双通道全光NRZ/RZ格式转换器设计

提出了一种双通道全光非归零码/归零码调制格式转换的方案.该方案中,非归零码信号与同步的时钟抽取光共同注入到高性能非线性光纤中,由高性能非线性光纤构成的参量放大器把非归零码信号转换为归零码信号,同时不改变信号光的波长.实验论证了10Gb/s非归零码双通道的码型转换器.转换后的归零码信号的光信噪比略低于输入光信噪比,其脉冲...     

利用TOAD实现10 Gbit/s全光非归零码到归零码的转换

利用从非归零（NRZ）信号中全光提取的时钟，采用太赫兹光非对称解复用器（TOAD）实现了10 Gbit／s非归零码到归零（RZ）码的码型转换。非归零信号采用半导体光放大器（SOA）进行时钟分量增强并用平面波导阵列（AWG）滤出相应的伪归零（PRZ）信号，然后采用半导体光放大器注入锁模光纤环形激光器进行时钟提取，提取的时钟信号和待转换的非归零信号分别作为抽运光和探测光输入太赫兹光非对称解复用器，在其中进行码型转换。转换后输出的归零信号的质量仅由恢复的时钟信号和非归零信号的质量决定，受太赫兹光非对称解复用器中半导体光放大器增益恢复时间的影响极小。实验测得转换后的归零信号消光比为8．7dB，码型效应非常低，其光谱明显展宽．并且出现谱间隔为0．08nm的多峰结构，与10 Gbit／s的比特速率相对应。该方法对时钟信号的码型效应有一定的容忍度。     

差分相移键控的非归零到归零格式转换研究

提出了一种全新的基于相位-强度混合调制和色散补偿的光差分相移键控(DPSK)信号的非归零(NRZ)到归零(RZ)格式转换器,理论分析了转换器参数对转换的影响,数值研究了恶化条件下的10 Gb/s的NRZ-DPSK到RZ-DPSK的格式转换。实验展示了10 Gb/s的DPSK信号格式转换及解调后的误码性能。计算结果表明,通过设计转换器参数可获得低占空比RZ-DPSK信号,且转换后信号质量较高。实验结果表明格式转换功率代价较低,转换后RZ-DPSK信号时间抖动较原NRZ-DPSK信号减小。该格式转换器还适合光四相差分相移键控(DQPSK)的非归零到归零格式转换及多波长操作。     

利用SOA和OBPF的40Gb/s RZ到NRZ全光码型变换

全光码型转换技术是实现未来全光网络的关键技术之一,为此提出了一种利用半导体光放大器（SOA）和光带通滤波器（OBPF）的归零（RZ）码到非归零（NRZ）码的信号转换方案。利用通信软件数值模拟了基于40 Gb/s的码型转换,仿真实现了稳定的不同占空比的RZ码到NRZ码的码型转换以及波长转换。     

利用MZ-DI装置的40Gb/s RZ到NRZ全光码型变换

利用马赫-曾德尔延时干涉(MZ-DI)装置对40Gb/s的归零(RZ)码到非归零(NRZ)码的全光码型转换方案进行研究.利用通信软件模拟了40Gb/s的码型转换过程,实现稳定的不同占空比的RZ码到NRZ码的码型转换.当占空比约为0.3时,转换效果最佳.     

OTDM网与WDM网接口间的码型转换技术研究

利用半导体光放大器(SOA)和光带通滤波器(OBPF)构成了一个全光码型转换器.理论分析了码型转换的原理,得出了码型转换取决于光带通滤波器的3dB带宽以及探测光中心波长相对于光带通滤波器中心波长失谐量的结论,实验测得3dB带宽为0.17nm,失谐量△λ=0.62nm.最后通过仿真实现了10Gb/s数据信号全光归零(RZ...     

基于偏振调制的新型非归零码—归零码转换器

设计了一种基于偏振调制(PolM)实现非归零码(NRZ)信号到归零码(RZ)信号转换的新型码型转换器,并采用光通信模拟软件对其进行了仿真验证。所设计的转换器,首先采用PolM,对输入的NRZ信号进行偏振调制,然后采用射频时钟信号,抑制信号的旁瓣,实现NRZ到RZ的转换。该码型转换器具有RZ信号占空比可控,经码型转换器后各信号波长相同,时间抖动小,转换效率高,成本低优点,可望在高速光通信网络中得到广泛应用。     

利用偏振延时干涉装置的NRZ到RZ全光码型变换

提出一种基于偏振延时干涉仪(PDI)的非归零(NRZ)码到归零(RZ)码的全光码型转换方案。理论推导光信号经过PDI时光场的演变过程,分析了码型转换的原理。数值仿真实现了10Gb/s速率下NRZ到RZ码的转换,通过比较得出转换后的RZ码具有更高的接收灵敏度。改变双折射介质的差分群时延可以得到不同占空比的RZ信号输出。     

