双抽运光纤光参变放大的全光多波长变换与码型转换

利用强度调制的数据信号光作为一路抽运光,与另一路直流或者正弦强度调制抽运光组合可以在双抽运光纤光参变放大过程中实现全光多波长变换或者在全光多波长变换的同时实现码型转换.理论上,从信号增益的角度分析了波长转换与码型转换的原理.实验上演示了2.5Gb/s的非归零(NRZ)码信号的全光多波长转换与到归零(RZ)码信号的转换.多波长转换实验表明:双抽运条件下的光参变过程可以实现多波长转换并得到正、反码的输出,还同时对信号有一定的再生作用.码型转换后信号的占空比为30%,消光比也得到提高.     

利用光参变放大同时实现双波长全光判决的实验研究

为了能够对多路光信号同时实现整形再生,提出了一种在高非线性光纤(HNLF)中利用单抽运光参变放大(OPA)同时实现双波长全光判决的实验方案。该方案基于一段500m长的HNLF,输入信号为两路不同波长的10Gb/s伪随机归零(RZ)码信号,抽运光为10GHz的时钟脉冲。信号光与抽运光在HNLF中发生参变过程,通过两个光带通滤波器,分别滤出两路闲频光波长信号,可以在同一段HNLF中同时实现双波长全光判决。实验中,对两路10Gb/s伪随机归零码信号进行了恶化,以仿真长距离传输损耗及失真,恶化后信号的消光比(ER)分别为9.17dB和8.27dB,判决后的信号ER分别提高到12.8dB和12.66dB。通过实验论证了一种双波长全光判决的实现方案。     

基于光子晶体光纤中双抽运四波混频效应的非归零到归零码型转换实验研究

提出并实验证实了利用色散平坦高非线性光子晶体光纤中双抽运四波混频效应实现非归零 (NRZ)到归零(RZ)码型转换的新方案, 将一束NRZ信号光与两束同步时钟脉冲光同时注入光子晶体光纤, 通过双抽运四波混频效应产生两个闲频光, 经过光学滤波后即可完成单到双全光NRZ-RZ码型转换. 与基于常规单抽运四波混频效应的码型转换方式相比, 本设计方案由于采用了双抽运四波混频效应, 因此具有双路组播信号波长可彼此独立选取的优点. 分析了码型转换器的波长调谐性及对输入光功率波动的容忍性, 得到转换信号的最优消光比和Q 因子分别为15 dB和5.4. 研究结果表明, 本方案既具有对比特率和调制格式透明的优点, 又避免了使用单抽运四波混频效应进行码型转换时两路组播信号波长相互制约的弊端, 且实现了全光波长转换和波长组播功能. 关键词： 码型转换 四波混频 双抽运 光子晶体光纤     

基于级联调制器的四进制幅移键控非归零码到归零码格式转换器

提出了一种全新的基于相位-强度级联调制器和色散补偿光纤(DCF)的四进制幅移键控(4-ASK)非归零码(NRZ)到归零码(RZ)格式转换方案.理论分析了新格式转换器的工作原理,并进行了20 Gb/s的四进制幅移键控NRZ到RZ的格式转换实验研究.结果表明,该方案能将四进制幅移键控NRZ信号转换为四进制幅移键控RZ信号,...     

40 Gb/s非零色散位移光纤传输系统中四种调制格式的性能比较

介绍了四种调制格式即非归零(NRZ),归零(RZ),载波抑制的RZ(CSRZ)和单边带RZ(SSB-RZ),用计算机仿真方法产生了这四种调制格式的40 Gb/s光信号,比较了其波形和光谱.也对这四种调制格式在非零色散位移光纤(NZDSF)上单信道传输进行了仿真,结果表明:在色散完全补偿情况下,RZ,CSRZ和SSB-RZ抗非线性能力都比NRZ强,其中CSRZ最强, CSRZ能够容忍的入纤光功率比NRZ大10.2 dBm;RZ,CSRZ和SSB-RZ 三种格式抗EDFA噪声能力差不多,但都比NRZ强.     

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.     

基于半导体光放大器交叉偏振调制效应实现正、反相波长变换

利用琼斯矩阵，对基于半导体光放大器中的交叉偏振调制效应实现全光波长变换进行了理论分析.结果表明，利用这种机制可以实现同相与反相波长变换.在实验上同时实现了10Gb/s归零信号的正相与反相波长变换，输出消光比分别达到了6.9 dB和8.1 dB.     

