Key Technologies For Optical Code Division Multiple Access Communication System

There are many advantages in using code division multiple access (CDMA) techniques in optical fiber communication networks, which is a select scheme for future all optical high-speed networks, recently, OCDMA system have attracted many researchers' attention, while compared with other multiplexing technologies, it is still at the stage of infancy. This dissertation is focus on some key technologies in OCDMA system, including one construction for Optical orthogonal code (OOC) by computer, the chromatic dispersion and nonlinear effect on fast frequency-hopping OCDMA system, method of breakthrough the problem on multiple access interference, to realize and analyze bipolar OCDMA system, study on applying bipolar code into OCDMA system, and combination of hybrid networks.The basic theory and configuration of system is introduced, the key technologies of OCDMA system is concluded, the history of OCDMA and obstacle to OCDMA are analyzed in the exordium.In chapter 2, an OOC is studied deeply, which is put into FFH-OCDMA system, and studied the performance of asynchronous FFH-OCDMA system with double hard-limiters, based on fiber optical Bragg grating, under the assumption of Poisson shot noise model for receiver photo-detector. The numerical result demonstrates the performance of the system is deteriorated by , considering the chromatic dispersion and nonlinearly effect of the transmission medium.In chapter 3, in order to realize huge capability and trustiness of OCDMA system . bipolar OCDMA system is investigated, and studied the performance of the system with spectrum-phase en/decoder. The analysis of impact on error of code position for the system, Gained the formula of BER of system under the case. The numerical result demonstrates the control of luminous power, structure of en/decoder and choice of code sequence, which are the key to the system. Based on the conclusion, the performance of OCDMA system using division-frequency channel and bipolar codes is studied,and theory formula of the system is deduced. The simulation result demonstrates that in the optical CDMA systems, improve the capacitance of the system, and excellent correlation can be achieved. and the system adapts to communication system for different traffics, based on multi-bit rate.In chapter 4, Several system structure schemes are proposed, all of these schemes will be hot topical in the future. For the orthogonality and the capacity of simultaneourse user of unipolar code is worse than bipolar code, the use of dipolar code in OCDMA is proposed. introduce the three typical dipolar code: m, Gold and Walsh code followed by the analysis of the properties of the three codes. In this section, we mainly analyze the correlation of the code sequence, the number of the code sequence and the bit error rate. According to the result of analysis, the Gold code is more fitable for OCDMA system. furthermore, we discuss the dipolar to unipolar methods, and use Gold to analyze the properties of the methods.In chapter 5, WDM/OCDMA networks scheme has been achieved in the section. The partition of optical bandwidth,code converter terminal and the structure of WDM/OCDMA networks have been analyzed; The formulation of bit error rate and throughput of the networks has been deduced. The simulation result demonstrate that the capacity of the WDM/OCDMA achieve better than that of the OCDMA, and construct networks more facility and agility.