| 摘要 |
PCT No. PCT/GB90/01119 Sec. 371 Date Jul. 22, 1991 Sec. 102(e) Date Jul. 22, 1991 PCT Filed Jul. 20, 1990 PCT Pub. No. WO91/04595 PCT Pub. Date Apr. 4, 1991.A voltage source is connected to a laser diode via a supply circuit and a control circuit serving to control current through the laser diode. The control circuit includes a transistor which is switched into conduction on the application of a threshold valued voltage. A light sensitive diode is optically coupled to the laser diode and is adapted to apply a control voltage to the transistor switch which is related to the optical power output of the laser diode, such that when the control voltage exceeds a predetermined threshold value, the transistor is rendered conductive to control current through the laser diode.
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