A bidirectional three-band lightwave transport system is proposed and experimentally demonstrated for both fiber-to-the-X (FTTX) and radio-over-fiber (RoF) networks. By cascading a phase modulator (PM) and a Mach-Zehnder modulator (MZM) to generate multiple coherent lightwaves, hybrid 1.25 Gbps baseband (BB), 1.25 Gbps/20 GHz microwave (MW), and 1.25 Gbps/40 GHz millimeter-wave (MMW) downstream signals and a 1.25 Gbps BB upstream signal are simultaneously transmitted. Furthermore, with an assistance of an optical signal-to-noise ratio (OSNR) enhancement circuit, sufficient low bit error rate (BER) values are experimentally achieved for both down-link BB/MW/MMW and up-link BB signals. No additional high-frequency local oscillator, mixers and upstream laser diode are required in both transmitter and receiver sites. Under this architecture, both wire-lined and wireless clients can be simultaneously served without using any extra device/equipment to convert the downstream signals among BB, MW and MMW formats.
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