WDM coding system with single parity-check channel

We propose a modified WDM coding system with a single parity-check channel to achieve an efficient and flexible WDM coding system. The system provides most of the advantages of the original WDM coding system with just one parity-check channel. The bit rate and the data sequences are unaffected by the coding processes, making it very attractive for practical lightwave systems with standard rates. Compared to serial coding systems, it is able to reduce the number of encoding/decoding pairs in an m-channel WDM transmission system operated at STS-N from m×N to one. We have evaluated the system performance and analyzed the performance of frame synchronization needed for the modified WDM coding system. An example shows that the WDM coding can reduce the error floor of a four-channel dispersion-limited WDM system from 10^-10 to 10^-19 with reliable frame synchronization     

WDM coding for high-capacity lightwave systems

An interchannel parallel coding scheme in the wavelength domain-the WDM coding system-is proposed. The system differs from the usual serial coding systems and provides many advantages. First, data channels are completely unaltered in the coding process, rendering it very suitable for practical lightwave systems with standard bit rate. Second, parallel encoding/decoding systems are simpler than those of serial coding systems, being easier to be implemented in high-speed optical systems. Third, compared with serial coding, WDM coding is able to reduce heavily the number of encoding/decoding pairs. For example, a (15, 11) Hamming coded WDM system reduces the number from 12×11=132 to 1 at the line rate of STS-12. Fourth, the WDM coding system could offer infinite coding gain in dispersion-limited lightwave systems. Finally, WDM coding systems could correct single-channel burst error. The system performance was evaluated and the system limitation imposed by bit-skew among wavelength channels was analyzed. The results indicated that a 15-channel Hamming coded WDM system can reduce the uncoded BER from 10^-9 to 3×10^-17 and the distance limitation imposed by bit-skew is 250 km if a dispersion-shifted fiber is used and a channel span of 30 nm is assumed     

A 1580-nm band WDM transmission technology employing opticalduobinary coding

This paper reports 1580-nm band wavelength division multiplexed (WDM) transmission employing optical duobinary coding over dispersion-shifted fibers. By using the 1580 nm band, the generation of four-wave mixing (FWM) over dispersion-shifted fibers (DSFs) can he suppressed. Optical duobinary coding is dispersion-tolerant because of its narrow bandwidth, and enables the use of the conventional binary intensity modulated direct detection (IM-DD) receiver. First, comparisons are made for WDM transmission performance in the 1580-nm band between conventional binary nonreturn-to-zero (NRZ) coding with and without postdispersion compensation, and optical duobinary coding by computer simulation is described. From the numerical simulations, it is found that the optical duobinary coding has superior transmission performance to the conventional binary coding without any dispersion compensation, and that the difference in the transmission performance between two coding methods is very small even if postdispersion compensation at the optical receiver is applied to the NRZ coding method. Second, transmission performance between the conventional binary NRZ and the optical duobinary signals without any dispersion compensation is compared with the straight-line experiment over 500-km dispersion-shifted fiber. The experimental results reveal that the transmission distance with optical duobinary coding is doubled in comparison with that of the conventional binary NRZ signals. Finally, 16-channel, 10-Gb/s optical duobinary WDM signals in the 1580-nm band are successfully transmitted over 640 km (80 km×8) of DSF without any dispersion compensation or management     

Network coding based all-optical multicast in WDM networks

Wavelength division multiplexing(WDM) has been becoming a promising solution to meet the rapidly growing demands on bandwidth. Multicast in WDM networks by employing free wavelength is an efficient approach to saving bandwidth and cost. However, the free wavelength may not identical between different hops in a multicast light-path, particularly in heavy load optical WDM networks. In order to implement multicast applications efficiently, a network coding(NC) technique was introduced into all-optical WDM multicast networks to solve wavelength collision problem between the multicast request and the unicast request. Compared with the wavelength conversion based optical multicast, the network coding based optical multicast can achieve better multicast performance with paying lower cost.     

