W-band RoF transmission based on optical multi-carrier generation by cascading one directly-modulated DFB laser and one phase modulator

We experimentally demonstrate that, adopting an optical multi-carrier source based on cascaded directly-modulated distributed-feedback laser (DML) and phase modulator (PM), any pair of subcarriers spaced by 100 GHz selected from the generated optical subcarriers can be used to generate 100-GHz millimeter-wave (mm-wave) frequency based on remote heterodyning technique, and thus realize 3.125-Gb/s on-off-keying (OOK) signal transmission over a radio-over-fiber (RoF) system at W-band. After 20-km large-effective-area fiber (LEAF) transmission and 2-m wireless delivery, the bit-error ratio (BER) of 1×10^-9 can be attained when the two selected subcarriers spaced by 100 GHz are simultaneously modulated before remote heterodyning. 1.5-dB power penalty at the BER of 1×10^-9 is caused by 2-m wireless delivery while almost no penalty is caused by 20-km LEAF transmission. However, because of different path lengths and the quite wide linewidth of the DML, the 3.125-Gb/s OOK signal after the same RoF transmission cannot be recovered when the two selected subcarriers are separated into two different optical paths and only one of them is modulated before remote heterodyning.