Simulation of light versus current characteristic of an injection laser using an optoisolator

A simple circuit which models the light-versus-current (
L-I
) transfer characteristic of a semiconductor injection laser is described. It is suitable for use in developing circuits for lightwave transmitters so that damage to the laser from transients can be avoided. Features include adjustment in lasing threshold, and differential quantum efficiency. Also a nonlinearity (kink) can be placed in the simulated
L-I
characteristic, emulating a feature often seen in actual lasers.