Study On The Electrical Domain Amplitude Limiting Of Two-dimensional OCDMA Electronic Encoder/Decoder And MAI Suppression

Optical code division multiple access technology(OCDMA),generally combined the code division multiple access(CDMA)with the optical communication technique,is a novel communication technology with numerous advantages,such as high security,asynchronous access,flexible volume,multi-rate transmission,strong comprehensive service,which make it become one of the more advantageous technologies in optical communication technology.The research of OCDMA primarily focus on some contents to make a study including the design of optical code,the structure of encoder/decoder,multiple access interference(MAI)suppression,and so on.At present,all-optical codec as the most widely codec still suffered some unexpected problems that contain high implementation cost,inflexible modify address,and serious multiple access interference.Therefore,the main detail of our thesis is to study the electrical domain limiting codec with flexible variable address.The main research work of this dissertation has three parts as follow:First,the typical all-optical OCDMA system is introduced to design a project about the electrical domain amplitude limiting of two-dimensional OCDMA electronic encoder/decoder on the basis of the construction of two dimensional OCDMA.The project,which has the characteristic of strong refactoring and flexible modify address,utilizes the electronic codec and decreases the implementation cost and complexity.Beside,we utilize the optical communication simulation software(Optisystem)to design an transmission system simulation of three user transmission with the 5Gbit/s rate of single way,which demonstrated the electrical domain amplitude limiting can restrain the multiple access interference.Second,FPGA is a popular electronic device to implement the electrical domain amplitude limiting of two-dimensional OCDMA electronic encoding-decoding system.We exploit the development platform of FPGA to set up a logical model of the electrical domain limiting of two-dimensional OCDMA electronic encoding-decoding system and utilize the description language of Verilog HDL hardware to come true the function of codec so that to extend the interface of variable address.The FPGA function simulation tool that combined with the Modelsim verified the function of codec and the ability of test variable address.Finally,the OCDMA optical transmission system is built by using the Xilinx ML605 development kit and the FM-S14 backplane and accomplishes a optical transmission experiment with a transmission distance of 10 KM,which can accommodate six access users,with a 312.5Mbps access ratesand the line rates at 3.125 Gbps.Third,error correction code is proposed to resist the multiple access interference in electronic codec.Based on this,we utilize FPGA to design the convolution code module and decoding module(Viterbi).Then,the convolution code module and decoding module(Viterbi)is integrated into the electrical domain limiting of two-dimensional OCDMA electronic encoding-decoding system and come true the simulation of three users.This simulation result indicated that the error correction of coding can restrain the multiple access interference and distinctly reduced the error rate of transmission,which provide a novel reference to reduce the multiple access interference.