【作者】 刘燕；

【导师】 李传起；

【作者基本信息】 广西师范大学 ， 电子科学与技术， 2023， 硕士

【摘要】 光码分多址（Optical Code Division Multiple Access,OCDMA）是一种光域扩频通信技术,通过不同的地址码来区分用户信息,从而实现用户的随机接入。OCDMA在保密通信、卫星通信、局域网等领域有重要应用价值,能有效地提高光纤的利用率和传输容量,实现高速、高容量的信息传输。在OCDMA系统中,地址码是实现多用户同时传输的基础。同时,地址码的码长、码重、互相关等因素会对系统的性能产生重要影响,性能优良的地址码可以提高系统的数据速率、抗干扰性能和多用户接入能力,从而满足更高的通信需求。本文围绕OCDMA系统中地址码的设计进行研究,并分析了码字性能,进行了系统仿真与实验验证,主要工作内容如下:1.设计了一种适用于谱幅编码光码分多址（Spectral Amplitude Coding-Optical Code Division Multiple Access,SAC-OCDMA）系统的一维变重地址码——变重零互相关拉丁方（Variable Weight Zero Cross-correlation Latin Square,VW-ZLS）码。基于标准的拉丁方阵和变重算法,既可以直接构造双码重变重码,又可以利用映射技术得到多码重变重码。该码字具有构造方式简单多样、码重选择灵活、互相关为零和可提供多服务质量（Quality of Service,Qo S）的优点。首先,本工作在Matlab中进行数值仿真,并采用基于理论推导得到的VW-ZLS码的误码率公式进行计算,当误码率为10^-9时,码字速率可达到4.8Gbit/s,比同类型码字至少提高了0.5Gbit/s。其次,利用Opti System对SAC-OCDMA系统进行4用户仿真。当数据速率为2Gbit/s,传输距离达到25km时,仍可得到较为清晰的眼图且误码率不高于10^-9。2.设计了一种适用于SAC-OCDMA系统的基于频域/空间域的二维等重地址码——二维多服务光正交码（Two-dimensional Multi-Service Optical Orthogonal Code,2D-MSOOC）。2D-MSOOC对一维多服务（One-dimensional Multi-Service,1D-MS）码的频域和空间域进行扩展,实现灵活地选择用户数,同时具有互相关小、容量大的优点。本工作推导了该码字的误码率公式,并在Matlab中进行了数值仿真。结果表明:当误码率为10^-9时,2D-MSOOC比同类型码字容纳更多的用户数,最大用户数达到148;所需的有效功率更低,低至-18d Bm;同时支持更快速的码字传输。通过Opti System对2D-MSOOC方法进行4用户仿真的验证。当用户数据速率为1Gbit/s,通过星型耦合器传输时,误码率约为10^-18,Q因子约为8.6,码字性能良好。3.设计了一种适用于OCDMA系统的基于频域/时域的二维变重地址码——二次全等跳频码/变重固定右移（Quadratic Congruence-Hop Codes/Variable Weight Fixed Right Shift,QCHC/VW-FRS）码。QCHC/VW-FRS码将频域编码与时域编码相结合,以QCHC作为波长跳频序列,VW-FRS码作为时间扩频序列,得到一种码字容量大,码重选择灵活且提供多Qo S的地址码。本工作通过理论推导得到误码率公式,并在Matlab中进行数值仿真。在只考虑多址干扰的情况下,得到了误码率与用户数、码长、码重和波长数的关系,并证明了QCHC/VW-FRS码的性能优于同类型码字。其次,本工作在Opti System中对OCDMA系统进行两用户仿真。当用户数据速率为15Gbit/s且传输距离为10km时,可得到清晰端正的眼图。码重为4的用户误码率比码重为3的用户低2个数量级,表明该码字具有提供多Qo S的优点。此外,本工作在两用户的二维变重OCDMA编解码系统实验平台进行验证,实验结果表明:用户1的误码率为10^-9,用户2的误码率为10^-8,在BERTWave测试仪上得到比较清晰的眼图,QCHC/VW-FRS码具有良好的性能。更多还原

