全光高速同步时钟信号的产生

采用 2 5GHz光脉冲序列作为低速时钟 ,将其注入一含半导体光放大器 (SOA)的锁模光纤激光器中 ,利用SOA的交叉增益调制效应 ,采用有理数谐波锁模技术 ,产生了 2～ 7倍同步群路时钟信号。利用这一技术可以为未来高速光时分复用 (OTDM)通信网络中心处理单元提供同步控制时钟。     

基于LiNbO3调制器的高速时钟信号的提取

对在高速光时分复用系统中(2×10 GHz)基于铌酸锂(LiNbO3)调制器的注入光电混合振荡器的时钟提取方法进行了实验验证,提取的时钟抖动小于0.5 ps.实验分析了入射光功率、LiNbO3调制器的开关窗口及复用信号非等幅和延时不等时对时钟信号的影响,为未来应用于更高速率的光时分复用系统中支路信号的时钟提取提供了实验依据.     

4×10Gbit/sOTDM系统中10GHz帧时钟提取技术

本文介绍了利用非等幅原理进行帧时钟分量提取的原理;阐述了40Gbit/s光时分复用(OTDM)系统中利用电时钟提取技术实现10GHz帧时钟的理论模型和实验框图;分析了OTDM光信号参数和时钟提取单元参数对系统的影响,并给出了理论分析结果;分析了应用于实际中的时钟提取单元的实现过程和实验结果;并对理论结果和实验结果进行了分析和比较.     

基于不同Q值F-P滤波器的40GHz全光帧时钟提取

对用不同Q值的F-P滤波器提取40 GHz光帧时钟的方案进行了实验比较.实验表明,用高Q值F-P滤波器提取的帧时钟信号好,但是建立、消失时间长;用低Q值F-P滤波器提取的帧时钟,信号质量较差,但可以保证帧时钟的快速建立和快速消失.实验还表明,半导体放大器(SOA)的自增益调制效应(SGM)可以有效地提高时钟的建立速度,对于时钟信号的抖动也有一定程度的改善.抖动的改善与滤波器的Q值有直接的关系.用上述方案对40 GHz的帧信号进行了全光帧时钟提取,得到了建立时间为15个信号周期,消失时间为115个信号周期,抖动为2.35 ps的帧时钟信号.     

基于锁模脉冲源和高速光开关的时分抽样模数转换

提出了一种基于锁模脉冲源和高速光开关的时分抽样模数(A/D)转换系统。使用高重复频率、窄脉宽的锁模脉冲串对射频信号进行抽样,利用高速光开关进行时分复用,将高采样率的信号转换为并行的多路低采样率信号,以适应现有的电模数转换器进行量化和编码,并且通过改变光开关的频率,可以灵活地改变解复用后每路信号的频率。系统的优点在于可扩展性高,只需一个锁模脉冲源。使用10 GHz重复频率的锁模脉冲和1.25 GHz的高速光开关验证了系统方案的可行性。利用实验中得到的采样点可以较好地恢复出时域信号,并且得到了各个频率的频谱图。其信噪比可达32.02 dB,等效于5.03 bit的有效比特数。     

基于半导体光放大器环形腔的全光频率倍增/恢复

提出了一种利用具有干涉作用的半导体光放大器(SOA)环形腔实现全光频率倍增/恢复的新方法,该方法同相关实验比较具有显著优势.数值结果表明:2.5 GHz的光脉冲序列注入SOA环形腔,可输出重复频率为5～25 GHz振幅均衡、与入射光偏振无关的光脉冲序列;SOA的偏置电流对SOA环形腔输出脉冲振幅的均衡度影响显著,对于基频为2.5 GHz和10 GHz输入脉冲序列分别存在一最佳的SOA偏置电流值;从传输速率为2.5 Gbit/s的27-1伪随机信号中可提取出重复频率为分别2.5 GHz和5 GHz的幅度均衡的时钟信号.     

