A spatial optical filter based on splice misalignment between optical fibers with different cladding dimensions is proposed for gas refractometry. The sensing head is formed by a 2 mm-long optical fiber with 50 μm diameter spliced with a strong misalignment between two single mode fibers (SMF28) and interrogated in transmission. This fiber structure causes a Fabry-Pérot-behavior along the reduced-size fiber giving at its output end a well defined spatial filtering selectivity. Depending on the misalignment position of the lead-out SMF28, it is possible to obtain two different spectral responses, namely, bandpass or band-rejection filters. It is shown that this filter device is highly sensitive to refractive index changes on a nitrogen (N₂) environment by means of the gas pressure variation. A maximum sensitivity of -1390 nm/RIU for the bandpass filter was achieved.

Date Published: 17 October 2012
PDF: 4 pages
Proc. SPIE 8421, OFS2012 22nd International Conference on Optical Fiber Sensors, 842137 (17 October 2012); doi: 10.1117/12.974991

Published in SPIE Proceedings Vol. 8421:
OFS2012 22nd International Conference on Optical Fiber Sensors
Yanbiao Liao; Wei Jin; David D. Sampson; Ryozo Yamauchi; Youngjoo Chung; Kentaro Nakamura; Yunjiang Rao, Editor(s)