超结构光纤光栅时域相位编解码器的半边带应用

光源与编解码器的匹配关系是光码分多址(OCDMA)系统设计的重要内容.提出了时域相位编解码器的半边带应用问题,即:等效相移超结构光纤光栅(EPS-SSFBG)编解码器反射谱的半边带已包含了编解码器结构的所有信息,光源只需要覆盖半边带就能完成编解码功能.仿真分析了光源脉宽与编解码器反射谱的对应关系对编解码性能的影响,仿真结果验证了半边带应用的可行性.在应用等效相移光栅编解码器的实验中验证了半边带应用的编解码性能,实验结果与半边带应用的理论规律相符.     

Design of FBG En/Decoders in Coherent 2-D Time-Wavelength OCDMA Systems

A novel fiber Bragg grating (FBG)-based en/decoder for the two-dimensional (2D) time-spreading wavelength-hopping optical coding is proposed. Compared with other 2D en/decoders, the proposed en/decoding for an optical code-division multiple-access (OCDMA) system uses a single phase-encoded FBG and coherent en/decoding. Furthermore, combined with reconstruction-equivalent-chirp technology, such en/decoders can be realized with a conventional simple fabrication setup. Experimental results of such en/decoders and the corresponding system test at a data rate of 5 Gb/s demonstrate that this kind of 2-D FBG-based en/decoders could improve the performances of OCDMA systems.     

An Encoder/Decoder Scheme of OCDMA Based on Waveguide

1　ＩｎｔｒｏｄｕｃｔｉｏｎＯｐｔｉｃａｌＣｏｄｅＤｉｖｉｓｉｏｎＭｕｌｔｉｐｌｅＡｃｃｅｓｓ(ＯＣＤ ＭＡ)ｓｙｓｔｅｍｓｈａｖｅｂｅｅｎｉｎｖｅｓｔｉｇａｔｅｄ[1 ] .Ｍａｎｙｅｎ ｃｏｄｅｒｓ/ｄｅｃｏｄｅｒｓｈａｖｅｂｅｅｎ ｐｒｏｐｏｓｅｄ ,ｆｏｒｅｘａｍｐｌｅ,ｏｐｔｉｃａｌｆｉｂｅｒｄｅｌａｙ ｌｉｎｅｓ[2 ] .Ｉｎｔｈｉｓｐａｐｅｒ,ｗｅｅｍｐｌｏｙｔｈｅｌｏｗ ｗｅｉｇｈｔＯｐｔｉｃａｌＯｒｔｈｏｇｏｎａｌＣｏｄｅ(ＯＯＣ ｓ) [3～5] ｗｉｔｈｔｈｅｌｅｎｇｔｈＭａｎｄｔｈｅｗｅｉｇｈｔΩａｓｏ…     

A Multiexposure Technology for Sampled Bragg Gratings and its Applications in Dual-Wavelength Lasing Generation and OCDMA En/Decoding

In this letter, a multiexposure technology for sampled Bragg gratings is proposed and investigated for the first time. Combined with reconstruction-equivalent-chirp technology, the useless zeroth-order channel can be eliminated and the $pm$1st-order channels can be enhanced significantly. The proposed method is applied experimentally to achieve a dual-wavelength fiber laser and is studied both numerically and experimentally in two ways for the optical code-division multiple access en/decoding system. Its properties may lead to more efficient design and fabrication of grating-based optical devices.      

用于10Gb／s WDM系统色散补偿的波长取样啁啾光纤光栅

研制出一种新型色散补偿光纤光栅--波长取样啁啾光纤光栅,它具有10个周期性为0.8nm的波长结构,每个周期的反射特性和色散特性都基本相同,其带宽为0.6nm、峰值反射率为90%、色散量为1300ps/nm、时延抖动小于50ps,光栅长度为10cm.利用此波长取样啁啾光纤光栅,在8×10Gb/s波分复用(WDM)系统中,进行了NRZ码140km标准单模光纤的色散补偿实验,补偿效果良好.     

