An optical element such as a beam splitter for interferometer separates a heterodyne
beam from the laser into separate beams having different the frequencies and orthogonal
polarizations. Optical fibers can conduct the separate beams to a beam combiner
for interferometer optics. The PBS and/or the beam combiner can use a coating to
reflect one linear polarization and transmit an orthogonal linear polarization.
To improve extinction ratios in the PBS or the beam combiner, a yaw angle for an
input beam is non-zero and corresponds to a peak in the extinction ratio of a reflected beam.
