Abstract
A compact sensor based on step-changed are-induced long-period fiber gratings was implemented to discriminate between temperature and strain. The proposed sensor consists of a single long-period grating with two sections written consecutively in the SMF-28 fiber using the electric are discharge technique. The two sections have the same period but different fabrication parameters. The operation of the sensor relies on the existence of a difference between the values of temperature and strain sensitivity of two neighboring resonances observed in the spectrum of the step-changed grating. The temperature and strain resolutions obtained for the sensor are 0.2 degrees C and 35 mu epsilon, respectively. (c) 2007 Optical Society of America.

Abstract
The paper presents the application of temperature acquisition systems integrating thermocouples, a thermographic camera and fibre Bragg grating (FBG) sensors in gas metal arc welding (GMAW) process, MIG ( metal inert gas) welding type. Efficient procedures to use FBG sensors and thermocouples were developed. The paper presents and compares measurements made in welded plates of aluminium alloy 6082-T6. Tests were performed in both plate surfaces and good agreement between the three techniques was found.

Abstract
This work shows the changes of bending curvature sensitivity when the same long- period fibre grating has different phase shifts. From the knowledge that the coupling constant is reduced as curvature increases, we theoretically and experimentally assess the possibility that the bend sensitivity follows the grating spectrum evolution during the point- to-point fabrication technique. We also show that control of bend sensitivity can be applied to the simultaneous measurement of bend and temperature.

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.

Abstract
Integrated optics (IO) technology has been primarily used in optical communication applications but it is expanding fast into the field of optical sensing. In this work we report the fabrication of integrated devices using hybrid sol-gel technology and in particular its application in the fabrication of a refractive index integrated sensor based in a Mach-Zehnder interferometric configuration. In one of the interferometer arms, a analysis chamber is created by exposing the waveguide through the removal of the device cladding. On the same arm, two Bragg gratings with the same period are fabricated: one in the unprotected waveguide area and another in close proximity (cladded area); because of the different effective index in the two grating regions, two peaks are observed in reflection if the device is tested with a broadband source. Any change of the refractive index of the material filling the analysis chamber can be detected in two ways: by measuring the intensity of the interferometric output (at a wavelength different from the Bragg wavelength of the two gratings) or by measuring the spectrum of the reflected signal. The high sensitivity is obtained by measuring the interferometric output, while the high dynamic range can be achieved by measuring the reflected signal from the grating structures.