This paper gave a brief introduction to the very short reach optical transmission system, analysed features of current word alignment circuits, and proposed a novel parallel binary search word alignment circit specifically for SDH systems. 简要介绍甚短距离光传输系统,分析各种帧对齐电路的性能,提出一种针对同步数字体系(SDH)高速数据的全新的基于二分查找的并行帧对齐电路。