On the performance of high order QAM signals for analog and digital radio over fiber systems

Abstract

Radio over Fiber (RoF) system is a unified broadband network that supports both the optical and wireless technologies. Compared to RoF analog optical link, the digital RoF system shows number of advantages and thus, extensively studied in several research works. To improve the data rate for next generation optical-wireless access network, the use of high order quadrature amplitude modulation (QAM) signals for digital RoF is necessary and also recommended by IEEE 802.11ac standard. In this paper, the performance of both analog and digital RoF system is measured in the presence of high order QAM signals. The fiber transmission distance is determined with respect to resolution bits of analog-to-digital converter (ADC), error vector magnitude (EVM) limit and received optical power. The result shows that the digital RoF system can support long fiber distance over 30 Km and 20 Km for 64-QAM and 256-QAM signals within the required EVM limit and acceptable optical received power.