| 摘要 |
PROBLEM TO BE SOLVED: To stably control the output signal level of the optical fiber amplifier. SOLUTION: An input optical signal λs and excitation light λp are inputted to an optical amplification fiber 12 through an wavelength multiplexer(WDM) coupler 11 and the signal is amplified. A filter 13 removes components other than the neighborhood of signal wavelength from an optical signal S12 outputted from the fiber 12. The optical signal 512 made incident upon a photodiode (PD) 14a is converted into an electric signal and the electric signal is amplified by a wide band amplifier 14b. The amplitude of an output signal S14 from the amplifier 14b is detected by a peak detection circuit 15. A difference S16 between the detection value S15 of the circuit 15 and reference voltage S17 is inversely amplified by an operational amplifier 18. An output signal S18 from the amplifier 18 is inputted to a laser diode(LD) 19 and the light emission quantity of the LD 19 is controlled so that the detection value S15 becomes the same level as the reference voltage S17. Consequently the amplitude of the output signal S14 from the amplifier 14b is fixed. |
