and a half wave plate and minimizes the diffraction losses by having multiple thinner faraday rotators with a total thickness equal to a single 45 u00b0 faraday rotator the absolute faraday rotation is proportional to the beam propagation length so that multiple thinner films operate in the same way as one single film of the same total thickness since the diffraction loss is a super linear function of the propagation distance it is possible to significantly reduce the diffraction loss by using multiple thin films rather than one thick film 0041 fig9 is a graph depicting the waveguide core diameter required to limit the diffraction loss to 0 25 db and 0 5 db respectively when the total film thickness given is 0 5 mm the graph shows clear improvements with multiple films over a single film for a single faraday rotator a large mode width of gt 23 u03bcm in diameter is required to curtail the overall diffraction loss to lt 0 5 db while the 5 film counterpart requires only u02dc 12 u03bcm a value that is close to the typical mode size of silica fibers 0042 fig1 is a functional block diagram of an exemplary embodiment of a nonreciprocal phase shifter 1000 the phase shifter includes faraday rotators 1002 and a half wave retarder 1004 the 45 u00b0 faraday rotators rotate the input polarization axis by u00b1 45 u00b0 with the sign depending on the magnetic field direction by having opposing magnetic fields for both optical paths 90 u00b0 difference between the axes of polarization in the two paths will be obtained by placing a half wave plate in each of the two interferometric paths with an angle of 45 u00b0 between their slow axes an additional u00b1.