| 摘要 |
PURPOSE:To hold an optical output of an optical fiber constant even if a tracking error exists by controlling a bias current from a driving circuit based on a sensed result of a photodiode for sensing an output of a rear light of a laser diode and a resistance value of a thermistor for sensing a peripheral temperature of the diode. CONSTITUTION:When a peripheral temperature of a laser diode 11 rises, an optical output 113 of an optical fiber 12 is increased. In this case, a resistance value of a thermistor 44 of an automatic optical output controller 4 is reduced, and a potential of a non-inverting input terminal of an operational amplifier 41 is reduced. Thus, since the base potential of a transistor 45 is lowered, its collector current is reduced. Accordingly, the bias current of the diode 11 is reduced, and its output is reduced. Accordingly, if the output of the diode 11 is reduced in response to its peripheral temperature by suitably selecting a constant indicating the ratio of variation in the resistance value of second thermistor 44 with respect to its temperature, the output 113 of the fiber 12 can be maintained constant irrespective of the peripheral temperature of the diode 11. |
