A High Spectral Efficiency Microwave Photonic Link With Optimization of Chromatic-Dispersion-Induced Power Fading

A novel microwave photonic link to simultaneously realize high spectral efficiency and optimization of chromatic-dispersion-induced power fading based on dual-drive polarization division multiplexing Mach-Zehnder modulator (PDM-MZM) is proposed and demonstrated. Two microwave vector signals are IQ modulated on an optical carrier in one polarization state via the upper sub-MZM (IQ modulator) of the PDM-MZM. The optical carrier with orthogonal polarization state is unmodulated and transmitted together with the modulated optical signal. At the receiver, a polarization controller and polarizer are cascaded to change the phase of the optical carrier. By properly changing the phase of the optical carrier, the two microwave vector signals are respectively recovered and the chromatic-dispersion-induced power fading is optimized simultaneously. Since two microwave vector signals are transmitted over a single optical carrier, the spectral efficiency of the link is doubled. A proof-of-concept experiment is performed. The transmission of a 50-Msym/s 16-QAM signal and a 100-Msym/s QPSK signal both at 6 GHz over a 25-km SMF is realized, and its transmission performance in terms of error vector magnitude (EVM) and bit error rate (BER) is evaluated. The optimization of the chromatic-dispersion-induced power fading is also verified by the experiment.