Abstract
A novel sensing head for simultaneous measurement of strain and temperature is demonstrated, based on two Bragg gratings arranged in a twisted configuration. Choosing an appropriate twisting period, the grating resonance wavelengths show similar temperature sensitivities but different strain responses, permitting simultaneous discrimination of these parameters with rms deviations of +/- 1.5 degrees C and +/- 4.7 mu epsilon respectively.

Abstract
A scheme for the simultaneous determination of temperature and analyte concentration for application in luminescence-based chemical sensors is proposed. This scheme is applied to an optical oxygen sensor, which is based on the quenching of the fluorescence of a ruthenium complex. Temperature measurement is performed using the excitation radiation and an absorption long-pass filter. Preliminary results are presented that show the viability of an oxygen measurement that is independent of temperature and optical power level. The possibility of self-referenced temperature measurements with semiconductor nanoparticles is also investigated. In order to optimize the sensor design, several different optical fiber probe geometries for oxygen sensing are tested and compared, including different methods of coupling radiation into the optical fiber system. Polyvinyl alcohol (PVA) and polyacrylamide membranes are tested as supports for sensor immobilization in fiber-optical pH sensing devices in aqueous solution. Some results are presented that show the feasibility of using fiber-optical pH indicators for remote monitoring.

Abstract
The study of a single short length Bragg grating for sensing applications is presented. The dependences of the central wavelength, reflected optical power and spectral width of a 250 mu m length grating on strain and temperature are analyzed. The obtained results indicate the feasibility of this novel sensing head for simultaneous measurement of strain and temperature.

Abstract

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.