一种基于扩展素数码和单重合序列的二维光正交码EPC/OCS

以扩展素数码(EPC)作为时间扩频伪随机序列，单重合序列(OCS)作为波长跳频伪随机序列，构造了一种新的二维光正交码EPC/OCS，并分析了码字的互相关性能.与修正素数跳频码MPHC相比，EPC/OCS的波长数并不局限于素数，可以是任意整数，不仅构造灵活，而且可充分利用MW OCDMA系统的有效波长数.当系统的有效波长数大于某个素数时，EPC/OCS不仅码字容量大于MPHC，而且互相关性能也有所改善.理论分析表明，EPC/OCS可降低MW OCDMA系统误码率.     

一种跳频扩时码的构造及性能分析

以一维二次同余码(QCC)作为扩时模式，以光正交码(OOC)和QCC码作为频域跳频模式，通过时域和频域的组合，构造了适用于光码分多址(OCDMA)系统的QCC/QCC和QCC/OOC 2种跳频扩时码，并对码的容量及其相关性进行了分析。与一维QCC码相比，QCC/QCC跳频扩时码的容量扩大了p 1倍（p为码重），相关性得到改善，并且码字异相自相关限λa=1，互相关限λc=2；QCC/OOC跳频扩时码具有更大的码容量和更好的相关性，码字异相自相关限λa=0，所有码字按一定规律可分成p 1组（p为码重），每组内码字的互相关限λa=1，不同组间码字的互相关限λa=2。所得结果为光码分多址系统中跳频扩时码的构造提供了一种新的方法。     

用遗传算法构造光正交码

提出了一种利用遗传算法构造任意码长、码重、自相关限、互相关限光正交码(GA-OOC)的方法,设计了新的码字矩阵;分析了基于GA-OOC的光CDMA系统的误码率性能。仿真结果表明:该算法具有构造算法简单、易于编程实现的特点;与基于PC,EPC,QC和BIBD-OOC的光码分多址系统相比,GA-OOC的光码分多址系统具有更好的误码率性能。GA-OOC有望用于构造二维光地址码。     

基于超结构光纤光栅的正交四相光码分多址编/解码器

正交四相序列编码相比于二相序列具有更大的码字容量和更好的互相关特性,因此更适用于光码分多址(OCDMA)无源光接入网.提出并实现了一种基于超结构光纤光栅的正交四相光码分多址编/解码器.该编/解码器采用A族四相序列作为地址码,在制作的过程中仅需一个均匀相位掩模板即可实现编码功能,并且在性能上与传统工艺制作的编码器相当.为了与不同波长信道相匹配,提出了变信道编码技术,仿真结果表明采用该技术的编码器具有更高频谱效率,因此得到更好的编/解码性能.对一个码长63,长度4.1 cm的正交四相编/解码器进行了信息速率为2.5 Gb/s.码片速率为156 Gchip/s的编/解码实验,取得了较好的编/解码效果.     

BCH信道编码对降低快跳频OCDMA系统中色度色散的影响

提出BCH信道编码的方案来降低色度色散对降低快跳频OCDMA系统性能的影响.采用BCH信道编码后,单重合码的长度将变短,即可以用较少的波长数来构造码字,因此降低了色度色散的影响.分析结果表明,在相同的信息比特速率、脉元间隔、资用波长数的情况下,BCH信道编码能显著改善FFH-OCDMA系统的误码率性能.同时,由于单重合码的长度将变短,大大降低了光纤光栅的制作难度.由于BCH信道编码在电域中实现,其硬件技术已相当成熟,所以对整个BCH/FFH-OCDMA系统的代价影响不大.     

