相位编码扩谱OCDMA系统性能分析

相位编码扩谱光码分多址(OCDMA)通信系统是近年来OCDMA研究的热点之一.本文建立了采用相位掩模板的相位编码扩谱OCDMA通信系统理论模型,分析了系统性能.数值结果表明:较长的码字和短的初始脉冲有利于提高系统性能.     

波分复用OCDMA系统的性能分析

分析了波分复用(WDM)光码分多址(OCDMA)系统的归一吞吐量性能。当同时用户数均匀分配到不同的波长时,得到了WDM OCDMA系统归一化吞吐量性能的上界;当同时用户数尽量分配到同一个波长时,得到了WDM OCDMA系统归一化吞吐量性能的下界。在所有用户均匀分配到不同波长信道的条件下,比较了WDM OCDMA与多波长(MW)OCDMA系统的归一化吞吐量性能。结果表明,当负载较小时,两者的性能基本相当;当负载较大时,WDM 0CDMA的性能优于MW OCDMA系统。同时,WDM OCDMA的归一化吞吐量峰值高于MW OCDMA系统的归一化吞吐量峰值。     

Coupled-Mode Analysis of an NRD-Guide Coupler Based on Singular Perturbation Technique

A coupled-mode formulation for an NRD-guide coupler is presented using the singular perturbation technique. The first-order and second-order perturbations are taken into account in the analysis and the coupled-mode equations based on the eigenmodes of each waveguide in isolation are derived. The propagation constants obtained by these equations are compared with those by the exact theory, conventional coupled-mode theory, and improved coupled-mode theory. The numerical results of present formulation are in good agreement with the exact theory and superior to those of the other formulations.     

一种具有平衡互补结构的新型OCDMA解码器

提出了一种新的具有平衡互补结构的解码器,与相应的编码器配合可以在一个光学信道上实现双极性编码的容量和多址干扰指标,给出了解码器的结构,分析了其工作原理,并与其它方案进行了比较。     

混沌多值序列用于光码分多址系统的性能分析

针对光码分多址(OCDMA)系统对地址码的要求,提出了一种利用3阶Chebyshev混沌多值序列编码的方案,给出了码字的生成方法;基于相移超结构光纤布拉格光栅(SSFBG)编/解码器,利用传输矩阵法仿真分析了系统相关特性与码字长度、量化级数的关系.结果表明,多值混沌序列用于OCDMA频谱相位编码是可行的.     

OCDMA/DWDM混合系统接入网的参数配置

研究了接入网中光码分多址/波分多址(OCDMA/DWDM)混合系统影响系统性能的因素,通过理论分析和仿真,得出系统比特差错概率(BER)的半解析表示,最终仿真结果表明,为了满足通信质量,在配置系统时要严格控制同时在线的地址码用户数K,而复用信道数M可在成本允许的范围内灵活选择.初步解决了满足系统正常传输所需要的系统配置问题,为以后实际系统的用户数设计提供了一定的参考价值.     

基于Gold序列的相干OCDMA系统性能分析

随着相位编解码器关键技术的突破,相干光码分多址(OCDMA)系统也受到更多关注.采用前向纠错(BCH)信道编码技术,分析了相位编码光码分多址系统误比特率的计算方法,定义了相干OCDMA系统的频谱效率,讨论了系统端到端误比特率和平均丢包率的计算及其影响因素.得到使用BCH信道编码可以降低系统的误比特率和提高系统频谱效率的结论,并证明相位编码OCDMA系统适合传输变长数据包,网络中节点数目的增加对其误比特率影响不大.     

Performance of an incoherent temporal-spreading OCDMA system with broadband light sources

The effect of the coherence time of light sources on the performance of an incoherent temporal-spreading optical-code-division multiple-access (OCDMA) system is studied in this paper. Broadband noise-like light sources, such as amplified spontaneous emission (ASE) sources, are used by the transmitters. Three different kinds of receiver structures are examined and compared. Results show the impact of the nonideal light sources on the system performances relative to the ideal case. Analysis shows that to achieve the best performance when the available optical bandwidth and data rate are fixed, there is an optimal range for the spreading code length.     

Spectral efficiency of OCDMA systems with coherent pulsed sources

We present a model to evaluate the upper limit of the spectral efficiency of optical code-division multiple-access (OCDMA) systems with coherent sources. Phase-encoded and direct-sequence OCDMA systems are evaluated using this model. The results show that a spectral efficiency of 2.24/spl times/10/sup -2/ b/s/spl middot/ Hz can be achieved with a maximum bit error rate of 10/sup -10/ in these systems of the number of users. This result demonstrates that the maximum spectral efficiency of OCDMA systems with coherent sources is at least a factor of 5 higher than OCDMA systems with incoherent sources.     

