Radio-over-free space optical space division multiplexing system using 3-core photonic crystal fiber mode group multiplexers

Abstract

Radio over free space optics (Ro-FSO) systems have previously relied on the signal intensity, wavelength and polarization for multiplexing data streams in order to increase to the signal quality and achievable link range. This work leverages on optical space division multiplexing by using novel three-core photonic crystal fiber (PCF) mode group multiplexers and hexagonal mid-gapped tiered PCF mode group equalizers for improving the signal quality and increasing the achievable link range in a rural environment. At the transmitter, a three-core PCF mode group demultiplexer converts the fundamental mode into three distinct mode groups used as carriers for independent transmission of three radio frequency signals. At the receiver, the three PCF successfully equalizes the power from the received signal, with the channel impulse responses showing an improvement in the signal quality. An increment between 13.6% and 31.1% in the achievable link range for all channels is evident under medium and heavy fog conditions at the same bit error rate level, using the designed PCF mode group multiplexers and equalizers.