LTE signals transmission with modulation efficiency and robustness against chromatic dispersion improved based on DEMZM modulation in cloud-RoF access networks

Optical fiber has been considered as the preferred medium for Long Term Evolution (LTE) backhaul, since optical fiber guarantees the ultimate bandwidth scalability, energy efficiency and the performance metrics suitable for 3G to 4G and beyond applications. LTE optical double sideband (ODSB) radio-over-fiber (RoF) transmission presents the drawbacks of low receiver sensitivity and power fading induced by chromatic dispersion after transmission of a few dozen fiber kilometres. In order to mitigate these two drawbacks, ODSB-reduced carrier (ODSB-RC) modulation and modulation chirp of a dual-electrode Mach-Zehnder modulator (DEMZM) are considered in this paper. In the RoF transmission of LTE signals of 20 MHz bandwidth, complying with release 8 of the respective standard, the introduction of controlled negative modulation chirp of a DEMZM in the ODSB-RC modulation was demonstrated to mitigate the power penalty induced by chromatic dispersion and to improve the transmission efficiency. Furthermore, transmission through up to 80 km of 20 MHz LTE signals with negative power penalty has been numerically demonstrated.