| 摘要 |
PURPOSE:To input an optical signal with a prescribed intensity to an light receiving device or the like by controlling the intensity of the optical signal automatically in response to a loss of an optical transmission line. CONSTITUTION:A signal light outputted from an optical signal amplifier section 19 of an optical amplifier 5 is reflected in an optical partial reflector 6 to be returned to an optical transmission line 3 and a reflected returned light is separated from the optical transmission line 3 by an optical circulator 22. A gain control circuit 24 changes the gain of an optical signal amplifier section 19 based on the reflected returned light and an optical output signal to control the luminous intensity. |
