The Research On Optical Code Division Multiple Access (OCDMA) Systems

Optical code division multiple access (OCDMA) has many outstanding advantages such as large capacity, high security and excellent anti-interference, which make OCDMA the hot topic of the researches on the all-optic access network, LAN and all optical switching. In this paper, we introduce OCDMA technology in detail and research the performance of OCDMA by experiments.1. The encoding/decoding theories and system performance theories for 1-D OCDMA codes such as prime codes, algebraic congruent codes,optical orthogonal codes and optical frequency hopping codes are analyzed. The bit error rate (BER) are simulated and the performances of different codes are compared.2. The system capacity and BER of multiple-phase codes are studied. The reflected spectrum of the phase encoder/decoder of Fiber Bragg Grating (FBG)are theoretically analyze and numerically emulated.3. The transmission characteristics of spectrum amplitude and spectrum phase encode systems are analyzed. The MAI(multi-user interference)of spectrum encoding OCDMA system is analyzed and an experiment is executed to delete MAI with balance-detection. A new wavelength allocation is proposed to reduce beat noise.4. The encoding/decoding theory and systematic performance ofλ?t2-D OCDMA are analysis and experiment about the time/frequency encoding/decoding optical CDMA system with fiber Bragg grating(FBG) arrays is developed. The data rate of user can exceed the rate decided by FBG's distance when the simutaneous user number is not very large.5. A new code and the system model to accomplish the multi-rate OCDMA system is proposed. The performance of BER of the new system is analyzed and the relevant experiments have been done and confirm the theory.6.The security of OCDMA system have been discussed. The performance is related with the code capacity and technique of the eavesdropper.