An optically amplified gain control circuit is disclosed, which comprises
an optically amplifying medium for amplifying an optical signal, a
exciting light coupler for combining exciting light with the optical
signal optically amplified by the optically amplifying medium, and a
control circuit for controlling an output of the exciting light combined
with the optical signal by the exciting light coupler, wherein the optical
signal to be amplified is composed of a main signal, an SV signal, and a
tone signal which are multiplexed, and wherein the control circuit
controls the output of the exciting light corresponding to the tone signal
on the preceding stage of the optically amplifying medium and the tone
signal on the next stage of the optically amplifying medium so as to
control the amplification of the optical signal by the optically
amplifying medium.
