多种通信手段和互联网络的广泛应用 ,以及多种形式的信息 (声音、图像、数据等 )大量涌入 ,使得铁路传输网的信息流量剧增 ,并且呈逐年上升之势。通信量的增加和对通信质量要求的提高呼唤宽带、大容量和高可靠性的传输网和接入网的出现 ,而光通信网以其绝对的优势在这类网中占? The widespread use of multiple means of communication and the Internet, as well as the influx of various forms of information (sound, image, data, etc.) have led to a dramatic increase in the information flow on the railway transmission network and a year-on-year increase. The increase of traffic and the improvement of communication quality call for the appearance of transmission network and access network of broadband, large capacity and high reliability, and the optical communication network accounts for the absolute superiority in this kind of network?