An optical fiber load sensor made of transducers with alternate Poisson's ratio sign.

What is it about?

This work is about an optical fiber sensor that exploits an exotic property of some transducer structure, i.e. the capability of shrinking in one direction when a load is applied to the orthogonal direction. This feature is described by a negative Poisson's ratio and structures like those are known as auxetic structures. Common materials and structures undergo to an elongation along one direction when loaded at the orthogonal direction. In this work we have realized a sensor made of a concatenation of structures that have positive and negative Poisson's ratio, alternatively. This sensor encodes uniformly vertical loads into local horizontal elongation and shortening, alternatively, which are measured by means of an optical strain sensing technique, either distributed (e.g. Rayleigh) or semi-distributed (e.g. FBG). This approach prevents the non-uniform response behavior, usually observed in optical fiber cables when subjected to pressure. The prototype realized to prove the concept shows high sensitivity and a resolution of few centimeters (determined by the length of the constitutive sub-structures ).

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Photo by T.H. Chia on Unsplash

Photo by T.H. Chia on Unsplash

Why is it important?

This work is a first attempt to tackle the problem of distributed pressure/load sensing. Furthermore it is an interesting demonstration of the synergic interaction between exotic materials properties and optical fiber sensing.

Perspectives