恶化非归零码信号的全光时钟恢复

全光时钟提取结构应对输入信号的恶化程度有一定的容忍度.在一种半导体光放大器(SOA) 啁啾光纤布拉格光栅(CFBG) 受激布里渊散射(SBS)的方式实现非归零(NRZ)码信号的全光时钟提取结构中,半导体光放大器和啁啾光纤布拉格光栅共同作用实现了非归零码信号的时钟分量增强,基于受激布里渊散射的全光时钟提取结构提取出非归零码的光时钟信号.实验通过对不同恶化程度的非归零码信号的时钟提取比较发现,恶化信号的信噪比是影响光时钟提取的关键.输入非归零码信号的信噪比越差,光时钟信号光谱的噪声水平越高,提取出的光时钟信号的幅度越低.当时钟增强非归零码信号的时钟数据抑制比低于-10 dB时,无法实现非归零码信号的时钟提取.     

40Gb/s光纤通信系统中不同码型传输特性的实验研究

在高速光纤通信系统中码型的选择是决定系统传输质量和光谱效率的主要因素。码型的选择和信道速率、信道波长间隔、光放大器的选择、光放大器放置间隔、光纤的类型、色散管理策略等各种因素密切相关。分析了非归零码（NRZ）、归零码（RZ）和载波抑制归零码（CSRZ）码型的产生方式及特点。采用单信道和掺铒光纤放大器（EDFA）放大方式对三种码型进行了40Gb/s的100kmG.652光纤通信传输实验。比较了三种码型的系统传输持性、最佳入纤功率和不同入纤功率下的功率代价：载波抑制归零码最佳入纤功率为9dBm，功率代价小于非归零码和归零码。结果表明，在相同的色散补偿条件下，载波抑制归零码比归零码和非归零码有更优的非线性容忍度。     

Multi-wavelength conversion at 10 Gb/s and 40 GHz based on nonlinear effects in HNLF

We present experimental results and numerical simulations of multiple-wavelength conversion of 10 Gb/s non-return-to-zero (NRZ) signals based on 2-pumps four-wave mixing and of 40Gb/s return-to-zero (RZ) signals through supercontinuum (SC) generation in a highly nonlinear fiber (HNLF). Two pumps with a 100 GHz separation located in the region of anomalous dispersion of the HNLF were combined to form a beat signal The 10 Gb/s NRZ signal anchored on ITU grid was converted with gain into 6 new signals and 6 idlers with 100 GHz separation. High quality sc with bandwidth exceeding 50 nm was generated when the HNLF was pumped with 25 dBm average power. Sliced sc can be used as a source for all-optical multicasting.     

Optical Signal-to-Noise Ratio Estimation Using Reference Asynchronous Histograms

This paper presents and experimentally demonstrates a novel method for the estimation of optical signal-to-noise ratio (OSNR) based on the comparison of an asynchronous histogram of the signal under analysis with a reference asynchronous histogram. The latter is acquired from the signal under analysis at a calibration stage. The proposed method allows the use of optical amplification to increase the sensitivity of the optical monitoring system (OMS) by a factor 20 dB, when using an erbium doped fiber preamplifier. In addition, the use of a semiconductor optical preamplifier, initially designed for nonlinear operation at 2.5 Gb/s is used in the OMS to preamplify 40-Gb/s signals, achieving a sensitivity gain of 10 dB. It will be experimentally demonstrated that the proposed method is applicable to 40-Gb/s nonreturn to zero (NRZ) signals arbitrarily degraded by group velocity dispersion (GVD). Furthermore, accurate monitoring of the OSNR of return-to-zero (RZ) signals will also be possible using a simple RZ-to-NRZ converter based on narrow-band optical filtering within the OMS. The proposed method also allows estimating of the GVD-induced OSNR penalty between the signal under analysis and the signal at the calibration stage.     

Amplitude Regeneration of RZ-DPSK Signals in Single-Pump Fiber-Optic Parametric Amplifiers

The input power tolerance of a single-pump fiber-optic parametric amplifier (FOPA) is experimentally shown to be enhanced for return-to-zero differential phase-shift keying (RZ-DPSK) modulation compared to RZ on–off keying modulation at 40 Gb/s. The improved nonlinear tolerance is exploited to demonstrate amplitude regeneration of a distorted RZ-DPSK signal in a gain-saturated FOPA. An optical signal-to-noise ratio penalty of 3.5 dB after amplitude distortion is shown to be reduced to 0.2 dB after the FOPA, thus clearly demonstrating the regenerative nature of saturated FOPAs for RZ-DPSK modulation.      

