Subject of study. Afiber-optic temperature sensor, based on a Fabry-Perot interferometer obtained bywelding 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 C20 degrees C to C380 degrees 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/degrees C at distances between mirrors corresponding to 5, 8, and 11mm, 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 spectrumanalyzers and interrogators. (c) 2024 Optica Publishing Group

Summary This work is devoted to the development of a fiber optic channel for measuring temperature and pressure. The channel includes temperature and overpressure sensors, an interrogator and cable lines for signal transmission. Pressure and temperature sensors are based on fiber Bragg gratings (FBG). To measure temperature in the range from -50 to +240°C, a single FBG is used. To measure pressure in the range from 0 to 20 MPa, an array of two FBGs is used (one directly for measurements, the second for temperature compensation). The fiber optic interrogator is based on a vertical-cavity surface-emitting laser. The laser is powered by current pulses. The use of this mode of operation allows for controlled tuning of the wavelength of the generated radiation (range up to 4 nm). Analysis of the signals reflected from the FBG using a photodetector makes it possible to determine its resonant wavelength. These processes are controlled by FPGA. The number of interrogator channels is 8, the sampling frequency is up to 1 kHz. The transmission of signals between the sensors and the interrogator is carried out using a special cable assembly. The assembly is implemented on the basis of an armored fiber optic cable and protected connectors. The presented fiber optic channel for measuring temperature and pressure is used as part of complex systems in order to control their operating modes and control parameters.

This paper proposes the interferometric method for arrays inscription of type I Bragg gratings on the unified segment of the standard telecommunication single-mode optical fiber, using preliminary inscription of the gratings with low diffraction efficiency. The accuracy of setting the Bragg resonance wavelength of each individual diffraction structure is at least 50 pm with the reflection coefficient close to 100%. Also, the results of chirped fiber Bragg gratings arrays inscription in a fiber with a high content of germanium dioxide (GeO2) in the core are obtained. An analysis of the spectral characteristics of the inscribed periodic structures of modulation of the refractive index is made.

Tilted fiber Bragg gratings with different tilt angles have been inscribed in single-mode isotropic optical fiber with an increased photorefractivity using Talbot interferometer and KrF-excimer laser system. Their spectra are studied. Using a confocal laser scanning luminescent microscope the images of gratings in transmitted light were obtained. The calculated dependence of the slope angle of the grating recorded in the Talbot interferometer on the angle between the strokes of the interference pattern created in the interferometer and the transverse section of the optical fiber is experimentally verified.

The results of investigations of the spectral characteristics of chirped fiber Bragg gratings induced in an optical fiber using a Talbot interferometer and a KrF excimer laser system of the master oscillator-power amplifier type with enhanced coherence are presented. Dependences of the full width of the reflection spectrum at half maximum and the reflectivity of chirped fiber Bragg gratings on their length are obtained and analyzed. Through the inscription of seven superimposed chirped fiber Bragg gratings, a diffraction structure with a spectral width of 32 nm was obtained. In addition, a chirped fiber Bragg grating whose spectral response shape is almost rectangular is presented. (C) 2018 Optical Society of America

С использованием интерферометра Тальбота и KrF

In this paper, we showed a technique for the formation of phase-shifted fiber Bragg gratings. The analysis of the efficiency of the obtained structures was carried out with the help of an optical spectrum analyzer with the subsequent calculation of the full width at half maximum of a bandpass in reflection spectrum. Fiber Bragg gratings inscription was performed on the Talbot interferometer, the KrF excimer laser system was used as a UV radiation source, and a phase shift was introduced by the electrical discharge of an arc fusion splicer. The experimental dependence between the length of the obtained structure and the full width at half maximum of a bandpass in reflection spectrum of a phase-shifted grating was presented, the value of the last parameter varies in the range from 24 pm to 96 pm.

In this paper, we present results on the inscription of superimposed Bragg gratings in various optical fibers, including specialized light guides produced in Russia, using an inscription setup based on the Talbot interferometer. A KrF excimer laser system of the master oscillator type-an Optosystems CL-7550 power amplifier-is used as the source of ultraviolet radiation for the experimental stand. The spectral characteristics of superimposing a different number of fiber Bragg gratings are demonstrated and the inscription of several Bragg gratings in the same region of the optical fiber is investigated. (C) 2017 Optical Society of America

Решается задача обеспечения стабильности работы чувствительного элемента волоконно-оптического тензометрического датчика в условиях одновременного воздействия механических напряжений и температуры окружающей среды.В качестве одного из наиболее перспективных чувствительных элементов волоконно-оптических датчиков физических величин используются волоконные брэгговские решетки.Показано, что разработанная структура чувствительного элемента на основе двух решеток Брэгга с различными специально подобранными покрытиями может разделить влияние деформационного и температурно

results in visualization of fiber Bragg gratings of type II recorded in birefringent single-mode optical fibers with an elliptical stress cladding with a high concentration of germanium dioxide are shown. Periodic structures of the induced refractive index are inscribed by a single pulse of an excimer laser with a working- gas mixture of ArF using the phase mask. Fiber Bragg gratings into anisotropic optical fiber were investigated by optical and scanning-probe microscopes. It is shown that single-pulse recording by ArF excimer laser creates in the fiber, both inside and on the surface of the quartz cladding, periodic structures, the spatial period of which corresponds to the period of the phase mask, optimized for the +1/–1 diffraction order.

Представлен лабораторный стенд для записи волоконных решеток Брэгга с использованием интерферометра Тальбота.В качестве источника УФ-излучения используется эксимерная KrF-лазерная система MOPA CL-7550 типа задающий генератор -усилитель, которая обеспечивает высокий уровень временной и пространственной когерентности.Решается задача контроля параметров лазерного излучения и оптимизации процесса записи волоконных решеток Брэгга с требуемыми характеристиками.Приведено описание лабораторного стенда

In this work the comparative results on the dynamics of fiber Bragg gratings inscription in both the conventional and the subjected to hydrogenation birefringent optical fiber with elliptical stress cladding as well as in the same type of lightguide with the increased GeO2 concentration are presented. Also the research on the thermal impact on the fiber Bragg gratings written in the birefringent fiber with elliptical stress cladding has been carried out. The dependences of the fiber Bragg reflectance coefficient on the time of the thermal impact, obtained by annealing of the refractive index gratings, induced in the optical fibers with increased photorefractivity, are shown.

This paper presents comparative results of the recording of fiber Bragg gratings in birefringent optical fiber with an elliptical stress coating, subjected and not subjected to hydrogenation, as well as with an increased concentration of germanium dioxide. It is shown that both techniques for increasing the photorefraction of a fiber lightguide are effective for solving the problem of recording Bragg gratings. Time dependences are obtained for the shifts of the Bragg resonances of fiber gratings recorded in hydrogenated and unhydrogenated optical fibers. (C) 2017 Optical Society of America

The article presents the results of writing of high-performance fiber Bragg gratings in birefringent optical fibers with an elliptical stress cladding by a single 17 ns pulse of ArF excimer laser (193 nm). The gratings’ efficiency produced by a single pulse was up to 100%. Experimental results on visualization of these gratings are presented.