| 摘要 |
<P>PROBLEM TO BE SOLVED: To eliminate the need of photodetector means on a prestage of an external attenuation medium, prevent SN deterioration, and reduce required excitation light power. <P>SOLUTION: Attenuation amount detection means 3 detects an amount of attenuation of signal light caused by a variable optical attenuator 6 and the external attenuation medium 7 from prestage photodetection means 1a of a prestage optical amplifier 1, provided on a front stage of a variable optical attenuator 6 and an external attenuation medium 7 connected in series and from a subsequent stage photodetection means 2a of a subsequent stage optical amplification part 2 provided on a subsequent stage. Attenuation amount control means 4 controls the variable optical attenuator 6 such that an attenuation amount of signal light detected by the attenuation amount detection means 3 remains unchanged. Connection detection means 5 detects disconnection and connection of the external attenuation medium 7 in response to an amount of attenuation of the signal light when the amount of the attenuation of the variable optical attenuator 6 is minimum. <P>COPYRIGHT: (C)2007,JPO&INPIT |