自启动的非归零/归零码和光电时钟信号发生器及码型转换

采用双波长注入一包含伪随机码发生器与相位调制器的光电振荡器可以同时得到非归零(NRZ)码,归零(RZ)码以及光,电时钟信号输出。该方案使用了光域耦合的双环路结构,在不增加有源器件的条件下实现边模抑制。相位调制器用于反馈调制并同时实现占空比可调的非归零码到归零码的转换。双波长的注入排除了编码信号在振荡器中引入的非时钟频率成分。实验给出了10 Gb/s工作速率下的结果,得到了抖动为637 fs的光信号输出。转换得到的归零码信号占空比约为33%。输出电时钟信号的相位噪声在频偏10 kHz处为-109 dBc/Hz,边模抑制比为58 dB。     

基于光子晶体光纤中四波混频效应的单到双非归零到归零码型转换

归零(RZ)码与非归零(NRZ)码是波分复用和时分复用系统中广泛采用的两种码型, 全光NRZ到RZ码型转换能完成从波分复用到时分复用的网络接口功能, 是未来透明光子网络中一项重要的全光信号处理技术. 提出并实验证实了一种基于色散平坦高非线性光子晶体光纤中四波混频效应的单到双NRZ到RZ码型转换方法, 将一束信号光与同步时钟脉冲同时输入色散平坦高非线性光子晶体光纤中, 通过四波混频过程, 产生两个携带该数据信息的闲频光, 从而实现了单到双的NRZ到RZ码型转换功能, 码型转换器工作波长在193 nm范围可调谐, 最大转换效率为-21 dB, 最优消光比和品质因子分别为11.9 dB和7.2. 该方法的特点在于基于光纤中的四波混频效应工作, 因而具有对调制格式和比特率透明的优点, 同时, 光子晶体光纤特有的高非线与色散平坦性, 既避免了使用传统光纤需要较长的长度, 又避免了波长设置不灵活的弊端, 并具备可进一步增加带宽的能力, 且在码型转换的同时, 实现了波长转换, 完成了双通道波长组播功能. 整个系统为全光纤设计, 结构简单, 性能可靠, 并易于与现有的光纤通信系统相容, 对促进超高速大容量光子网络的发展具有重要意义. 关键词： 码型转换 四波混频 光子晶体光纤     

基于光纤中四波混频效应的全光串-并转换研究

 为了实现高速信号的降速处理,设计并通过实验演示了一种高速全光串-并转换系统。在方案中,利用时钟脉冲自身的频谱宽度和光纤中四波混频的高速响应特性,可以从一个光分频时钟脉冲出发,利用光纤中群速度色散（GVD）致脉冲展宽效应,把一个重复频率为10 GHz的时钟窄脉冲在时域上展宽,并通过光纤中的四波混频过程,将一路40 Gb/s 的归零（RZ）码信号转换成为4路10 Gb/s信号,完成串-并转换功能。该方案响应速率高,对波长和码率透明,并具有很大的转换路数可拓展性。     

Novel orthogonal modulation format DRZ-FSK/DPSK for high-speed long-haul optical communication

We propose a novel advanced orthogonal modulation format dark return-to-zero frequency shift keying/differential phase shift keying （DRZ-FSK/DPSK） and its realization scheme. The DRZ-FSK/DPSK is generated by the combination of a 40-Gb/s return-to-zero （RZ） signal and a DRZ signal which is converted from the RZ using a semiconductor optical amplifier （SOA） based on nonlinear cross polarization rotation （XPR） and then re-modulated by high-bit-rate DPSK at 40 Gb/s. The feasibility of the scheme is exper-imentally demonstrated. Bit error rate （BER） results of the total 80-Gb/s DRZ-FSK/DPSK orthogonal modulation signal with a subsequent 100-km single-mode fiber （SMF） transmission link show its potential for future high-speed long-haul optical communication.     

