Abstract

Abstract
Long period fibre gratings (LPFG) have found an increasing interest due to the easy fabrication in any kind of fibre through the induced electric arc technique with low cost and flexibility. They have been used in applications such as gain-flattening and band-rejection, and for sensing strain, temperature and chemical and biological parameters. The sensitivity of LPFG increases when the fibre is coated with certain thin films. In this short review it is presented the recent developments and applications of these kind of sensors.

Abstract
After carrying out a revision of the literature on the enhancement of Er3+ diffusion in LiNbO3 crystals by Er3+/Ti4+ co-diffusion and analyzing our own experimental results, we conclude that no reproducible results were reported, meaning that further research on this subject is necessary.

Abstract

Abstract
It is presented the fabrication and characterization of optical fiber sensors for refractive index measurement based on localized surface plasmon resonance (LSPR) with gold nano-islands obtained by single and by repeated thermal dewetting of gold thin films. Thin films of gold deposited on silica (SiO2) substrates and produced by different experimental conditions were analyzed by Scanning Electron Microscope/Dispersive X-ray Spectroscopy (SEM/EDS) and optical means, allowing identifying and characterizing the formation of nano-islands. The wavelength shift sensitivity to the surrounding refractive index of sensors produced by single and by repeated dewetting is compared. While for the single step dewetting, a wavelength shift sensitivity of similar to 60 nm/RIU was calculated, for the repeated dewetting, a value of similar to 186 nm/RIU was obtained, an increase of more than three times. It is expected that through changing the fabrication parameters and using other fiber sensor geometries, higher sensitivities may be achieved, allowing, in addition, for the possibility of tuning the plasmonic frequency.

Abstract
It is established that FTIR with chemometrics is a reliable technique to predict deterioration of meat from game species and from species grown in the wild such as, fallow deer and goat. Meat was minced and stored for periods of 12-432 h and examined for FTIR, pH, lipid oxidation, microbiological analysis, colour, and sensory analysis (SA). Spectral data was analysed with PCA and LDA. PLS-R was employed to establish relationships between spectral data and the microbiological counts. From PCA it was determined that wavenumber from 1656 to 1002 cm(-1) are linked to alterations during storage. LDA of spectral data was applied to sustain SA data. For fallow deer the room mean square error of prediction values for external samples were 0.75, 0.61, 0.81 and 0.73 log cfu g(-1), for TVC, psychrotrophs, LAB, and Enterobacteriaceae, respectively. For goat, the corresponding values were 0.74, 0.68, 0.78 and 0.79 log cfu g(-1). FTIR spectroscopy can be used as a reliable method for assessment of freshness of meat from fallow deer and goat during storage.