Contents Introduction
Radio-over-Fiber (RoF) links are an elegant way for feeding remote antennas with signals originating from centralized radio equipment. Such systems are increasingly being installed, especially for cellular repeater applications. However, a multitude of other applications such as WLAN, WiMax, ultrawide-band (UWB) signals, RFID signals, etc. can benefit from consolidation of electronics equipment in a central location and a fiber-based radio distribution network. Fiber has multiple advantages relative to copper-based solutions. Besides very low fiber loss up to high frequencies, RoF systems take advantage of the fact that any loss coming from the optical system is only varying minimally for any distance that is important for short-range systems and any frequency, making multiple-service deployments and system layout simple. Additional advantages are low cross section, light weight, availability of small high fiber-count cables, bending flexibility and availability of pre-connectorized solutions. For most applications a rigorous low-cost approach is required in order to minimize overall deployment costs with a radio-over-fiber network. For in-building or other short-range deployment scenarios, multimode fiber (MMF) is widely used as a cost-effective way for optical signal distribution. Especially with the combination of VCSELs, an overall low-cost link design becomes feasible. Low-cost RoF systems based on VCSELs and MMF have been studied in the recent past and will be reviewed.
