The use of non-uniform thinned fiber Bragg gratings (ThFBGs) for self temp. compensated refractive index measurements is proposed. The multi-parameter sensor consists of a std. Bragg grating where the cladding layer is partially or totally removed along half of the grating length. The perturbation leads to a wavelength-splitting of the spectral response in two sep. peaks: the peak at lower wavelengths corresponds to the thinned region and is dependent on the outer refractive index and the local temp., while the peak at longer wavelength would respond only to thermal changes. The simultaneous measurements of the Bragg wavelengths related to the different grating regions allow the accurate measurements of the refractive index and the temp. by a single sensing element. Here, a simple and cost effective fabrication technique based on wet chem. etching in a buffered HF soln. and a proper package were used to realize the sensing probe. Exptl. characterization for a 8-Ým thinned cladding sensor is reported in terms of thermal and refractive index sensitivities. To prove the sensor capability to be used as self temp. referenced refractometer, sugar concn. measurements were carried out in non-isothermal conditions.
Self temperature referenced refractive index sensor by non-uniform thinned fiber Bragg gratings
Giordano M;
2006
Abstract
The use of non-uniform thinned fiber Bragg gratings (ThFBGs) for self temp. compensated refractive index measurements is proposed. The multi-parameter sensor consists of a std. Bragg grating where the cladding layer is partially or totally removed along half of the grating length. The perturbation leads to a wavelength-splitting of the spectral response in two sep. peaks: the peak at lower wavelengths corresponds to the thinned region and is dependent on the outer refractive index and the local temp., while the peak at longer wavelength would respond only to thermal changes. The simultaneous measurements of the Bragg wavelengths related to the different grating regions allow the accurate measurements of the refractive index and the temp. by a single sensing element. Here, a simple and cost effective fabrication technique based on wet chem. etching in a buffered HF soln. and a proper package were used to realize the sensing probe. Exptl. characterization for a 8-Ým thinned cladding sensor is reported in terms of thermal and refractive index sensitivities. To prove the sensor capability to be used as self temp. referenced refractometer, sugar concn. measurements were carried out in non-isothermal conditions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
