An optical amplifying apparatus is composed of a light amplifying part for amplifying
light and an input light controlling part for inputting, to the light amplifying
part, probe light that serves to adjust the optical power of input light of the
optical amplifying part. Receiving light having constant optical power, the optical
amplifying part operates stably. In particular, the optical amplifying part stably
operates even in a case where input light is a WDM optical signal and the number
of multiplexed optical signals increases or decreases. The OADM of the present
invention comprises such an optical amplifying apparatus.
