Multimode optical fiber interferometer for measuring small displacements

An experimental investigation shows that small displacements can be measured by multimode fiber-optic interferometers in which the partial waves excited by different fiber modes interfere to produce the fringe pattern. An additional phase difference between the fiber modes can be produced by changing the external pressure on the fiber, thus making it possible to use the interferometer to measure pressure as well. A diagram of the experimental system and of the interferometer is provided.