Department of Physics2024-11-0920221874-650010.1007/978-94-024-2138-5_132-s2.0-85130794774http://dx.doi.org/10.1007/978-94-024-2138-5_13https://hdl.handle.net/20.500.14288/9453Cavity ring down spectroscopy is a sensitive optical detection technique but it makes use of expensive electronics and data fitting algorithm. Both of these factors put a limitation on its performance for sensing applications. In this study cost effective and easy to use phase shift cavity ring down spectroscopy (PS-CRDS) technique, has been demonstrated for refractive index sensing. A refractive index sensor consisting of a tapered single mode optical fiber and two fiber Bragg gratings (FBGs) is proposed. In this sensing methodology, an intensity modulated laser beam centered at 1550 nm from a DFB laser is scanned at a narrow wavelength range and cavity modes are excited. Later the phase shift corresponding to these cavity modes is measured using a lock-in amplifier. Sucrose solutions of various concentrations are used for performance analysis of the refractive index sensing device. The resultant limit of detection (LOD) came out to be ~6.4 × 10−6 refractive index units (RIUs), which can be improved further by using thinner fiber tapers or fiber Bragg gratings with higher reflectivity. © 2022, Springer Nature B.V.CavityTrace gasExternal cavityBook Chapterhttps://www.scopus.com/inward/record.uri?eid=2-s2.0-85130794774&doi=10.1007%2f978-94-024-2138-5_13&partnerID=40&md5=92ce3845e26902123e47f8711f88818c524