光传输网络性能与前向纠错

为了提高光传输网络性能,人们将前向纠错技术应用于高速光纤通信系统中。文章对同步数字系列/密集波分复用(SDH/DWDM)传输网络性能进行了简要分析,讨论了前向纠错技术以及它对系统误码率的改善。     

OTN中FEC技术的应用

光传送网(OTN)是随着WDM技术的发展而产生的,ITU—T在2001年提出了其接口标准——G．709建议。该建议采用数字包封技术,定义了数据的封装格式,将前向纠错(FEC)技术引入光传送网标准接口中。文章分析了OTN的帧格式,着重介绍了其采用的FEC技术。将G.709标准应用到实际光接口盘的设计中,并通过实验验证了FEC技术的良好效果。     

Equalization and FEC techniques for optical transceivers

In this tutorial paper, we present the application of well-known DSP techniques used in lower speed wireline and wireless applications, to high-speed optical communications. After an introduction on today's optical network architecture and typical optical channel impairments, we study techniques such as fiber equalization, maximum likelihood detection, and current and next generations Forward Error Correction (FEC), with special emphasis on VLSI implementation     

10- and 40-Gb/s forward error correction devices for optical communications

Two standard forward error correction (FEC) devices for 10- and 40-Gb/s optical systems are presented. The first FEC device includes RS(255, 239) FEC, BCH(4359, 4320) FEC, and standard compliant framing and performance monitoring functions. It can support a single 10-Gb/s channel or four asynchronous 2.5-Gb/s channels. The second FEC device implements RS(255, 239) FEC at a data rate of 40 Gb/s. This paper presents the key ideas applied to the design of Reed-Solomon (RS) decoder blocks in these devices, especially those for achieving high throughput and reducing complexity and power. Implemented in a 1.5-V, 0.16-/spl mu/m CMOS technology, the RS decoder in the 10-Gb/s, quad 2.5-Gb/s device has a core gate count of 424 K and consumes 343 mW; the 40-Gb/s RS decoder has a core gate count of 364 K and an estimated power consumption of 360 mW. The 40-Gb/s RS FEC is the highest throughput implementation reported to date.     

Simulations and Experiments on the Effective Optical Gain of FEC in a GPON Uplink

This letter studies the effective optical gain of Reed-Solomon (RS) forward-error correction (FEC) in a burst-mode gigabit passive optical network (GPON) uplink. Numerical simulations are made of the performance of an RS (255, 239) FEC code. For the first time, FEC performance is measured in a 1.25-Gb/s burst-mode GPON uplink in the presence of mode partition noise (MPN). Measurements show that the effective optical gain of RS (255, 239) can be considerably higher than 2.7 dB when MPN dominates     

AN ADAPTIVE FEC SCHEME FOR Ka-BAND SATELLITE COMMUNICATIONS

Rain attenuation is the major problem for Ka-band satellite communications, and the fading due to rain can be well described by a lognormally distributed, first-order autoregressive model. Forward Error-control Coding (FEC) techniques can be used to reduce the effect of the rain attenuation, but the use of FEC causes a reduction in the bandwidth efficiency. In order to increase the bandwidth efficiency as well as maintain high link availability, an Adaptive Forward Error-control Coding (AFEC) scheme with rain fading prediction is proposed and analyzed in this paper. The results show that AFEC offers a good trade-off between link availability and bandwidth efficiency.     

光纤通信中级联码的码型

论述了光纤通信中级联码的码型选择,从净电编码增益、编码效率、相对色散代价以及实现的复杂程度等方面讨论了几种级联码,并认为RS(255,239)-BCH(2184,2040,12)级联方案在编码效率、色散代价以及实现的复杂程度方面具有较大的优越性。     

Modeling and verification of FEC performance for optical transmission systems using a proposed uniformly quantized symbol error probability model

We investigate the estimation of the bit-error rate (BER) performance of optical transmission systems with forward error correction (FEC) coding using a proposed uniformly quantized symbol error probability model. This model has been verified by the measurement of BER characteristics of coded and uncoded 10 Gb/s optical signals transmitted over 100 km. The measured results are very similar to the calculated results from the proposed model as well as Monte Carlo (MC) simulations. Our results suggest that the proposed uniformly quantized symbol error probability model using more than 8-decision levels can be applied to estimate BER performance for coded systems without degrading accuracy.     

Performance of zero cross correlation resultant weight spectral amplitude codes in lower Earth orbit‐based optical wireless channel system

A consolidated performance investigation and design of newly constructed zero cross correlation resultant weight (ZCCRW) code is presented without mapping over optical wireless channel (OWC) in lower Earth orbit (LEO). Multiple access interference (MAI) is suppressed by incorporating proposed 1‐D code at 10 Gbps with an algorithm. A further state of the art comparison of diverse optical code division multiple access (OCDMA) codes such as multi diagonal codes and diagonal double weight codes is accomplished with proposed code in terms of root mean square (RMS) jitter, extinction ratio, MAI, quality factor (QF), and bit error rate (BER) at different linewidths, chip sizes, link lengths, and active users. It is perceived that for ZCCRW code, QF obtained is 16.5 for chip size (0.1 ns), and at 4000 km, BER 10^‐9 is achieved using the forward error correction (FEC) technique. OWC system in LEO with lasers in spectral amplitude code (SAC) OCDMA is proposed for the first time as per the author's best knowledge.     

