Field Trial of Duplex, 10 Gbps $,times,$8-User DPSK-OCDMA System Using a Single 16$,times,$ 16 Multi-Port Encoder/Decoder and 16-Level Phase-Shifted SSFBG Encoder/Decoders

An optical code-division multiple access (OCDMA) over wavelength-division multiplexing (WDM) system could be one promising solution to the symmetric Gigabit access network with high spectral efficiency, cost effective, good flexibility and enhanced security. A cost-effective OCDMA/WDM system using a single multi-port en/decoder at an optical line terminal (OLT) and superstructured fiber Bragg grating (SSFBG) encoder/decoders at each optical network unit (ONU) in an optical network has been proposed and demonstrated. In this paper, we prepare 16-chip, 16-level phase-shifted SSFBG encoder/decoders and develop the full-asynchronous 10 Gigabit Ethernet (10 GbE) interface OCDMA prototype for the first time. Field trials of duplex, fully-asynchronous, 10 Gbps$,times,$8-user DPSK-OCDMA system over 100 km using hybrid multi-port and SSFBG encoder/decoder are demonstrated.      

10 Gb/s-Based PON Over OCDMA Uplink Burst Transmission Using SSFBG Encoder/Multi-Port Decoder and Burst-Mode Receiver

In this paper, we propose a novel 10 Gb/s-based passive optical network (PON) over optical code division multiple access (OCDMA) system to realize the new generation full capacity optical access network which is easily upgraded from existing time division multiplexing PON (TDM-PON) without sacrificing the currently uplink bandwidth assigned to the individual user. 16-ONU (4-OCDMA x 4-packet) uplink burst transmission, an upgrade scenario by a factor of four of conventional 10 Gb/s-based PON, is experimentally demonstrated by using multi-level phase-shift-keying (PSK) super-structured fiber Bragg grating (SSFBG) encoder/multi-port decoder and burst-mode receiver. In the discussions, it will be shown that 32 users can be accommodated in 10 Gb/s-based PON over OCDMA system, and a key is newly introduced multi-level phase-shifted en/decoding, of which auto-correlation waveform can be preferably adopted in the burst-mode reception at 10 Gb/s.      

光码分多址技术在光接入网中的应用

无源光网络是光接入网的主要发展方向,ＦＴＴＨ是ＰＯＮ的最终方式,将ＯＣＤＭＡ,ＷＤＭ等技术用于光接入网中,是帝现接入网宽带化的途径之一。介绍了ＯＣＤＭＡ的技术报目前光接入网中多址技术的弊端,探讨了ＯＣＭＤＡ用于光接入网的可能性和优势,提出实现无源光网络多址接入的ＷＤＭ／ＣＤＭＡ方案。     

基于超结构光纤光栅的混沌序列OCDMA系统

提出了一种双极性编解码的光码多分址(OCDMA)系统,采用混沌序列作地址码,并使用超结构光纤布拉格光栅(SSFBG)作编/解码器。三阶Chebyshev映射能够产生具有良好相关性且适用于异步CDMA系统的双极性混沌序列,通过对三阶Chebyshev映射赋予一定初值,并进行反复迭代,得到一定长度的双极性混沌序列。根据地址码的特征,通过控制FBG的折射率分布形成SSFBG,利用SSFBG产生相应的双极性混沌序列作OCDMA系统的编/解码器。对系统性能进行了定量分析,在完全异步的情况下,推导了信噪比(SNR)与误码率(BER)的表达式。仿真分析了系统在不同码长下的BER随接入用户数的变化,并和使用Gold序列的情况进行了比较。结果表明,随着码长的增加,在接入用户数一定的情况下,系统具有较低的BER;由于混沌序列良好的自互相关性,相应的混沌序列OCDMA系统与使用Gold序列的系统相比具有较低的BER,并可以容纳更多的用户数。     

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.     

基于等效相移光栅的双用户光码分多址系统

报道了基于等效相移光纤光栅编/解码器的2.5G b/s双用户光码分多址系统.系统中的两个并发用户可以各自独立地解码,并得到清晰的眼图.测量了单用户情况下系统的误码率曲线,误码率为10-9时编/解码引起的功率代价为0.7 dB.实验表明,使用基于等效相移光栅的编/解码器能够搭建可容纳多个用户的光码分多址系统.     

