| 摘要 |
PURPOSE:To protect a laser diode under severe conditions such as outdoor installation by passing an input noise component to a laser diode included in an optical transmitter through a means limiting in frequency, a means limiting with time and a means limiting in power. CONSTITUTION:In a protective circuit 20, only a frequency band required to an input signal is passed through a high-pass filter 2, and an unnecessary band is cut. In a protective circuit 30, one part of a signal input to a laser diode 12 is detected by a signal detecting section 4, a protective switch 6 is turned OFF immediately after a level larger than required is detected, and the state of an over--input to the laser diode 12 is shortened as much as possible. In a protective circuit 40, the output voltage of an amplifier 8 for driving the laser diode is suppressed to the input maximum rating or less of the laser diode 12, and the application of power lower than maximum rating to the laser diode 12 is prevented. |
