Abstract

Abstract
A multiplexer/demultiplexer for 100GHz channel spacing based on chirped fibre Bragg gratings with different bandwidths and optical circulators is presented. The spectral characteristics, specifications and operation of these passive devices are described, showing its potential use in dense wavelength division multiplexing (DWDM) applications.

Abstract
A new scheme is presented for simultaneous measurement of strain and temperature using a sampled fibre Bragg grating based on a long period structure written using the electric are technique. The temperature and strain measurement resolutions are estimated to be +/-0.50degreesC/rootHz and +/-3.38 muepsilon/rootHz, respectively.

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
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.