The Code Interference Research Of Optical Code Division Multiple Access System

Fiber-optical code division multiple access(OCDMA) system is one of researching hotspot and standby scheme in optical communication networks, because it can supply even more bandwidth and more rapid signal disposal speed than electrical systems. There are many ways account for the impact of MAI, for example, the choosing of addresses: OOC'S, prime codes and improved codes, Manchester's codes, and so on; Also it can increasing different optical parts: optical switches and optical hard limiters (OHL). This article would put forward resolved ways in allusion to optical receiver for eliminating MAI. The double optical hard-limiters were proposed for optimizing system's transfer performance. Then the bit error probability for the optical systems was improved much highly. The idiographic works are First, in domain amplitude code optical CDMA system, it was used optical orthogonal codes (OOC'S) as address and detecting directly, considering hot and APD noise. Through numerical analysis, this paper presents the relations of OOC parameters, user's number, throughput optical power and the system's bit error probability. This paper proposed receiver with double OHL comparing with the receiver without or with only OHL on the bit error probability. Secongdly, in domain amplitude code optical CDMA system, It was used by single mode fiber (SMF) and dispersive compensate fiber (DCF) for diminishing group dispersion and MAI. The last, in frequency-hopping/time-speading optical CDMA system, using codes based on OOC'S and analyzing MAI in allusion to above system model. Through numerical analyzing, the effect of group dispersion, the available measures can be proposed for improving performance.The results showed: the bit error probability of the OCDMA system's receiver without and with only OHL was contiguous and descended little, so it was proposed the decoder with double OHL'S for improving the system's performance. The bit error probability of system with double OHL'S was much smaller than the single and had minimum of the two systems when accessing user's number N was bigger than the code weight k. Otherwise, the bit error probability of the single OHL system had minimum because the system eliminated channel interference incompletely. But the bit error probability of the system with double OHL'S hadn't minimum and descended linearly along with optical power because this decoder can eliminate interference completely. For transmission channels, it was adopted SMF and DCF for diminishing group dispersion affection. This paper would analyze the bit error probability of the OCDMA system.