Radio access network using radio over fibre

A radio communication system comprising:

• an optical carrier generator for generating at least a pair of frequency spaced optical carrier signals;
• a transceiver configured to:
• modulate a first portion of the pair of spaced optical carrier signals with downlink (DL) information to generate a modulated first optical signal;
• combine an unmodulated second optical signal formed of a remaining unmodulated second portion of the pair of spaced optical carrier signals with the modulated first optical signal to form a combined optical signal for transmission over an optical link;
• receive an optical uplink (UL) signal from said optical link, said optical UL signal comprising UL information modulated on said unmodulated second portion of the spaced optical carrier signals;
• and
• down convert said received optical UL signal using a photodetector to output an electrical signal at a baseband frequency
• a remote radio head (RRH) unit for receiving said combined optical signal, said RRH configured to recover said modulated first optical signal and said unmodulated second optical signal into respectively, a third polarised signal and fourth polarised signal, wherein said third polarised signal is down converted using a photodetector to output a DL electrical signal at an RF frequency to be broadcasted by an antenna, and wherein said fourth polarised signal is modulated by the UL electrical signal at an RF frequency received by said antenna to generate a modulated fourth polarised optical signal;
• and
• an optical link coupling the BBU and RRH, wherein the BBU and RRH are configured to have respective optical link interfaces to simultaneously communicate over the optical link the modulated first polarised signal, the unmodulated second polarised and the modulated fourth polarised optical signal forming the UL optical signal, wherein the optical carrier generator includes:
• a single laser source to generate a laser signal;
• a tunable electrical local oscillator (LO) to generate a signal for a radio communication band;
• an electro-optic modulator to modulate the laser signal with the LO signal to generate the frequency spaced optical carriers in an optical communication band;
• and a polarization beam splitter to generate mutually orthogonally polarised optical carriers.