Abstract
A simple nanostrain direct current (DC) measurement system based on a chirped Bragg grating Fabry-Perot (FP) structure is presented. The FP cavity, formed between the chirped fiber Bragg grating (CFBG) and the fiber end face, presents an aperiodic behavior due to the CFBG. A laser located in the fringe pattern slope is used to interrogate the sensing head. The optical power parameter is analyzed when strain is applied, for long and short period fringe pattern wavelengths, and sensitivities of -2.87 µW/µe and -5.48'µW/µe are respectively obtained. This configuration presents a resolution of 70 ne. © The Author(s) 2011.

Abstract
In this work, a multiwavelength fiber Raman laser based on a highly birefringent photonic crystal fiber loop mirror is presented. A laser resonator is formed when the Raman amplification with cooperative Rayleigh scattering in a dispersion-compensating fiber is used as a distributed mirror and combined with a photonic crystal fiber loop mirror filtering structure. Stable multiwavelength lasing at room temperature is achieved due to the low temperature sensitivity of the highly birefringent photonic crystal fiber.

Abstract
In this work, two all-fibre interferometric configurations based on suspended core fibres (SCF) are investigated. A Fabry-Perot cavity made of SCF spliced in-between segments of single-mode and hollow-core fiber is proposed. An alternative sensing head configuration formed by the insertion of a length of SCF as a birefringence element in a Sagnac interferometer is also demonstrated. The sensitivity to pressure and temperature was determined for both configurations.

Abstract
The development of an interferometric optical fiber inclinometer is described in this paper. A weak tapered region is induced in a standard single mode fiber in the vicinity of the cleaved fiber tip, using a standard fusion splicer. In this situation an in-fiber Michelson interferometer is constructed that is sensitive to curvature applied in the tapered region. It is shown that depending on the angular range, fringe visibility and/or peak position depend strongly on the applied curvature enabling low cost dielectric inclinometer to be setup that is suitable for high voltage applications. It is presented an analysis of the sensor response by means of experimental measurements and manipulation of these experimental data through computational simulations. The results coming from the numerical simulations indicate a good performance of the sensor within range of angular variation between 3 and 6 degrees and 10 and 14 degrees. A low cost strategy to interrogate the response of sensor using electrically modulated fiber Bragg gratings, a photodetector and frequency analysis is described. The results presented by this electric interrogation technique show a good sensitivity in the range 3.5 to 5.5 degrees.

Abstract
Hollow-core photonic crystal fibres have a high potential for gas sensing applications, since large light-gas interaction lengths can be effectively attained. Nevertheless, in order to enhance effective diffusion of gas into the fibre hollow-core multi-coupling gaps are needed, which raise coupling loss issues that must be evaluated prior to the development of practical systems. In this communication we present a study on the coupling losses dependence on lateral and axial gap misalignment for single-mode fibre and two different types of hollow-core photonic crystal fibres. In addition, experimental results on the splicing of these fibres are also presented.

Abstract
A novel Mach-Zehnder interferometer based on a fibre multimode interference structure combined with a long period fibre grating is proposed. The multimode interference is achieved through the use of a multimode fibre section splices between two sin-le-mode fibres, with a length adjusted to couple a fraction of light into the cladding modes. A LP placed after the multimode fibre couples light back into the fibre core completing the Mach-Zehnder interferometer. The novel configuration was demonstrated as a bending sensor.