| Summary: | 碩士 === 國立臺灣大學 === 電信工程學研究所 === 99 === The Optical code division multi-access (OCDMA) system is commonly used in passive optical network (PON) because it provides multiple users to access the network simultaneously with high data transmission rate and moderate security. However, when many users access the network simultaneously, multi-user interference (MUI) will severely degrade the system performance. Hence, the spectral amplitude coding (SAC) OCDMA systems were proposed to solve the MUI problem. When applying code with fixed cross-correlation in SAC OCDMA PONs, we can eliminate the MUI completely at the receiver. Nevertheless, the noncoherent broadband light source is used in SAC OCDMA systems, the system performance suffers from phase induced intensity noise(PIIN).
In this thesis, we propose a new SAC OCDMA PON which uses a new code family called extended super perfect difference(ESPD) codes. In our system, we use cyclic shifted property of ESPD code and arrayed waveguide router to construct a simpler spectrum encoder. Furthermore, the numerical results show that the proposed system using our code has better performance than the systems using other codes.
Moreover, we also present an experiment according to our theoretical model which uses ESPD codes with cardinality equal to 8. The goal of our experiment is to verify the feasibility and performance of applying our code family to the SAC OCDMA PON. Because the number of active users and effective received power are the two main factors that limit the system performance, we change these parameters separately during our experiment. The experimental results show that our system can support maximum number of 8 users when transmission rate is 622Mbps and 7 to 8 users when transmission rate is 1.25Gbps.
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