Performance degradations of multigigabit-per-second NRZ/RZlightwave systems due to gain saturation in traveling-wave semiconductoroptical amplifiers

A nonlinear model for a travelling-wave semiconductor optical amplifier has been used to determine eye closure degradations for 2.4 and 10 Gb/s NRZ/RZ lightwave systems due to gain saturation effects in the optical amplifier. At 10 Gb/s, with a carrier lifetime of 300 ps, the results indicate that the penalty is less than 1 dB for both NRZ and RZ systems provided that the ratio of the input power (P_in ) to the saturation output power (P_sat) is less than -17 dB. The NRZ system penalty is slightly larger than the RZ penalty when P_in/P_sat is larger than -17 dB. For example, with P_in/P_sat=-10 dB, the NRZ system penalty is about 2.8 dB versus 2 dB for the RZ system. The system penalty at 2.4 Gb/s is slightly less than that at 10 Gb/s. At P _in/P_sat=-10 dB, the NRZ system penalty is about 2.5 dB versus 1.5 dB for RZ     

All-Optical Conversion From RZ to NRZ Using Gain-Clamped SOA

An all-optical converter from return-to-zero (RZ) pulses to the nonreturn-to-zero (NRZ) format is presented. The converter operates in two stages: the laser generated in a gain-clamped semiconductor optical amplifier (SOA) is modulated with the data signal; afterwards this signal is wavelength-converted by cross-gain modulation in a common SOA. The setup is noninverting and can feature wavelength conversion. Experimental error-free conversion from 5- and 40-ps RZ pulses to NRZ format is presented at 10 Gb/s using a 2¹¹-1 bit sequence     

光纤传输系统中基于相位预调制的信号整型

利用相位预调制技术解决高速长距离光纤传输系统中面临的接收灵敏度降低和色散容限问题。通过在发射端对非归零(NRZ)的光信号进行比特同步相位预调制,使非归零码在传输过程中得到波形重整,演变为归零(RZ)的波形,从而提高眼图开启度。实验观测了普通非归零码和相位预调制的非归零码在不同相位调制深度和色散下的光谱、眼图和功率代价。10Gb/s的传输结果表明,链路色散绝对值小于1000ps/nm时,施加相位预调制的非归零信号功率代价小于1dB,比普通非归零信号具有更高的接收灵敏度和更低的色散功率代价。因此,基于相位预调制的信号整型技术可减轻系统对光信噪比和色散管理的要求,延长传输距离。     

NRZ versus RZ in 10-40-Gb/s dispersion-managed WDM transmissionsystems

We compare nonreturn-to-zero (NRZ) with return-to-zero (RZ) modulation format for wavelength-division-multiplexed systems operating at data rates up to 40 Gb/s. We find that in 10-40-Gb/s dispersion-managed systems (single-mode fiber alternating with dispersion compensating fiber), NRZ is more adversely affected by nonlinearities, whereas RZ is more affected by dispersion. In this dispersion map, 10- and 20-Gb/s systems operate better using RZ modulation format because nonlinearity dominates. However, 40-Gb/s systems favor the usage of NRZ because dispersion becomes the key limiting factor at 40 Gb/s     

不同调制码型的偏振模色散补偿研究

在40Gb/s的光纤通信系统中,用三段模拟器模拟光纤传输中的一阶与二阶偏振模色散(PMD),采用单偏振态的偏振度(DOP)作为多级PMD补偿器的反馈信号,对归零(RZ)码、非归零(NRZ)码、载波抑制归零(CSRZ)码和啁啾归零(CRZ)码分别进行四个自由度的一级、六个自由度的二级和十个自由度的三级PMD补偿器的补偿.仿真得到了四种码型的DOP与误码率(BER)的关系,同时补偿后的BER、DOP和PMD的变化关系表明,对RZ和NRZ码采用二级补偿器的效果比一级和三级补偿器要好得多,对CSRZ码和CRZ码采用单偏振态的DOP作为反馈信号进行PMD补偿的效果并不理想.     

Low insertion loss and low dispersion penalty InGaAsP quantum-well high-speed electroabsorption modulator for 40-Gb/s very-short-reach, long-reach, and long-haul applications

We present a metal-organic-chemical-vapor-deposition-grown low-optical-insertion-loss InGaAsP/InP multiple-quantum-well electroabsorption modulator (EAM), suitable for both nonreturn-to-zero (NRZ) and return-to-zero (RZ) applications. The EAM exhibits a dynamic (RF) extinction ratio of 11.5 dB at 1550 nm for 3 Vp-p drive under 40-Gb/s modulation. The optical insertion loss of the modulator in the on-state is -5.2 dB at 1550 nm. In addition, the EAM also exhibits a 3-dB small-signal response (S21) of greater than 38 GHz, allowing it to be used in both 40-Gb/s NRZ and 10-Gb/s RZ applications. The dispersion penalty at 40 Gb/s is measured to be 1.2 dB over /spl plusmn/40 ps/nm of chromatic dispersion. Finally, we demonstrate 40-Gb/s transmission performance over 85 km and 700 km.