基于半导体光放大器的非归零信号时钟恢复

提出了一种基于半导体光放大器加窄带光纤光栅滤波器,将非归零信号转换为伪归零信号,再把伪归零信号注入到主动锁模环行腔激光器进行时钟提取的非归零信号时钟恢复方案.利用该方案实现了10 Gb/s伪随机非归零信号的全光时钟恢复,对工作原理和结果进行了分析和讨论.实验证明该方案具有结构简单,调整容易,输出波形好的特点.     

10 GHz全光帧时钟提取的理论和实验研究

提出了一种新型的10 GHz全光帧时钟提取的提取方案。采用低精细度的法布里-珀罗(F-P)滤波器直接提出帧时钟,保证帧时钟的快速建立和快速消失。利用半导体光放大器(SOA)的自增益调制效应(SGM)对法布里-珀罗滤波器提取的帧时钟进行整形,降低帧时钟的幅度噪声。并推导了法布里-珀罗滤波器的精细度和半导体光放大器的自增益调制效应对帧时钟建立时间、消失时间的影响。通过理论分析表明,利用半导体光放大器的自增益调制效应可以降低帧时钟的幅度噪声并加快帧时钟建立速度。实验中,用上述方案对10.075 GHz的帧信号进行了全光帧时钟提取,得到了建立时间为8个信号周期,消失时间为22个信号周期,抖动为2.35 ps的帧时钟信号。     

40 Gb/s信号全光3R再生实验

提出一种新型40 Gb/s全光3R再生器方案。采用高精细度法布里-珀罗滤波器进行时钟提取。时钟提取前,通过高稳定光源对输入信号光波长变换实现信号光波长和法布里-珀罗滤波器梳状窗口对准;时钟提取后,接半导体光放大器(SOA)进一步消除时钟信号噪声。全光判决中,采用双半导体光放大器串联增大非线性性能,提高了判决门的响应速度。判决输出接窄带滤波器去除脉冲啁啾拖尾,减小码型效应。实验中,恶化40 Gb/s光脉冲信号通过全光3R再生器可以得到再生脉冲。输入恶化信号时间抖动大于5 ps,脉冲宽度大于16 ps,再生得到的信号时间抖动小于1.5 ps。再生信号相对于输入信噪比改善14 dB。连续稳定工作记录大于15 h。通过实验验证,这种全光3R再生器方案成功地实现了40 Gb/s信号的再生。     

10 Gb/s全光3R再生的研究

报道了对10Gb／s恶化数据信号的全光3R(再放大、再定时、再整形)再生的实验研究。针对利用基于半导体光放大器的注入锁模环形激光器进行时钟恢复时的码型效应问题,提出了利用梳状滤波器对信号进行预处理。利用这个技术极大的减小了由于码型效应造成的时钟信号的幅度和时间抖动,从恶化的数据信号中恢复出无码型效应的高质量光时钟脉冲。信号整形的关键是光判决门,性能良好的判决门可以进一步提高信号的消光比、减小抖动。研究了基于电吸收调制器的信号再整形。利用上述器件构成的3R再生器,实现了10Gb／s恶化信号的全光3R再生。     

一种新型多速率归零码全光帧时钟提取系统

提出了一种新型的、低成本的多速率归零(RZ)码全光帧时钟提取方案。采用低精细度的法布里-珀罗滤波器(F-P)直接提取不同速率的帧时钟,保证帧时钟的快速建立和快速消失。利用不同的偏振延时干涉仪(PDI)和低自由光谱区(FSR)的法布里-珀罗滤波器构成组合滤波器以实现多速率帧时钟提取。利用半导体光放大器(SOA)的自增益调制效应(SGM)对组合滤波器提取的帧时钟进行整形,降低帧时钟的幅度噪声和时间抖动。实验中,利用光开关切换不同的偏振延时干涉仪构成不同自由光谱区的组合滤波器实现了10 GHz、20 GHz和40 GHz的帧时钟提取,得到了高质量、低时间抖动的多速率帧时钟信号。     

基于法布里-珀罗滤波器的40 GHz全光时钟提取实验

研究了在基于法布里-珀罗（F-P)滤波器的全光时钟提取实验中法布里-珀罗滤波器的精细度和信号码型对时钟提取的影响.根据理论分析,利用精细度为1012的F-P滤波器进行了时钟提取实验,并利用SOA进一步抑制时钟信号中的幅度抖动噪音,改善了时钟信号的质量.最终提取出低幅度起伏、低时间抖动的40 GHz 时钟信号.     

