An optical millimeter-wave vector signal generation scheme by frequency quadrupling

This paper demonstrates a novel optical millimeter-wave vector signal generation scheme by frequency quadrupling. Unlike traditional frequency quadrupling modulation schemes, which modulate data on both of the two optical sidebands, and are only suitable for on-off keying modulation format, the proposed scheme modulates the electrical vector signal on the -1st order optical sideband, and generates a pure RF tone on the 3rd order optical sideband. Therefore, frequency quadrupling can be implemented without constellation overlapping after direct detection. A proof of concept simulation experiment is conducted by modulating a 625-Msymbol/s QPSK signal on a 60-GHz RF signal. After transmission over 20-km single-mode fiber, the EVM penalty is negligible.