Performance Enhancement of an OFDM Ultra-Wideband Transmission-Over-Fiber Link Using a Linearized Mixed-Polarization Single-Drive X-Cut Mach–Zehnder Modulator

We investigate by theory and experiment the performance improvement of an orthogonal frequency division multiplexing (OFDM) ultra-wideband (UWB) transmitted in a radio-over-fiber (RoF) system using a linearized mixed polarization single-drive X-cut Mach-Zehnder modulator (sd-xMZM). The third-order nonlinearity is suppressed due to the polarization dependent electrooptic coefficients of an X-cut MZM. It is found that the improvement of more than 4 dB in 1-dB compression RF power P_{1 dB} is predicted in theory and verified experimentally. In addition, the adjacent channel power ratio and third-order intermodulation distortion to carrier power ratio of an OFDM UWB signal transmitted by an RoF link using mixed polarization sd-xMZM are expressed in closed forms. Finally, it is verified that the bias voltage can be optimized to improve the error vector magnitude by up to ~ 9 dB for an OFDM UWB signal transmission-over-fiber link using mixed polarization sd-xMZM.