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.     

All-optical clock recovery of 20 Gbit/s NRZ-DPSK signals using polarization-maintaining fiber loop mirror filter and semiconductor optical amplifier fiber ring laser

All-optical clock recovery (CR) from 20 Gbit/s nonreturn-to-zero differential phase-shift-keying (NRZ-DPSK) signals are demonstrated experimentally by using a polarization-maintaining fiber loop mirror filter (PMF-LMF) and a semiconductor optical amplifier (SOA) fiber ring laser. Only by adjusting polarization controller (PC), NRZ-DPSK signals were conveniently and fast converted to pseudo return-to-zero (PRZ) signal via PMF-LMF. Then the PRZ signals are injected into the SOA fiber laser for CR. The recovered clock signals is with the extinction ratio (ER) of 10 dB and the root-mean-square (RMS) timing jitter of 750 fs in 2³¹ − 1 long pseudorandom binary sequence (PRBS) NRZ-DPSK signals measurement. Moreover, the broad wavelength tunability of recovered clock stemmed from the use of SOAs as modulator and the gain medium are shown too.     

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. Alloptical 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.     

All-optical error-bit amplitude monitor based on NOT and AND gates in cascaded semiconductor optical amplifiers

This paper proposes and simulates a novel all-optical error-bit amplitude monitor based on cross-gain modulation and four-wave mixing in cascaded semiconductor optical amplifiers （SOAs）, which function as logic NOT and logic AND, respectively. The proposed scheme is successfully simulated for 40 Gb/s return-to-zero （RZ） signal with different duty cycles. In the first stage, the SOA is followed by a detuning filter to accelerate the gain recovery as well as improve the extinction ratio. A clock probe signal is used to avoid the edge pulse-pairs in the output waveform. Among these RZ formats, 33% RZ format is preferred to obtain the largest eye opening. The normalized error amplitude, defined as error bit amplitude over the standard mark amplitude, has a dynamic range from 0.1 to 0.65 for all RZ formats. The simulations show small input power dynamic range because of the nonlinear gain variation in the first stage. This scheme is competent for nonreturn-to-zero format at 10Gb/s as well.     

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.     

基于UNI开关的40 GHz注入锁模全光时钟提取实验

基于超快非线性干涉仪UNI开关具有超过40 Gbit/s的开关速度,提出一种在锁模环形腔内利用UNI开关进行时钟提取的新方案.按此方案进行实验,对40 Gbit/s伪随机信号进行时钟提取,得到了清晰稳定的时钟脉冲.与利用SOA的交叉增益调制注入锁模时钟提取方案相比,在此方案中注入到SOA的信号功率仅0.5 dBm,降低了7 dB左右,对SOA的运行更安全.     

一种减少基于SOA的全光时钟提取码型效应的新方法

全光位时钟提取是3R全光再生的关键技术,本文针对利用基于半导体光放大器注入锁模激光器进行位时钟提取时的码型效应,提出一种利用非线性偏振旋转自稳幅效应减少码型效应的新方法,对40Gb/s的半导体光放大器注入锁模激光器位时钟提取,通过数值模拟计算证明,利用非线性偏振旋转可以有效地减少码型效应的影响.     

High-speed optical signal processing using semiconductor optical amplifiers

The authors report on all-optical switching devices based on semiconductor optical amplifiers (SOA) in applications for optical time division multiplexing (OTDM) transmission technology. The report includes a discussion on the basic properties of an SOA, on the nonlinear processes of cross-phase modulation and four-wave mixing in the SOA used for all-optical switching, and on the application of the SOA as demultiplexer, add-drop multiplexer, clock recovery and wavelength converter. The devices considered here operate at data rates in excess of \Gb80, where electrical signal processing is not available today.     

