Quasi-acoustic impedance matching distributed opto-mechanical sensor with aluminized coating optical fibers

Abstract

The uncoated optical ber has been extensively researched as an optomechanical sensor since it can achieve substance identi cation of the surrounding media by exciting and detecting transverse acoustic waves via forward stimulated Brillouin scattering (FSBS), yet within danger of being easily broken.Although polyimide-coating bers are reported to allow transverse acoustic waves transmission to the coating for reaching the ambient while maintaining the mechanical properties of the ber, it still suffers from the problems of humidity sensitivity and spectral instability. Here, we propose for the rst time a robust distributed FSBS-based optomechanical sensor using an aluminized coating optical ber. Bene ting from the quasi-acoustic impedance matching condition of the aluminized coating and silica core-cladding, aluminized coating optical bers not only have stronger mechanical properties and higher transverse acoustic wave transmission e ciency but also has a higher signal-to-noise ratio, compared to the polyimide-coating bers. The distributed measurement ability is veri ed by identifying air and water around the aluminized coating optical ber with a spatial resolution of 2 m. In addition, the proposed sensor is immune to the external relative humidity changes, which is a preponderance for liquid acoustic impedance measurements.

Robust acoustic impedance monitoring based on forward stimulated Brillouin scattering in an aluminum-coated optical fiber

“…Additionally, by applying aluminum coatings, the mechanical properties of optical fiber can also be improved for practical applications. 11 Owing to the alteration in the fiber structure, the conventional approach of calculating acoustic impedance using the full width at half maximum (FWHM) spectral width of the FSBS spectrum, typically utilized for uncoated fibers, cannot be directly applied to aluminum-coated optical fibers. As a result, distinguishing different external liquid environments can be realized utilizing the variation in the FWHM spectral width, but the acoustic impedance values were not calculated.…”

“…A recent study shows that aluminum-coated optical fibers are insensitive to humidity variation in the surrounding environment. Additionally, by applying aluminum coatings, the mechanical properties of optical fiber can also be improved for practical applications 11 . Owing to the alteration in the fiber structure, the conventional approach of calculating acoustic impedance using the full width at half maximum (FWHM) spectral width of the FSBS spectrum, typically utilized for uncoated fibers, cannot be directly applied to aluminum-coated optical fibers.…”