We report the results of our study of the spectral shifts caused by surrounding refractive index changes (SRI) in bent fibre tapers. Fused and etched fibre tapers were fabricated using a gas burner and HF acid. Spectral shifts as high as 200 nm have been observed for SRI variations from 1.33 to 1.44 and sensitivity as high as 830 nm/r.i.u. around water RI values. We present results for refractometric measurements of cow milk of varying fat content and compare results with those obtained with conventional Abbe refractometers and high sensitivity double resonance LPGs.
In the present paper we study the response to surrounding refractive index (SRI) changes of bent fused fiber tapers. The core-cladding mode interference response occurs at particular bending angles and the refractometric response exhibits different sensitivities. The sensitivities greater than 3000 nm/r.i.u. for SRI (surrounding refractive index) larger than 1.43 and as high as 6000 nm/r.i.u. are reached for SRI above 1.44.