中文摘要：

针对光通信系统日益发展的需要,提出了一种的基于有限域准循环低密度奇偶校验（QC-LDPC）码的构造方法。该构造方法简单易行,可以有效避免四环的出现,具有良好的围长特性,同时能够自由地选择码长码率。仿真分析表明：通过该构造方法所构造的码率为93.7%的QC-LDPC（3780,3540）码的纠错性能优于利用随机构造方法所构造的SCG-LDPC（3969,3720）码和已广泛用于ITU-T G.975中的RS（255,239）码和ITU-T G.975.1中的LDPC（32640,30592）码,因而其更适合于光通信系统。

英文摘要：

According to the requirements of the increasing developments for optical communication systems, a construction method of Quasi-Cyclic Low-Density Parity-Check（QC- LDPC） codes, based on the finite field, is presented. This construction method is simpler and easier to implement, can effectively avoid the grith-4 phenomena and has the advantages such as better girth-length properties and more flexible code-length code-rate adjustment. The simulation results show that the error-correction performance of the QC-LDPC（3780,3540） with the code- rate of 93. 7% structured by this construction method is better than those of the SCG-LDPC （3969,3720） structured by the random construction method, the classic RS（255,239） code which is widely used in optical communication systems in ITU-T G. 975 and the LDPC（32640,30592） code ITU-T G. 975.1. Furthermore, the constructed QC-LDPC（5334,4962） code is more suitable for optical communication systems.