A novel type of optical modem is presented. The optical modulator includes high frequency DFB laser diode modules, APC circuits and ATC circuits. Fiber of 5 kilometers is used to transmit information. The optical demodulator consists of PD modules of high speed transimpedance amplifier and broadband low noise amplifier. The fiber transfer of microwave broadband signal with high linearity, low distortion, longdistance is realized in the item.