Abstract: An optical amplification apparatus has a first optical amplification unit and a second optical amplification unit connected in tandem with an optical attenuator between them. A temperature sensor is located in the vicinity of an optical fiber included in the second optical amplification unit. A reference voltage generation circuit controls an automatic gain control (AGC) circuit according to an output signal of the temperature sensor Alight signal detector detects maximum or minimum power from among the powers of the wavelength components output from the second optical amplification unit. The AGC adjusts the pumping power to set maximum/minimum to a predetermined value.

Abstract: An optical transmitting device that compensates for waveform distortion in an optical signal path.. The device has an amplifier for amplifying an optical signal input through an optical transmission line. A plurality of dispersion compensators are used to compensate for various degrees of waveform distortion due to dispersion distortion in the optical transmission line by having different dispersion compensating characteristics. A selection switch selects one of the dispersion compensators and connects the first amplifier output with the selected dispersion compensator. Another amplifier is used to amplify the optical signal output by the selected dispersion compensator.

Abstract: It is the object of the invention to detect and locate fails in the optical network by superposing monitoring signals on respective WDM optical signals in the transmitter part of the pass-monitoring apparatus and detecting the monitoring signals on the output side of the matrix switch in an receiver part of the same. The output signals of the matrix switch are respectively splitted by the optical splitters and converted into electrical signals by O/E-converters. The monitoring signals are respectively extracted by variable band-pass filter, center frequencies of which are established by an switching information signal, from the aforementioned electrical signals. The fails of them are respectively detected by an alarm processing circuit, signals are generated for the respective transmission lines. At the same time, the alarm signal is again supplied to the matrix switch and the switching information signal is again generated.