Sofya D. Bochkova

Subject of study. The methodology for determining the optimal operating spectral range of a Fabry–Pérot interferometer (FPI) based on chirped fiber Bragg gratings (CFBGs) is studied. Aim of study. The aim of this study is to develop and investigate a methodology for selecting the optimal operating wavelength range of a CFBG-based FPI (CFBG-FPI). Method. The proposed methodology involves the sequential tuning of the central wavelength of a vertical-cavity surface-emitting laser, followed by an analysis of the signal-to-noise ratio of the data obtained from a CFBG-FPI integrated into an experimental setup. The measurements are performed after applying pulsed acoustic excitation to a steel plate. During signal analysis, the operating spectral range is selected based on the maximum signal-to-noise ratio achieved using the setup. Main results. An original methodology for determining the optimal operating wavelength range of a CFBG-FPI is developed. A signal-to-noise ratio of 23.5 dB is achieved. Data repeatability assessments show that the standard deviation of the signal-to-noise ratio values is 0.4 dB. Practical significance. The proposed methodology can be used to develop new technological solutions, particularly for the nondestructive testing of industrial objects. Owing to their high sensitivity, CFBG-FPIs can be applied under more challenging conditions, ensuring stable registration of low-intensity acoustic measurements.

A method is described for determining the position of an acoustic source in composite materials using Fabry–Perot fiber-optic interferometers. The proposed method is based on the analysis of the time of arrival of acoustic signals to sensitive elements during mechanical action on a composite material. The relative times of arrival of signals to the sensitive elements, which depend on the location of the source of impact, were modeled and the method was calibrated by finding the optimal threshold values for the correct recording of the time of arrival of the acoustic signal. The experimental setup is described and the experimental conditions are indicated. The developed localization method was implemented in the experimental laonet of the acoustic emission signal recorder and studied in the experiment. The error of the proposed method is estimated. The directions of further research and ways to improve the proposed method are considered.

The article discusses a system for testing fiberoptic lines for pyroautomatic systems. An optical fiber is proposed to use to deliver the control signal to the optical detonator or to the automaton in such systems. The integrity of the optical line is checked by measuring back reflections. The basis of the developed device is an optical fiber, working as a dielectric, that eliminates the possibility of electrical interference or static. The prototype of the system was assembled from the following components: multimode fiber splitters, a delivery optical fiber and an input unit with a dielectric mirror sprayed at the end. The recipe and the model of a reflective dielectric coating are given. The power laser diode was tested in critical temperature conditions. The results of checking the integrity of the fiber-optic circuit are presented. Such a system can be used in the mining industry for initiating explosives by laser radiation.

The authors of this article developed the configuration of a fiber optical diffuser within the core. When this radiation diffuser is stretched, the back reflections change, and it was detected by the photodetector. This article dwscribes this experiment. Thus, a tension sensor was developed, which can be used in winches, crane systems, mechanical engineering, in laboratories and stage equipment. According to the results of processing the experiment, the tensile sensitivity was 2 picometers per 1 microstrain.

The article presents a specially developed stand that allows to investigate the properties of a laser beam near the surface of the components of bulk and fiber optics with high precision (up to 0.15 μm) and high spatial resolution (up to 12000 points). The originality of the stand lies in the ability to scan the field directly at the output surface of an optical object. The working radiation power being studied can reach dozens of watts. In the world there are no analogues with the above described set of properties among the commercially available equipment. The paper presents the prototypes on which research was carried out and the components used to create the automated stand. The results of measuring the laser waist diameter on the surface of a GRIN lens and of an optical fiber are given. The beam properties after passing through the GRIN lens and through the optical fiber are also studied. The designed stand finds practical application for measuring the quality of the M2 beam.

This paper presents a mathematical model that describes the influence of defects in an anisotropic optical fibre on its polarised frequency domain reflectograms. The model relies on the Jones matrix formalism. Calculated reflectograms are presented for a uniform axial twist of an optical fibre. As input data for simulation, we use real distributed optical parameters of the fibre determined by polarised light Brillouin reflectometry.

The paper discusses the theoretical aspects of the design of automated research systems based on the principles of optical reflectometry in the time and frequency domains. The basic expressions for the construction of simulation models of optical reflectometers of both types are presented. The basic principle of the system is described, the results of the functioning of its separated modules are presented. Some initial conclusions on the work of the elements of the system were made, key areas of activity were identified Рассмотрены теоретические аспекты проектирования автоматизированных исследовательских систем на принципах оптической рефлектометрии временной и частотной области. Представлены основные выражения для построения имитационных моделей оптических рефлектометров обоих видов. Изложен базовый принцип работы системы, представлены результаты функционирования ее отдельных модулей. Сделаны первичные выводы о работе элементов системы, определены ключевые направления деятельности.