Abstract: An optical transmitter has a modulator for modulating data onto an optical signal for transmission to the receiver, the modulated signal having components at one or more constellations of points of different amplitudes and phases. The modulator is tunable such that distortions of the points of the one or more constellation can be tuned, and a tuning controller is provided for receiving a feedback signal from the receiver indicating a distortion measured at the receiver, and for tuning automatically the modulator to adjust the modulation based on the received feedback signal to pre-compensate for the measured distortion. Such pre-compensation can reduce the amount of distortion in the transmission system and thus enable more transmission capacity, without the need for a complex transmitter.

Abstract: An optical demultiplexing structure and method for demultiplexing channels from a wavelength multiplexed optical signal comprising a first optical filter (115), a second optical filter (117), and at least one third optical filter (120), wherein the first filter has a band-pass characteristic for extracting a first set of channels from the optical signal, and the second filter has a cut-off wavelength corresponding to a wavelength within the pass-band of the first filter, and wherein the first filter is connected to the second filter, the second filter extracting a second set of channels from the channels that remain after extraction of first the set of channels by the first filter, and wherein the at least one third filter has a passband to extract a subset of channels from the second set of channels spaced apart from the first set of channels. The corresponding multiplexing structure and method are also described.

Abstract: An optical demultiplexing structure and method for demultiplexing channels from a wavelength multiplexed optical signal comprising a first optical filter (115), a second optical filter (117), and at least one third optical filter (120), wherein the first filter has a band-pass characteristic for extracting a first set of channels from the optical signal, and the second filter has a cut-off wavelength corresponding to a wavelength within the pass-band of the first filter, and wherein the first filter is connected to the second filter, the second filter extracting a second set of channels from the channels that remain after extraction of first the set of channels by the first filter, and wherein the at least one third filter has a passband to extract a subset of channels from the second set of channels spaced apart from the first set of channels. The corresponding multiplexing structure and method are also described.