Polarization-independent optical device and method for polarization-independent processing of a signal

Optical device comprising a wave-guide and a polarisation converter, wherein the wave-guide and the polarisation converter comprise an integral unit and the length of the wave-guide is such in relation to the rotation of the polarisation-state of an input signal that the device is substantially polarisation independent, the wave-guide being active and the device being a laser-amplifier.

Optical filter comprising a passive wave-guide and a polarisation converter, wherein the wave-guide and the polarisation converter comprise an integral unit and the length of the wave-guide is such in relation to the filter's rotation of the polarisation-state of an input signal that the filter is substantially polarisation independent, the wave-guide further comprising a corrugation filter.

Amplifying filter comprising a wave-guide and a polarisation converter, wherein the wave-guide and the polarisation converter comprise an integral unit and the length of the wave-guide is such in relation to the filter's rotation of the polarisation-state of an input signal that the filter is substantially polarisation independent, the wave-guide comprising a first active part and a second passive part, the passive part comprising a corrugation.

Method for polarisation-independent processing of an optical signal, the signal going through a wave-guide, wherein the signal is polarisation-rotated during its passage through the wave-guide, comprising the step of providing the length of the wave-guide such that the polarisation rotation of the signal is substantially independent of the signal's polarisation-state upon incidence on the wave-guide.

Method for filtering by optical reflection an incident optical signal, comprising the step of providing the incident optical signal to a wave-guide, wherein the optical signal is polarisation-rotated during its passage through the wave-guide, the wave-guide comprising a periodically asymmetric perturbation for achieving the rotation and a corrugation for wave-length selection, the length of the wave-guide being such that it rotates the polarisation-state of the optical signal by substantially a multiple or .pi. radians.