Tunable Super-Structured Fiber Bragg Gratings with Perfect Sequences Based on m-Sequence

Recently, a tunable fiber Bragg grating (FBG) was developed by using stress-responsive colloidal crystals. In this paper, we have simulated the application of these nanoparticles into the super-structured fiber Bragg grating (SSFBG) written with perfect sequences derived from a short maximal-length sequence. A tunable SSFBG will be available to overcome the prohibitive temperature variation of the optical codecs. Nevertheless, we presented a method to implement coherent time spreading optical code-division multiple-access (OCDMA) where a unique code (or perfect sequence) can be reused and mixed with different wavelengths to obtain a tunable wavelength-division multiplexing (WDM) system. In order to maximize the binary throughput, we have selected a unique short maximal-length sequence composed of 7 chips that can be tuned with 7 different optical wavelengths. We found thousands of different tunable combinations that presented power contrast ratios (P/C) higher than 12 dB. When a WDM-OCDMA system used 2 different combinations simultaneously, the perfect binary detection with error correction codes was achieved successfully. The tunable SSFBG with colloidal crystals will be a simple and good alternative choice for fiber-to-the-home (FTTH) communications.     

Performance Limitations of Subcarrier Multiplexed WDM Signal Transmissions Using QAM Modulation

We theoretically investigate the performance limitations of subcarrier multiplexed (SCM) wavelength-division-multiplexing (WDM) systems using optical double-sideband (DSB) modulated, 16-quadrature amplitude-modulated (QAM) signals. The performance limitations are investigated using crosstalk power and SCM channel spacing for various transmission conditions, including impairment factors such as dispersion and fiber nonlinearities for a single wavelength channel first. The effects of WDM channel spacing on SCM systems with multiwavelength channels are also evaluated via the calculated bit error rate (BER) performance, based on the performance limitations found in the single-wavelength simulation. This enables us to provide guidelines for the design of SCM/WDM systems for fiber-to-the-home (FTTH) network in WDM–passive optical network (PON) architecture, based on the performance limitations.      

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.     

基于等效相移光栅的光码分多址编/解码实验

基于直接序列扩频(DSSS)的时域编码是目前光码分多址(OCDMA)系统中常用的编码方式。报道了利用带有等效相移(EPS)的超结构光纤布拉格光栅(SSFBG)对重复频率为2.5 GHz,宽度为7 ps的超短光脉冲串进行编/解码的实验,实验中所用码为31位的m序列。正确解码和不正确解码信号的对比度为5∶1,与理论计算结果相符。实验结果表明,等效相移光栅能够代替相移光栅作为光码分多址系统的编/解码器。且当入射脉冲宽度小于码片持续时间时,能获得良好的编/解码效果。     

Fiber to the Home Using a PON Infrastructure

Traffic patterns in access networks have evolved from voice- and text-oriented services to video- and image-based services. This change will require new access networks that support high-speed (> 100 Mb/s), symmetric, and guaranteed bandwidths for future video services with high-definition TV quality. To satisfy the required bandwidth over a 20-km transmission distance, single-mode optical fiber is currently the only practical choice. To minimize the cost of implementing an FTTP solution, a passive optical network (PON) that uses a point-to-multipoint architecture is generally considered to be the best approach. There are several multiple-access techniques to share a single PON architecture, and the authors addressed several of these approaches such as time-division multiple access, wavelength-division multiple access, subcarrier multiple access, and code-division multiple access. Among these multiple techniques, they focus on time-division multiplexing (TDM)-PON and wavelength-division multiplexing (WDM)-PON, which will be the most promising candidates for practical future systems. A TDM-PON shares a single-transmission channel with multiple subscribers in time domain. Then, there exists tight coupling between subscribers. A WDM-PON provides point-to-point optical connectivity using a dedicated pair of wavelengths per user. While a TDM-PON appears to be a satisfactory solution for current bandwidth demands, the combination of future data-rate projections and traffic patterns coupled with recent advances in WDM technology may result in WDM-PON becoming the preferred solution for a future proof fiber-based access network     

Ten-user truly asynchronous gigabit OCDMA transmission experiment with a 511-chip SSFBG en/decoder

A ten-user truly asynchronous gigabit coherent-optical-code-division-multiple-access (OCDMA) transmission was experimentally demonstrated without using any timing coordination. The enabling technologies are a record-length 511-chip superstructured-fiber-Bragg-grating (SSFBG) en/decoder and a supercontinuum (SC)-based optical-thresholding technique to significantly suppress the signal interference beat noise as well as the multiple-access-interference (MAI) noise.     

基于WDM/OCDMA的混合PON技术研究

基于WDM/OCDMA的混合PON作为一种大容量、易升级、对称性和高度保密性的新一代光接入网技术,被认为是未来宽带光接入网的重要发展方向.文章分析了波分复用和码分多址技术结合的可能性,介绍了混合WDM/OCDMA-PON的基本结构和工作原理,并给出了三种混合PON系统的实现方案,提出了应用前景.     

