Characteristics of directly modulated ROF link for wireless access

The radio-over-fiber (ROF) link is of much interest to provide broadband wireless access. In this paper, we discuss some characteristics of a directly modulated ROF link in CDMA and FDMA environments. These RF measurement results show that, though the ROF link has adequate bandwidth to support several radio channels, nonlinear distortion and power loss, mainly due to electrical to optical conversion process and vice versa, limit the performance. Especially, the AM-PM type nonlinearity that starts at low power levels is a bigger concern. Furthermore, the spurious free dynamic range (SFDR) decreases because of the increases with the bandwidth of the RF signal.