| 摘要 |
In a fiber optic laser controller for use in digital transmission a digital data stream and a DC bias are applied to the laser. During a monitoring period, the DC bias is stepped from a zero to a peak current. At a first threshold current, lasing occurs in response to digital '1' modulating current but not in response to digital '0' modulating current. At a second higher threshold current lasing occurs in response to both digital '1' and '0'. The threshold currents are identifiable as peaks in the second derivative d2L/dI2 where L is the light output for an applied bias current I. A feedback circuit including a photodiode, D/A and A/D converters and a microprocessor controller are used to maintain the bias current at the second threshold current in spite of changes in the laser characteristics caused by device aging or temperature change.
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