| 摘要 |
PROBLEM TO BE SOLVED: To easily prevent production of optical surge. SOLUTION: An optical fiber amplifier 10 has an optical isolator 2 and an optical multiplexer 3 to stimulate an erbium in an optical fiber 5 with a stimulated light from a stimulation light source 4 and to give a signal light Ii to an EDF 5 (Er doped optical fiber) so as to cause stimulated emission of radiation thereby amplifying the Ii. As the Ii is smaller, the amplifier gain of the EDFA 10 (Er doped fiber amplifier) is larger and a natural emission optical power is increased. An optical demultiplexer 6 is used to apply wavelength demultiplexing a natural emission light Iedf(A) not including a signal optical wavelength component from an output light of the EDFA 10 and the Iedf(A) is given to a photodiode 7, in which the light is converted into a voltage Va, the voltage Va is compared with a reference voltage Vref at a voltage comparator 8 and in the case of Va<Vref, a control voltage Vcont is inverted to an L level, supply of the stimulated light from the stimulated light source 4 to the EDF 5 is stopped to block the increase in the amplifier gain of the EDF 5 so as to prevent an optical surge signal caused when the Ii is increased from a very small level. |
