| 摘要 |
PROBLEM TO BE SOLVED: To transmit a monitoring control signal, without especially having to provide signal transmission lines and at the same time, to amplify and output only an input light signal. SOLUTION: A modulation part 2 is provided at the first prescribed position of an optical fiber 12 for transmitting communication signal light for superposing a control signal to the communication signal light, and an optical amplifier 3 using an erbium-doped fiber is provided at a second prescribed position away from the first prescribed position to amplify the communication signal light. Then, a photodiode 7 is provided on the downstream side of the optical amplifier 3, one portion of the communication signal light where the control signal has been superimposed is extracted and is converted to an electrical signal, the electrical signal is supplied to a laser diode driver 6 for performing APC operation, and a control signal is extracted from a control signal extracting part 8 with the output signal of the laser diode driver 6 as input and is supplied to the laser diode driver 6. |
