Development of a fiber-optic temperature sensor based on chirped Bragg gratings and modulation of optical radiation intensity

Subject of study . A fiber-optic temperature sensor based on measurement of the reflected optical power is studied. Aim of study . A fabrication technique for fiber-optic temperature sensors based on chirped fiber Bragg gratings and measuring the reflected optical power is developed. Method. The fiber-optic temperature sensor consists of a brass probe with two chirped Bragg gratings, one of which is also enclosed in a steel capillary tube and has higher temperature sensitivity than the other grating. Changes in temperature modulate the overlap between the spectra from the first and second Bragg gratings, enabling detection of changes in the optical power reflected by the structures. Main results. An approach is being developed for creating a fiber-optic temperature sensor based on measurement of optical radiation intensity. The sensor has a design operating range of −20 ∘ C to +80 ∘ C. The sensor was tested by varying the temperature from −20 ∘ C to +80 ∘ C in 10°C intervals, revealing a sensor sensitivity of −0.015dB/ ∘ C. The sensor was also found to have a temperature measurement error of 1.0% (relative to a thermocouple). The deviation in the sensor readings at a steady temperature value is estimated to be 0.06°C. Practical significance. The temperature sensor developed herein is part of the worldwide trend towards cost-effective design solutions. This measurement technique based on modulation of the optical intensity enables the use of a readily available interrogation scheme that does not require expensive equipment such as an optical spectrum analyzer or interrogator. This interrogation scheme also has the advantages of high data recording speed, relatively simple design, and the absence of strict requirements with respect to operating conditions.