Coherent-detection radio-over-fiber link with high spectral efficiency based on digital phase noise cancellation

A radio-over-fiber (RoF) link with high spectral efficiency using digital phase cancellation is proposed and experimentally verified. The link can be utilized to transmit four microwave vector signals. The four microwave vector signals are modulated on optical signals by using a dual-polarization dual-parallel Mach-Zehnder modulator at the transmitter. The optical signals subsequently pass through a spool of single-mode fiber (SMF) and are sent into a coherent receiver. A digital signal processing (DSP) algorithm is proposed to eliminate the phase noise and frequency difference caused by two free-running lasers at transmitter and receiver. Two 16-quadrature amplitude modulation (16-QAM) vector signals at 6 GHz and another two 16-QAM vector signals at 7 GHz transmit over a 10-km SMF and are successfully recovered after a DSP algorithm. In order to evaluate the transmission performance of the RoF link, error vector magnitudes and bit error rates are also estimated.