ETU “LETI” was able to improve the quality of diagnostics of underwater fiber optic cable connections by 10%

In 2018, in the Russian Federation, as part of the national Digital Economy project, a plan was developed to build a wide network of underwater fiber-optic communication lines in hard-to-reach, including the Arctic, territories of the country. So, two years later, the construction of a similar submarine line from Murmansk to Vladivostok was announced. The goal of the project is to provide broadband Internet access to local settlements, infrastructure facilities for the extraction and transportation of hydrocarbons in the Arctic, as well as to solve geological exploration problems.

Tomographic image of cable connection

The considerable length of such communication lines has caused the need for precise control of cable transitions. To solve this problem, LETI researchers have developed the X-ray device RUNK-50, which has no analogues in Russia, which makes it possible to detect defects in the connections of information and power lines. To date, consumers have already received 4 devices of this type, and one of them is already operating in the Arctic zone. In 2022, it is planned to deliver several more units for the needs of domestic companies.

“We have developed a scheme for performing a tomographic method for inspecting sleeves in a fiber optic cable. The results of the studies showed that, compared to traditional X-ray, our new technology allows us to increase the detection of defects by more than 10%.” says the assistant in the Department of Electronic Instruments and Devices (EPU) at St. Petersburg Electrotechnical University “LETI” Ivan Alekseevich Larionov.

To perform connection testing, the examined part of the cable connection is placed in the X-ray protection chamber of the RUNK-50 installation and fixed with special devices. After that, with the help of the installation control program, the process of tomographic control is started, which consists of an automated set of a discrete set of angular projections (x-rays) in the range from 0 to 210 degrees.

The application of mathematical algorithms for tomographic reconstruction to the resulting set of projections makes it possible to obtain a set of longitudinal sections of the object under study, based on the analysis of which the defects in the controlled joint are automatically checked.

The fundamental difference between the proposed technology compared to that used in the first version of the installation is the use of tomographic control instead of radiographic. The technique of radiographic control leaves the possibility to skip a defect or get it with low contrast, depending on its location in the control object. The tomographic control method, in turn, lacks this disadvantage due to the receipt of a whole set of projections of the test compound. At the same time, the additional introduction of an automated assessment of coupling joint defects based on the obtained longitudinal sections of the object also makes it possible to equalize the influence of the operator’s subjective assessment of the connection.

Ivan Larionov, Assistant at the Department of Electronic Instruments and Devices, St.  Petersburg Electrotechnical University

Ivan Larionov, Assistant at the Department of Electronic Instruments and Devices, St. Petersburg Electrotechnical University “LETI”

The resulting X-ray images can be analyzed in manual and semi-automatic mode using the specialized “Analysis+” software developed by LETI researchers.

“Detecting defects in made connections or their insulation in time can significantly reduce the risk of laying damaged sections of cable lines and, consequently, get rid of the financial costs of their re-laying”, – explaining Ivan Alekseevich Larionov.

The development of a new technology is an integral part of the work of researchers at the EPU department with the study of hidden objects and defects in industrial facilities using X-ray and tomographic control methods. The base of the team of developers is associate professor at the department of EPU Viktor Borisovich Bessonov and Assistant to the Department of EPU Ivan Alekseevich Larionovwho developed a program to apply the new technology. The creation of equipment was mainly carried out by the engineers of CJSC “ELTECH-Med” and the assistant of the department of EPU Klonov Vladimir Valerievich.

Scientific work was carried out, among other things, under the RFBR grant (no. 19-37-90098).

Information and images provided by the Center for Scientific Communications at St. Petersburg Electrotechnical University “LETI”

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