基于光纤光栅编解码和修正素数跳频码的一种光码分多址系统方案研究

在素数跳频码（PHCs）的基础上，研究了修正素数跳频码（MPHCs）的构造方法和性能，提出了基于光纤布拉格光栅（FBG）编解码实现修正素数跳频码这种二维地址码的光码分多址（OCDMA）系统方案。并通过对素数跳频码和修正素数跳频码这两种码字误码性能的分析，得到以下结论：对于相同的素数P，当系统误码率（BER）B≤10^-9，P≥37时，修正素数跳频码所容纳的最大用户数大于素数跳频码；在光纤布拉格光栅阵列上修正素数跳频码所需要的编码光栅数相对素数跳频码减少（P一1）／2个，从而降低了光纤布拉格光栅阵列的制作难度。     

Novel Encoder/Decoder Using Subsampled Bragg Grating for a WDM-Compatible OCDMA System

Optical code-division multiple-access (OCDMA) technology is attractive for optical broadband access network. It is very interesting to use the super-structure fiber-Bragg-grating-based en/decoders to construct a wavelength-division-multiplexing (WDM)-compatible OCDMA system. Based on the equivalent phase-shift technique, we have proposed a subsampled-Bragg-grating (S-SBG)-based en/decoder. Based on the proposed method, only a single uniform phase mask can be used to accommodate different WDM channels with relevant central wavelengths and spectrum width. Using the S-SBG-based en/decoder, we can make different WDM channels have similar as well as better encoding efficiency and correlation performance. S-SBG-based en/decoders with 127 chips for two different wavelength channels are fabricated and measured. The experiments indicate the advantages revealed by the theoretical simulation.     

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.     

基于超结构光纤光栅的双边带编/解码器

分析了基于等效相移(EPS)技术的超结构光纤光栅(SSFBG)相位编/解码器的原理及特点,提出并实现了一种双边带编/解码器.该编/解码器在不改变光纤光栅长度的前提下,实现了+1级和+3级编解码谱的级联,并很好地继承了等效相移技术所具有的设计灵活、制作精度低和与波分复用(WDM)系统兼容能力强等诸多的优点.理论及实测数据仿真结果均表明,在光脉冲源匹配最佳的前提下,双边带编/解码器较传统等效相移编/解码器而言,使得基于该光纤光栅相位编/解码器的窄带相干光码分多址(OCDMA)系统的编解码性能提高了3 dB,通过对比分析得到其本质原因在于双边带编/解码器结构提高了其单位长度内携带的相位信息量.     

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.     

四相移超结构光纤布拉格光栅编／解码器特性

利用传输矩阵法研究了四相移超结构光纤布拉格光栅(SSFBG)光码分多址(OCDMA)编/解码器的结构和工作原理、频谱特性、相关特性.仿真结果表明码字的相关特性直接决定了编/解码器之间的相关特性,这对基于频谱相位编码的OCDMA编/解码器的设计具有一定的指导意义.     

OCDMA系统ST-OOC码字构造及性能研究

本文通过在有限Galois域上建立仿射平面,以及在仿射平面上建立Steiner系统,研究了仿射平面上Steiner系统的存在性;分析了部分点阵与Steiner系统的关联;建立了Steiner系统参数与OOC码字参数的对应关系.据此提出了基于仿射平面上Steiner系统的OOC码字设计方案;给出了ST-OOC码字(qk,k,1)的具体设计步骤和设计结果;分析了ST-OOC的码字性能和特点和灵活的码长码重对应关系;指明了ST-OOC码字的主要应用领域.     

