A data communications system comprising: a plurality of controller area network nodes configured to operate electrically; a plurality of signal converters (24a-n) electrically coupled to respective controller area network nodes of the plurality of controller area network nodes, each signal converter comprising electrical circuitry configured to convert differential signals to digital signals and vice versa; a plurality of transmit optical subassemblies (26a-n) electrically coupled to respective signal converters of the plurality of signal converters, each transmit optical subassembly comprising a respective transmitter configured to convert digital signals from a respective signal converter to optical pulses; a plurality of receive optical subassemblies (28a-n) electrically coupled to respective signal converters of the plurality of signal converters, each receive optical subassembly comprising a respective receiver configured to convert optical pulses to digital signals which are sent to a respective signal converter; and a fiber optical network optically coupled to the transmitters and receivers for enabling the plurality of controller area network nodes to communicate with each other, characterised wherein the fiber optical network comprises a reflective optical star, wherein the fiber optical network comprises a plurality of optical Y-couplers (30a-n) optically coupled to the reflective optical star, each optical Y-coupler comprising transmit and receive branches which are respectively optically coupled to the transmitter and receiver associated with a respective signal converter, and wherein the transmit branch of each optical Y-coupler comprises a first optical fiber having a first side face, the receive branch of each optical Y-coupler comprises a second optical fiber having a second side face configured to confront the first side face, and each optical Y-coupler comprises a layer of reflective material disposed between the first and second side faces of the transmit and receive branches. a plurality of controller area network nodes configured to operate electrically; a plurality of signal converters (24a-n) electrically coupled to respective controller area network nodes of the plurality of controller area network nodes, each signal converter comprising electrical circuitry configured to convert differential signals to digital signals and vice versa; a plurality of transmit optical subassemblies (26a-n) electrically coupled to respective signal converters of the plurality of signal converters, each transmit optical subassembly comprising a respective transmitter configured to convert digital signals from a respective signal converter to optical pulses; a plurality of receive optical subassemblies (28a-n) electrically coupled to respective signal converters of the plurality of signal converters, each receive optical subassembly comprising a respective receiver configured to convert optical pulses to digital signals which are sent to a respective signal converter; and a fiber optical network optically coupled to the transmitters and receivers for enabling the plurality of controller area network nodes to communicate with each other, characterised wherein the fiber optical network comprises a reflective optical star, wherein the fiber optical network comprises a plurality of optical Y-couplers (30a-n) optically coupled to the reflective optical star, each optical Y-coupler comprising transmit and receive branches which are respectively optically coupled to the transmitter and receiver associated with a respective signal converter, and wherein the transmit branch of each optical Y-coupler comprises a first optical fiber having a first side face, the receive branch of each optical Y-coupler comprises a second optical fiber having a second side face configured to confront the first side face, and each optical Y-coupler comprises a layer of reflective material disposed between the first and second side faces of the transmit and receive branches.