An Encoder/Decoder Scheme of OCDMA Based on Waveguide

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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.      

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。     

A 10 Gbit/s OCDMA system based on electric encoding and optical transmission

An electric encoded/optical transmission system of code division multiple access （CDMA） is proposed. It encodes the user signal in electric domain, and transfers the different code slice signals via the different wavelengths of light. This electric domain encoder/decoder is compared with current traditional encoder/decoder. Four-user modula- tion/demodulation optical CDMA （OCDMA） system with rate of 2.5 Gbit/s is simulated, which is based on the optical orthogonal code （OCC） designed in our laboratory. The results show that the structure of electric encoding/optical transmission can encode/decode signal correctly, and can achieve the chip rate equal to the user data rate. It can over- come the rate limitation of electronic bottleneck, and bring some potential applications in the electro-optical OCDMA system.     

用于OCDMA的光延迟线编/解码器

基于光码分复用的时域编解码原理 ,研究了光延迟线编解码器的设计及采用该编解码器的稳定性问题 ;光延迟线编 /解码器的延迟误差将严重影响系统性能 ,提出在光电检测后对信号进行低通滤波处理 ,或选用具有适当占空比的 RZ脉冲作为信号脉冲 ,可避免或减少采用这种编解码器时可能出现的甚窄脉冲     

大容量可共享光编解码器的设计与性能分析

提出了一种二维时间/波长、大容量、可共享的光码分多址(OCDMA)解编码器,以很少的硬件实现多用户的应用.编解码器利用阵列波导光栅实现多用户的同时共享,通过可编程的结构对OCDMA的编程,实现对其他用户的再分配.该OCDMA系统利用二维时间/波长Reed-Solomon 码,降低了硬件的数量.运用VPI软件模拟该系统,得到了眼图和BER结果,验证了系统的性能.     

An optical CDMA system based on chaotic sequences

In this paper, a coherent asynchronous optical .code division multiple access （OCDMA） system is proposed, whose encoder/decoder is an all-optical generator. This all-optical generator can generate analog and bipolar chaotic sequences satisfying the logistic maps. The formula of bit error rate （BER） is derived, and the relationship of BER and the number of simultaneous transmissions is analyzed. Due to the good property of correlation, this coherent OCDMA system based on these bipolar chaotic sequences can support a large number of simultaneous users, which shows that these chaotic sequences are suitable for asynchronous OCDMA system.     

Code-Empowered Lightwave Networks

In this paper, an architecture for code-empowered optical CDMA (OCDMA) lightwave networks is presented. The architecture is based on reconfigurable optically transparent paths among users of the network to provide high-bandwidth optical connections on demand over small areas such as local area networks or access networks. The network operates on the transmission of incoherent OCDMA codes, each network station being equipped with an OCDMA encoder and decoder. The routing at a network node is based on the OCDMA code itself. The destination address, as well as the next node on the path, is given by the code as in a code-empowered network. A node consists of an OCDMA router built from parallel code converter routers that perform switching, routing, and code conversion. The latter enables a virtual code path for increased scalability. Commonly available delay lines enable the tunability of the encoder, decoder, and router for a reconfigurable and flexible network. Flexibility and granularity are also accentuated by OCDMA encoding. An OCDMA lightwave network can therefore respond to changes in traffic load, traffic conditions, failure, and other network impairments. We describe the possible architectures and the routing constraints of such OCDMA lightwave networks. We present a power analysis and focus on the performance issues of dynamic routing. The effect of coding, topology, load condition, and traffic demand is analyzed using simulations. The obtained results show that the flexibility of OCDMA and the large offered cardinality can be a solution to the needs of local area and access networks.     

DS-OCDMA encoder/decoder performance analysis using optical low-coherence reflectometry

Direct-sequence optical code-division multiple-access (DS-OCDMA) encoder/decoder based on sampled fiber Bragg gratings (S-FBGs) is characterized using phase-sensitive optical low-coherence reflectometry (OLCR). The OLCR technique allows localized measurements of FBG wavelength and physical length inside one S-FBG. This paper shows how the discrepancies between specifications and measurements of the different FBGs have some impact on spectral and temporal pulse responses of the OCDMA encoder/decoder. The FBG physical lengths lower than the specified ones are shown to affect the mean optical power reflected by the OCDMA encoder/decoder. The FBG wavelengths that are detuned from each other induce some modulations of S-FBG reflectivity resulting in encoder/decoder sensitivity to laser wavelength drift of the OCDMA system. Finally, highlighted by this OLCR study, some solutions to overcome limitations in performance with the S-FBG technology are suggested.     

OCDMA系统组网技术和核心部件的分析研究

光码分多址(OCDMA)技术近年发展迅速,将成为宽带光纤通信网的主要扩频技术之一.详细分析了OCDMA系统网络的结构原理、组网技术、光交换技术;较为全面地论述和评价了几种主要的光编码器、光解码器的实现方案、技术特点和应用范围;重点讨论了基于布拉格光纤光栅阵列波导光栅的光编界解码器的编解码原理和实现技术.分析了OCDMA技术在现代光纤通信中的应用前景.     

