Abstract
A sensing head for simultaneous measurement of temperature and strain is presented and analyzed. The proposed configuration is based on the combination of two Bragg gratings, written in different fibres and with different reflectivities, to form a single signature with a reflected step spectrum profile. This characteristic minimizes the spectrum allocated to each sensor in a series multiplexing topology. By measuring the changes in the peak wavelength and spectral width of this signature, resolutions of +/- 0.65 degrees C/root Hz and +/- 2.55 mu epsilon/root Hz were achieved for temperature and strain measurements, respectively.

Abstract
In this article, approaches reported in the literature for multi-parameter measurement relying on fiber grating technology are reviewed. Due to its importance, the particular case of temperature/strain simultaneous measurement is addressed in further detail, as well as the techniques and sensing heads for temperature-independent strain measurement. Specific criteria are also proposed for sensing head classification in the context of multi-parameter measurement.

Abstract
In this work two sensing heads based on fibre Bragg grating structures are demonstrated, one for temperature independent measurement of strain and the other for simultaneous measurement of these two parameters. The first one relies on a single Bragg grating inscription in a microstructured optical fibre, resulting for two input orthogonal polarizations in two distinct resonance peaks with similar temperature sensitivities and different strain sensitivities. In the second structure two gratings were considered, one written in the same microstructured fibre and the other on a standard SMF fibre. Considerably different strain and temperature sensitivities were obtained for these two gratings, enabling simultaneous temperature and strain measurement with resolutions of +/- 1.5 degrees C and +/- 10.7 mu epsilon over a measurement range of 100 degrees C and 2000 mu epsilon, respectively.

Abstract
In this work, two sensing heads based on the fibre Bragg gratings written in fused biconical fibre taper for simultaneous measurement of temperature and strain are proposed. In the first configuration a comparison between a uniform Bragg grating and a grating written on a tapered fibre section, resulting in a chirp grating, is evaluated. The second sensing head consists of two gratings written in two different regions of the taper section. This fibre taper has a different geometry in each conical section, achieved by stretching the fibre at different velocities during the fabrication process. These two configurations are based on the different strain and similar temperature sensitivities of the Bragg gratings used to discriminate the two physical parameters. The performances are assessed and compared. The second structure presents good performance and more sensitivity, compared to the first sensing head.

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.