical amplifier(SOA)and optical filter for optical time division multiplexing differential quadrature phase shift keying(OTDM-DQPSK)system is proposed and investigated experimentally.With only a common half baudrate electrical clock modulated 33%duty cycle return-to-zero(RZ-33)optical clock signal as pump,this scheme is cost-effective,energy-efficient,and integration-potential.A proof-of-concept experiment is carried out for the demultiplexing of a 2×40-GBd OTDM-DQPSK signal.Error-free performance is demonstrated,and the average power penalty for both channels is about 3 dB.     

非等幅OTDM信号的全光时钟提取

理论上推导了非等幅均匀复用的OTDM信号中时钟分量与各路脉冲幅度的关系式,并分别从频域和时域的角度给出了利用以半导体光放大器（SOA）作为调制器的锁模光纤激光器进行时钟提取的物理机制,对时钟提取的物理过程给出了形象解释.实验上通过利用锁模光纤激光器成功地从非等幅均匀复用的8×2.5 GHz OTDM信号中提取了2.5 GHz单路时钟和20 GHz群路时钟光脉冲.利用该方案提取的时钟脉冲稳定性好,对偏振态不敏感,是较理想的时钟源.此技术可用于高速OTDM信号的时钟提取.     

高功率法拉第隔离器多模退偏特性

理论分析了隔离器在高功率多模激光入射时的自退偏特性.结果表明:线性双折射致退偏与圆双折射致退偏均与入射光功率的平方成正比,线性双折射致退偏与光斑大小无关,而圆双折射致退偏随光斑半径的增大而减小.当光斑半径与旋转晶体半径相比很小时(R0/r0≥80)圆双折射引起的退偏大于线性双折射引起的退偏,当光斑半径接近旋转晶体半径(R0/r0≤3)时,与线性双折射引起的退偏相比,圆双折射引起的退偏可以忽略.对比单模激光入射,在同种条件下,多模入射使得线性双折射致退偏减小了0.4倍, 最小圆双折射致退偏减小为0.05倍.     

激光星间链路终端技术发展与展望北大核心CSCD

激光星间链路主要用于卫星之间高速数传,是构建天基信息网络的关键技术。目前国外通信、遥感、导航和中继等卫星系统都已计划部署激光通信终端,激光星间链路技术已从在轨演示验证向大规模组网应用阶段发展。简要梳理了国际上现有组网卫星系统的激光星间链路终端技术发展情况,对激光星间链路的技术体制和终端分类进行了总结;侧重分析了我国激光星间链路终端技术发展现状及大规模应用面临的主要问题,针对重难点技术的解决途径进行了思考;对激光星间链路终端未来的发展趋势做了展望,尤其是轻小型化设计与实现、宽带化、一对多光学天线和网络化等技术发展趋势进行了分析。     

All-optical clock recovery from 10-Gb/s NRZ data and NRZ to RZ format conversion

A non-return-to-zero (NRZ) to pseudo-return-to-zero (PRZ) converter consisting of a semiconductor optical amplifier (SOA) and an arrayed waveguide grating (AWG) is proposed, by which the enhancement of clock frequency component and clock-to-data suppression ratio of the NRZ data are evidently achieved. All-optical clock recovery from NRZ data at 10 Gb/s is successfully demonstrated with the proposed NRZ-to-PRZ converter and a mode-locked SOA fiber laser. Furthermore, NRZ-to-RZ format conversion of 10 Gb/s is realized by using the recovered clock as the control light of terahertz optical asymmetric demultiplexer (TOAD), which further proves that the proposed clock recovery scheme is applicable.     

Performance evaluation for 160-Gb/s optical phase conjugation systems considering dispersion mapping and third-order dispersion

The impact of third-order dispersion (TOD) is investigated by numerical simulations in 160-Gb/s single-channel systems incorporated with dispersion mapping and optical phase conjugation (OPC). System performances using retrun-to-zero (RZ) or carrier-suppressed RZ (CSRZ) modulation format are evaluated on the optimized dispersion map. The results indicate that even though TOD has been fully compensated, the intra-channel nonlinearity induced by local TOD would degrade the system performance in nonlinear regime. The scheme with an optimized dispersion map provides a much higher performance and offers a larger tolerance on a variation of pre-compensation. CSRZ modulation format is more robust due to its tradeoff between tolerances on intrarchannel nonlinearity and dispersion.     

基于电吸收调制器的高速时钟信号的提取

对高速光时分复用系统中(2×10 Gb/s)基于电吸收调制器(EAM)的注入光电混合振荡器的时钟提取方法进行了实验验证. 实验证明,光电混合振荡器必须保证一定的增益才能提取出时钟,在此基础上,无论光电混合振荡器内或外的光功率的增加,将增加提取时钟的幅度,减小提取时钟的时间抖动.当偏置电压一定时,射频幅度增加,则电吸收调制器的窗口变窄,提取时钟幅度增大,抖动减小.     

基于TOAD的10Gb/s全光或门

基于太赫兹光非对称解复用器（TOAD），提出了一种全光或门的实现方案.从TOAD原理出发，从理论上证实了该方案实现全光或运算的可行性.在此基础上进行了实验研究，成功实现了10 Gb/s的全光或运算.实验采用1100和0110编码的两路数据信号，完全验证了或运算真值表中各种可能的情况，并显示出该方案对实现任意编码或伪随机码数据或运算的潜力.对SOA增益恢复时间对结果的影响提出了改进办法.最后分析表明,该方案具有实现超高速高消光比或运算的潜力.     

TCP在光突发交换试验网络中性能的实验研究

在光突发交换试验网络中对TCP的性能进行了实验研究.首先研究了丢包对网络性能的影响,表明突发包丢失将导致TCP吞吐量的快速下降,并且丢包率越高,可用的TCP传输带宽越窄.然后分别详细研究了OBS试验网络中的延时损伤和报文段关联增益,以及对TCP传输性能的影响.最后综合考虑这些因素.实验结果表明,在本OBS试验网络中存在一个不随丢包率变化的最优化突发包组装时间250us使得可用TCP带宽最大化.为了最大限度地提高TCP的传输性能,组包时间应该选择等于或稍大于这个最优值.     

基于电吸收调制晶体(EAM)的超短光脉冲特性研究

数值模拟了两种形式的基于电吸收调制晶体(EAM)的超短光脉冲源(单EAM)和级联EAM形式)的输出脉冲宽度及消光比与外加反向偏压、射频信号幅度之间的变化关系.数值模拟结果表明,在重复率为10GHz情况下,对于单EAM形式,可以获得的最小脉宽大约为13ps,其消光比大于20dB,脉冲波型接近sech2孤子波型;对于级联EAM形式,我们得到了小于5ps的超短脉冲,消光比也较单EAM形式有较大的提高.因此,单EAM形式的超短脉冲源可以满足20Gb/s的OTDM系统需求,也同样适合于超长距离的光孤子通信系统;级联形式EAM可以满足40Gb/s的OTDM系统光源需求.