High dynamic range and wavelength-reused bidirectional radio-over-fiber link.

We propose and experimentally demonstrate a bidirectional radio-over-fiber (RoF) link based on a Sagnac loop incorporating a polarization modulator (PolM) to generate simultaneously a polarization-modulated optical signal and an unmodulated optical signal for wavelength reuse and for increasing the dynamic range. Thanks to the traveling-wave nature of the PolM, a polarization-modulated optical signal and an unmodulated optical signal are generated at the output of the Sagnac loop, which are combined at a polarizer and detected at a photodetector. By controlling the powers of the two optical signals, the third-order intermodulation distortion terms can be fully suppressed to increase the dynamic range for downstream transmission. The unmodulated optical signal is reused for upstream transmission. A bidirectional RoF link to transmit 2.5 Gb/s 16QAM downstream and upstream signals, and a 7.1 Gb/s 128 subcarrier orthogonal frequency division multiplexing 16QAM downstream and upstream signals using a single wavelength over a 10.5 km single-mode fiber are experimentally demonstrated. The transmission performance versus the dynamic range is also studied.