LOCAL OSCILLATOR SYNCHRONIZATION METHOD OF PON SYSTEM, ONU AND OLT

摘要

Disclosed are a local oscillator synchronization method of a passive optical network (PON) system, an optical network unit (ONU) and an optical line termination (OLT). The method is respectively applied in the ONU and the OLT, comprising: the ONU sending an uplink spread spectrum signal to the OLT; the OLT de-spreading the uplink spread spectrum signal and estimating a local oscillator frequency of the ONU; generating a frequency control word according to a frequency offset value between the local oscillator frequency and a channel specified by the OLT; modulating the frequency control word into a downlink spread spectrum signal and sending the signal to the ONU; the ONU demodulating the downlink spread spectrum signal to obtain the frequency control word; and adjusting the local oscillator frequency according to the frequency control word. According to the method, the local oscillator frequency of each ONU is pulled to the channel specified by the OLT, thereby avoiding the overlap of signal spectrum after each ONU is started. Local oscillator synchronization of the PON system is realized without affecting the normal communication of in-transmitting users.