Phase-shifted modal interferometers for high-accuracy optical fiber sensing

The use of two separated, compact modal interferometers (MIs) with an adequate phase shift is proposed for precision optical fiber sensing. The output spectrum of interferometers with such features is a well-defined peak. Changes in the wavelength position or amplitude of the peak caused by a measurand can be detected with high precision. The advantages of phase-shifted interferometers for optical sensing include sensitivity enhancement, easy implementation, simple interrogation, and compactness, among others. The concept is demonstrated by placing two supermode interferometers in series that were built with multicore fiber to sense vibrations with low frequencies and low amplitudes. The sensing architecture proposed here can also be implemented with other types of optical fiber interferometers, and the advantages mentioned above can be achieved. (C) 2019 Optical Society of America