Long-period gratings in optical fibres for chemical sensor applications

Analysis of long-period fibre grating (LPG) parameters and their mutual dependences are presented. LPGs were studied and optimized specifically for chemical sensor applications. It was found that absorption by the fibre cladding of some environmental gases, such as oxygen or water vapour, may result in a false signal generation. The principal limitation of the sensor sensitivity is connected to the longitudinal homogeneity of the fibre refractive indices.