Abstract: The invention relates to improvements in or relating to optical networks. Methods and apparatus are disclosed for providing communications services to at least one user. Transmission of an optical signal in the downstream direction is described comprising at least one Wavelength Division Multiplexing channel such that at least one of the channels is an unmodulated channel. The unmodulated channel is arranged to transmit user data from the at least one user in the upstream direction.

Abstract: An optical PON network comprises a central office which generates N DPSK modulated optical signals, where N is an integer greater than 1, an optical coupling which connects the N signals to at least one optical fibre, a passive distribution mode located remotely from the central office which has at least one input port that is coupled to the fibre and a plurality of output node being arranged to transmit a first wavelength of the N signals to at least one of its output ports, and at least one optical network unit connected through a respective optical fibre to the first output port of the passive distribution node. The passive distribution node comprises an arrayed waveguide grating which provides a passive optical connection between its input port and the first output port and which for that connection functions as a bandpass filter having a profile and bandwidth selected such that the DPSK optical signal passed to the input node is converted to an intensity modulated signal at the output port.