Patent ID: 8027586

Claim:
An optical line terminating apparatus (OLT), in a passive optical network (PON), connected to a plurality of types of optical network units (ONUs) having different signal transmission speeds through an optical distribution network, the optical line terminating apparatus comprising: an optical transmitter-receiver connected to the optical distribution network; an electrical/optical converter connected to the optical transmitter-receiver; a transmission/reception line interface connected to a wide area network; an OLT controller that generates downstream frames; a downstream frame processing section for converting frames received by the transmission/reception line interface from the wide area network and downstream frames generated by the OLT controller into downstream frames containing identification information on a destination ONU in a header; and a downstream transmission controller, wherein when the downstream transmission controller transmits a new downstream frame at a changed modulation speed, the downstream transmission controller outputs a communication end notification of a current signal transmission speed to the electrical/optical converter, then outputs a communication start notification containing a clock synchronization bit corresponding to a new signal transmission speed to the electrical/optical converter prior to transmission of the new downstream frame, and wherein the electrical/optical converter converts the communication end notification, the communication start notification, and the new downstream frame transmitted from the downstream transmission controller to optical signals and outputs the converted optical signal to the optical transmitter-receiver.