Patent ID: 7916765

Claim:
A control driver circuit for a semiconductor laser diode that emits signal light, comprising: a laser diode driver configured to supply a driving current to said laser diode; a monitor photodiode configured to detect a portion of said signal light and to generate a source signal corresponding to said portion of signal light; and a current limiter including a master control, a switch, a memory, and an APC controller, said APC controller constituting an APC feedback loop by a co-operation with said laser diode, said monitor photodiode, and said laser diode driver, said master control connecting said laser driver with said APC controller by turning said switch on to activate said APC feedback loop to determine said driving current in a normal mode, said driving current in said normal mode being stored in said memory, wherein said master control connects, when said APC feedback loop falls in a failure mode, said laser diode driver with said memory to provide said driving current stored in said memory.