Improved radio over fiber performance using predistortion linearization

Abstract

This paper describes improvements to Radio Over Fiber photonic links obtained by increasing the linearity of Mach Zehnder modulators using predistortion. The work was conducted at the Ku and X-band satellite uplink frequencies with a 1550 nm laser, but should be applicable to any microwave or even millimeter frequency band and any externally modulated laser. Link performance was evaluated for 2-tone intermodulation distortion, noise power ratio (NPR) and WCDMA adjacent channel power. Intermodulation distortion was reduced by more than 15 dB, and more than a 6 dB increase in effective signal power was demonstrated for typical system requirements.