Abstract
Nafion has been evaluated as a sensing phase of an optical fibre humidity sensor based on a low-finesse Fabry-Perot interferometer. The sensor was constructed by manual deposition of a drop of a Nafion solution on the tip of a single mode optical fibre, forming a Fabry-Perot resonant cavity. The absorption of water by the Nafion film makes it swells, changing its refractive index and the length of the cavity, which produces a phase shift in the interference signal. The sensitivity, stability and response time of the sensor were evaluated in the RH range from 22 to 80% by analysing the correspondent reflection spectra of the interference fringes. As a result, it was obtained that Nafion can be used as sensing phase of an optical fibre humidity sensor based on optical fibre Fabry-Perot interferometry, presenting a response time of 242 ms (3% RH variation) and a sensitivity of 3.5 nm/%RH.

Abstract
We present a new method for coupling light to high-Q silica whispering gallery mode resonators (WGMs) that is based on long period fiber gratings (LPGs) written in silica fibers. An LPG allows selective excitation of high-order azimuthally symmetric cladding modes in a fiber. Coupling of these cladding modes to WGMs in silica resonators is possible when partial tapering of the fiber is also implemented in order to reduce the optical field size and increase its external evanescent portion. Importantly, the taper size is about one order of magnitude larger than that of a standard fiber taper coupler. The suggested approach is therefore much more robust and useful especially for practical applications. We demonstrate coupling to high-Q silica microspheres and microbubbles detecting the transmission dip at the fiber output when crossing a resonance. An additional feature of this approach is that by cascading LPGs with different periods, a wavelength selective addressing of different resonators along the same fiber is also possible. (C) 2014 Optical Society of America

Abstract
Traditionally, uorescence-based analytical methods were associated with high-cost bulky laboratory equipment. However, a diversity of technological advances taking place over the last 20 years concurred to change this picture. In the eld of optoelectronics, the advent of low-cost blue and UV lasers and LEDs, together with new miniature CCD spectrometers and high-sensitivity avalanche photodiodes (APDs), is enabling a new generation of spectroscopy tools to be developed and deployed in eld applications. On the other hand, chemistry and material sciences are delivering new types of uorescent materials with enhanced sensing properties, such as long-lived metallo-organic complexes or highly photostable quantum dots (QDs). Such developments are expanding the uses of uorescence and enabling new applications such as long-term multiwavelength imaging, ow cytometry analysis in microuidic chips, high-throughput DNA sequencing, and ber-optic-based diagnostic probes. © 2015 by Taylor and Francis Group, LLC.

Abstract
This work presents a demonstration of the potential of fiber cavity ring-down for remote sensing, by using an OTDR to send impulses down similar to 20 km of optical fiber at the end of which the fiber ring cavity was placed. The OTDR showed almost no losses in the fiber, so other ring-down cavities could be spliced along the same fiber. To study the sensitivity of the cavity ring an intensity sensor based on a taper was placed in the ring and glued to a translation stage. A displacement of the stage imposes a curvature on the taper and an associated loss. The configuration had a sensitivity of (11.8 +/- 0.5) mu s/mm.

Abstract
An interferometric Fabry-Perot cavity based on hollow-core ring photonic crystal fiber combined with a silicone diaphragm is proposed for low pressure sensing. The sensor exhibits a sensitivity of 0.086 nm/mmHg for a pressure range between 0 and 337.5 mmHg. These values are in the range of physiological pressures, such as intravascular pressure. (C) 2014 Wiley Periodicals, Inc.

Abstract
This work presents a fiber CRD configuration for the measurement of strain. An Optical Time-Domain Reflectometer was used to send impulses down into the fiber loop cavity, inside of which a chirped fiber Bragg grating was placed to act as a strain sensing element. This technique could provide strain results with both conventional CRD-based configuration and the OTDR.