SOA功率均衡技术的误码率性能分析

对光交叉连接 (OXC)节点中采用半导体光放大器 (SOA)功率均衡技术的方案性能进行了理论分析。首先模拟计算了链路中引入SOA后的功率代价 ;然后逐一讨论了发射机消光比 ,信号码率 ,SOA的噪声系数对系统性能的影响 ;最后计算了OXC节点级联链路的误码率性能。从而为OXC节点和网络设计提供了理论分析和指导依据。     

SOA工作条件对全光异或输出性能的影响研究

理论分析了SOA动态模型和SOA-MZI全光异或原理,采用光通信系统设计软件OptiSystem搭建了基于SOA-MZI的全光异或实验模型,仿真研究了注入SOA的数据信号光功率、连续探测光功率、偏置电流等工作条件对异或输出消光比、Q值以及误码性能的影响,取得了一组最佳工作条件,即数据信号光功率为3dBm,连续探测光功率为0dBm,偏置电流为600mA,此时可以得到最佳的异或输出性能:消光比约11.5dB,Q值约22,误码率约10-108量级。研究方法和相关结论可以推广到基于SOA的其他全光信号处理应用中,为未来全光网络的全面建设做准备。     

Impact of the Signal and Nonlinearity Extinction Ratios on the Design of Nonideal 2R All-Optical Regenerators

The impact of the signal and nonlinearity extinction ratios on the optimum parameters of a reamplification and reshaping (2R) all-optical regenerator is investigated for different nonlinearity characteristic shapes. The bit error ratio (BER) is numerically evaluated along the 2R all-optical regenerator chain using the rigorous distribution and the Gaussian distribution for the optical power. It is shown that, when the extinction ratio of the signal at the transmitter output decreases, the optimum nonlinearity threshold increases. The results also show that, independent of the nonlinearity characteristic shape, the requirements on the extinction ratio of the nonlinearity can be strongly relaxed when the extinction ratio of the nonlinearity is higher than the extinction ratio of the signal at the transmitter output. Numerical results show that, only for nonlinearities with a small degree of nonlinearity and small extinction ratio, the Gaussian distribution correctly estimates the optimum regenerator parameters. For a small extinction ratio of the nonlinearity or a small extinction ratio of the signal at the transmitter output, the Gaussian distribution only provides correct estimates of the minimum BER along the regeneration chain. Furthermore, for high and moderate extinction ratios and degrees of nonlinearity, and for high and moderate extinction ratios of the signal at the transmitter output, the Gaussian distribution fails to correctly estimate the optimum regenerator parameters and minimum BER.     

波分复用-光时分复用波长转换信号的消光比研究

对基于半导体光放大器(SOA)交叉增益调制(XGM)效应的全光波分复用一光时分复用(WDM—OTDM)转换后的两路时分复用输出信号的消光比(ER)特性进行了分析。研究了两路波分复用的输入抽运光和探测光的功率、波长、抽运光的消光比、数据速率以及半导体光放大器的偏置电流、腔长和模场限制因子对转换信号消光比的影响。模拟结果表明，增大抽运光输入功率，选择长波长抽运光，可以增加转换光相应信道消光比，但减小了相邻信道的输出消光比；增加抽运光消光比，可以提高转换光消光比，但各个信道增长幅度不同；减小探测光输入功率，选取短波长探测光波长，增加半导体光放大器的腔长和模场限制因子以及大的偏置电流可提高转换光消光比；对于两路或多路波分复用信号转换时分复用信号的过程中，一定要考虑转换光每个信道消光比的均衡。     

Study of Optical Transmission Performance in IP‐over‐WDM Networks Based on FSK/ASK Combined Modulation Format

The transmission performance of optical labeling based on a combined frequency shift keying/amplitude shift keying (FSK/ASK) format is studied by numerical simulation. The simulation demonstrates that the bit‐error ratio (BER) characteristic of an ASK signal is limited by the extinction ratio, received optical power, and dispersion, simultaneously. However, an FSK signal is mainly limited by the extinction ratio (ER) and received optical power when the peak spectrum, which is used to detect the FSK signal, is relatively narrow.     

