Optical signal transmission system and signal transmission method

To provide a signal transmission system which can increase the number of slave stations being coupled with a simple configuration, A master station 10 communicates with a plurality of slave stations 20 each having an antenna 25. The slave station 20 includes a frequency converter 26 for converting a signal of a radio frequency band received through the antenna into an intermediate frequency band signal, and an E/O converter 27 for converting an electrical signal into an optical signal. The master station 10 includes O/E converters 14a to 14c for converting signals received from the slave stations 20 into electrical signals, respectively, a synthesizer 17 for synthesizing the signals thus converted into the electrical signals and a frequency converter 18 for converting the synthesized signal into a radio frequency band signal.