Clipping Distortion Suppression of Directly Modulated Multi-IF-over-Fiber Mobile Fronthaul Links Using Shunt Diode Predistorter


Herein, we demonstrate clipping distortion suppression of directly modulated multi‐IF‐over‐fiber links using a simple shunt diode predistorter. The dynamic range of a directly modulated analog fiber optic link is limited by nonlinear distortions caused by laser‐diode clipping. We investigate the link performance in the context of carrier‐to‐noise and distortion ratio (CNDR) and error vector magnitude (EVM) requirements when supporting LTE‐A services. We also design an analog predistorter with a shunt‐diode structure, and demonstrate experimentally that the predistorter has the ability to suppress clipping‐induced third‐order intermodulation distortions of the link by at most 14 dB. It also improves the CNDR and EVM of the 4‐IF‐multiplexed LTE‐A carriers by 7 dB and 2.9%, respectively.

ETRI Journal