The study of temperature and refractive index sensitivity of polyimide coated etched (3LPGs-FBG) sensor

Abstract

In this study, a new sensor configuration based on optical fiber grating sensor is fabricated and evaluated experimentally. A combination sensor of three Long Period Gratings LPGs and one Fiber Bragg Grating FBG is fabricated and coated by polyimide in order to enhance the performance and the sensitivity of the new sensor for temperature and refractive index measurements. The gratings were written on the chemical etchant Single Mode Fiber SMF and then coated by polyimide. The new sensor was tested under different temperatures range from 25 °C to 38 °C and under different concentration of NaCl solution ranging from 0% to 5% corresponding to 1.3305 RIU to 1.3410 RIU. An investigation of sensor performance, repeatability and stability tests were carried out. The sensor exhibits a linear performance and a good stability during one hour of testing. For the (3LPGs-FBG) sensor, the temperature sensitivity was estimated to be 2.8 pm/°C and the refractive index sensitivity was estimated to be 16.078 nm/ RIU. The new (3LPGs-FBG) sensor provides number of advantages among other configurations such as low costs, compactness, accurate sensitivity and finally easy fabrication process.