Multilevel modulated signal transmission for millimeter-wave radio over fiber system

quadrature phase-shift keying (QPSK), 16 quadrature amplitude modulation (QAM), and 64-QAM data transmission at 6 MS/s are successfully demonstrated in a 60 GHz millimeter-wave over fiber system with good error vector magnitude performance recorded for the downlink. The system utilizes a photonic method to produce the 60 GHz carrier by employing a dual wavelength source consisting of an optical phase modulator and DWDM filter. The transmission of the data over a 20 km span of fiber has been performed with very good stability over a measurement period of 128 minutes.