| 摘要 |
PURPOSE:To obtain a stable signal by inputting a reference signal in place of a modulation input signal and adjusting a bias signal on the basis of a signal at that time. CONSTITUTION:A changeover switch 32 inputs a modulation input signal to an adding circuit 35 on normalcy. The adding circuit 35 adds the modulation input signal and a bias signal, and excites a semiconductor laser element 12 on the basis of the result of the addition. The element 12 generates a signal in response to the excitation. When a correction command signal is generated once, a monostable multivibrator 42 subtracts a fixed quantity from the bias value. The switch 32 inputs a reference signal to the circuit 35 in place of the modulation input signal. An AND gate 40 gradually increases the bias value. The increase of the bias value is continued until the modulation input signal is input to the circuit 35 by the switch 32 or intensity detected by a photodiode 26 is compared by a comparator 38 and larger intensity than a reference value is decided and an AND gate 39 is operated. |
