| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical transmitter which does not issue false alarms erroneously recognizing as an optical output level drop when the marking rate of a data signal drop extreme. SOLUTION: A reference voltage proportional to a making rate, that is, a making rate detecting voltage 18 is extracted from a marking rate detecting circuit 12, and an optical output of a front surface of an LD 17 is branched with an optical coupler 20 for photodetection, and an optical output level detecting voltage 19-2 proportional to the optical output level of the front surface of the LD 17 is extracted, and an alarm detecting circuit 15 is operated by comparing these two voltages. By employing such a constitution as this, erroneous issuance of alarm is prevented even when a marking rate of a data signal becomes extremely low. |
