Abstract
In this work a novel optical fiber sensor based on silica microspheres array is proposed. Different sensing heads are presented and compared, differing on the number of microspheres. These structures, ranging from arrays of one to five, are spliced in series. The sensor is subjected to different physical parameters, such as strain, temperature, refractive index and bending. Depending on the number of microspheres the sensitivities to strain and bending are different. The sensor also presents a high sensitivity to temperature of 20.3 pm/degrees C.

Abstract
This paper presents an overview of optical fiber sensors based on Fabry-Perot interferometers with a focus on high temperature applications. The next generation of these fiber types interferometers are based in photonic crystal fibers, microfabrication as well as by chemical etching of special structures. High temperature measurements with linear behavior are observed namely in un-doped fibers, i.e., with a pure silica composition. Three new configurations are presented as possible solutions to be considered in extreme conditions.

Abstract
A combination of focused ion beam milling and chemical etching is proposed for the creation of Fabry-Perot cavities in microwires. Both simple cavities and cantilevers are created on 15 mu m-diameter microwires and characterized in temperature. The cantilever structure shows sensitivity to vibration and is capable of measuring frequencies in the range 1 Hz - 40 kHz.

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
A Fabry-Pérot microcavity tip sensor based on the post-process of a special design double-cladding optical fiber is proposed. The sensor is subjected to temperature variations in both air and water. © OSA 2013.