Laser dc bias controller

Abstract

A laser DC bias controller is disclosed for controlling and monitoring the laser of a fiber-optic transmitter. The arrangement comprises an optical power monitor including a light detector for converting the light output by the laser into photo current. The photo current is converted by the optical power monitor into a voltage representation of the magnitude of the light output by the laser. The voltage representation is output to a DC constant current source which uses the voltage to provide operating current to the laser of sufficient magnitude to keep the laser operating at a set output level. A transmit data detector monitors the incoming data signals to the fiber optic transmitter and outputs to the optical power monitor a current signal which indicates a failure of the data signal. The optical power monitor converts the current signal to a voltage representation which is output to the DC constant current source. The DC constant current source subsequently turns off the operating current to the laser and an alarm signal representing a failure of the data drive circuit is output to a controller interface. Finally, an optical output detector connected to the optical power monitor is provided to compare the voltage output by the optical power monitor to a set value. When the voltage falls below the set value, the optical output detector sends an alarm signal to the controller interface indicating that the laser has failed.