全光纤锁模腔结构的全光时钟提取实验研究

分析并实验验证了一种全光纤锁模激光器结构的全光时钟提取方案。方案中,采用高非线性光纤(HNLF)替代传统结构中的半导体光放大器(SOA),利用光纤中的交叉相位调制(XPM)效应实现腔内的非线性调制,避免了以SOA作为非线性光调制器件的锁模激光器全光时钟提取方案中,由于载流子恢复时间较长从而限制工作速率的缺点,以达到突破"电子瓶颈"的目的。理论分析了光纤中交叉相位调制的特性以及环形锁模腔的时钟提取原理,并通过实验,从40Gbit/s的光归零码(RZ)信号中提取出了高质量的光信号时钟。该方案可以直接在更高速率条件下工作。     

OTDM系统时钟提取和解复用研究北大核心

为了从高速OTDM(光时分复用)信号中提取出支路时钟并实现解复用,实现高速光信号与相对低速电信号之间的接口,首次展示了一种基于商用的MZM(马赫-曾德调制器)和PolM(偏振调制器)级联的OEO(光电振荡器)实现从2×40GBaud/s OTDM信号中提取支路时钟并同时解复用的实验方案。利用这种改进的OEO,成功地从2×40GBaud/s的OTDM DQPSK(差分四相相移键控)调制格式的高速光信号中提取出了40GHz电时钟,该时钟的相位噪声在10kHz频偏处达到-98.62dBc/Hz,与微波源(Agilent Technologies,E8267D)的相位噪声质量几乎相同。这种OEO还同时实现了从OT-DM信号中解复用出两个支路信号的功能,即将160Gbit/s的PRBS(伪随机二进制序列)OTDM信号成功解复用为两路高质量的80Gbit/s支路信号。     

OTDM实用化关键技术分析

本文介绍了光时分复用技术（OTDM）的特点和现状，并从OTDM超短脉冲源和帧时钟信号提取2个方面分析了OTDM技术走向实用化的2个关键技术。     

半导体激光器的设计与数值研究

设计了半导体激光器的模型,它包含两个半导体光放大器(SOA),其中一个SOA充当调制器(调制SOA),另一个SOA充当增益介质(增益SOA)。对该模型进行了理论分析及数值模拟,结果表明:适当调节调制SOA的偏置电流,在增益SOA的偏置电流实现小信号净增益大于零的情况下,激光器能够输出高峰值功率、窄脉宽的锁模脉冲;调节注入脉冲,最终可以输出重复频率为25GHz的稳定光脉冲序列。     

4×10Gb/s OTDM复用与解复用结构优化技术研究

基于40Gb/s OTDM复用结构,利用电吸收调制器(EAM)及时钟提取模块组成的解复用模型,实现了10GHz时钟分量的提取和信号的解复用.针对OTDM复用后信号的非等幅现象以及对应频谱中含有10GHz、20GHz等其他频谱分量的情况,进行了仿真分析及讨论.同时通过实验对不同的时钟提取与解复用结构提取出的时钟信号的质量进行了对比,优化了解复用结构,得到了抖动更小的帧时钟信号.     

Efficient time gating in ultrafast optical TDM networks

Ultrafast optical communication is the backbone of high-speed global networking infrastructure. Optical time division multiplexing (OTDM) is a popular technique for embedding data from many simultaneous users on a single optical channel. This paper studies the optimal clock signal used in optical time gating to extract the data of the desired user in an OTDM network. We show that the pulse width of the clock signal can be optimized to achieve a minimum bit error rate (BER) in these networks. In this paper, we assume that the optical clock signal used for time gating has jitter, and there is therefore a delay variation between the clock and data signals. We model this delay as a zero mean Gaussian random variable. Using this model, an analytical BER expression is derived for systems with Gaussian pulses. In the numerical results, we find the optimal values of the clock pulse width by evaluating the BER versus the pulse width for different variances of the delay. Simulation results are also presented to evaluate the accuracy of the analytical expression.     