一种符号阵列编码结构光三维检测方法

编码结构光检测技术是一种主动视觉方法,利用投射的模式光,通过三角原理获得深度信息。根据伪随机阵列的特性,提出了一种可用于检测场景目标的一次投射模式的结构光三维检测方法。符号的拐点、交叉点比传统的基于伪随机序列及M阵列模式提供了更多的检测点。符号阵列能够提供足够多的码字使所有的子模式获得全局唯一性。基于符号链分解算法及角度变化的轮廓特征,解码方法能够识别绝大多数码字。重建实验表明可以对一定曲面变化的物体进行检测,并能重建其形廓。     

时域相位光码分多址系统性能分析

给出了时域相位光码分多址系统(OCDMA)的噪声模型,提出了由码间串扰(ISI)所引起的自差拍噪声(SB)概念.利用鞍点近似法分析了多址干扰(MAD、码间串扰、自差拍等噪声对系统性能的影响,给出了系统误码率公式.对最佳门限接收系统以及采用光硬件限幅器的系统性能进行了仿真研究.表明"1"码的误判概率是影响系统的决定性因素.也是开关键控(OOK)系统难以克服的主要问题.最后给出一种采用双编/解码器平衡检测系统的原理框图,分析其性能,并与传统OOK系统比较,结果表明其性能有较大的提高.     

一种二维光CDMA地址码的构造及实现方法

对光正交码(OOC)的特性和二维地址码的构造方法进行研究,介绍了一种用于OCDMA系统的二维时间/频率组合码的构造方法,分析该地址码的自相关和互相关特性,以及该地址码的实现方法.分析结果表明,由单极性码OOC构造而成的二维时间/频率组合码OOC/OOC不仅具有良好的自相关和互相关特性,而且可以通过采用光纤布拉格光栅编解码器和阵列波导光栅编解码器实现快速、灵活编码.     

OCDMA系统二维RS地址码的设计方案及性能分析

首次在有限伽罗瓦域GF(7)上以本原元3构造出RS地址序列码.在一维RS素数码的基础上,给出基于二素数的二维RS矩阵码(2D-RSC)的设计方案.系统地研究了2D-RSC的OCDMA系统总体性能：分析了2D-RSC码字的相关性;导出了系统的最大用户容量;研究了2D-RSC系统以多址干扰为主的误码性能.结果表明：2D-RSC系统性能较之一维RS码有明显的改进. 特别是在大信息量传输时,采用两个较大的素数,基于2D-RSC的OCDMA系统的总体性能远优于一维素数码.     

光通信系统中基于有限域的LDPC码的构造(英文)

基于有限域中域特征提出一种新型LDPC码的构造法.所构造LDPC码的校验矩阵由基于有限域循环置换矩阵的阵列组成,可以有效地降低编译码复杂度.针对光通信的特点,构造出适合于光传输系统的且具有高码率和高编码增益的码字.仿真结果表明:本文构造的码率为93.7%的LDPC(3780,3542)码与其它几种构造法构造出的具有相同码率的码字相比具有更高的编码增益,更适合应用于光通信系统中.     

适用于同步光码分多址通信系统的同步光码及其全光可调编/解码器

异步光码分多址通信系统,要求用户地址码具有好的循环自相关和互相关特性,因此,系统中的用户数受到很大的限制;而对同步光码分多址通信系统,只要求光地址码是非循环相关意义下的准正交,从而可实现较大的用户数,因此具有广阔的应用前景.实现同步光码分多址的关键之一是同步光码的设计和可调光编/解码器的实现.本文介绍了同步光码的构造方法,给出了同步光码的构造过程,分析了码的容量,提出了全光可调同步光码编/解码器的实现方法.     

A high efficiency construction method of multilength optical orthogonal codes with correlation constraint two for OCDMA multimedia network

In order to construct multilength optical orthogonal codes (ML OOCs) with correlation constraint 2 for multi-rate OCDMA passive optical networks, a high efficiency construction method is presented. The main idea is to construct high efficiency mapping sequences to map optimal short length OOCs with cross correlation 2 into long length OOCs with cross correlation 2. Fundamental of constructing high efficiency mapping sequence is derived, and the mapping sequences based on multiplication table of integer domain is examined. Simulations based on the method show that the cardinality of long length OOCs is just slightly lower than Johnson bound. Therefore, it has very high variable length efficiency.     

