Patent ID: 7558449

Claim:
An apparatus, comprising: a coupler for coupling an optical signal into a first arm and a second arm; wherein the first arm includes: an optical demultiplexer; a plurality of non-waveguiding electro-optic phase adjusters optically coupled to the optical demultiplexer; and a control unit coupled to the plurality of electro-optic phase adjusters; further comprising: a mirror; and a quarter-wave plate coupled between the mirror and the electro-optic phase adjusters on the other side of the phase adjusters to the demultiplexer so that an optical signal passes from the demultiplexer through the electro-optic phase adjusters, the quarter-wave plate and is then reflected back by the mirror through the quarter-wave plate, the electro-optic phase adjusters and the optical demultiplexer; and the second arm includes a waveguide linking the coupler to the quarter wave plate for passing an optical signal in the second arm through the quarter wave plate to be reflected by the mirror back through the quarter wave plate and second arm to the coupler where the optical signals in the first and second arms are recombined.