Abstract
The development of fiber optical sensor in which the sensing head comprises a long period fiber grating (LPG) whose attenuation peak varies as function of its bending was investigated. Various arc-induced LPGs were fabricated in the spectral region of the optical source. The spectral power evolution was taken from a streched to a bending position with the optical spectrum analyzer. The developed fiber optical sensor demonstrated its capability of micro-displacement measurement.

Abstract

Abstract
We have studied the effect of gamma radiation on Long Period Fiber Grating (LPFG) temperature sensors fabricated in a pure-silica fiber, using the arc discharge technique. The temperature sensitivity of the LPFGs remains unchanged by the irradiation.

Abstract
Type S thermocouples were assembled in situ by applying high intensity electric are discharges to the contact junction of two platinum (Pt) and Pt-10% rhodium (Pt-10% Rh) wires, inserted on a silica capillary. The electrically insulated thermocouples built in this way were afterwards employed to estimate the temperature of an optical fiber subjected to arc discharges. For typical values of the arc discharge parameters used to arc-induce long-period fiber gratings (electric current I = 9 mA and arc duration t = 1 s), a capillary peak temperature value of 1420 degreesC +/- 400 degreesC was obtained by extrapolation of the experimental data for the limit situation of having a thermocouple with negligible diameter. The temperature profiles in the capillary and in an optical fiber were calculated based on a heat transfer model implemented by a finite element algorithm and fitted to the experimental temperature distribution in the Pt and Pt-10% Rh wires. The correspondent peak temperatures computed for the capillary and for the fiber were 1450 degreesC and 1320 degreesC, respectively. A good agreement between the capillary temperature values determined graphically and numerically was obtained.

Abstract
A new sensing configuration is proposed for simultaneous measurement of strain and temperature that relies on a single long period grating written by the electric arc technique. The underlying principle is the azimuthal asymmetry induced by the electric arc fabrication technique, which results in a device with polarization dependent insertion loss sensitive to both temperature and strain. With the proposed configuration, resolutions of +/- 2.8 degreesC/rootHz and +/- 13.9 muepsilon/rootHz are obtained for temperature and strain measurements, respectively.

Abstract
The radiation emitted by an optical fiber during heating due to an electric arc discharge was detected using a Cronin spectrometer. The fitting of the emission spectrum to the blackbody radiation, allowed the estimation of the temperature range attained by the fiber.