Abstract: An optical receiving device includes: an optical amplifier configured to amplify a wavelength multiplexed optical signal; a demultiplexer configured to demultiplex the amplified wavelength multiplexed signal into optical signals of a plurality of wavelengths; optical receivers configured to regenerate the demultiplexed optical signals; error correction units configured to correct a bit error in the regenerated optical signals; and main control unit. The control unit adjusts RXDTV of the optical receiver for receiving optical signals of a given wavelength to the optimal value in the state where the gain of the optical amplifier is lowered from that of a normal operation such that the occurrence of bit errors in the optical signals of the other wavelengths does not exceed the correction capability of the error correction unit.

Abstract: A frame transmission system includes a frame transmitter and a frame receiver. The frame transmitter includes a frame fragmentation unit and a reproduction header appending unit. The frame fragmentation unit fragments an input frame and outputs transfer frames when the length of the input frame exceeds a predetermined fragmentation reference frame length, and does not fragment the input frame and outputs the input frame as a transfer frame when the length of the input frame is less than or equal to the fragmentation reference frame length. The reproduction header appending unit appends a reproduction header to the transfer frames outputted from the frame fragmentation unit. Here, the reproduction header being required when the transfer frames are reproduced at a receiving side. The reproduction header appending unit varies the header length of the reproduction header to be appended to the transfer frame, according to the length of the input frame.

Abstract: A communication system includes a plurality of communication devices forming a ring network and a monitoring device. Each of the plurality of communication devices appends, to a frame that the communication device relays, an ID tag indicating the number of communication devices relaying that frame in the ring network. The monitoring device refers to frames received by a predetermined communication device and having the ID appended thereto, and tallies an amount of data for frames for each number of relaying communication devices.

Abstract: An excitation light source, for Raman amplification, includes a polarization beam splitter (PBS) for splitting a laser beam from an excitation laser into two polarization components, and a polarization beam combiner (PBC) for combining the two polarization components, and a time difference generator provided between PBS and PBC. The time difference generator generates a difference in propagation time between the two polarization components.

Abstract: An OLT, which is a station-side apparatus in a PON system, is connected to an ONU via an optical fiber. The OLT includes: an optical receiver which receives a burst signal from an ONU; a burst header detection unit which detects a certain delimiter pattern included in a received burst signal so as to establish synchronization of the burst signal; and a control unit which allows the burst header detection unit to perform detection of a delimiter pattern during a predicted reception period of a burst signal.