Performance of a 60-GHz DCM-OFDM and BPSK-Impulse Ultra-Wideband System with Radio-Over-Fiber and Wireless Transmission Employing a Directly-Modulated VCSEL

The performance of radio-over-fiber optical transmission employing vertical-cavity surface-emitting lasers (VCSELs), and further wireless transmission, of the two major ultra-wideband (UWB) implementations is reported when operating in the 60-GHz radio band. Performance is evaluated at 1.44 Gbit/s bitrate. The two UWB implementations considered employ dual-carrier modulation orthogonal frequency-division multiplexing (DCM-OFDM) and binary phase-shift keying impulse radio (BPSK-IR) modulation respectively. Optical transmission distances up to 40 km in standard single-mode fiber and up to 500 m in bend-insensitive single-mode fiber with wireless transmission up to 5 m in both cases is demonstrated with no penalty. A simulation analysis has also been performed in order to investigate the operational limits. The analysis results are in excellent agreement with the experimental work and indicate good tolerance to chromatic dispersion due to the chirp characteristics of electro-optical conversion when a directly-modulated VCSEL is employed. The performance comparison indicates that BPSK-IR UWB exhibits better tolerance to optical transmission impairments requiring lower received optical power than its DCM-OFDM UWB counterpart when operating in the 60-GHz band.