| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that the logic of a failure detection circuit output terminal does not change as far as a CELL signal input terminal does not change to a low level when an LD(laser diode) emits light once in a circuit for detecting the failed state of the LD that is driven by a conventional burst signal, and hence a non-emitted state cannot be detected even if the LD fails in the middle of the burst signal. SOLUTION: The light signal of a laser diode 1 and the drive current of the laser diode are used to detect a logic, thus detecting the failure in the laser diode within the burst signal. Then, even if the non-emitted state of a laser diode light signal continues for fixed time, failure cannot be detected erroneously. |
