| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that variation in light output-forward direction current characteristics by temperature change or change with time can not be followed when the bias current of a laser diode is fixed. SOLUTION: A loop for setting bias by a photodiode PD→comparators 12-1 to 12-n→sample hold circuits 13-1 to 13-n→voltage-current converting circuits 14-1 to 14-n→a computing circuit 15→a current adder 17→a driving circuit 18→a laser diode LD is provided other than an APC loop by a photodiode PD→a comparator 12-1→a sample hold circuit 13-1→a voltage-current converting circuit 14-1→a switch circuit 16→a current adder 17 a driving circuit 18→a laser diode LD. Currents I1-In corresponding to reference voltages Vref1-Vrefn are obtained and a threshold current Ith is determined by the computing circuit 15 with the currents I1-In. A bias current Ibias is set on the basis of the threshold current Ith. COPYRIGHT: (C)2004,JPO
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