A layered coding system for very low bit rate video coding

Known coding techniques for transmitting moving images at very low bit rates are explained by the source models on which these coding techniques are based. It is shown that with motion-compensated hybrid coding, object-based analysis-synthesis coding, knowledge-based coding and semantic coding, there is a consistent development of source models. In consequence these coding techniques can be combined in a layered coding system. From experimental results obtained for object-based analysis-synthesis, coding estimates for the coding efficiency of such a layered coding system are derived using head and shoulder video telephone test sequences. It is shown that an additional compression factor of about 3 can be expected with such a complex layered coding system, when compared to block-based hybrid coding.     

MIMO-OFDM系统中的一种空时频编码方案

基于MIMO-OFDM系统,本文提出了一种空时频编码方案,其利用扩展码,使数据符号在空域、时域、频域得到扩展,通过设置合适的参数,能够在频率选择性衰落信道下获得满空间分集和满频率分集,同时该方案的编解码复杂度不高。仿真结果表明,该方法在低信噪比下,也具有良好的误码率性能。     

波分复用系统的发展和面临的挑战

密集波分复用系统的发展光纤传输技术在十九世纪就开始出现，但是直到二十世纪后半叶才开始得到迅速发展。WDM系统从二十世纪九十年代中期开始商用，短短的几年时间里使整个电信业发生了翻天覆地的变化。从骨干网、区域网到城域网甚至接入网，WDM技术已被公认为是一种最佳的网络扩容方式。目前，WDM技术已经发展到了相当成熟的阶段，点到点的WDM系统正在大规模商用，信道数从8波发展到160波，单波长信道速率已从2.5Gb/s上升到10Gb/s、正向40Gb/s迈进，基于波长交换的全光网络也逐步开始商用。但是，随着业务量的进一步增长，业务种类…     

A multilevel WDM access protocol for an optically interconnectedmultiprocessor system

Scalable, hierarchical, all-optical WDM networks for processor interconnection in multiprocessor systems have been recently considered. The principal objective of this paper is to introduce an access protocol for this type of network which supports a distributed shared memory (DSM) environment. The objectives of the protocol are reduced average latency per packet, support of broadcast/multicast, collisionless communication, and exploitation of inherent DSM traffic characteristics. The protocol is based on a hybrid approach that combines reservation access and preallocated reception channels for a WDM system. The proposed approach trades maximum capacity for reduced communication latency to improve system response. The performance of the protocol is analyzed through semiMarkov analytic and simulation models with varying system parameters such as number of nodes and channels. The performance of the new protocol is compared to a TDM-based protocol and their relative merits are examined     

WDM/OCDMA混合系统中一种新型的接收机

文章针对波分复用/光码分多址(WDM/OCDMA)混合系统中存在窄带干扰(NBI)的问题,提出了一种新颖的用户接收机模型.从理论推导得知,该方案能完全滤除WDM用户间的NBI.同时,仿真结果也验证了系统的误码率(BER)有显著的降低,系统性能得到了改善,且归一化门限值为0.28时,BER最小.     

基于CycloneⅢ构成的RS编码系统

本文采用Altera公司的FPGA器件Cyclone Ⅲ系列EP3C10作为核心器件构成了R-S(255,223)编码系统;利用Quartus Ⅱ 9.0作为硬件仿真平台,用硬件描述语言Verilog_HDL实现编程,并且通过JTAG接口与EP3C10连接。R-S(Reed-Solomon)码是一类纠错能力很强的特殊的非二进制BCH码,能应对随机性和突发性错误,广泛应用于各种通信系统中和保密系统中。R-S(255,223)码能够检测32字节长度和纠错16字节长度的连续数据错误信息。     

一种码率自适应信源信道联合编码系统

双LDPC码系统是新近出现的一种信源信道联合编码系统,该系统的性能虽然好但不稳定,在信源熵增加时会产生很高的误码平台。为了解决这一问题,提出了一种码率自适应双LDPC码系统,此系统采用码率自适应LDPC码作为信源码,当信源熵变化时可以灵活地调整信源码率,从而保证系统在高低不同的信源熵情况下都具有优秀、稳定的性能。仿真结果显示,在高低不同的信源熵情况下,所提出的码率自适应双LDPC码系统性能均好于传统双LDPC码系统,而且在误比特率为10-6时都没有出现误码平台。     

基于WDM和TDM的串联FBG高速列车定位系统

介绍了一种基于波分复用(WDM)和时分复用(TDM)串联光纤Bragg光栅(FBG)的高速列车定位系统.用快速的光功率监测替代FBG的波长监测,定位时延较小(0.2 s);波长漂移转化为光功率的一对负正脉冲波动,提高了定位自动识别的准确性;同时WDM与TDM相结合的系统结构设计,扩大了列车定位系统监测的总长度.     

