OPTICAL TRANSMISSION APPARATUS AND LIGHT ATTENUATION AMOUNT CONTROL METHOD

PROBLEM TO BE SOLVED: To provide an optical transmission apparatus capable of detecting a communication failure even after switching a multiple channel transmission to a minor channel transmission.SOLUTION: A storage section 1a stores information of a channel to be dropped from a subsequent stage node 2. A determination section 1b determines a switch from a multiple channel transmission to a minor channel transmission. A control section 1c makes an attenuation amount of a no-signal channel to be dropped higher than a predetermined value, when the no-signal channel within a predetermined wavelength range is the channel which is dropped at the subsequent stage node 2 from a signal light channel of the minor channel transmission by referring to the storage section 1a corresponding to the determination by the determination section 1b.