Patent ID: 7242865

Claim:
An optical transmission equipment in an optical communication system having plural sets of the optical transmission equipment of which neighboring two optical transmission equipment sets are interconnected by a main transmission line and a backup transmission line, and optical signals are transmitted on one of the optical transmission lines, said optical transmission equipment comprising: an optical amplifier amplifying optical signal inputs from one transmission line in use for optical signal transmission out of the main transmission line and the backup transmission line respectively interconnecting the optical transmission equipment concerned with neighboring upstream optical transmission equipment, and outputting optical signals including a signal component and a noise component; and a controller controlling an optical signal level of output from the optical amplifier so that the signal component in the optical signal output from the optical amplifier reaches a predetermined level, and wherein the controller corrects the optical signal level of output from the optical amplifier when the transmission line transmitting the optical signal is switched either from the main transmission line to the backup transmission line or from the backup transmission line to the main transmission line, either between the optical transmission equipment concerned and the neighboring upstream optical transmission equipment, or between other two optical transmission equipment sets located on the upstream side, the controller performs correction based on a first noise component included in the optical signal being input to the optical amplifier and a second noise component generated by the optical amplifier concerned, and the controller performs the correction so that the optical signal level being output from the optical amplifier reaches a sum of a post-amplification level of the first noise component amplified by the optical amplifier, the second noise component level, and the predetermined signal component level.