Abstract
A review in fiber post-processing for sensing applications is presented. The review is divided in three parts. Tapers devices, chemical etching for Fabry-Perot cavities and focused ion beam (FIB) as post-processing applied in optical fibers are considered. The most recent results as sensing elements are shown. © 2014 OSA.

Abstract
This review is focused on microstructured optical fiber sensors developed in recent years for liquid RI sensing. The review is divided into three parts: the first section introduces a general view of the most relevant refractometric sensors that have been reported over the last thirty years. Section 2 discusses several microstructured optical fiber designs, namely, suspended-core fiber, photonic crystal fiber, large-core air-clad photonic crystal fiber, and others. This part is also divided into two main groups: the interferometric-based and resonance-based configurations. The sensing methods rely either on full/selective filling of the microstructured fiber air holes with a liquid analyte or by simply immersing the sensing fiber into the liquid analyte. The sensitivities and resolutions are tabled at the end of this section followed by a brief discussion of the obtained results. The last section concludes with some remarks about the microstructured fiber-based configurations developed for RI sensing and their potential for future applications. © 2014 by the authors.

Abstract
Tapering single-mode-multimode-single-mode structures to enhance sensitivity is proposed and experimentally demonstrated. 50-mm-long coreless multimode fiber sections are spliced between single-mode fibers (SMFs) and tapered. They are characterized in strain, and an increase in strain sensitivity is obtained with taper diameter reduction. Sensitivities as high as -23.69 pm/mu epsilon for the 15-mu m taper are attained. Temperature sensitivities also depend on taper diameter. A combination of two different diameter tapered SMF MMF-SMF structures, with cross-sensitivity to strain and temperature, is proposed as a sensing system for the simultaneous measurement of strain and temperature with resolutions of +/-5.6 mu epsilon and +/-1.6 degrees C, respectively. A good condition number of 3.16 is achieved with this sensing structure.

Abstract
Acoustic sensing is nowadays a very demanding field which plays an important role in modern society, with applications spanning from structural health monitoring to medical imaging. Fiber-optics can bring many advantages to this field, and fiber-optic acoustic sensors show already performance levels capable of competing with the standard sensors based on piezoelectric transducers. This review presents the recent advances in the field of fiber-optic dynamic strain sensing, particularly for acoustic detection. Three dominant technologies are identified - fiber Bragg gratings, interferometric Mach-Zehnder, and Fabry-Pérot configurations - and their recent developments are summarized. © 2014 The Author(s).

Abstract
A gas pressure sensor based on an all-fiber Fabry-Perot interferometer (FFPI) is reported. The sensing head consists of a small section of silica rod spliced with a large offset between two single-mode fibers. The silica rod is used only as mechanical support so that an air cavity can be formed between both SMF. 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 - sensitivities of 6.2, 4.1 and 3.6 nm/MPa, respectively, were attained. The refractive index change on nitrogen environment by means of gas pressure variation was also determined and a sensitivity of 1526 nm/RIU was obtained. The response of the sensing device to temperature variations in air was also studied and a sensitivity of -14 pm/degrees C was attained.

Abstract
A sensor based on Fabry-Perot interferometry with a hollow microsphere cavity embedded in a 3D printed structure is proposed. The sensor was tested for lateral loading and temperature, showing promising results. By imprintring the sensor on the structure, the dynamic range of application is severely increased enabling the application of the sensor in harsh environments.