Multiplexed long period gratings with differential interrogation

Abstract

In this work we present experimental results in which we simultaneously detect spectral changes of three long period fiber gratings (LPG) connected in series. The gratings can independently measure surrounding refractive index (SRI) changes Δn, temperature T and strain ε in any combination. We have successfully tested them with to simultaneous moisture/evaporation sensing based on SRI change measurements. Such arrangements can be used for simultaneous tracking of hazardous liquid ingress or spill in structural health monitoring applications. © 2010 IOP Publishing Ltd.