Transmission limitations of WiMax over fibre transmission employing optical up-conversion schemes

WiMax is a promising technology for the delivery of last mile wireless broadband access which when combined with fibre access networks can provide cost effective solution for next generation integrated networks. WiMax fibre transmission employing up-conversion techniques by means of external modulation of an optical carrier by LiNbO₃ Mach-Zehnder (MZ) modulators has proven to be a reliable approach. However, robustness of such techniques against dispersion is impaired by the finite extinction ratio (ER) encountered in commercially available MZMs which is typically 20-35 dB. This paper analyses through simulation the effect of the ER on the transmission over optical fibre of up-converted WiMax signals emphasizing the importance of configurations able to compensate the finite extinction ratio of commercially available MZ modulators.