Patent ID: 7414952

Claim:
A laser driving apparatus including; a laser driving circuit for supplying a drive current to a laser, and radio frequency current superimposing means for generating a radio frequency current and superimposing said radio frequency current on said drive current comprising: current monitoring means for monitoring said drive current; optical detection means for detecting an optical output of said laser; amplitude control means for controlling an amplitude of said radio frequency current to be superimposed on said drive current said amplitude control means controls whether said radio frequency current is superimposed on said driving current or not; optical output control means for controlling said laser driving circuit to maintain said optical output of said laser at a constant level; and control means for controlling said amplitude of said radio frequency current on the basis of values of said drive current obtained by said current monitoring means at a plurality of said amplitudes of said radio frequency current obtained by said amplitude control means or detection values of said optical output of said laser obtained by said optical detection means at said plurality of said amplitudes of said radio frequency current obtained by said amplitude control means, said control means obtains a difference between said driving current monitored when said radio frequency current is superimposed on said driving current and said driving current monitored when said radio frequency current is not superimposed on said driving current, and controls said amplitude of said radio frequency current on the basis of said difference under the condition that said optical output of said laser is maintained at said constant level.