An optical network comprising: a first optical transmitter; an optical splitter; a plurality of optical receivers; a first optical fibre connecting the first optical transmitter and the optical splitter; a plurality of second optical fibres, each second optical fibre connecting the optical splitter to a respective optical receiver of the plurality of optical receivers, wherein the first optical transmitter is configured to transmit a first optical signal to each optical receiver of the plurality of optical receivers via the first optical fibre, the optical splitter and a respective second optical fibre of the plurality of second optical fibres; and a plurality of second optical fibre phase correction units, each second optical fibre phase correction unit being associated with a second optical fibre of the plurality of second optical fibres, each second optical fibre phase correction unit comprising a reference optical transmitter, a reference error signal generator and a reference phase shifter, wherein: each reference optical transmitter is configured to transmit a reference optical signal on the associated second optical fibre of the plurality of second optical fibres, each reference error signal generator is configured to generate a reference error signal based on a reflection of the reference optical signal transmitted on the associated second optical fibre of the plurality of second optical fibres, and each reference phase shifter is configured to apply a phase shift to the first optical signal based on the reference error signal. a first optical transmitter; an optical splitter; a plurality of optical receivers; a first optical fibre connecting the first optical transmitter and the optical splitter; a plurality of second optical fibres, each second optical fibre connecting the optical splitter to a respective optical receiver of the plurality of optical receivers, wherein the first optical transmitter is configured to transmit a first optical signal to each optical receiver of the plurality of optical receivers via the first optical fibre, the optical splitter and a respective second optical fibre of the plurality of second optical fibres; and a plurality of second optical fibre phase correction units, each second optical fibre phase correction unit being associated with a second optical fibre of the plurality of second optical fibres, each second optical fibre phase correction unit comprising a reference optical transmitter, a reference error signal generator and a reference phase shifter, wherein: each reference optical transmitter is configured to transmit a reference optical signal on the associated second optical fibre of the plurality of second optical fibres, each reference error signal generator is configured to generate a reference error signal based on a reflection of the reference optical signal transmitted on the associated second optical fibre of the plurality of second optical fibres, and each reference phase shifter is configured to apply a phase shift to the first optical signal based on the reference error signal. each reference optical transmitter is configured to transmit a reference optical signal on the associated second optical fibre of the plurality of second optical fibres, each reference error signal generator is configured to generate a reference error signal based on a reflection of the reference optical signal transmitted on the associated second optical fibre of the plurality of second optical fibres, and each reference phase shifter is configured to apply a phase shift to the first optical signal based on the reference error signal.