| 摘要 |
PURPOSE:To separate easily the electric signal carrier wave frequency for transmission/ reception in optical space transmission two-way communication by converting a received optical signal into an electric signal, mixing the converted output with the output of a transmission side carrier wave frequency oscillator and converting the mixed signal into an intermediate frequency signal to demodulate the signal. CONSTITUTION:A carrier from the carrier frequency oscillator 14 is modulated by a modulator 11 at its phase or the like on the basis of a digital signal from a terminal 15 and the modulated output is amplified by a driver 12. An electrooptic converting element 13 is driven by an output signal of a driver 12 to convert an electric signal into an optical signal and transmit the optical signal. A photoelectric conversion element 16 converts the received optical signal into an electric signal and the outputted electric signal is inputted to a mixer 17. The mixer 17 mixes the carrier wave frequency from the oscillator 14 with the electric signal frequency from the element 16, a signal with the frequency of the difference of both frequencies is amplified by an intermediate frequency band amplifier 18 and the output signal of the amplifier 18 is demodulated by a demodulator 19 and outputted as a digital signal. Thus, two-way communication can be attained without crosstalk at the transmission/reception only by changing the frequency of the oscillator 14. |
