An optical communications system comprising a plurality of optical transmitters (215a, 215b) for transmitting signals (H pos, H neg) and at least one optical receiver for receiving the one or more signals (H pos, H neg), wherein: the transmitters (215a, 215b) and/or receivers have an angular dependence, such that at least one response of the receivers to a received signal and/or at least one property of the signals transmitted by the transmitters (215a, 215b) is angularly dependent; the receiver and transmitters (215a, 215b) and/or the signals (H pos, H neg) transmitted by the transmitters (215a, 215b) of two or more transmitter-receiver pairs have a distinct associated angular arrangement or relationship, wherein the at least one angularly dependent response of the receivers to the signal (H pos, H neg) and/or the at least one angularly dependent property of the signal (H pos, H neg) is dependent on the angular arrangement or relationship; and the system is configured to use the angularly dependant property and/or response to identify or discriminate the transmitter (215a, 215b) from which the signal (H pos, H neg) was transmitted and/or at least one communication channel associated therewith; wherein the system is or comprises a cellular system comprising a plurality of cells, each cell comprising or being associated with one or more pairs of transmitters (215a, 215b);and one of the transmitters of one or more or each cell or pair is spaced apart from one or more other transmitter in the respective cell or pair and configured to concurrently transmit a signal (H pos) that interferes destructively, at a receiver located in a cell different from said respective cell, with the signal (H neg) transmitted by the at least one or more other transmitter of the respective cell or pair. the transmitters (215a, 215b) and/or receivers have an angular dependence, such that at least one response of the receivers to a received signal and/or at least one property of the signals transmitted by the transmitters (215a, 215b) is angularly dependent; the receiver and transmitters (215a, 215b) and/or the signals (H pos, H neg) transmitted by the transmitters (215a, 215b) of two or more transmitter-receiver pairs have a distinct associated angular arrangement or relationship, wherein the at least one angularly dependent response of the receivers to the signal (H pos, H neg) and/or the at least one angularly dependent property of the signal (H pos, H neg) is dependent on the angular arrangement or relationship; and the system is configured to use the angularly dependant property and/or response to identify or discriminate the transmitter (215a, 215b) from which the signal (H pos, H neg) was transmitted and/or at least one communication channel associated therewith; wherein the system is or comprises a cellular system comprising a plurality of cells, each cell comprising or being associated with one or more pairs of transmitters (215a, 215b);and one of the transmitters of one or more or each cell or pair is spaced apart from one or more other transmitter in the respective cell or pair and configured to concurrently transmit a signal (H pos) that interferes destructively, at a receiver located in a cell different from said respective cell, with the signal (H neg) transmitted by the at least one or more other transmitter of the respective cell or pair.