Bandpass Sampling in digital coherent receiver with free-running local oscillator laser for phase modulated radio-over-fiber systems

We have experimentally presented a novel radio-over-fiber (RoF) based digital receiver architecture for coherent heterodyne detection. It demonstrates the application of using bandpass sampling in a RoF communications system to overcome the high sampling rate requirement of conventional receivers and front-end hardware dependency. In particular, we modified the uniform bandpass sampling theorem to cope with frequency offset produced by independent free running optical local oscillator. Thereafter, a 40Mbit/s QPSK modulated data signal at 2.4GHz RF carrier frequency is experimentally demonstrated by using phase modulated and digital signal processing aided RoF links.