Fast frequency modulation optical code division multiple access communication system

An optical fast frequency modulation code division multiple access communication system is proposed. In this system, an electrically controlled tunable optical filter (TOF) is used to encode the modulated broadband light source. The code depends on the function set to the controller. Two-dimensional code named functional code is also proposed based on a shifted sine function. The function defines the dynamic coding pattern of the central wavelength of the transmitted narrowband optical signal. Thus, the system will allow for an easy reconfiguration of the transmitter without the need for sophisticated encoder. At the receiver, a synchronized TOF with the same function is used as a decoder. The performance of this system is shown to be better compared with a fast frequency hopping and a spectral amplitude coding systems.     

SIR optimization in wavelength-hopping time spreading optical code routed networks

In this work, we investigate the performance of a distributed power control algorithm (DPCA) for signal-to-interference (SIR) optimization in wavelength-hopping time spreading code routed networks. These networks are based on 2D codes (time/wavelength) to establish end-to-end optical code paths (OCPs). The SIR model considers multiple access interference (MAI) between OCPs and amplified spontaneous emission (ASE) at cascaded amplified spans. The utilization of power control has a significant impact on both performance and capacity of practical optical networks. The DPCA can be effectively implemented in each node because uses only local parameters or measurements.     

Performance analysis of wavelength/spatial coding system with fixed in-phase code matrices in OCDMA network

This paper proposes a wavelength/spatial (W/S) coding system with fixed in-phase code (FIPC) matrix in the optical code-division multiple-access (OCDMA) network. A scheme is presented to form the FIPC matrix which is applied to construct the W/S OCDMA network. The encoder/decoder in the W/S OCDMA network is fully able to eliminate the multiple-access-interference (MAI) at the balanced photo-detectors (PD), according to fixed in-phase cross correlation. The phase-induced intensity noise (PIIN) related to the power square is markedly suppressed in the receiver by spreading the received power into each PD while the net signal power is kept the same. Simulation results show that the W/S OCDMA network based on the FIPC matrices cannot only completely remove the MAI but effectively suppress the PIIN to upgrade the network performance.     

Integrated photonic decoder with complementary code processing and balanced detection for two-dimensional optical code division multiple access

We propose a novel integrated photonic decoder for two-dimensional (time spreading, wavelength hopping) optical code division multiple access. The decoder is composed of multiplexers-demultiplexers, variable delay lines, and a coupler, which processes complementary codes and utilizes balanced detection to reduce unwanted cross-correlation interference. We successfully carried out a 10 Gbit/s transmission that demonstrated its effectiveness.     

Cardinality enhancement of spectral/spatial modified double weight code optical code division multi-access system by PIIN suppression

A new two-dimensional (2-D) optical code division multiple access (OCDMA) scheme to increase the achievable system capacity is proposed. The code exhibits good cross-correlation property time and wavelength shift. Performances are analyzed on code size and correlation properties affecting two important system parameters, bit error rate (BER) as a function of cardinality generated and optical power transmission requirement. The proposed system can effectively suppress phase-induced intensity noise (PIIN) and has multi-access interference (MAI) cancellation property. Results in a good agreement indicate that 2-D modified double weight (MDW) offers 163.7% and 336.2% larger cardinality compare to 2-D perfect difference code (PDC) and 2-D modified quadratic congruence (MQC) code. By increasing spatial code (N) and keeps similar code length system performance can be further optimized. 2-D MDW (M = 45, N = 18) accommodates 252.2% and 18.3% cardinality increment and low effective transmitted power (P_sr) at −17.9 dBm, compare to 2-D MDW (M = 247, N = 3) and (M = 84, N = 9) at 10⁻⁹ BER error floor. The architecture of the spectral/spatial MDW OCDMA system with property of MAI cancellation is presented.