Patent ID: 8422888

Claim:
An optical transmission system comprising: an optical transmission apparatus operative to transmit an optical main signal; an optical reception apparatus operative to receive the optical main signal; an optical transmission line that is placed between the optical transmission apparatus and the optical reception apparatus and is redundantly configured with an active system optical transmission line and a standby system optical transmission line; an optical switch operative to switch an optical transmission line between the active system optical transmission line and the standby system optical transmission line; a variable dispersion compensator placed between the optical switch and the optical reception apparatus; a dispersion amount measuring unit operative to measure the dispersion amount of the standby system optical transmission line when the active system optical transmission line is being selected by the optical switch; a dispersion compensation amount setting unit operative to set the amount of dispersion compensation to be applied to the standby system optical transmission line based on the measured dispersion amount of the standby system optical transmission line; and a control unit operative, when the optical transmission line is switched from the active system optical transmission line to the standby system optical transmission line by the optical switch, to control the variable dispersion compensator so that the amount of dispersion compensation becomes the set amount of dispersion compensation; wherein the dispersion amount measuring unit includes: a supervisory control signal control unit operative to generate a supervisory control signal having a wavelength different from that of the optical main signal and to shuttle the supervisory control signal between the optical transmission apparatus and the optical reception apparatus; a round-trip time measuring unit operative to measure the time required for the supervisory control signal to travel back and forth between the optical transmission apparatus and the optical reception apparatus; and a dispersion amount calculation unit operative to calculate the distance of the standby system optical transmission line based on the measured round-trip time and then to calculate the dispersion amount of the standby system optical transmission line based on the distance and on a dispersion coefficient of the standby system optical transmission line that is set in advance.