Optical line terminal

摘要

To enable optical line terminal to detect input disconnection of optical burst signal accurately in spite of changes of transmission rate of optical-burst signal received from optical network unit, OLT (optical line terminal) includes photo-detector for converting the optical-burst signal received to current signal; preamplifier for converting the current signal to voltage signal; input disconnection detecting circuit for comparing output amplitude of preamplifier with threshold, and for outputting input disconnection signal indicating disconnection of input of the optical-burst signal; and control circuit for controlling conversion gain of preamplifier in a manner that the conversion gain becomes conversion gain corresponding to the transmission rate of the optical-burst signal received, and for controlling input disconnection detecting circuit in a manner that it outputs the input disconnection signal in response to the threshold corresponding to the transmission rate of the optical-burst signal received.

主权项

1. An optical receiver that receives optical burst signals with different transmission rates from transmission sources via an optical transmission line, the optical receiver comprising:
a photo-detector to convert the optical burst signal received to a current signal; a preamplifier circuit to convert the current signal to a voltage signal; an amplitude detecting circuit to detect the amplitude of the voltage signal undergoing the conversion of the preamplifier circuit; a threshold circuit having a plurality of thresholds which correspond to the transmission rates of the optical burst signals and are set in advance; and an input disconnection detecting circuit including a plurality of comparator circuits to compare the amplitude detected by the amplitude detecting circuit with each of the plurality of thresholds output from the threshold circuit, and to individually output an input disconnection signal indicating disconnection of input of the optical burst signal if the amplitude is lower than the threshold, and a selector to select one of the plurality of input disconnection signals output from the plurality of comparator circuits, wherein the selector selects the input disconnection signal in accordance with the threshold corresponding to the transmission rate of the optical burst signal received.