Design And Performance Analysis Of Two-dimensional Address Code And SAC Address Code In OCDMA System

The Optical Code-division Multiple Access(OCDMA)is a communication mode which introduces the Code-Division Multiple Access(CDMA)technology into optical fiber communication.OCDMA has many advantages,such as well security,random access,over the electronic bottleneck,which is one of the best options of the next generation of broadband access network.Currently,because of the lack of the good performance optical code,the OCDMA system has not yet been commercialized.This paper focuses on the design of optical code and analyzing their Bit Error Rate(BER).The main contents can be outlined as follow:1)We star to study one two-dimensional optical address code named Extend Prime Code/One-Coincidence Sequence(EPC/OCS)which was constructed with EPC as time spreading sequence and OCS as wavelength hopping sequence,and the BER of this code was simulated.On this basis,a new two-dimensional optical address code named Reed-Solomon Code/One-Coincidence Sequence(RSC/OCS)was designed with RSC as time spreading sequence and OCS as wavelength hopping sequence.We analyzed the performance of this code and analyzed the BER of this code by simulation.Compared to the 2D-RSC,under the condition of the same code length and the number of wavelengths,the BER of RSC/OCS is basically the same as that of Two-Dimensional Reed-Solomon Codes(2D-RSC),but it is more flexible when selecting the number of wavelengths of RSC/OCS,The BER of RSC/OCS is more than one order of magnitude lower than that of 2D-RSC by increasing the number of wavelengths of its;under the same conditions,Compared to Synchronous Quadratic Prime Code/One-Coincidence Sequence(SQPC/OCS)and EPC/OCS,the BER of RSC/OCS is at least one order of magnitude lower than that of SQPC/OCS and EPC/OCS.Finally,a new two-dimensional optical address code named Extend Square Prime Code/Quadratic Congruence-Hop Code(ESPC/QCHC)was constructed with ESPC as time spreading sequence and QCHC as wavelength hopping sequence,The theoretical analysis and simulation analysis of the code capacity and BER of the code were carried out respectively.Theoretical analysis shows that the code capacity of ESPC/QCHC is q-1(q is the number of their wavelengths)times that of ESPC/OCS and EPC/OCS,and is q times that of PC/OCS and MSPC/OCS.Simulation analysis shows that the BER of ESPC/QCHC isslightly higher than that of ESPC/OCS,compared with PC/OCS,EPC/OCS and MSPC/OCS,the BER of ESPC/QCHC is the lower half to an order of magnitude of the three codes.2)Firstly,we study two one-dimensional Spectral-Amplitude Coding(SAC)codes,named Modified Quadratic Congruence(MQC)code and Partitioned Diagonal Code(PDC),the performance of the two codes were analyzed.Then two one-dimensional SAC codes named Modified Internal Recycle Prime Code(MIRPC)and Modified Synchronous Square Prime Code(MSSPC)were constructed.At the same time,one conventional detection techniques named complementary subtraction technique was studied,we also used a new partial balance detection technique for SAC-OCDMA system.Finally,under an ideal source and channel,the principle of the two detection techniques of eliminating Multiple Access Interference(MAI)was explained.The BER of MIRPC system and MSSPC system were analyzed in the consideration of the shot noise,Phase Induced Intensity Noise(PIIN)and thermal noise,The BER of them were also analyzed by simulation.The results show that compared with Generalized Matrix Partitioning Code(GMPC),First One Code(FOC)and EMD,MIRPC and MSSPC require the shortest code length when accommodating the same number of users,so their systems can save more spectrum resources;compared with MQC,PDC and FOC,the BER of MIRPC system is always lower than three orders of magnitude when they have the same code weight;for identical weight and similar code length,MSSPC can support 38.5% more active users as compared with PDC.3)One-dimensional SAC code system can completely eliminated MAI,but the code length will become very long as the increase of active users,which makes the system need more band sources,therefore,in this paper,we also research two two-dimensional SAC codes,named Two-Dimensional Maximal Area Matrices(2D-MM)code and Two-Dimensional Multi-Diagonal(2D-MD)code.The BER of the two SAC codes were analyzed in the consideration of the shot noise,PIIN and thermal noise.The results show that for 2D-MM,when the given total number of users is the same,there is an optimal N(N is the length of its spatial code sequence)value so that the system can accommodate the most users at a given BER.For2D-MD,under the condition of equal code weight,the BER of 2D-MD is lower than six orders of magnitude as compared with MIRPC,MQC,PDC,and FOC,and the code system can support more than 2 times active user than that of their.