Abstract

Abstract
The electric arc technique allows the inscription of long-period gratings (LPGs) virtually in all types of fibers, including non-photosensitive fibers, the case of non-Ge doped photonic crystal fibers being of particular interest. LPGs written in standard fibers using this technique have shown a high thermal stability. Also, the resistance to. - radiation of LPGs arc-induced in pure-silica-core fibers is being assessed and the achieved results are very promising. We have also demonstrated that the combination of arc-induced LPGs and UV-induced fiber Bragg gratings (FBGs) leads to sampled FBGs that are able to address sensing functionalities with enhanced performance. Therefore, as a result of their properties, gratings induced by arc-discharges can find a wide range of applications in optical communications as well as in fiber sensing.

Abstract
A study on arc-induced long-period fibre gratings (LPFGs) revealed that their strain sensitivity depends on the electric current of the arc discharge. Based on that property, a sensor scheme comprising two concatenated LPFGs was implemented for discrimination of temperature and strain effects. This sensor presented resolutions of +/-0.1 degreesC/rootHz and +/-35 muepsilon/rootHz, respectively.

Abstract
Permanent long-period gratings were written using arc discharges in two aluminosilicate fibers, one of which was doped with erbium. Reversible gratings were also mechanically induced in both fibers. The thermal behavior of the arc-induced gratings was investigated at up to 1100 degrees C. It was found that the shift of the resonant wavelengths exhibited a well-defined linear dependence on temperature up to 700 degrees C. (c) 2005 Optical Society of America.

Abstract
We experimentally study the effect of ionizing radiation on the properties of long-period gratings fabricated in two pure-silica-core fibers with the arc-discharge technique. It is observed that the spectra of the gratings remain almost unchanged after being subjected to doses in excess of 0.5 MGy. The results also show that the gratings' temperature and strain sensitivities are not affected by gamma radiation. (c) 2005 Optical Society of America.

Abstract
A compact sensor able to discriminate between temperature and strain related effects was implemented. The proposed sensing head comprises a single long-period grating with two sections written consecutively in the SMF-28 fiber, by the electric arc discharge technique, using different fabrication parameters. The sensor performance is based on the distinct temperature and strain sensitivity values presented by two neighbor resonances belonging to each grating section. The temperature and strain resolutions are +/- 0.1 degrees C and +/- 40 mu epsilon, respectively.