用于局域网的OCDMA技术

文章基于光码分复用编／解码技术，阐述了光纤延迟线时域编／解码器和利用光栅的频域编／解码器；提出了一种两层网络的拓扑结构：在OCDMA星形局域网拓扑结构的基础上构造WDM环网。     

基于频谱分割的光码分多址接入系统实验研究

利用频谱分割技术进行了光码分多址接入 (OCDMA)系统传输实验。该实验的编解码器利用可调谐法 珀腔的不同自由谱域来区分不同用户 ,分析、测量了多址干扰对系统性能的影响 ,对系统中的光源、信道和编解码器的特性进行了讨论。测试表明 ,该接入系统在速率为 15 5Mb s ,MAI值是接收用户光功率 30倍的情况下 ,传输 11km普通单模光纤后 ,误码率优于 10 - 9。该系统实现简单 ,成本低 ,是全光接入的可选方案。     

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。     

Compact bi-directional optical CDMA encoder/decoder with low power dissipation

One decoding structure with power saving ability is proposed for spectral-amplitude-coding (SAC) optical code-division multiple access (OCDMA) system. This decoding structure can avoid unnecessary power loss in the decoder based on fiber Bragg gratings, thus thermal noise in the photodiodes of the decoder is suppressed. In addition, this decoding structure can cooperate with the encoding structure based on arrayed-waveguide grating (AWG) routers with power saving ability to enhance the system performance. Code families generated from cyclic difference sets (CDSs) can be used in this encoding/decoding pair based on AWG routers due to their cyclic properties. Therefore network application such as passive optical network can adopt OCDMA with simper coder configuration and accommodate the same number of users with lower source power.     

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.      

2.5 Gbit/s码位重叠快跳频光码分多址实验系统

设计并实现了单用户、数据速率2.5 Gbit/s的码位重叠快跳频光码分多址(SO-FFH OCDMA)实验系统。采用波长数为7和码长为4的单重合码,在数据速率2.5 Gbit/s时设计和制作了基于光纤布拉格光栅(FBG)的光编码/解码器,并测试了光编码器和光解码器的频谱图。脉冲发生器产生2.5 Gbit/s的非归零(NRZ)脉冲信号,外调制放大自发辐射(ASE)宽带光源后,通过光环行器进入光编码器进行光信号的扩频编码。编码后的光信号经掺铒光纤放大器(EDFA)放大后,输入到光解码器进行扩频解码,并通过2.5 Gbit/s接收模块转换为电信号。从解码信号的波形看,在用户数据速率为2.5 Gbit/s时,该系统能够正确解码用户的数据信息。实验结果表明,相对于传统的快跳频光码分多址系统,码位重叠快跳频光码分多址可大大提高用户的数据速率。     

The impact of group velocity on frequency-hopping optical codedivision multiple access system

In this paper, we develop a systematic method that employs transfer function considering encoder, fiber channel, and decoder to analyze the frequency-hopping (FH) optical code-division multiple-access (OCDMA) system. We analyze the FH-OCDMA system when both single-mode fiber and dispersion-shifted fiber are employed as the transmission medium. The difference of group velocities affects system performance more seriously than dispersion effect does. The results show that single-mode fiber is not proper for a FH-OCDMA system, even if the transmission length is no more than 1 km. The dispersion-shifted fiber is suitable for a FH-OCDMA system, especially in an access network. We also propose an optical device to compensate the group velocities     

基于二次全等跳频码的跳频光码分多址系统

从跳频光码分多址(FH-OCDMA)系统的扩频特征出发,推导出具有良好相关性能的扩频码所能达到的最大码容量,再利用二次全等理论为跳频光码分多址系统构造出一种具有最大码容量的扩频码——二次全等跳频码(QCHC),并给出了构造实例。在此基础上,运用光纤布拉格光栅序列作为编解码器设计了一种跳频光码分多址系统的实现方案,并对该系统的性能进行了详细的分析。结果表明,采用二次全等跳频码的跳频光码分多址系统具有设计简单、用户容量大和误码率低等方面的优点。     

基于线性组合码的多速率光码分多址接入系统

线性组合码(LCC)具有码族容量大、误码率(BER)低等优点,是实现光码分多址(OCDMA)的一种有效手段。通过改变组成线性组合码的子码字数可以实现多速率传输。利用基于线性组合码的二维时域/频域光纤光栅编/解码器,建立了多速率随机接入实验平台,成功实现了双用户发送和双用户接收的双速率光码分多址数据通信。线性组合码选用素数跳频码(PC)为子码族,实验中取素数为3的素数码控制时间扩频和波长跳频。实验验证了线性组合码多速率光码分多址接入系统方案的可行性。     

Cyclic optical encoders/decoders for compact optical CDMA networks

For compact optical code-division multiple access (CDMA) networks, a novel cyclic optical encoder/decoder based on an arrayed waveguide grating (AWG) router is proposed. The proposed encoder/decoder treats multiple codewords of the two-dimensional Reed-Solomon code simultaneously using the cyclic property of the AWG router and the code, and multiple subscribers can share the encoder/decoder in networks. With the proposed encoder/decoder, optical CDMA networks become compact and cheap, since the number of encoders/decoders required in the network is reduced. The feasibility of the proposed encoder/decoder is demonstrated experimentally