Abstract: An optical communication assembly (2) suitable for use underwater, the assembly comprising, a plurality of optical communication modules (3), each module (3) comprising at least one optical receiver (3a) which can receive optical signals, and at least one optical transmitter (3b) which can selectively transmit data in the form of an optical signal; wherein each module (3) is configured to initiate the transmission of data in response to the module (3) receiving a transmit command, and, wherein each module (3) is configured to receive the same clock signal (Clk) which clocks when the module (3) transmits said data, so that the optical transmission of the plurality of modules (3) is synchronised; a bus cable (5), which is connected to all of said optical communication modules (5), along which data can be sent, and along which the clock signal (Clk) can be sent; a control module (11) which is connected to the bus cable (5), and which is configured to selectively provide a data signal along the bus cable (5), whi