Low-latency dynamic bandwidth allocation for 100 km long-reach EPONs

We propose a new dynamic bandwidth allocation (DBA) method for long-reach passive optical networks that can reduce the upstream latency. With this method, an optical line terminal allocates bandwidth to long-distance (up to 100 km) optical network units (ONUs) with a transmission request prediction and reduces the latency of the long-distance ONUs. This has no influence on the latency of short-distance ONUs even if they coexist with long-distance ONUs. The results of real machine experiments show that this new DBA method achieves a smaller latency with long-distance ONUs than the conventional DBA technique, and that there is no influence on short-distance ONUs. The latency time and jitter are kept below 1300 μs and 1000 μs, respectively, for both long- and short-distance ONUs. The experimental results also reveal the effect of the proposed method on bandwidth utilization efficiency and fairness. The degradation in bandwidth utilization efficiency when one long-distance ONU is added is small (0.3%), and the fairness index degradation is negligible (less than 0.1%), when the parameters are optimized. These results indicate the validity of the proposed DBA method.