Laser interferometry is an extensively used diagnostic for fusion experiments. Well-known problems of the method such as vibration, stability of the initial phase, a refraction and uncertainty in the phase shift are resolved in this paper as a result of the matching of the interferometer parameters with parameters of the GOL-3 multimirror trap. An initial phase of CO2 ( = 10.28 m) Michelson interferometer is controlled remotely with piezoelectric. The piezoelectric ceramics is also used to calibrate the interferometer. To exclude the effects of stray magnetic fields all elements of the interferometer is made of dielectric materials. The LN2 cooled HgCdTe photodiode is used for interferogram registration with time resolution of ~10 ns. The interferometer showed excellent performance with minimal maintenance.