Fiber-optic refractive-index sensors based on transmissive and reflective thin-core fiber modal interferometers

TCF-MMF-TCF fiber structure based interferometer for refractive index sensing

“…However, these grating based sensors require precise and expensive phase masks and photolithographic procedures for FBG and LPG inscription. In recent years, the in-fiber Mach-Zehnder interferometer (MZI) [5][6][7] for SRI sensing has attracted more attention because of their low cost, ease of fabrication and intrinsic in-fiber characteristics. As known, the cross-sensitivity of SRI and temperature of MZI is the key problem in the SRI measurement.…”

A comprehensive analysis verified by experiment of a refractometer based on an SMF28–small-core singlemode fiber (SCSMF)–SMF28 fiber structure

“…More importantly it is very difficult to control the etching process to achieve a repeatable fiber diameter and a smooth fiber surface, both of which will significantly influence the transmission behavior of the etched fiber and hence the performance of the SMS fiber structure based refractive index sensor. An alternative approach is to use a small core singlemode fiber (SCSMF) as a substitute for the etched MMF to construct an SMF28-SCSMF-SMF28 structure based refractometer which was reported recently [21][22]. By depositing a humidity sensing material on the SCSMF, this structure can also be used as a humidity sensor [22][23].…”

Single-mode fiber refractive index sensor with large lateral offset fusion splicing between two abrupt tapers

“…As described by Xia et al 12 the interference signal reaches its minimum when the phase difference between cladding and core modes satisfies the following condition:…”