Bidirectional Radio-over-Fiber architecture based on frequency up- and down-conversion with lightsource and LO-source free BS

Radio-over-Fiber (RoF) is a promising technology to fulfill future broadband access requirements with reliability, transparency and flexibility. We propose bi-directional RoF system with high RF carrier support. Downlink scheme utilizes optical frequency up-conversion while uplink scheme is based on electrical frequency down-conversion. For downlink, an un-modulated micro-wave band signal, fLO electrically combined with DPSK encoded digital data stream sub-carrier modulated at intermediate frequency (IF) is intensity modulated at an optical carrier, fIF in control station. An un-modulated high frequency carrier, local oscillator (LO) is also modulated over separate wavelength, fLO at CS. At remote node (RN), semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI) is used for photonic mm-wave mixing (between fIF and fLO) and frequency up-conversion. After photo-detection at BS of optical channel modulated with up-converted RF signal, fRF up-converted downlink data signal at high RF (fRF) is extracted, down-converted to IF, de-modulated and tested for BER. During mixing process at RN, fLO also gets up-converted and modulated over wavelength fRF. For uplink, data at high RF is down-converted to IF at BS by extracting and using up-converted fLO from downlink electrical signal. Further wavelength re-use concept was employed for uplink where down-converted uplink signal is modulated over extracted optical carrier (from downlink signal) and transmitted to CS. Hence, it does not require sending separate optical LO, fLO to each BS. Cost-effective bi-directional solution is proposed with acceptable performance measures by employing wavelength reuse and remote LO delivery concepts.