基于WDM和TDM的串联FBG高速列车定位系统

介绍了一种基于波分复用（WDM）和时分复用（TDM）串联光纤Bragg光栅（FBG）的高速列车定位系统。用快速的光功率监测替代FBG的波长监测,定位时延较小（0．2s）;波长漂移转化为光功率的一对负正脉冲波动,提高了定位自动识别的准确性;同时WDM与TDM相结合的系统结构设计,扩大了列车定位系统监测的总长度。     

Low-disparity binary coding system

The coding system described minimises the d.c. component in the transmitted binary signal by inverting characters when this will reduce the accumulated mark and space disparity. An added digit indicates when inversion has taken place. Conversion to and from unrestricted binary coding is relatively simple.     

Optimization of WDM lightwave systems (BAC) design using error control coding

In a binary asymmetric channel (BAC) it may be necessary to correct only those errors which result from incorrect transmission of one of the two code elements. In optical fiber multichannel systems, the optical amplifiers are critical components and amplified spontaneous emission noise in the optical amplifiers is the major source of noise in it. The property of erbium doped fiber amplifier is nearly ideal for application in lightwave long haul transmission. We investigate performance of error correcting codes in such systems in presence of stimulated Raman scattering and amplified spontaneous emission noise with asymmetric channel statistics. Performance of some best known concatenated coding schemes is reported.     

一种低编码复杂度可分级的视频编码系统

在可分级视频编码（SVC,scalable video coding）的框架下,利用分布式视频编码（DVC,distributed video coding）技术,设计了一种低编码复杂度的SVC方案。该系统具有空间可分级的特性,各分层中仅用到了传统的帧内编码技术和DVC技术,最大限度的减小了SVC系统的编码复杂度。在该...     

基于TSSA软件架构的视频压缩编码系统

针对数字监控系统的需求提出了一种基于多媒体DSP PNXl300 TSSA架构的适用的MPEG-4视频编码方案，介绍了TSSA的概念，TSSA中AL和OL层的关系以及如何使用TSSA来搭建视频压缩编码系统。     

WDM系统传输容量的仿真研究

基于Optisystem详细讨论如何构建一个完整的WDM仿真系统,分别给出4波长和8波长WDM系统在传输距离为340km和500km的合波器与分波器输出信号及其仿真眼图,并进行比较分析.结果表明此仿真系统能够很好的模拟WDM长距离传输系统,为进一步对WDM传输系统进行平滑升级扩容提供参考.     

A subband coding, BCH coding, and 16-QAM system for mobile radiospeech communications

A combined subband speech coding (SBC), Bose-Chaudhuri-Hocquenghem (BCH) error-correction coding, and 16-level quadrature amplitude modulation (16-QAM) scheme with switched diversity and speech postenhancement is proposed. The system's performance is dramatically improved by deploying some degree of fade tracking capability over fading channels. Further quality enhancement accrues by using appropriate mapping between the SBC speech codec and the Gray coded QAM words. Various BCH codes are utilized to adequately match the error-correcting power to the perceptual importance of the SBC bits. One of the proposed systems operates at 7 kBd and yields good communications-quality speech for channel signal-to-noise ratios (SNRs) in excess of 20 dB and encounters a maximum overall system delay of 55.125 ms. A more complex arrangement uses second-order switched diversity to reduce the channel SNR required to around 16 dB and the transmission rate to 5 kBd when the vehicular speed is 30 mph while the system delay is unchanged at 55.125 ms     

Laser based WDM multichannel video transmission system

The results of a WDM experiment involving the transmission of three video channels using AM-VSB modulation on each of three lasers in the 800?900 nm range are presented. A weighted video signal/noise ratio greater than 40 dB was achieved at each wavelength for a laser modulation index of 0.3 over a 1.1 km link.