We propose and experimentally demonstrate a potentially simple and cost-effective optical multi-carrier source based on electro-absorption modulated laser (EML) cascaded with phase modulator (PM) driven by synchronous sinusoidal radio-frequency (RF) signal, which can generate 10 subcarriers with frequency spacing of 12.5 GHz and power difference less than 3 dB. We further experimentally demonstrate a novel W-band radio-over-fiber (RoF) system based on EML cascaded with PM, which can realize the generation and transmission of 25-Gb/s quadrature-phase-shift-keying (QPSK) modulated millimeter-wave (mm-wave) signal at 100 GHz adopting optical remote heterodyning and heterodyne coherent detection. The bit-error ratio (BER) after 80-km single-mode fiber-28 (SMF-28) transmission and 2-m wireless delivery can be less than the forward-error-correction (FEC) threshold of 3.8×10<sup>-3</sup>.
We propose and experimentally demonstrate four-level pulse-amplitude-modulation (PAM-4) signal delivery in a radio-over-fiber system for the first time. Over 8-Gbit/s PAM-4 signals have been transmitted over 20-km single-mode fiber-28 and 1-m wireless distance. The signal after transmission is detected directly by an envelope detector at the receiver side. The maximal bit rate could be increased if the bandpass amplifier and envelope detector have more bandwidth.