A high sensitivity refractometer based upon a long period grating Mach-Zehnder interferometer

A low cost interrogation scheme is demonstrated for a refractometer based on an in-line fiber long period grating (LPG) Mach-Zehnder interferometer. Using this interrogation scheme the minimum detectable change in refractive index of Deltansimilar to1.8x10(-6) is obtained, which is the highest resolution achieved using a fiber LPG device, and is comparable to precision techniques used in the industry including high performance liquid chromatography and ultraviolet spectroscopy. (C) 2002 American Institute of Physics.