基于FEC的LDPC编码在远距离光通信系统中的研究

在研究超强FEC的LDPC编码在光通信中的应用性能分析的基础上,设计了采用超强FEC技术的OTU,给出了LDPC编码器与译码器具体设计,最后进行了实验方案分析和LDPC码型在远距离光通信系统中的仿真。     

基于光通信系统的前向纠错技术研究

描述了光通信系统的不同连接码方案并进行了仿真,仿真结果显示采用硬解码方法可获得8dB的净编码增益,而采用迭代软解码获得的净编码增益可达到10dB。进一步分析了光通信系统的前向纠错净编码增益裕度的影响。     

星际激光链路中的前向纠错编码技术研究

建立了简化的星际光通信链路模型,将背景光噪声和光放大器自发辐射噪声引入星际光通信链路中,提出利用前向纠错编码技术来改善星际光通信误码性能的方法。介绍了喷泉码的编译码特点,将喷泉码引入链路模型中。通过仿真研究表明,喷泉码相比于RS码对链路的抗误码性能有很大提高,且随着信噪比的增大改善更加明显。     

星际激光链路中的前向纠错编码技术研究

建立了简化的星际光通信链路模型, 将背景光噪声和光放大器自发辐射噪声引入星际光通信链路中, 提出利用前向纠错编码技术来改善星际光通信误码性能的方法。介绍了喷泉码的编译码特点, 将喷泉码引入链路模型中。通过仿真研究表明, 喷泉码相比于RS码对链路的抗误码性能有很大提高, 且随着信噪比的增大改善更加明显。     

10-Gb/s upgrade of bidirectional CWDM systems using electronic equalization and FEC

We discuss options for upgrading coarse wavelength-division multiplexed (CWDM) optical access links over standard single-mode fiber (SSMF) by increasing per-channel data rates from 2.5 to 10 Gb/s. We identify electronic equalization and forward error correction (FEC) as the enabling technologies to overcome the dispersion limit of SSMF. In addition, we show how FEC enhances the tolerance to in-band crosstalk, and paves the way toward fully bidirectional CWDM transmission. Due to the lack of CWDM sources rated for 10-Gb/s operation, we demonstrate full-spectrum (1310 to 1610 nm) 10-Gb/s CWDM transmission over standard-dispersion fiber using uncooled, directly modulated lasers specified for 2.5 Gb/s. All 16 CWDM channels could be transmitted over more than 40 km, yielding a capacity-times-distance product of 6.4 Tb/s/km. The longest transmission distance (80 km) was achieved at 1610 nm, equivalent to 1600 ps/nm of chromatic dispersion.     

光码标签交换网络边缘节点FEC的研究

构建了光码标签交换网边缘节点的结构,结合光码分复用技术提出了转发等价类(FEC)分组结构的设计方案。分组结构适合变长数据分组的传输,在核心节点能够实现对标签信息的可并行处理,提高了处理效率。在此基础上,针对开销比对网络传输性能的影响,对FEC结构中的各参量与开销比的关系进行了仿真研究;采用了固定时隙算法对数据分组进行封装,对到达率和封装时延与分组丢失率的关系进行仿真分析。     

Demonstration of over 128-gb/s-capacity (12-User/spl times/10.71-gb/s/user) asynchronous OCDMA using FEC and AWG-based multiport optical encoder/decoders

For the first time, an arrayed-waveguide-grating (AWG)-based multiport optical encoder/decoder (E/D) and forward-error-correction (FEC) technique are applied in an optical code-division multiple-access (OCDMA) system. The AWG-based OCDMA E/D with high power contrast ratio between auto-/cross-correlation can significantly suppress the interference noises in an asynchronous OCDMA system without using ultralong optical codes and optical thresholder. A 12-user 10.71-Gb/s asynchronous OCDMA experiment has been successfully demonstrated to transmit ITU-T G.709 OTN frames including FEC.     

High-speed optical FSK modulator for optical packet labeling

We described a novel optical label swapping (OLS) technique for optical packet systems using frequency-shift-keying (FSK) optical labeling. High-speed optical FSK signal can be generated by using an external FSK modulator consisting of four optical phase modulators. The FSK modulator was based on optical single-sideband (SSB) modulation technique, and comprised of traveling-wave electrodes for high-speed frequency switching. We demonstrate 10 Gbps FSK transmission, and simultaneous modulation by FSK and intensity modulation (IM). OLS using double-sideband modulation was also demonstrated, where this technique can be used for a bundled wavelength-domain-multiplexing (WDM) channels without using an array of pumping light sources.     

IMDD OFDM无源光网中的非线性分析和信号失真消除

提出一种子载波演化方法分析基于强度调制直接探测的正交频分复用无源光网络中的非线性。该无源光网络中的非线性主要来源于调制过程中的子载波混合干扰和啁啾。传输过程的光纤色散会导致调制时的各子载波最佳相位匹配条件不能维持,进一步导致信号恶化。设计了一种新的Volterra数字滤波器除信号失真。修正的Volterra数字滤波器不仅包含相同的采样点,还包括了不同的采样点。通过实验验证了该滤波器去除信号失真的效果;在FEC为10-3的情况下,实验结果与已经报道的结果相比提升3 dB了功率效益;传输25 km光纤与背对背相比,FEC为10-3时的功率亏损小于0.5 dB;系统的数据传输速率达到24.5 Gbps,频谱效率达到7 bits/s/Hz。实验结果表明提出的方法可以有效地消除信号的线性和非线性失真,能够有效地恢复信号。     

Error-free, 12-user, 10 Gbit/s/user O-CDMA network testbed without FEC

Error-free operation of a 12/spl times/10 Gbit/s synchronous, time-slotted spectral phase-encoded time-spreading optical code division multiple access (O-CDMA) network testbed without using forward-error-correction (FEC) is demonstrated. A nonlinear optical loop mirror time gate and nonlinear thresholding minimise multiuser interference.