【Abstract】 Optical Code Division Multiple Access（OCDMA）is an optical spread spectrum communication technology that uses different address codes to distinguish user information and achieve random user access.OCDMA has important applications in secure communication,satellite communication,local area networks,and other fields.It can effectively improve the utilization and transmission capacity of optical fibers,and realize high-speed and high-capacity information transmission.In an OCDMA system,the address code is the basis for multi-user transmission.At the same time,factors such as the code length,code weight,and cross-correlation of the address code will have an important impact on the system’s performance.Address codes with excellent performance can improve the system’s data rate,anti-interference performance,and multi-user access capacity,thereby meeting higher communication needs.This article focuses on the design of address codes in OCDMA systems,analyzes the performance of code words,conducts system simulations and experimental verifications.The main work contents are as follows:1.A One-dimensional variable weight zero cross-correlation Latin square code（VW-ZLS）code was designed for use in spectral amplitude coding optical code division multiple access（SAC-OCDMA）systems.Based on standard Latin squares and variable-weight algorithms,this code can be used to construct both double-weight and multi-weight codes directly or through mapping techniques.The code has the advantages of diverse and simple construction,flexible weight selection,zero cross-correlation,and can provide multiple quality of service（Qo S）options.First,numerical simulations were conducted in Matlab,and the bit error rate formula derived from theoretical analysis of the VW-ZLS code was used to calculate the results.When the bit error rate is 10^-9,the code rate can reach 4.8Gbit/s,which is at least 0.5Gbit/s higher than other codes of the same type.Second,a 4-user simulation of the SAC-OCDMA system was performed using Opti System.Even at a data rate of 2Gbit/s and a transmission distance of 25km,clear eye diagrams were obtained and the bit error rate was no higher than 10^-9.2.A Two-dimensional equi-weight address code based on frequency domain/space domain,called the 2D multi-service optical orthogonal code（2D-MSOOC）,has been designed for SAC-OCDMA systems.The 2D-MSOOC extends the frequency and space domains of the one-dimensional multi-service（1D-MS）code,allowing for flexible selection of the number of users,while also having the advantages of small cross-correlation and large capacity.The error rate formula for the code is derived in this work and numerical simulations are conducted in Matlab.The results show that,at an error rate of 10^-9,2D-MSOOC can accommodate more users than similar codes,with a maximum of 148 users;it requires less effective power,as low as-18d Bm;and it supports faster code transmission.The 2D-MSOOC method is validated through a 4-user simulation using Opti System.When the user data rate is 1Gbit/s and transmitted via a star coupler,the error rate is approximately10^-18 and the Q factor is approximately 8.6,indicating good code performance.3.A Two-dimensional variable weight address code,quadratic congruence-hop codes/variable weight fixed right shift（QCHC/VW-FRS）code based on spectral/time for OCDMA systems is proposed.By combining spectral coding and time coding,QCHC is used as wavelength hopping sequence,and VW-FRS code is used as time spreading sequence,resulting in an address code with large capacity,flexible weight selection,and ability to provide multiple Qo S.The bit error rate formula is derived theoretically,and numerical simulations are performed in MATLAB.When considering only multi-access interference,the relationship between bit error rate and number of users,code length,code weight,and wavelength number is obtained,and the performance of QCHC/VW-FRS code is shown to be better than that of other similar codes.Furthermore,the OCDMA system is simulated with two users in Opti System.When the user data rate is 15Gbit/s and the transmission distance is 10 km,a clear and correct eye diagram can be obtained.The user with a code weight of 4 has an error rate that is two orders of magnitude lower than the user with a code weight of 3,indicating that the QCHC/VW-FRS code has the advantage of providing multiple Qo S.In addition,the experimental platform of the two-user 2D variable-weight OCDMA encoding and decoding system is verified in this work,and the experimental results show that the error rate of user 1 is 10^-9 and that of user 2 is 10^-8,and clear eye diagrams are obtained with the BERTWave tester.The QCHC/VW-FRS code has good performance.更多还原