| 摘要 |
PURPOSE:To stably amplify a deteriorated pumping laser by a simple constitution by connecting mutually an input terminal of an optical coupling part to an output terminal through an attenuating part, and lowering the attenuation amount at the time when an output of the pumping laser falls. CONSTITUTION:An input terminal of the side which is not connected to a pumping laser part of optical coupling parts 2a, 2b is connected to an output terminal of the side which is not connected to an erbium dope fiber amplifier of the optical coupling parts 2b, 2a. Usually, the attenuation amount of attenuating parts 5a, 5b are set in advance so that light does not pass through, and the optical coupling parts 2a, 2b are cut off in advance. In such a state, when a fall of an output level of a down pumping laser part 1b is detected by a monitoring control part 6, the attenuation amount if lowered by driving the attenuating part 5a, so that light can pass through. In such a way, a part of an output of a pumping laser 1a is supplied to an amplifying fiber 4b through the optical coupling part 2a, the attenuating part 5b, the optical coupling part 2b and a wavelength multiplexing part 3b, and a signal light is amplified and can be sent out to a transmission line. |