High-gain mode-adapted semiconductor optical amplifier with12.4-dBm saturation output power at 1550 nm

A mode-adapted semiconductor optical amplifier (SOA) has been fabricated and packaged. At the gain peak, 1500 nm, the fiber to fiber gain was measured to be 32.5 dB. Statistics for eight packaged devices indicate that a fiber-to-fiber gain of 26.3 dB ± 1.3 dB and a saturation output power of 12.4 dBm ± 0.4 dBm are typical at a bias of 500 mA for λ = 1550 nm. Polarization sensitivity at 1550 nm was measured to be 1.1 dB ± 0.4 dB and the transverse electric (TE) polarization state noise figure (NF) was determined to be 7.0 dB ± 0.5 dB. The coupling loss was 1.3 dB ± 0.1 dB per facet. This SOA, with a 1.3-nm filter, was used as an optical preamplifier in a 10-Gb/s return-to-zero (RZ) system testbed with a pseudorandom binary sequence (PRBS) of 2³¹ -1. A 14.5-dB improvement in receiver sensitivity was observed at a bit error rate (BER) of 10^-11     

High-power ultralow-chirp 10-Gb/s electroabsorption modulator integrated laser with ultrashort photocarrier lifetime

A high-power, ultralow-chirp electroabsorption modulator (EAM) integrated with a distributed-feedback laser diode (EML) having ultrashort lifetime of photogenerated holes in the EAM quantum-well (QW) structure is reported for the first time. A shallow QW structure having a small valence band offset to enhance the sweepout of photogenerated holes was employed as EAM absorption layer. The measured hole lifetimes were 7-11 ps, and the measured frequency chirp (/spl alpha/-parameter) was low or negative at low EAM reverse bias voltages even under high optical output power conditions. Successful 10-Gb/s 80-km normal-dispersion single-mode fiber transmission (chromatic dispersion D=1600 ps/nm) and the record average fiber optical output power (P/sub f/) of +5.3 dBm were achieved at 25/spl deg/C. In addition, semicooled operation of EML at enhanced bit rates has been demonstrated for application in small-form-factor protocol-agnostic optical transceivers. A 10.7-Gb/s 1600-ps/nm transmission was achieved at 45/spl deg/C and P/sub f/=+3.0 dBm.     

2.488 Gb/s-318 km repeaterless transmission using erbium-dopedfiber amplifiers in a direct-detection system

The authors have achieved a 2.488 Gb/s, 318 km repeaterless transmission without any fiber dispersion penalty through a nondispersion-shifted fiber in a direct detection system. The system was loss limited with a T-R power budget of 57 dB. Three key components enabled the authors to achieve this result: (1) a Ti:LiNbO₃ external amplitude modulator enabling a dispersion-free transmission, (2) erbium-doped fiber amplifiers increasing the transmitting power to +16 dBm, and (3) an erbium-doped fiber preamplifier enabling a high-receiver sensitivity of -4.1 dBm for 10^-9 BER. To the author's knowledge, this result is the longest repeaterless transmission span length ever reported for direct detection at this bit rate. From the experimental results and a theoretical model, the authors identified the sources of the receiver sensitivity degradation from the quantum limit (-48.6 dBm) and estimated the practically achievable receiver sensitivity of ~-44 dBm (~-124 photons/bit) for 2.5 Gb/s optical preamplifier detection     

基于DFB激光器实现波长转换误码特性的研究

作为自动交换光网络中的核心器件,全光波长转换器将在全光通信系统中发挥重要作用.根据半导体激光器实现波长转换的理论模型,重点研究了基于DFB实现波长转换器的误码特性.包括工作电流、输入信号光功率等参量对消光比、误码率的影响.并利用自行搭建的基于DFB实现波长转换的实验平台,进行了实验分析,发现理论分析结果和实验数据十分吻合.这对于优化基于DFB结构的全光波长转换器有重要参考价值.     

