| 摘要 |
PROBLEM TO BE SOLVED: To reduce costs without being affected by the dispersion of an optical fiber by transmitting one of optical spectrums having the same information as an original radio signal and one of non-modulated optical carrier wave components through an optical fiber, and modulating and demodulating them into an intermediate frequency band signal having frequencies equivalent to those of a transmitted optical signal, and obtaining the information of the original radio signal. SOLUTION: A radio terminal 11 converts information to be transmitted into a millimeter wave radio signal in DPSK modulation techniques using a millimeter wave radio signal generating part 19, and transmits the millimeter wave radio signal from a millimeter wave antenna 20 at the radio terminal side to an antenna base station 10. The millimeter wave radio signal propagating through a free space is received by the millimeter wave antenna 20 at an antenna base station side, and the millimeter wave radio signal 25 is amplified to a required power by a millimeter wave band amplifier 21. A pilot signal 26 is intensity modulated by an optical modulator for modulating a radio signal, and an up link modulation signal 28 is amplified by another light amplifier 15, and only a necessary optical spectrum is obtained by an optical band filter 22. |