PON接入技术在城域网中的应用定位

光接入是宽带接入的发展方向,无源光网络(PON)是实现光纤到户(FTTH)的首选方案.本文首先分析了城域网概念的引入对接入网发展的影响和PON接入网的原理特点,指出PON拓扑结构完全符合城域网边缘的业务汇聚和接入模式,符合城域网概念引入后的用户业务引入段和接入层的结构特点,最后给出了PON技术与MSTP(多业务传送平台)结合构建多业务城域网的策略和PON技术在移动网络中的应用定位.     

一种在接入网中实现OCDMA/DWDMA的新方法

研究了光码分多址接入/密集波分复用系统应用于接入网的可行性,分析了使用电编解码器 OCDMA 系统实现码分多址的过程,对激光器谱线宽度的要求和一个 OCDMA 码组的用户使用一个 WDM 信道的可能性。由此得到当 OCDMA 和 DWDM 用现有的成熟技术在接入网中相结合,接入网的接入数量和数据容量将更容易满足要求。     

具有多个波长通道的光纤光栅相位编/解码器

光码分多址(OCDMA)技术是实现未来宽带全光接入网的最佳技术之一.提出了一种基于超结构光纤光栅(SSFBG)的光码分多址时域相位编/解码器.编/解码器根据等效相移原理,采用Sinc函数作为采样函数,仅仅利用一块均匀的相位掩模板即实现了多个性能一致的编/解码信道,可以并行对不同波长通道的用户同时进行编/解码,既节省了成本又提高了系统容量.对该编/解码器的结构和性能进行了分析,并进行了计算机仿真.结果表明,对于使用127位Gold序列的编/解码器,各通道自相关峰瓣比(P/W)大于16.3 dB,峰瓣比波动小于0.4 dB,归一化自相关峰值波动小于0.04,各个编码通道取得了与纯相移编/解码器相近的性能,可用于光码分多址/波分复用(WDM)混合系统.     

基于等效相移超结构光纤光栅编解码器的2.5 Gbit/s 60 km光码分多址传输实验

稳定的窄脉冲光源、高性能编解码器和具有旁瓣/噪声抑制功能的接收机是光码分多址(OCDMA)系统设计实现的3个关键模块。实验中利用增益开关脉冲光源,63位等效相移超结构布拉格光栅(EPS-SSFBG)相位编解码器和接收机门限调整技术实现了2.5 Gbit/s 60 km传输并得到了相应的误码曲线,系统在误码率(BER)等于10-9时的灵敏度为-22.5 dBm。实验结果表明,等效相移超结构布拉格光栅编解码器兼具高性能和可实现性,可用于实用化的光码分多址系统,而综合利用光域和电域的手段抑制旁瓣和噪声的影响是提高系统性能的重要手段。     

Investigation of superstructured fiber Bragg grating-based OCDMA system

The bit error rate (BER) performance of a superstructured fiber Bragg grating (SSFBG)-based optical code division multiple access (OCDMA) system is investigated with different input pulse widths and grating refractive index modulation amplitudes, and the corresponding crosstalk ratio is considered at different data-rates. Simulation results show that increasing the input pulse width or grating refractive index modulation amplitude will degrade the BER performance apparently. Moreover, with fixed code length and chip-rate detection, a lower data-rate system has better tolerance to an increasing input pulse width, while a higher data-rate system has better tolerance to an increasing grating refractive index modulation amplitude.     

Cost and quantity analysis of passive double-star optical-access-network facilities for broadband service multiplexing

In this paper, the authors propose the most suitable passive double-star network (PON) configuration for multiplexing more than two kinds of broadband service by wavelength division multiplexing (WDM) in optical access networks. They calculate the cost and number of facilities in outside plant and central offices by using the latest cost trend and investigate their dependence on certain structural conditions such as the number of splits, network configuration, and fiber structure, and service conditions such as multiplexing service number and service penetration. Moreover, the required network configuration for multiplexing more than three services was investigated. As a result, the most suitable PON network for cost-effective service provision and fiber to the home (FTTH) deployment was determined.     

PON的多址接入技术研究

当前网络用户及高带宽业务不断增加,人们对大容量带宽的接入网提出更高要求.若重新铺设光纤,将花费大量成本,因此,如何在接入网中利用现有光纤提高带宽容量成为研究重点.分别对基于TDM、WDM、OCDMA、SCM的PON及混合无源接入网进行了研究,分析了各种网络结构优缺点.