Patent ID: 7031060

Claim:
An add/drop device comprising: first and second optically coupled polarising beamsplitters; a wavelength filter disposed between the first and second polarising beamsplitters; first and second polarisation rotators disposed between the filter and the first polarising beamsplitter and the filter and the second polarising beamsplitter, respectively; first and second input ports optically coupled to the first and second polarising beamsplitters, respectively, each of the first and second input ports for launching a beam of light having a predetermined polarisation; first and second output ports optically coupled to the first and second polarising beamsplitters, respectively; and first and second polarisation switches optically coupled to the first input port and one of the first and second output ports, respectively, each of the first and second switches for selectably rotating the polarisation of a beam of light launched therethrough and configured to work in cooperation with the other.