利用布拉格光栅阵列实现二维光码分多址的研究

利用布拉格光栅阵列，实现了在波长和时问上的素数跳频码的编解码。利用该编解码器，完成了在两个发送用户和一个接收用户的条件下，传输速率从20Mb／s到1．4Gb／s的光码分多址通信系统。研究了当系统传输速率超过相邻布拉格光栅间距限制条件时，系统的性能变化情况。结果表明当用户数不超过(3／2)Ps(素数跳频码的扩展因子)时，速率超限对系统性能基本无影响。在同样误码率要求条件下，地址码较长的系统，传输速率可以达到限制速率的2～3倍而不会造成明显的系统性能下降。这表明相邻布拉格光栅间距条件所限制的系统速率并非不可逾越的。

The Study of Time/Frequency Encoding Optical Code Division Multi-Access Communication with Bragg Gragting Arrays

Optical code division multiple access system, usually known as OCDMA, can provide very attractive features, such as asynchronous access, privacy and security in transmission, ability to support variable bit rate and scalability of the network. A time/frequency encoding/decoding OCDMA system with high quality Bragg grating arrays is developed, and transmission rates up to 1.4 Gb/s per user can be achieved. The effects of data rate on the performance of the system are studied theoretically and experimentally. It is proved that even if the data rate is beyond the critical value determined by the distance between Bragg gratings essential for the prevention of code overlapping, the performance of the system can still be satisfying,when the user number is lower than (3/2) times of P s (pulse number of time in a code) or the code length is larger than 289, the system's error rate will not increase obviously as the data rate exceeds the critical value.