An asymmetrical twin-core fiber based Michelson interferometer
is reported as a refractive index sensor. One core of the twin-
core fiber locates at the fiber center and the other core is 26
μm away from the central core. Part of the cladding of the twin-
core fiber over a small length is removed by chemical etching to
make the effective refractive index of the fundamental mode of
the side core is sensitive to the ambient refractive index.
Therefore, the interference spectrum between the central core
and the side core shifts with the variation of the ambient
refractive index. The sensitivity of such a Michelson
interferometer is ~270 nm/RIU in the range of 1.34–1.38. © 2011
IEEE Ai Zhou, Guangping Li, Yanhui Zhang, Yuzhuo Wang, Chunying
Guan, Jun Yang, and Libo Yuan, "Asymmetrical Twin-Core Fiber
Based Michelson Interferometer for Refractive Index Sensing," J.
Lightwave Technol. 29, 2985-2991 (2011)