Abstract

Abstract
In this paper, we report the development of a reduced temperature sensitivity optical fiber sensor for refractive index measurement based on Superimposed Long-Period Gratings (SLPG) inscribed by the electric arc technique in standard fiber. The reduced sensitivity to temperature is achieved by calculation of the difference between resonance wavelengths of two guided cladding modes.

Abstract
A simple optical inclinometer based on a phase-shifted Bragg grating in a taper configuration is proposed. Two phase-shifted fiber Bragg gratings were fabricated using a DUV femtosecond laser technique in the taper region, with taper waist diameters of 30 mu m and 50 mu m. Both sensing heads were compared based on their response to angle and strain. Whereas the higher diameter sensor yielded a higher sensitivity to curvature (23.8 +/- 0.3 pm/degree), the lower diameter one was more sensitive to strain (8.94 +/- 0.04 pm/mu epsilon).

Abstract
An interferometric tip sensor based on the post-process of a special design double-cladding optical fiber is proposed. Due to the sensing head design, it is sensitive to environmental variations. In order to analyze this effect, the sensing head is subjected to temperature variations both in liquid and gas (at 1 atm). Comparing the two signals, it is possible to discriminate the contribution of the liquid refractive index variation with temperature. Not only the amplitude of the signal varies with the surrounding medium, but also the phase of the interferometric pattern alters. This is due to the presence of a thin diaphragm at the end face of the fiber structure turning the sensing head in a three wave interferometric device. An indirect measurement of the water refractive index is performed, by subjecting the sensing head to temperature variations in air and water. Even though the sensitivities obtained are lower than the ones reported in the literature, it should be highlighted that there is no core exposition of the fiber to the external medium. The sensor is easy to fabricate, robust, and reproducible.

Abstract
The recent burst of R&D activity in Plasmonics, associated with the possibility of materials nanostructuring which enables the access to metamaterials, has been strongly impacting many branches of optics such as imaging, data recording and sensing. This talk details the factors that turned the combination Plasmonics and Metamaterials a huge opportunity to optical sensing.© OSA 2014.

Abstract
A new type of fibre-optic refractive index sensor based on a long period fibre grating (LPFG) coated with a titanium dioxide (TiO2) thin film was demonstrated. The wavelength shift of the attenuation bands of this LPFG sensor to changes in the refractive index of the external media from 1.30 to 1.64 RIU was investigated. In order to optimize the sensor the TiO2 thin film thickness deposited around the LPFGs was varied from 10 to 80 nm. It was found that the TiO2 thin film increases the wavelength sensitivity of the LPFG to changes in the surrounding refractive index for values lower and higher than the cladding refractive index. As opposed to the bare LPFG it was shown the possibility to monitor refractive indices lower and higher than cladding refractive index tailoring the TiO2 thickness. An average wavelength sensitivity of 5250 nm/RIU was achieved in the range 1.444 to 1.456 RIU for a TiO2 thickness of 50 nm. In the region between 1.46 and 1.48 RIU the average sensitivity of about 825 nm/RIU was measured for a 40 nm thick film.