The Study On Optical Code Division Multiple-Access (OCDMA) Technology In Optical Local Area Access Network

As a scheme of multiple access, 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. In this paper, we introduce OCDMA technology in detail and research the performance of OCDMA by experiments:At first, beginning at the analysis of 1-D OCDMA codes, the encoding/decoding theories and systematic performance theories for prime codes, algebraic congruent codes, optical orthogonal codes and optical frequency hopping codes are analyzed. The bit error rate (BER) curves are simulated using MATLAB and the performances of different address codes are compared.Secondly, giving three types of 2-D OCDMA encode/decode schemes: Temporal/Spatial (T/S) OCDMA, WDM+OCDMA,λ?t2-D OCDMA, their capacity and performance are discussed and compared. Our discussion is focus on the analysis of the encoding/decoding theory and systematic performance ofλ?t2-D OCDMA. An experiment about the time/frequency encoding/decoding optical CDMA system with high quality Bragg grating arrays is developed in order to verify the feasibility of 2-D OCDMA.Later, the possibility of supporting the data with multi-rate and various QoS (quality of service) demands in the future OCDMA access network is discussed. Base on the existing theory of multi-length OCDMA and multi-weight OCDMA, We introduce a novel way to realize the multi-rate OCDMA system. The performance of BER of our system and the possible improvement of the performance when using the hardware-limit is evaluated. The relevant experiments are done to verify the theory.Finally, as the bipolar codes and 4-phase sequences can prove better system capacity and performance comparing to unipolar codes, we introduce the encoding method of 4-phase sequences codes using in OCDMA and emulate the system performance. We theoretically analyze and numerically emulate the reflected spectrum of the phase encoder/decoder of Fiber Bragg Grating (FBG).