QPSK Vector Signal Generation Based on Photonic Heterodyne Beating and Optical Carrier Suppression

We propose a novel scheme for quadrature phase-shift keying (QPSK) modulated vector signal generation based on photonic heterodyne beating, phase precoding, and optical carrier suppression (OCS). Different from our previous OCS-based vector signal generation schemes, in our proposed scheme, the precoded vector signal at the radio-frequency (RF) band, which is used for the drive of the intensity modulator operating at its OCS point, is generated by photonic heterodyning beating rather than a single digital-to-analog converter (DAC). Photonic heterodyne beating accomplishes the upconversion of the precoded vector signal from the baseband to the RF band, and thus, the DAC in our proposed scheme is used to generate the precoded vector signal at the baseband rather than that at the RF band, which significantly reduces the DAC bandwidth requirement. We experimentally demonstrate 17.6-GHz QPSK modulated vector signal generation based on our proposed scheme. The generated 17.6-GHz vector signal can carry up to 3-GBd QPSK data with a bit error ratio (BER) less than the hard-decision forward-error-correction (HD-FEC) threshold of $3.8\times 10^{-3}$.