S, C, L-band signal transmission using a widely tunable optical clock generator

A widely tunable optical clock pulse train generation and transmission experiments with the generated pulse train are demonstrated. The clock pulse train is generated by means of all-optical wavelength conversion using seed clock signal, probe signal, and single semiconductor optical amplifier (SOA) with the gain peak wavelength at short side. By adjusting the injected signal powers into the converter, the generated clock pulse train at the bit-rate of 10 Gb/s has high optical signal-to-noise ratio (OSNR) and low excess timing-jitter in a wide operating wavelength range. We also demonstrate 20-km transmission experiment using the generated signal in the range of 1460–1610 nm. In this experiment, we achieve transmission performances comparable to that of 1550 nm seed clock signal.     

基于半导体光放大器和受激布里渊散射的全光非归零码时钟提取

利用半导体光放大器(SOA)的增益饱和特性、自相位调制(SPM)效应和啁啾光纤光栅(CFBG)的滤波和啁啾特性共同作用实现了10 Gbit/s非归零码(NRZ)信号的时钟分量增强。经过该结构的非归零光谱的时钟分量增强后,其时钟数据抑制比提高了12.9 dB。时钟分量增强后的信号经基于受激布里渊效应(SBS)的时钟提取结构后实现了对非归零信号的全光时钟提取。这种新型非归零全光时钟提取结构具有对数据速率及数据格式透明,低抖动,不受码型效应的影响等优点。     

Amplitude Regenerative Characteristics of RZ-DPSK Wavelength Converter Based on Four-Wave Mixing in SOA

We investigate the phase-preserving amplitude regenerative characteristics of the return-to-zero （RZ） differential- phase-shift-keying （DPSK） wavelength conversion based on four-wave m/xing （FWM） in a semiconductor optical amplifier （SOA）. The Q-factor and the optical signal-to-noise ratio （OSNR） before and after conversion are experimentally obtained and analysed in different input noise power levels. In both the continuous-wave and synchronous clock pumping cases, we find that there is amplitude clamping in the FWM conversion due to the gain saturation of SOA, which can suppress the amplitude fluctuation of the converted DPSK signal before and after demodulation. We have achieved 2-dB Q penalty improvement in our experiment demonstration of lOGbit/s RZ-DPSK signal with OSNR lower than 19dB.     

Wavelength-spacing continuously tunable multi-wavelength SOA-fiber ring laser based on Mach–Zehnder interferometer

A Mach–Zehnder interferometer (MZI) which is used as a wavelength-spacing tunable comb filter in a fiber ring laser is built by employing an optical variable delay line (OVDL). Stable multi-wavelength semiconductor optical amplifier (SOA)-fiber ring laser based on an SOA and the MZI comb filter is achieved. Wavelength spacing can be continuously tuned by adjusting the OVDL and, as an example, multi-wavelength lasing with the wavelength spacing of 0.4, 0.8, or 1.6 nm is demonstrated. The output of the proposed multi-wavelength SOA-fiber ring laser is quite stable at room temperature and the output spectrum can be adjusted by controlling the bias current of the SOA.     

半导体光放大器的光-光互作用及其应用

半导体光放大器（SOA）中的非线性系数约为普通光纤的10^9，为光子晶体光纤的10^7，而且有4种光-光互作用，即交叉增益调制（XGM）、交叉相位调制（XPM）、交叉偏振调制（XSM）及四波混频（FWM），可以灵活地组成各种光信号处理器件，如波长变换器、全光触发器、全光逻辑、全光时钟恢复、全光缓存器……等，正成为整个光信号处理的基础。文章介绍了它们的原理和简单应用。     

10、20、40Gb/s速率下恶化信号的光时钟提取

报道了一种全部由10GHz带宽的元件构成的、用于时钟提取的双环注入锁模光纤激光器.这种装置集光电振荡器(OEO)与注入锁模光纤激光器的优点于一体,利用它不仅从恶化的数据信号中实现了10Gb/s的位时钟提取,在采用了光电振荡器的分频、锁模光纤激光器的有理谐波锁模以及F-P梳状滤波器的频率倍乘技术以后,还从20Gb/s和40Gb/s的恶化信号中提取出了位时钟.该方案的另一个优点是无码型效应.