无源光网络主干保护系统中提前测距原理与应用

Pre-Ranging Mechanism in a PON System with Type B Protection

文章在分析无源光网络及其主干保护系统的基础上,为了提高保护倒换的效率,提出了一种无源光网络主干保护系统中的提前测距方法。该方法主要通过主用OLT在主用通道上测距,备用OLT在备用通道上被动侦听测距响应及其到达时间。通过测距信息、测距响应及到达时间便可计算出备用通道的测距结果。文章还提出了提前测距方法在无源光网络主干保护系统的实际应用中所涉及的主备OLT之间的信息交换和时间同步、测距过程发起、测距结果更新等具体措施。

In this paper, we analyze a PON system that uses type B protection and has a pre-ranging mechanism for fast protection switching. With this mechanism, working channel range information can be received by the working optical line terminal （OLT）, and the range response and arrival time of backup OLT can be monitored by the backup OLT. Then, the range result of the backup channel can be calculated by the upstream range responses, arrival time of backup OLT, and the range information of the working channel. In this paper, we also discuss the pre-ranging mechanism applications, including information exchange and time synchronization between the working and backup OLTs, initiation of ranging process, and ranging results refreshing.