Optical system having extremely low polarization dependent loss and polarization mode dispersion

An optical system of the present invention includes a polarization beam separator for receiving an input beam and separating the input beam into a first component that propagates along a first path and a second component a polarization opposite that of the first component, the second component being directed along a second path spatially separated from the first path, a polarization changer provided in the first path for changing the polarization of the first component to the same polarization as the second component, a redirecting optical subsystem for receiving the first and second components and redirecting the first component back in superposition along the second path and the second component back in superposition along the first path, and a polarization beam combiner for combining the redirected first and second components to provide an output beam.