Phase-Shifted White-Light Interferometry for the Absolute Measurement of Fiber Optic Mach–Zehnder Interferometers

An all-fiber 3 times; 3 coupler based phase-shifted white-light interferometry is presented, with which the absolute optical path difference (OPD) of a Mach-Zehnder interferometer can be measured automatically. The continuous test shows that the variation is ±0.5 μm when measuring a beam length of ~10 m with an OPD of 1847 μm. The technique is successfully demonstrated to measure static measurands, including strain, temperature and weight.