| 摘要 |
PURPOSE:To keep a bias light power constant and to adjust a degree of optical modulation (OMD) to an optimum value even when the operating environment of the transmitter is fluctuated. CONSTITUTION:In the optical transmitter provided with a laser diode 22 sending an optical signal corresponding to a modulation signal inputted externally, a photodiode 23 detecting an optical output of the sent optical signal and controlling a bias current supplied to a laser diode 22, in response to the optical output to vary bias optical power, and an APC circuit 25 and sending an optical signal, a signal detection circuit comprising a band pass filter 29, a detection circuit 30, a low pass filter 31 and an amplifier 32 detects a peak voltage of the modulation signal, the detected peak voltage and an optical output level of the optical signal are divided by a divider circuit, the ratio is calculated and a comparator 34 and an AGC circuit 35 control the signal current of the modulation signal to be inputted in response to the ratio. |
