| 摘要 |
<P>PROBLEM TO BE SOLVED: To shorten the change time of a protection path by simply starting up loop control. <P>SOLUTION: An optical variable attenuator 15 adjusts an amount of optical attenuation. A monitoring part 16 monitors optical power by being installed a rear stage of the optical variable attenuator 15. A control unit 18 controls an amount of attenuation of the optical variable attenuator 15, and the level of an optical detection threshold is equal to one of noise light discharged from an optical amplifier 11a. When a monitor value reaches a noise light level, it is transited to an ALC mode, and loop control for adjustment of the optical level is started up. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
