| 摘要 |
The present invention provides an auto-power control (APC) circuit and a method to stabilize the extinction ratio of an optical output from a laser diode (LD) in an optical transmitter. The APC circuit according to the invention includes two feedback loops for the modulation I<SUB>M </SUB>and the bias current I<SUB>B </SUB>each having variable loop gain. The extinction ratio of the optical output from the LD is kept constant by setting the ratio of the loop gains of respective APC circuits to be ER-1.
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