LASER DIODE TRANSMITTER WITH PROTECTION AND ALARM SIGNALLING CIRCUIT

摘要

Laser diode transmitters contain control circuits for the preconduction current and the modulation current of the laser diode which are controlled via a monitor diode optically coupled to the laser diode. Disablement of the monitor diode may result in an excessively low optical transmission level being deceptively simulated for the control circuit and the modulation current of the laser diode then being increased to the point where the latter is endangered. According to the invention, an improved laser diode transmitter is described which protects the laser diode against excessively high modulation current and transmits an alarm signal to a monitoring device even if the monitor diode fails completely.