中文摘要：

针对长距离无源光网络（LR—PON）中不同ONU到OLT的传播时延差异较大的特点，提出一种基于空闲填充的部分多线程轮询算法（VF-PMTP）。该算法中，OLT对长距离ONU采用在线调度和离线调度相结合的混合调度方式，并根据信道的空闲情况动态调整长距离ONU的授权次数。

英文摘要：

A void-filling based partial multi-thread polling algorithm （VF-PMTP） has been proposed for long reach passive optical networks （LR-PON） with heterogeneous propagation delays. In VF-PMTP algorithm, OLT works on a combined online and offline scheduling scheme for the coexisting long-distance ONUs. Besides, VF-PMTP algorithm can adjust the grant times of the coexisting long-distance ONUs depending on whether the channel is idle.