Abstract
This work describes an all-fiber Fabry-Perot interferometer (FFPI) that is sensitive to gas pressure variations. The geometry of the air cavity consists on splicing a small section of silica rod with a large offset in between two singlemode fibers. It is shown that the FFPI sensor is sensitive to gas pressure variation and when submitted to different gaseous environments, namely carbon dioxide, nitrogen and oxygen, it presented different sensitivities of 6.2, 4.1 and 3.6 nm/MPa, respectively. This result is obtained due to refractive index difference between gases. The refractive index change on nitrogen environment by means of the gas pressure variation resulted in a sensitivity of 1526 nm/RIU. The response of the sensing device to temperature in air was also determined and a sensitivity of -14 pm/degrees C was attained.

Abstract
Suspended core fiber tapers with different cross sections (with diameters from 70 µm to 120 µm) are produced by filament heating. Before obtaining the taper, the spectral behavior of the suspended core fiber is a multimode interference structure. When the taper is made, an intermodal interference between a few modes is observed. This effect is clearly visible for low taper core dimensions. Since the core and cladding do not collapse, two taper regions exist, one in the core and the other in the cladding. The cladding taper does not affect the light transmission, only the core is reduced to a microtaper. The spectral response of the microtaper based-suspended core fiber is similar to a beat of two interferometers. The strain is applied to the microtaper, and with the reduction in the transverse area, an increase in sensitivity is observed. When the taper is immersed in a liquid with a different index of refraction or subjected to temperature variations, no spectral change occurs. © 2012 The Author(s).

Abstract
An intensity-based highly birefringent (Hi-Bi) fiber loop mirror (FLM) sensor is proposed which uses a wavelength-division multiplexing (WDM) fiber coupler. The effect of integrating the WDM coupler in a FLM configuration is first studied. A section of Hi-Bi (bow-tie) fiber of length 0.26 m is then placed in the fiber loop, making the spectral response of the device simultaneously dependent on the Hi-Bi fiber section and WDM coupler characteristics. When strain is applied to the sensing head, the spectral signal is modulated in amplitude, in contrast with the conventional Hi-Bi FLM sensors in which there are wavelength shifts. The sensor was characterized in strain and a sensitivity of (-2.2 +/- 0.4) x 10(-3) mu epsilon(-1) for a range of 300 mu epsilon was attained. The self-referenced character of the sensor is noted. (C) 2013 Optical Society of America

Abstract
Two interferometers were proposed with different types of twin core fiber. Both are characterized in temperature and the topology based on photonic crystal fiber presents higher sensitivity. © OSA 2013.

Abstract
Optical fibre Bragg grating (FBG) sensors are now quite established and widely used in strain measurements of composites. However, insufficient understanding of the limitations of the embedment and measuring techniques often lead to inaccurate and inconclusive results. In this study, a novel method to improve the reliability and accuracy of the strain measurements on unidirectional composites using embedded FBG sensors was successfully developed. Using a carbon/epoxy prepreg system, test specimens were manufactured with longitudinally embedded FBG sensors. The combined behaviour of the sensors and the host material was characterized and a calibration rule (correction factor) was determined for the chosen material. The consistency of the results with both theoretical and empirical assumptions suggests that the proposed method is applicable to a wide range of FBG sensors and host materials.

Abstract
A simple optical inclinometer based on phase-shifted Bragg grating in a taper configuration is proposed. The phase-shifted FBG was fabricated using a DUV femtosecond laser technique in the taper region. The sensing head was characterized for different angle curvatures and also to strain. The angle and strain sensitivities of the inclinometer are 13.15 pm/degree and 8.96 pm/mu epsilon.