Abstract
We discuss the writing of arc-induced long-period fiber gratings to be used as optical filters in Er/Yb fiber lasers and for flattening the gain spectra of Er-doped fiber amplifiers. A new approach for the fabrication of filters with complex profiles is also presented. (c) 2008 Wiley Periodicals, Inc.

Abstract
The electric arc technique is used to apodize fiber Bragg gratings (FBGs). Arc discharges applied to the ends of the grating produce a smoothing of the refractive-index modulation profile reducing the sidelobes of the reflection spectrum at longer wavelengths. A sidelobe reduction of 17 dB was obtained. (c) 2007 Wiley Periodicals, Inc.

Abstract
The thermal behavior of long-period gratings arc-induced in B/Ge codoped fibers is presented. We also demonstrated the possibility to erase gratings written in Ge-doped and B/Ge codoped fibers through uniform exposure to UV-laser radiation. The gratings spectra were afterward recovered by thermal annealing. permanent thermally induced refractive index changes were found. (C) 2007 Wiley Periodicals, Inc.

Abstract
Long-period gratings were written in a pure-silica-core fiber using the electric arc technique. To assess the influence of stress relaxation on grating formation, tomographic stress measurements were performed inside the grating. No stress annealing could be observed within the accuracy of the stress measurement, suggesting a negligible photo-elastic contribution to the arc-induced perturbation of the index profile. In contrast, stress relaxation was found inside a splice of pure-silica-core fiber where discharge conditions are different, indicating the general potential to alter the fibers stress and thus the index profile using an electric arc.

Abstract

Abstract
This paper presents a comparative study of the behaviour of different kinds of optical fibre sensors in response to high temperatures. It compares the performance of regenerated fibre Bragg gratings (FBGs) written in hydrogen-loaded and non-loaded fibres with long period gratings (LPGs) written through the two different processes of ultraviolet (UV) irradiation and electrical arc discharges. This work shows the importance of the use of hydrogen-loaded fibres to achieve regenerated FBGs capable of withstanding high temperatures as high as 955 degrees C. In addition, the results demonstrated that LPGs recorded by electric arc discharges have higher thermal resistance than LPGs written by UV radiation.