Patent ID: 7009710

Claim:
An interferometer comprising: a source of a heterodyne beam; a beam splitter positioned to split the heterodyne beam into a first beam and a second beam having different frequencies; a first AOM in a path of the first beam, the first AOM operating to increase a difference between frequencies of the first and second beams; interferometer optics that generate measurement and reference beams from a recombined heterodyne beam; and a beam-combining unit positioned to receive the first and second beams and provide the recombined heterodyne beam to the interferometer optics, wherein the beam combining unit comprises: a beam combiner; a first optic cable assembly that carries the first beam; a second optic cable assembly that carries the second beam to the beam combiner; and a first manipulator on which the first fiber optic cable assembly is mounted, the first manipulator being adjustable to control a direction of the first beam upon exit from the first fiber optic cable assembly, wherein adjustment of the first manipulator controls an incident angle of the first beam on the beam combiner.