Development and studies of a fiber-optic temperature sensor based on a Fabry–Perot interferometer obtained by welding optical fibers

Subject of study. A fiber-optic temperature sensor, based on a Fabry–Perot interferometer obtained by welding optical fibers, is developed and characterized. Aim of study. The aim is to develop and characterize a temperature sensor based on a fiber-optic Fabry–Perot interferometer obtained by arc welding and evaluate its temperature-sensing performance. Method. The design of the temperature sensor is implemented based on a Fabry–Perot interferometer obtained by welding optical fibers. The reflecting mirrors of the sensor comprise layers of thin films of titanium dioxide. The interferometer interrogation method is based on the use of a vertically emitting laser operating in the pulsed generation mode. The principle of registering the phase shift between radiation reflected from the interferometer mirrors with changes in temperature is based on auxiliary modulation of the laser radiation wavelength due to a periodic change in the pulse duration. Main results. During the temperature evaluation of the developed sensor, the phase characteristics of the Fabry–Perot interferometer were obtained in the temperature range of +20∘C to +380∘C. A shift in the operating point was registered with changes in the ambient temperature. The results of the experiment indicated that an increase in the ambient temperature leads to an increase in phase difference between the radiation reflected from the first and second mirrors of the interferometer. Results suggest that the phase sensitivity to temperature change is 0.96, 1.68, and 2.35 rad/°C at distances between mirrors corresponding to 5, 8, and 11 mm, respectively. Practical significance. The proposed fabrication method for the Fabry–Perot interferometer provides sufficient opportunities for the formation of a resonator with different lengths and also makes it possible to exclude the use of additional materials in its design. Hence, the interferometer exhibits small weight and size parameters, and thus, it can be used in a wide range of applications, including as a sensitive element of a temperature sensor. The sensor interrogation method employed in the study eliminates the need for costly spectral measuring instruments such as optical spectrum analyzers and interrogators.