Patent ID: 6947619

Claim:
A polarization independent optical isolator/circulator comprising: first and second Mach-Zehnder waveguide interferometers, each having two input ports and two output ports, and each one having two interferometer arms; each said arm comprises one or a plurality of half-wave retarders or quarter wave retarders, with the effect of the totality being half-wave retardance; and wherein the slow axes of the retarders are either parallel or perpendicular to each other so that with phase or power compensation between the two paths of each Mach-Zehnder interferometer by either active or passive means, a light that enters through one of the input ports in the first interferometer is split into two linearly polarized orthogonal components and recombined into one of the output ports in the second interferometer; one or more Faraday rotators with a total rotation of 45°; and a half-wave retarder with the slow axis at 22.5° relative to either of the orthogonal polarizations at the output of said first Mach Zehnder interferometer, disposed between said first and said second Mach-Zehnder interferometers.