SIGNAL TRANSMISSION DEVICE

摘要

It is possible to automatically adjust the uplink and downlink signal level in a radio base station and a forward base station to predetermined levels with a simple configuration. In an interface unit (12), a pilot signal P of a predetermined level is generated by a pilot signal generator (120) and multiplexed with a downlink transmission signal (111) from a radio base station (11) by a coupler (121). The multiplexed signal is amplified with a constant gain by a downlink signal amplifier (122), after which it is converted into a downlink optical signal by an electric/optical converter (123), subjected to wavelength multiplexing by an opticalmultiplexer/demultiplexer (124), transmitted to an optical fiber (15), and then transmitted to the forward base station (13). In the forward base station (13), the downlink optical signal subjected to the wavelength demultiplexing by the optical multiplexer/demultiplexer (124) is converted to a downlink electric signal by the optical/electrical converter (125) and a pilot signal P is separated by a demultiplexer (133). A gain control unit (130) detects an absolute level of the pilot signal P and outputs such a gain control signal G1 that the level value becomes a predetermined value. A downlink signal gain variable amplifier (134) and an uplink signal gain variable amplifier (136) respectively amplify the downlink transmission signal and the uplink reception signal by a gain controlled by the gain control signal G1.