LEVEL LOWERING DETECTION DEVICE, OPTICAL AMPLIFYING DEVICE AND LEVEL LOWERING DETECTION METHOD

摘要

A level lowering of signal light on which data are superimposed is surely detected even in the case where a dynamic range for input light is set to be large at the time of the amplification of light. In order to solve this problem, a threshold value comparing unit (253) compares a signal light level with a threshold value and outputs a compared result to a signal lowering notice unit (256). A difference calculating unit (254) subtracts the signal light from a monitoring light level to calculate a difference ?. A threshold value comparing unit (255) compares the level difference ?P between the monitor light and the signal light with a predetermined relative value and outputs a compared result to the signal lowering notice unit (256). In the case where the compared result of the threshold value comparing unit (253) shows that the signal light level is lower than the predetermined threshold value or the compared result of the threshold value comparing unit (255) shows the level difference ?P is more than the threshold value, the signal lowering notice unit (256) provides a control unit (120) with an output to warn such a lowering alarm that the signal light is only lowered in light intensity.