频谱相位编码OCDMA系统的误码特性研究

本文利用中心极限定理和雅可比变换的方法，对频谱相位编码(spectral phase encoding)OCDMA系统中多址干扰和解码器输出信号的统计特性进行了研究，并据此推导出多址干扰和背景噪声共同作用下系统新的误码率公式．本文还分析了系统性能与判决门限选择的关系，数值结果表明：系统最佳的判决门限Rth=√P0/2，在此判决门限的条件下，系统的性能满足高速全光通信的需要．     

采用光硬限幅器和RS码的多波长OCDMA性能分析

提出了一种采用多个光硬限幅器和RS信道编码的多波长光码多分址（MW OCDMA）系统,理论分析了其误码率和（BER）和归一化吞吐量性能.结果表明,采用光硬限幅器的MW OCDMA系统BER性能将明显改善,进一步采用RS信道编码后,MW OCDMA系统BER性能将大大改善.另一方面,采用光硬限幅器的MW OCDMA系统的归一化吞吐量明显提高,特别是归一化吞吐量峰值提高了约1倍,但进一步采用RS信道编码后,MW OCDMA系统的归一化吞吐量并没有提高,在系统负载量不是很大的情况下还略有下降.     

OCDMA环网的码字消除功能及其性能分析

分析了一种光码分多址(OCDMA)环网中码字消除结构,使用马尔科夫链模型和状态转移概率矩阵得出了环中各用户的误码率(BER)的表达式,计算表明,该码字消除结构虽然能够有效地把码字从环网中消除掉,避免码字在环网中循环产生干扰累加,但是会明显恶化经过码字消除结构的其它用户的BER性能;讨论了环网中用户的BER性能与码长、判决阈值的关系;针对码字消除对OCDMA环网的重要性,提出了一种基于BER监测及反馈的方法来降低码字消除结构造成的BER恶化,仿真结果表明,该方法能有效改善用户的BER性能.     

A Clock-Less Jitter Spectral Analysis Technique

In this paper, we propose a method for extracting the spectral information of a multigigahertz jittery signal without using an ideal reference clock. This method utilizes existing on-chip single-shot period measurement techniques to measure single periods of a multigigahertz signal for analysis. Utilizing the same sampling and measuring principle, we propose another less computationally intensive method, based on the derivative principle, to extract only the random jitter component of the signal. To perform analysis on higher frequency signals, both methods are extended to measures multiple signal periods, instead of a single period, at each sampling. These methods do not require an ideal sampling clock, nor any additional measurement beyond existing techniques. Experimental results based on simulation show that these methods can accurately estimate the sinusoidal and random jitters of a multigigahertz signal. Extracted values can be used for estimating the bit-error rate of serial communication systems.      

双硬限幅器异步光码分多址系统误码性能分析

针对基于单硬限幅器（OHL）异步光码分多址（OCDMA）系统的解码器不能完全消除信道串扰产生的误码,提出了具有双OHL的解码器结构来优化系统传输性能。通过数值分析给出了地址码（光正交码,OOC）的码长、码重、用户数与系统误码率的关系,结果表明：双OHL异步OCDMA系统误码率相对于单OHL系统误码率下降明显,系统传输性能得到改善。     

Performance improvement of bandwidth-limited coherent OCDMA system

The performance of an optical code division multiplexing access (OCDMA) system employing the differential phase shift keying (DPSK) data format and turbo code is investigated and simulated. A bandwidth-limited coherent time spreading (TS) OCDMA system is considered. Theoretical results show that performance degradation due to bandwidth limitation could be effectively restrained by the application of the DPSK data format in a coherent OCDMA system, and further performance improvement could be achieved by incorporating turbo coding into the OCDMA system.

Beat Noise Mitigation of Spectral Amplitude Coding OCDMA Using Heterodyne Detection

In order to relax the limitation of the number of multiplexed signal lights caused by beat noise between signal lights, we investigate the applicability of a heterodyne detection technique to a spectral amplitude coding optical code division multiple access scheme. In this investigation, for the first time, we found analytically that the optical frequency chips that form parts of the signal and local lights require uniform phase differences even for envelope detection. We also confirm this requirement and our theoretical analysis experimentally.     

基于OCDMA的改进型室内可见光无线局域网分析

在原有的室内可见光无线通信网络结构的基础上,提出将用户终端适配器光源改为激光。用激光通信实现系统的上行链路,采用可见光通信与激光通信相结合的方式实现室内无线局域网,并基于光码分多址(OCDMA)技术,用光正交码(OOC)作为地址码对信号进行编码。仿真结果表明,改进后的系统误码率明显降低,能较好地满足通信的需求。     

Performance of Polarizers and Coupler in an All Polarization Maintaining Fiber Interferometer

It is given mathematical models and analyze the performance of polarizers and coupler in an all polarization maintaining fiber (PMF) Michelson interferometer. The optical coherent signal to noise ratio (CSNR) of the interferometer is calculated by means of the Jones matrix with cross coupling matrix elements.     

Design of an Overlay Directional Coupler by a Full-Wave Analysis

A full-wave analysis based on the spectral-domain method is applied to coupled overlay microstrips, coupled inverted microstrips, and coupled microstrips. Exclusive numerical data including frequency characteristics are included. A 10-dB overlay coupler was built according to the design theory, and experimental results are reported.     

熔锥型光纤耦合器的光学性能

利用可调谐光源和光谱分析仪建立的光无源器件测试系统,测试了熔锥型光纤耦合器的附加损耗、插入损耗、方向性和均匀性等光学性能,研究了光学特性与拉锥速度的相关规律.实验发现:器件的光学性能与制作工艺密切相关,如存在一个拉锥速度区间(这里为150μm/s附近的区间),使得光纤耦合器的损耗小、方向性好,离开此区间,器件的性能迅速下降.