The paper deals with the construction of an Interferometer, which works in
a wide temperature range using a helium optical cryostat, and with the accu
racy of the strain measurements. The suppression of cooling system vibratio
ns is a necessary condition for the measurements. The precision of the stra
in measurements of different piezoelectric samples (such as PMN-PT single-c
rystals, PZT ceramics, etc.) is discussed.