Spectral-Amplitude-Coded OCDMA Optimized for a Realistic FBG Frequency Response

We develop a methodology for numerical optimization of fiber Bragg grating frequency response to maximize the achievable capacity of a spectral-amplitude-coded optical code-division multiple-access (SAC-OCDMA) system. The optimal encoders are realized, and we experimentally demonstrate an incoherent SAC-OCDMA system with seven simultaneous users. We report a bit error rate (BER) of 2.7times10^-8 at 622 Mb/s for a fully loaded network (seven users) using a 9.6-nm optical band. We achieve error-free transmission (BER<1times10^-9) for up to five simultaneous users     

FBG编/解码器的原理及结构、特点介绍

概述了光纤光栅的光学特性,介绍了基于FBG编/解码器的编/解码原理,对光纤光栅-环形器编/解码器、多Bragg光纤光栅二维编/解码器以及OCDMA光编/解码器几种FBG编/解码器的结构和特点进行了分析和比较,并对光编/解码器的发展前景做了探讨.     

幅度非均匀取样信号的数字频谱研究

在并行交替式超高速数字化系统中,由于各个A/D客观上存在的偏置(offset)及增益(gain)的不一致性,造成取样信号幅度的不均匀性.本文首先提出了幅度非均匀取样信号的概念,然后研究了由于偏置产生的幅度非均匀取样信号的数字频谱,推导出了它的数字频谱表达式,详细分析了存在偏置时正弦信号的数字频谱,得到了系统的信噪比公式,最后给出了计算机仿真结果.     

FBG阵列波长偏差对OCDMA系统误码率的影响

文章给出了一种基于光纤布拉格光栅(FBG)阵列的可调谐二维编解码器结构.重点分析了在波长不匹配时由于编解码器解码输出的自相关峰值功率削弱,进而劣化系统的误码率的情况.仿真了随着跳频扩时(TS/WH)码字参数的变化,编解码器在相应波长发生偏差条件下的解码输出功率和误码率.分析结果表明,当波长偏差0.1 nm时,对于跳频个数为31的编解码器,系统的误码率仍然＜10-9,因而可以通过增加跳频波长数来降低编解码器对调谐精度的要求.     

基于OptiSystem软件的OCDMA系统仿真

分析了采用光素数地址码的异步OCDMA系统设计原理,阐述了OptiSystem软件针对光系统的强大仿真功能。在设计原理的基础上,采用光纤延时线编码技术给出了基于OptiSystem的异步OCDMA系统仿真模型,得出仿真结果并进行了分析,验证了系统设计的正确性和设计方案的可行性。     

Design of high reflectivity superstructured FBG for coherent OCDMA employing synthesis approach

For the first time to the authors' knowledge a design procedure of OCDMA en/decoders based on superstructured fibre Bragg gratings employing synthesis methods is proposed and experimentally demonstrated. Experimental results show a clear reduction of the insertion losses, maintaining unaltered the en/decoding capabilities in comparison with standard weaker devices.     

基于边缘滤波的FBG解调系统

实现了一种基于边缘滤波的FBG解调系统,系统采用宽带光源、隔离器、分束器、FBG、耦合器及边缘滤波器等光学元件,来采集变化的光信号,同时设计光电探测器进行光电信号转换及放大滤波处理,并采用NI USB-6361进行数据采集,将模拟信号转换为数字信号,最后采用Labview进行处理,最终得出所要测量值。     

波长漂移对时域相位光码分多址编解码器性能的影响

光码分多址(OCDMA)系统中,编解码器的性能是影响系统整体性能的关键因素之一,而波长漂移会影响编解码的性能.在分析等效相移超结构光纤光栅(EPS-SSFBG)作为光码分多址相位编解码器的基础上,仿真研究了不同码字、不同码长、不同编码带宽、不同编码效率和不同折射率调制深度的编解码器对波长漂移的容忍度(WDT).仿真结果表明,光源与编解码器之问的波长漂移容忍度较大;若光源脉宽相对较宽,光源的中心波长偏移编解码器的中心波长一定值时,解码输出的自相关峰旁瓣比(P/W)反而提高;不同码字、不同编码效率、不同折射率调制深度都会不同程度地影响波长漂移容忍度.