In this letter, a novel technique for direct conversion of an optical baseband quadrature phase-shift keying (QPSK) signal to a millimeter-wave wireless signal and subsequent signal demodulation is reported. Optical heterodyne mixing of the optical baseband QPSK signal with a free-running unmodulated laser for the wireless signal generation is employed. To correct for the phase and frequency offset originating from the heterodyne mixing of the two free-running lasers, wireless signal demodulation based on optical coherent detection in combination with baseband digital signal processing is implemented. As a proof of concept, 5-Gb/s amplitude-shift keying and up to a 16-Gb/s QPSK wireless signal in the band of 75–110 GHz was generated and successfully demodulated. All-photonic millimeter-wave wireless signal generation and digital coherent detection at baud-rate are employed without complex optical phase-locked loop.
Sambaraju, R., Zibar, D., Caballero Jambrina, A., Tafur Monroy, I., Alemany, R., & Herrera, J. (2010). 100-GHz Wireless-Over-Fiber Links With Up to 16-Gb/s QPSK Modulation Using Optical Heterodyne Generation and Digital Coherent Detection. I E E E Photonics Technology Letters, 22(22), 1650-1652. https://doi.org/10.1109/LPT.2010.2076801