Fiber Bragg grating temperature sensor of cladding with SrTiO3 thin film by pulsed laser deposition

Abstract

SrTiO3 (STO) thin film was coated on the cladding of a fiber Bragg grating (FBG) by pulsed laser deposition, and the associated temperature sensing properties were tested. The surface of the FBG coating was smooth, uniform, compact and without obvious defects; the structure and properties of the FBG were well protected. Temperature sensing results showed that the sensitivity of the STO coated FBG was about 9.97 pm °C−1, which is about 28% higher than that of the bare FBG (7.8 pm °C−1) before coating. In order to further study the thermal sensing properties of the FBG, a concatenated optical path, two optical paths based on a Michelson interferometer and a Sagnac interferometer, were constructed by using STO coated FBG and another bare FBG as the sensitivity results 9.0 pm °C−1, 10.5 pm °C−1 and 11.4 pm °C−1, respectively. Among them, the fiber sensor based on the Sagnac interferometer was more sensitive, which was increased by 46.2%. Moreover, the interference optical path has the advantages of simple structure and good practicality.