Simultaneous strain and temperature sensing using long-period gratings

We present experimental results to demonstrate the simultaneous strain and temperature measurement capability of long-period gratings, It is shown that the distinct spectral shifts of the multiple resonance bands in a single grating can be employed to separate the concurrent perturbations of axial strain and temperature. Static and quasi-static tests are performed to illustrate the effectiveness of a grating written in a standard optical fiber. It is demonstrated that cross-sensitivities and non-linearities in the temperature- and strain-induced shifts result in a tradeoff between the simplicity and the dynamic range of the sensing system. The advantages and limitations of the long-period grating simultaneous sensing configurations are also discussed.