Abstract
Temperature-independent strain measurement is achieved resorting to a taper fabricated on a Bragg fibre using a CO2 laser. The characteristic bimodal interference of an untapered Bragg fibre is rendered multimode after taper fabrication and the resulting transmission spectra are analysed as temperature and strain change. The intrinsic strain sensitivity exhibited by the Bragg fibre is increased 15 fold after tapering and reaches 22.68 pm/mu epsilon. The difference in wavelength shift promoted by variations in temperature and strain for the two fringes studied is examined and strain sensing with little temperature sensitivity is achieved, presenting a sensitivity of 2.86 pm/mu epsilon, for strain values up to 400 mu epsilon.

Abstract
Optical fiber sensors have evolved over the years in many different directions. One particular direction dictated by necessity is miniaturization and the creation of micro- and nano-optical fiber sensors. Many techniques now exist that allow the micro-structuring of optical fiber. One in particular is focused ion beam technology. This chapter aims to introduce this technique and present the latest work on the application of focused ion beam to optical fiber micromachining, more specifically, the fabrication of optical fiber microstructure sensors such as micro-gratings and micro-cavities.

Abstract
The effect of an erbium-doped fiber amplifier (EDFA) placed inside the fiber ring of a cavity ring down (CRD) configuration is studied. The limitations and advantages of this configuration are discussed, and the study of the ring-down time as a function of the current applied and gain to the EDFA is also presented. In this case, the power fluctuations in the output signal are strongly dependent on the cavity ring-down time with the EDFA gain.

Abstract
A smart material using fibre Bragg gratings (FBGs) embedded into carbon fibre-reinforced polymer for simultaneous measurement of physical parameters was designed, tested, and validated. Two FBGs were embedded in different sections of the composite sample, one fully unidirectional and the other bidirectional, which produced different sensitivities for each FBG sensor. The composite structure was characterized for strain/temperature and curvature/temperature measurements. The experimental results were compared with and agreed with finite element simulations.

Abstract
Long period fiber gratings produced by the electric arc technique have found an increasing interest by the scientific community due to their ease to fabricate, virtually enabling the inscription in any kind of fiber, low cost, and flexibility. In 2005 we have presented the first review on this subject. Since then, important achievements have been reached such as the identification of the mechanisms responsible for gratings formation, the type of symmetry, the conditions to increase fabrication reproducibility, and their inscription in the turning points with grating periods below 200 mu m. Several interesting applications in the sensing area, including those sensors working in reflection, have been demonstrated and others are expected, namely, related to the monitoring of extreme temperatures, cryogenic and high temperatures, and high sensitivity refractometric sensors resulting from combining arc-induced gratings in the turning points and the deposition of thin films in the transition region. Therefore, due to its pertinence, in this paper we review the main achievements obtained concerning arc-induced long period fiber gratings, with special focus on the past ten years.

Abstract
A reflection configuration setup for long-period fiber gratings is presented. It permits to obtain a unique band with attenuation double than that obtained in transmission configuration, which is interesting for applications where this value is reduced (e. g., the mode transition phenomenon). The method is based on the deposition of a silver mirror at the end of the optical fiber, which permits to absorb the power transmitted through cladding modes and to avoid the generation of interferometric bands. The method also solves the requirement of a precise cleave or to polish the end of the grating, a drawback present in other publications. The versatility of the setup has been proved by application of the cladding etching technique until the attenuation band corresponding with the first guided mode in the cladding is visualized in an optical spectrum analyzer. The experimental results are supported by the numerical data obtained with a method based on the exact calculation of core and cladding modes and the utilization of coupled mode theory.