Abstract: A compensator for compensating polarisation-mode dispersion, comprises a splitter (30) arranged to split light, according to the light's polarisation, between a first optical path and a second optical path; a combiner (40) arranged to combine light from the first optical path and the second optical path, and a monitor (15) for monitoring the light. An active wavelength-delay device (70) is provided in the first optical path and arranged such that components of the light travelling in the first optical path and having different wavelengths are subjected to different delays, the delays being selected according to an output from the monitor (15).

Abstract: A chromatic-dispersion compensator comprises a plurality of dispersive elements (Q in number. Q?2) each exhibiting a dispersion characteristic D (?) that varies substantially as a polynominal function of wavelength, the polynomial function being of an order (P?2) greater than 0, the dispersion characteristics being displaced in wavelength relative to each other such that the compensator has a net Pth-order dispersion characteristic Dp that is non-zero and does not vary substantially with wavelength an operating bandwidth.

Abstract: A method for transmitting a signal includes providing a source signal and splitting the source signal into a first and second split signal. The first split signal is modulated based on a first dataset. The second split signal is phase shifted and modulated based on a second dataset. The modulated second signal is orthogonally polarized with respect to the polarization of the modulated first signal and combined with the modulated first signal. The combined signal may also be modulated and transmitted.

Abstract: A chromatic-dispersion compensator comprises a plurality of dispersive elements (Q in number. Q≧2) each exhibiting a dispersion characteristic D (&lgr;) that varies substantially as a polynominal function of wavelength, the polynominal function being of an order (P−2) greater than 0, the dispersion characteristics being displaced in wavelength relative to each other such that the compensator has a net Pth-order dispersion characteristic DP that is non-zero and does not vary substantially with wavelength over an operating bandwidth.