A Radio-Over-Fiber System for Wireless Packet Radio Network Backhaul

A radio-over-fiber (RoF) link design is presented for remote use of antenna by radio transceiver in a digital packet radio network operating in the very high frequency (VHF) band. The base station and antenna were geographically separated by approximately 7.5 km and connected by the RoF system. A commercial RoF module was used to convert a digital VHF radio signal into an optical signal for backhaul over a patched fiber network. The optical signal was then received at a radio module that converted the signal back to the electrical domain and subsequently coupled it into a radio receiver for demodulation. An uplink and downlink RoF channel were coupled to common transmission lines with radio and antenna using radio frequency circulators. The link introduced 20 dB of gain, but also incurs a 10 dB increase in the noise floor relative to received signals likely due to the circulator. Nonetheless, the receiver was successful at monitoring packets from mobile users in the coverage area. Additionally, the packet traffic was able to be hosted on a local area network – enabling global access by way of virtual private network.