| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical transmission reception circuit that allows a PIN photo diode being a light receiving end to receive a constant optical reception signal at all times with a simple circuit configuration without the need for a high speed device for the extraction of control information. SOLUTION: An optical received signal received via an optical fiber transmission line 2 from an optical transmitter 1 is linearly amplified through an Er added fiber 30 of an optical direct amplifier 3 by a stimulated light from a stimulation semiconductor laser 37. Part of an output of the optical direct amplifier 3 is fed to a photo diode 33 from an optical branching device 32, a low frequency component of the optical signal is detected by a band-pass or low-pass filter 34 and negative feedback control is applied to a stimulation semiconductor laser drive circuit 36 via a gain control circuit 35 to control a drive current of the stimulation semiconductor laser 37. A PIN photo diode 40 applies photoelectric conversion to an optical reception signal in an optical receiver 4, a preamplifier 41 applies current/voltage conversion to the converted signal and an equalization amplifier 42 applies equalization amplification to the converted voltage. |
