Abstract: An optical switch, comprising a plurality of light inputs and a plurality of light outputs. The switch additionally includes a polarization beam splitter, configured to split light beams received through the input carriers into separate first and second polarization components and a plurality of semi-transparent mirrors and polarization rotators arranged to allow controllable deflection of the first and second polarization components from the beam splitter to a selected one of the light outputs, wherein the one or more different planes defined for at least 15% of the semi-transparent mirrors by the possible paths of the first polarization component passing through the semi-transparent mirror in the arrangement do not coincide with planes defined by the possible paths of the second polarization component passing through any of the semi-transparent mirrors in the arrangement.