An optical transmission apparatus includes a transmitting unit for
transmitting an optical signal with a specified wavelength, a
multiplexing unit for multiplexing the optical signal with the specified
wavelength and an optical signal with a wavelength other than the
specified wavelength and outputting the multiplexed signal as a
wavelength division multiplexed optical signal, an optical amplifier for
amplifying the wavelength division multiplexed optical signal outputted
from the multiplexing unit, a level detecting unit detecting a variation
of an optical power of the wavelength division multiplexed optical signal
inputted to the optical amplifier, and a level adjusting unit for
adjusting, when a variation of the optical power of the wavelength
division multiplexed optical signal is detected by the level detecting
unit, a transmitting power of the optical signal with the specified
wavelength transmitted from the transmitting unit so that an output power
becomes a level before the variation.