Coherent full duplex radio over fiber system with multiple signal transmission

Abstract

In this paper, a cost‐effective and simple full duplex RoF (radio over fiber) system is developed from a simplex coherent RoF. At the transmitter, utilizing the magnitude and phase of the vector carrier, four different information are encoded simultaneously on the carrier light wave. Dividing the total carrier power into two branches, enable the transmitter to modulate two distinct information on each branch. The working of the system is described in two main sections namely uplink section and downlink section. In the first section, encoding of uplink transmitting information and decoding downlink information at the central office (CO) is described. In the second section, modulating downlink transmitting information and demodulating coherently the uplink receiving information at the base station (BS) are described. An algorithm based on fast Fourier transform is described for effectively canceling the phase noise (PN) at the BS. Considering the cost of optical components, the source used to coherently detect the uplinked transmitted information, is again used as the carrier for downlink. Altogether, this system enables to transmit three different information on uplink and are faithfully received at the BS with an average of log(BER) value −23 dB. And for downlink, one information is transmitted and is successfully received at the CO with log(BER) of −9 dB. About 10 dB decrease in log(BER) values was found after the cancellation of PN.