Full-duplex wireless signal optical transmission system basedon external modulator

A full duplex vector signal transmission system based on double parallel Mach-Zehnder modulator was proposed. Traditional optical frequency doubling technology was only suitable for NRZ (not return to zero) that was intensity modulation format and not suitable for MPSK and MQAM vector signal modulation technique in wireless communication. Two sides of optical millimeter wave generated by the traditional multiplier were separated with a filter, and vector signal was modulated in a sideband so that the amplitude information and phase information were properly retained. Bandwidth requirements of optoelectronic device were reduced by using octonary module in the transmission process. Theoretical analysis and simulation results show that after 20 km single-mode optical fiber transmission, the error vector magnitude loss of 625-Msymbol/s 4QPSK signal generated by this method and carried in the carrier of 60 GHz can be neglected.