An optical bus 30 optically connects each board of a signal processing section 22 and each board of a transmission/reception section 40 for transmitting an optical signal output to the optical bus 30 by each board of the signal processing section 22 to each board of the transmission/reception section 40 in a non-block state. In contrast, the optical bus 30 transmits an optical signal output to the optical bus 30 by each board of the transmission/reception section 40 to each board of the signal processing section 22 in a non-block state.