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Thermo-Optical Effects and Fiber Optic Sensing Device Based on Polymer Dispersed Liquid Crystals

In this article, the thermo-optical properties of polymer dispersed liquid crystals (PDLCs) in confined geometry are experimentally investigated to demonstrate the feasibility of a fiber optic sensing device based on PDLCs. Since an unexpected behavior of PDLCs in confined geometry has been experienced, a systematic study of PDLCs’ thermo-optical properties in bulk is presented also to point out principal differences. Finally, bistable all fiber optic temperature sensors, in which a PDLC permits at the same time the opto-mechanical interconnection of two fibers and the modulation of light crossing the device, has been realized and characterized, for the first time. Being the modulation controlled by external temperature, the device has been proven to be suitable for the realization of a heat flow sensor. The sensor presents the typical advantages of both fiber optic sensors and liquid crystal technology. Moreover, due to its small thermal capacity, it should exhibit little influence on thermal equilibrium and, above all, it represents a significant improvement compared to a temperature fiber optic sensor based on liquid crystals (presented in the literature).