基于半导体光放大器的四波混频效应对正交频分复用光信号进行全光波长变换

实验研究了基于半导体光放大器(SOA)的四波混频(FWM)效应的单抽运光正交频分复用(OFDM)信号的波长变换系统.信号光源和抽运光源分别由两个不同输出波长的可调分布反馈式激光器(DFB-LD)产生.信号光源经2.5 Gb/s OFDM的电信号直接调制后再和抽运光源耦合,经光放大器后在SOA实现波长变换.实验结果显示,耦合信号经SOA四波混频效应后,产生新波长的信号光将携带OFDM信号,且转换效率与信号光和抽运光的功率、波长以及两者的偏振夹角有关.同时也测量了转换的OFDM信号的功率-误码曲线和接收星座图.     

Analysis of infrared wireless links employing multibeamtransmitters and imaging diversity receivers

We analyze the improvements obtained in wireless infrared (IR) communication links when one replaces traditional single-element receivers by imaging receivers and diffuse transmitters by multibeam (quasi-diffuse) transmitters. This paper addresses both line-of-sight (LOS) and nonline-of-sight (non-LOS) IR links. We quantify link performance in terms of the transmitter power required to achieve a bit error rate (BER) not exceeding 10^-9 with 95% probability. Our results indicate that in LOS links, imaging receivers can reduce the required transmitter power by up to 13 dB compared to single-element receivers. In non-LOS links, imaging receivers and multibeam transmitters can reduce the required transmitter power by more than 20 dB. Furthermore we discuss the use of multibeam transmitters and imaging receivers to implement space-division multiple access (SDMA). In a representative example with two users transmitting at a power sufficient to achieve a BER not exceeding 10^-9 with 95% probability in the absence of cochannel interference, when SDMA is employed, the system can achieve a BER not exceeding 10^-9 with a probability of about 88%     

用于SDH STM-64光发射机的GaAs PHEMT激光驱动器

介绍了用于SDH系统STM-64速率光发射机用的激光二极管/光调制器驱动器集成电路的设计。电路采用法国OMMIC公司的0.2μm GaAs PHEMTs工艺设计并制造,可以驱动激光二极管和电吸收式调制器。电路由输入匹配电路、预放大电路、源极跟随器、主放大电路、电容耦合电流放大器和输出电路组成。电路芯片面积1.0mm×0.9mm。测试结果表明,电路采用单一正5V电源供电,直流功耗1.4W,可以在10Gb/s速率下正常工作,眼图良好。最高工作速率高于20Gb/s,输出电压幅度2.8V。     

Experimental evaluation of the BER performance in optical OFDM system based on discrete Hartley transform precoding

We experimentally assess the bit error rate （BER） performance of an intensity modulation/direct detection （IM/DD） optical orthogonal frequency division multiplexing （OFDM） system based on discrete Hartley transform （DHT） precoding in single-mode fiber （SMF） link for 2.5 Gbit/s quadrature phase shift keying （QPSK） OFDM symbol rate. The experimental results show that for the optical OFDM system based on DHT-precoding, the receiver sensitivity at the BER of 10-4 after 100 km SMF transmission is about 1.5 dBm better than that of the original QPSK OFDM signal, and the DHT-precoded OFDM QPSK signal can achieve approximately 1.3 dB of peak-to-average power ratio （PAPR） reduction.     

基于SOA光纤环镜的NRZ信号时钟分量的提取

采用SOA(sem iconductor optical am plifier)光纤环镜将2 .5 Gbit/ s的NRZ(non- return- to- zero)信号转换为相应的PRZ(pseudo- return- to- zero)信号,实现了NRZ信号时钟分量的提取.并分析了SOA注入电流、环镜探测光光功率等系统参数的选取对转换输出的PRZ信号的光信噪比、消光比及环镜透过率的影响.     

