Simplified RF Carrier Extraction and Reuse in OFDM Radio-Over-Fiber Systems

We propose and experimentally demonstrate techniques for efficient RF carrier extraction and reuse in an orthogonal frequency-division multiplexing (OFDM) radio-over-fiber (RoF) system. In this system, an RF carrier is generated in the base station through optical heterodyning between two uncorrelated optical carriers delivered from the central office. The RF down conversion is accomplished by mixing the intermediate frequency signal with the extracted RF carrier. This not only relaxes the phase noise requirement on the RF carrier, but also minimizes signal-signal beat interference. We demonstrate an RoF network carrying 8.2 Gb/s QPSK data in OFDM modulation format for both downlink and uplink, which share the same RF carrier, which avoids the need of an additional RF oscillator in the customer unit.