The co-measurement of curvature and temperature using a single LPG in a standard single mode fibre

We propose and demonstrate the use of a single long period grating (LPG), having one cladding mode that is unresponsive to changes in curvature, for simultaneous measurement of curvature and temperature. We also demonstrate that such a cladding mode can be produced at different wavelengths in a standard single mode fibre (SMF). Furthermore, we show that harmonic modes of LPGs, that are often undesirable in many applications, can now be utilized along with such a curvature-insensitive cladding mode to achieve a sensor that can measure curvature and temperature simultaneously, whilst having the capability to compensate for induced strain.