Design Of Two-dimensional Optical Orthogonal Code And Performance Analysis In OCDMA System

Optical code research is one of the key technology in the Optical code division multiple access (OCDMA) system. Whether it can be practical and commercial, it depends on the optical code with good performance. Compared with the one-dimensional optical code, the two-dimensional optical code has much larger cardinality under the same condition and it can as possible as using the time/spectral domain, the time/space domain, or the spectral/space domain to improve the OCDMA system performances of BER and word capacity. The main contents can be outlined as follows:(1)We start to introduce the two-dimensional optical codes which contain the constant code length and constant code weight. They are both using One-coincidence Sequence (OCS) as wavelength hopping sequence, named Extend Prime Code/ One-coincidence Sequence (EPC/OCS) and Extend Secondary Prime Code/ One-coincidence Sequence (ESPC/OCS). And we analyze and simulate their performances of BER and word capacity. Base on that the methods, a new two-dimensional optical orthogonal code named Synchronous Quadratic Prime Code/ One-coincidence Sequence (SQPC/OCS) is constructed with SQPC as time spreading sequence and OCS as wavelength hopping sequence, The performances of BER and word capacity are compared work by theoretical analyzed and simulated. It has a better performance compared with the others' work.(2) We introduce the two-dimensional optical codes which contain the variable code length and variable code weight. Started with two-dimensional variable-weight optical codes (VWOOC/OCS), we analyze the performances of BER and word capacity of this kind of codes. By using One-coincidence Frequency Hopping Code (OCHCH), a new two-dimensional variable-weight multi-length optical code is constructed, which named VWMLOOC/OCFHC. This code can not only meet the different users with different requirement of quality of services (QoS) and bit rate. It also performs well in the OCDMA system with the different kinds of these codes. This kind of codes has significant meanings in the practical.(3) We introduce the development of the two-dimensional optical codes from another direction, the spectral/space domain code instead of the time/space domain code. Two dimensional multi-diagonal (2D-MD) code is introduced, and its' performances of BER and word capacity is deeply analyzed with considering the influence of the dark current noise, laser extinction ratio, background light and MAI in different systems. Based on 2D-MD code, two-dimensional cyclic shift multi-diagonal (2D-CSMD) code is proposed. The BER formula depends on the system is deduced in the system and performance is discussed in deeply.