All-optical NRZ-to-RZ format conversion with dual channel wavelength multicasting functions exploiting cross-phase modulation in a dispersion-flattened nonlinear photonic crystal fiber

All-optical single-to-dual channel format conversion from NRZ to RZ at 10 Gbit/s using cross phase modulation (XPM) in dispersion flattened highly nonlinear photonic crystal fiber (DF-HNL-PCF) is demonstrated. Format conversion with dual channels signal multicasting function is achieved by filtering simultaneously the blue- and red-chirped components of broadened optical spectrum induced by XPM between NRZ signal and clock light. Moreover, the wavelength tunability and dynamics characteristics of proposed format converter are also exploited experimentally by using NRZ signal light with different central wavelength and varying input power. Our results show that a wide wavelength operation range of 21.2 nm, extinction ratio (ER) and Q factor of over 10.9 dB and 6.1 are obtained. Furthermore, the influence of central wavelength offset of optical bandpass filter on converted RZ signal quality is investigated. The proposed scheme is simple, robust, and transparent to bit rate, which makes it very potential for application in future photonic networks.     

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.     

Simultaneous multichannel NRZ-to-RZ format conversion of 4-ASK signal based on phase-intensity hybrid modulation and dispersion compensation fiber

We propose and investigate a novel technique to realize non-return-to-zero （NRZ） to return-to-zero （RZ） format conversion of a multichannel 4-ary amplitude shift keying （4-ASK） signal. The proposed format converter composed of two modulators and a dispersion compensating fiber （DCF） is theoretically inves-tigated using numerical simulation as basis. Research shows that a 4-channel 20-Gb/s NRZ-4-ASK signal can be converted to a RZ-4-ASK signal simultaneously without wavelength shifting and signal quality degradation, with the converted signal multiplexed to 40 Gb/s.     

Label swapping and packet transmission of DPSK-labeled PPM signal in optical label switching

A label swapping scheme of an optical labeled signal with differential phase shift keying(DPSK) for label at 2.5 Gb/s and pulse position modulation(PPM) for payload at 40 Gb/s is demonstrated by simulation.Power penalties of ～1.8 and ～0.8 dB are achieved for both the payload and label over 80-km single mode fiber(SMF) transmission.This labeling scheme allows the use of four-wave mixing(FWM) in semiconductor optical amplifier(SOA) to perform label erasure,with advantages of transparence for bit rate,high processing rate,simple architecture,and low cost.Label swapping is demonstrated with appropriate penalties of-3.5 and 0.8 dB for PPM payload and new DPSK label,respectively.To further prove the effectiveness of the proposed scheme,label swapping in the case of using 10-Gb/s DPSK label is also investigated with the power penalties of 6 and 2 dB for PPM payload and new DPSK label.     

A novel optical picosecond-duration NRZ-to-RZ format converter with simultaneous wavelength multicasting using a single-stage Mach–Zehnder modulator

We propose a novel and simple scheme to achieve NRZ-to-RZ format conversion and simultaneous wavelength multicasting based on a single-stage dual-arm electro-optic Mach–Zehnder modulator (MZM) and a short single mode fiber (SMF). The format conversion and wavelength multicast process are achieved by chirp compensation under the condition of generation of optical flat frequency comb. 40 Gb/s NRZ-to-RZ conversion with one-to-five multiple-wavelength channel multicasting and transmission of the NRZ and the converted signals over 200 km dispersion-managed fiber-link are successfully demonstrated by numerical simulation. Research results show that 40 Gb/s 2 ps RZ signal with wavelength-preserving can be obtained after format conversion. The converted RZ signal presents good transmission performance and can easily be multiplexed to 160 Gb/s using optical time division multiplexing (OTDM) technology. All the multicast channels can be error free after 50 km transmission. Besides, the conversion operation can also greatly reduce the timing jitter of the degraded NRZ signal due to the retiming function of the proposed scheme.     

Multi-Channel NRZ/RZ-DPSK to CSRZ-DPSK Format Conversion Based on Nonlinear Polarization Rotation of SOA

We present an all-optical nonreturn-to-zero/return-to-zero(NRZ/RZ) to carrier-suppressed return-to-zero(CSRZ)format conversion scheme for differential phase-shift ke.ying(DPSK) signals. The conversion is based on nonlinear polarization rotation of a semiconductor optical amplifier(SOA). The 4-channel NRZ-DPSK or RZ-DPSK signals at 10 Gb/s are simultaneously converted to the corresponding CSRZ-DPSK signals, with-0.8 and 1.4 dB average power penalties, respectively. Additionall.y, high quality format conversion performanes are shown with the optical spectra and eye diagrams.