Design And Implementation Of A Multi-QoS Two-Dimensional Variable Weight OCDMA Coding And Decoding System

With the advent of 5G,emerging applications such as VR technology,AR technology,8K video,and cloud games etc.are emerging in endlessly.Data traffic is growing rapidly,and users'demands for high speed,security,low latency,and quality of service(QoS)continue to increase.Higher requirement are also put forward for the development of a new generation of optical communication networks.Optical Code Division Multiple Access(OCDMA)technology has the characteristics of excellent security,random access,soft capacity on demand,and support for multiple quality of service,which is very attractive to the optical access network and the elastic optical network for flexible dispatch of services.However,the traditional OCDMA system has a relatively fixed structure,relatively expensive price,and cannot flexibly provide users with multiple QoS requirements,which makes it difficult for this technology to be commercialized.Therefore,this paper mainly focuses on the research of OCDMA codec that supports multiple QoS,is reconfigurable and low cost.The main research content is as follows:1)An OCDMA codec system that flexibly supports multiple QoS is designed.According to the two-dimensional variable-weight address code codewords and the two-dimensional OCDMA encoding and decoding principles of the optical domain,a two-dimensional variable-weight OCDMA codec model is established.In the OptiSystem software,a three-user codec system with a data rate of 5Gbit/s and a transmission distance of 270Km was built and simulated.The simulation results show that the error rate values of three-user with different code weights differ by several orders of magnitude,which verifies the feasibility and correctness of the codec system.The results show that the system can provide different service quality requirements for different users.2)A two-dimensional variable-weight OCDMA encoding and decoding system based on FPGA is designed,which provides an additional solution to solve the problems of high cost and low reconfigurability of all-optical OCDMA systems.On the Xilinx ML605 FPGA development board platform,Virtex-6 chip is used,and users can use codewords of different code weights to perform OCDMA encoding and decoding according to their needs.The GTX high-speed serial transceiver performs high-speed transmission,and uses the IBERT core to test the bit error rate performance of the GTX high-speed channel.The test of a single module and the cascade debugging of the entire system are completed on the ISE 14.7 software.The test results show that the system can perform correct encoding and decoding functions.The system encodes and decodes in the electrical domain,can change the user's address code,and the system is economical,flexible and easy to reconfigure.3)The two-dimensional variable-weight OCDMA codec system experiment was carried out.A three-user system with a total transmission capacity of 15.625Gbps and a code weight of 5,4,and 3 was built.Under the three conditions of connecting a tunable optical attenuator,connecting a l0Km optical fiber and connecting a 10Km optical fiber plus an optical attenuator in the optical fiber link,the changes in the bit error rate,eye pattern and decoding waveform of users with different code weights were tested.The experimental results show that the user error rate value increases with the increase of the optical power attenuation value,but the greater the code weight,the better the user error rate performance.Different code weights correspond to different bit error rate performance,so as to meet the needs of multiple QoS application scenarios.4)Propose a two-dimensional electrical domain OCDMA codec system scheme based on CSRZ-DPSK modulation to solve the possible dispersion and nonlinear effects of the above-mentioned design system.This OCDMA system is compared with the OCDMA system based on CSRZ-OOK and NRZ-DPSK modulation.Under the conditions of two channels of users,a data rate of 15Gbit/s,and a transmission of 100Km,the variation of the Q factor of the three systems with the dispersion value and the variation of the system's bit error rate with the incident optical power are simulated.The simulation results show that the CSRZ-DPSK-OCDMA system has the best tolerance for dispersion and nonlinear effects,which is suitable for reducing the influence of dispersion and nonlinear effects when the two-dimensional variable-weight OCDMA system uses longer-distance fiber transmission.