Multi-dimensional crest factor reduction for multi-band directly-modulated radio-over-fiber links

A multi-dimensional crest factor reduction (MD-CFR) is proposed to improve the performance of multi-band radio-over-fiber (RoF) links. Cooperating with multi-dimensional digital predistortion (MD-DPD), MD-CFR increases the performance significantly for directly-modulated RoF links, in terms of error vector magnitude (EVM) and adjacent channel power ratio (ACPR). By implementing MD-CFR in conjunction with MD-DPD, more than 5 dB ACPR reduction is obtained, output EVMs are reduced from 11.83% and 12.47% to 7.51% and 7.26% for two bands respectively, while only a slight improvement to 11.58% and 10.78% is obtained solely using MD-DPD. As compared with the case solely using MD-DPD, the allowable RF input power applied to RoF links increases by ~1dB given an EVM threshold of 5%, indicating an distinct enhancement of RF power transmit efficiency.