5G is emerging, but the current fronthaul transmission technologies used for 3G and 4G may not be efficient and appropriate for 5G. It has been found that frequency division multiple access (FDMA) and timedivision multiple access (TDMA) based radio over fiber (RoF) may be considered the most appropriate for 5G fronthaul transmission technology. Due to analog RoF transmission, broadband linearization is required. In this work, both electrical and optical broadband linearization techniques are reviewed.