  Fourier transform interferometers usually need a dedicated reference light to
track optical path difference changes precisely. There are a few different ways
to incorporate the reference light into the optical system. This paper
conducted experiments to give a test of how different ways of incorporating
reference light are affected by mechanical disturbances. It found that placing
the reference light in different path than the test light can be very sensitive
to mechanical disturbance errors while propagating the reference light together
with the test light can be very robust against mechanical vibrations of optical
components. We hope that this study can be useful to researchers to help make
better design choices in their experiments.
