A Study Of OCDM Technology Based On 6.4Tbit/s Transmission System

Optical code division multiplexing(OCDM) is receiving more and more attention recently. Optical channel multiplexing and demultiplexing can be achieved through optical encode and matched optical decode. Many different channels share same time slot and same wavelength band , which can improve spectral efficiency. Combinating OCDM with wavelength division multiplexing(WDM), transmission rate can be improved greatly. OCDM is promising in future all optical communication. Supported by National High Technology Research and Development Program of China(863 Program-2002AA122035), this paper presents the theoretical and experimental research on quarternary phase shift key(QPSK) OCDM. The main contents are given as follows:(1) The research background and signification of OCDM is introduced. The primary technical solutions for OCDM are reviewed. According to the Program, a new OCDM technology of QPSK coherent phase encoding in time domain is considered to be studied.(2) The design principle of the encoder/decoder and the design of the address codes usually to be used are analyzed. The conclusion that bipolar coherent OCDM is superior to unipolar noncoherent OCDM is drawn through the performance compare of both. (3) The performance of quarternary bipolar code is superior to that of binary bipolar code according to Welch's well-known lower bounds on complex sequence. The theory of quarternary bipolar code based on Family A is researched and the method of generating period quarternary bipolar codes with quarternary shift register is given. The performance of period quarternary bipolar codes based on Family A is compared with that of binary bipolar codes usually to be used.(4) QPSK coherent OCDM in time domain of code length 3 is proposed. The period quarternary bipolar codes of code length 3 and code capacity 5 are generated with quarternary shift register. On the other hand, four aperiodic quarternary bipolar codes of better correlation performance are gotten through direct numerical simulation computing of aperiodic autocorrelation waveform and cross-correlation waveform. According to performance compare and our experimental condition, the later is chosen.(5) The matched encoder/decoder of code length 3 is designed based on the principle of match filter. The matched encoder/decoder consisting of separate optical devices and the matched encoder/decoder of superstructure fiber Bragg grating are proposed separately. The two schemes are analyzed.