选区外延制作单片集成单脊条形电吸收调制DFB激光器

报道了采用选区外延生长技术制作的可实用的单脊条形电吸收调制DFB激光器。激光器的阈值为 2 6mA ,最大光功率可达 9mW ,消光比可达 16dB。减小端面的光反馈后 ,从自发发射谱上观察不到波长随调制电压的变化 ,调制器部分的电容为 1 5pF ,初步筛选结果显示阈值、隔离电阻、消光比基本没有变化 ,可应用在 2 5Gb/s的长途干线光纤传输系统上。     

Rayleigh scattering influence on performance of 10 Gb/s opticalreceiver with Er-doped optical fiber preamplifier

The achievement of -30.8 dBm (630 photon/bit) receiver sensitivity at 10 Gb/s, with an Er³⁺-doped optical fiber preamplifier, is discussed. This is an 8.3-dB sensitivity improvement over the avalanche-photodiode/FET receiver. Power penalties caused by a noise increase due to Rayleigh backscattering by the transmission optical fiber have been evaluated. Approximately -30-dB Rayleigh scattering from a 20-km optical fiber resulted in a 3.5-dB power penalty for a 25-dB-gain optical amplifier     

Gain-shifted dual-wavelength-pumped thulium-doped fiber amplifierfor WDM signals in the 1.48-1.51-μm wavelength region

We constructed a gain-shifted dual-wavelength-pumped (1.05/1.56 μm) thulium doped fiber amplifier (TDFA) for wavelength-division-multiplexing (WDM) signals in the 1.48-1.51-μm, wavelength region. We obtained a gain of larger than 20 dB and a noise figure of less than 7 dB in the range from 1478 to 1505 nm. Amplifier saturated output power was +20.1 dBm with an optical-to-optical conversion efficiency of 9.1% for 12-channel WDM signals. We also obtained a successful bit error rate performance for signals modulated at 10 Gb/s when the gain-shifted TDFA was used in an optical preamplifier configuration. These results confirm the feasibility of using the gain-shifted TDFA as both a booster and an optical preamplifier in WDM networks     

Statistical analysis of fiber-optic CDMA communication systems. II. Incorporating multiple optical amplifiers

For pt. I see ibid., vol.20, no.8, p.1304-16 (2002). In this paper, we study and elaborate on the architectural consideration of using multiple optical amplifiers in an all-optical fiber-optic code-division multiple-access (FO-CDMA) network. Our study and considerations are based on obtaining the statistical characteristic functions for photon-counts of a string of output pulses that constitutes the address code in a FO-CDMA network. Optical orthogonal codes (OOCs) with minimum auto-and cross correlation are employed as the address or signature sequence codes. Our analysis is based on chip-synchronous interference only, which provides an upper bound on the system performance. Shot noise, thermal noise, and extinction ratio are considered in this analysis. Bit error rate (BER) results are obtained using two methods, namely, saddle-point and Gaussian approximations. From our BER analysis, we develop some insight into the optimum distribution of optical amplifiers and their corresponding gain setting parameter. Moreover, the effects of source power, code weight, number of users, bit rate, and amplified spontaneous emission noise are investigated.     

SOA-XGM全光波长变换器的特性分析

对基于半导体光放大器交叉增益调制实现的全光波长变换器的工作特性进行了分析，归纳了要取得较好的变换效果，应在输入信号光功率、波长、偏置电流、放大器腔体长度等方面作合理的选择，使输出信号的消光比、信噪比等指标符合要求。     

DWDM-based FTTC access network

This paper proposes a dense wavelength division multiplexing (DWDM)-based fiber-to-the-curb (FTTC) access network architecture for broad-band services. The reaches of four carrierless amplitude phase (4-CAP)-modulated very high-speed digital subscriber line (VDSL) signals over the hybrid-fiber twisted pair (HFTP) were simulated. The simulation results show that the effect of noise from the optical link is negligible as long as the signal-to-noise ratio (SNR) of the optical link output signal is 9-10 dB greater than the required SNR of a VDSL modem. The bit error rate (BER) of the VDSL transmission over HFTP was measured. Measurement results show that insertion of the optical link between the modem and twisted pair has no adverse effect on the transmission