Balanced Precoding Technique for Vector Signal Generation Based on OCS

The phase and amplitude precoding technique is essential in optical carrier suppression-based photonic constant-and multi-amplitude quadrature-amplitude-modulation vector signal generation at radio frequency bands. In this letter, a novel precoding scheme with constellations balanced distribution is proposed and investigated. We experimentally demonstrate 8-GBd quadrature-phase-shift-keying (QPSK) vector signal generation at 16 GHz enabled by a single Mach-Zehnder modulator-based oscilloscope modulation and the proposed precoding scheme. Compared with imbalanced precoding, this scheme can provide 2-dB receiver sensitivity improvement, and the obtained constellations at the receiver end is much more symmetrical, which represents the in-phase (I) and quadrature (Q) components have equal performance. The bit-error-ratio for 8-GBd QPSK vector signals can be under hard-decision forward-error-correction threshold of 3.8×10^-3 after a 25-km standard single-mode fiber transmission.