Optical Clock Recovery Using a Polarization-Modulator-Based Frequency-Doubling Optoelectronic Oscillator

We propose and demonstrate a flexible optical clock recovery scheme using a polarization-modulator-based frequency-doubling optoelectronic oscillator (OEO). The proposed system can extract both prescaled clock and line-rate clock from a degraded high-speed digital signal using only low-frequency devices. A simple theory is developed to study the physical basis of the optical clock recovery. The OEO operation from a free-running mode to an injection-locking mode is investigated. The locking range is quantitatively predicted. An experiment is then implemented to verify the proposed scheme. A prescaled clock at 10 GHz and a line-rate clock at 20 GHz are successfully extracted from a degraded 20 Gb/s optical time-division-multiplexed (OTDM) signal. The locking range and the phase noise performance are also experimentally investigated. Clock recovery from data signals that have no explicit subharmonic tone is also achieved. The proposed system can be modified to extract prescaled clock and line-rate clock from 160 Gb/s data signal using all 40-GHz devices.      

Injection-locked Fabry-Pe/spl acute/rot laser with electronic feedback for clock recovery from high-speed OTDM signals

We demonstrate the use of an injection-locked Fabry-Pe/spl acute/rot laser diode with electronic feedback for base-rate clock recovery in N/spl times/10 Gb/s optical time-division-multiplexing (OTDM) systems. Injection-locking enhances the resonance frequency of the laser and the electrical feedback achieves strong resonance at the base-rate frequency of the injected data streams, enabling ultrastable electrical clock signal generation at the base rate of 10 GHz. Experimental demonstrations for clock recovery at 10 GHz from 40-Gb/s OTDM data streams and 4-1 demultiplexing of the data using the extracted clock after fiber transmission is presented. The timing jitter measured in the recovered electrical clock is less than 0.25 ps.     

利用锁模光纤激光器做时钟提取器的OTDM通信系统

简短评述了大容量和超大容量光通信系统的ＷＤＭ和ＯＴＤＭ技术，提出了一个在ＯＴＤＭ通信系统中用锁模光纤激光器做时钟提取器的新方法，给出了一个利用设置波分预标时钟脉冲方案构成的新的全光型ＯＴＤＭ通信实验系统结构。     

Optical time division multiplexing: systems and networks

The recent advances in optical time division multiplexed (OTDM) systems and components research show the technique to be highly suited to the generation and transmission of high capacity data on a single optical carrier. This approach uses a single wavelength to carry capacities of at least 40 Gb/s. Such systems are based on a clock frequency and tributary data rates which are easily accessible using electronic components. Short optical pulses are used in a return-to-zero data transmission format with temporal interleaving to map a number of optical data channels into a single electronic clock cycle. It is an approach that can be used to achieve extremely high data-rate bit interleaved systems. This article summarizes the developments in this field and outlines a possible methodology to evolve transport networks to encompass the potential that both WDM and OTDM have to offer     

从非均匀分布的信号脉冲中提取基频时钟脉冲

提出从接收到的光信号脉冲串中提取光基频时钟的方案。此方案的要点是 :首先在光脉冲的复用过程中人为地使复用后相邻码的时间间隔不相等 ,即复用为非均匀码。其次 ,在接收端利用光纤环形锁模激光器提取与复用前原信号同频率的时钟脉冲。实验的初步结果及理论分析表明所提出的时钟提取方案是可行的。     

160-gb/s OTDM signal source with 3R function utilizing ultrafast mode-locked laser diodes and modified NOLM

High-quality 160-Gb/s optical time-division-multiplexing (OTDM) signal source with 3R functions was demonstrated using ultrafast mode-locked laser diodes (MLLDs) and a nonlinear optical fiber loop mirror (NOLM) modified with inline and external polarizers and an inline optical phase-bias compensator. Pulse quality for each OTDM channel was successfully improved and equalized owing to the clock extraction at the true data bit rate using a 160-GHz MLLD and also to the improvement of the switching performance of the NOLM.     

光时分复用超高速光通信技术

介绍光时分复用超高速光通信系统的构成及近来国外发展趋势重点介绍构成ＯＴＤＭ超高速光通信系统的关键技术；超短光脉冲发生技术，全光时分复用／去复用技术，光定时提取技术等。