Patent ID: 7113709

Claim:
An optical receiver for receiving an optical signal, comprising: variable optical attenuators located respectively on a plurality of optical transmission lines configured redundantly and for controlling optical loss values for the optical transmission lines based on a predetermined optical loss value; variable dispersion compensation modules located respectively on the plurality of optical transmission lines configured redundantly and for controlling wavelength dispersion values for the optical transmission lines based on a predetermined dispersion value; an optical loss/dispersion controller for measuring the optical loss value and the wavelength dispersion value of each of the optical transmission lines and outputting the predetermined optical loss value and the predetermined dispersion value so that the optical loss values and the wavelength dispersion values are equal in all of the optical transmission lines, and for controlling the variable optical attenuators and the variable dispersion compensation modules based on the outputted values; a receive amplifier for receiving an optical signal whose light level is kept constant as a result of controlling the optical loss value of each of the optical transmission lines and for amplifying the optical signal; and a transmission line switch controller for monitoring an optical signal level of a working optical transmission line and, if the optical signal level is lower than a threshold value, switching from the working optical transmission line to a protection optical transmission line.