Published on: 2026-08-17
Source: Peter the Great St. Petersburg Polytechnic University –
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Scientists at Peter the Great St. Petersburg Polytechnic University have created and tested a multisensor platform based on spectral interferometry. A fiber microprobe the thickness of a human hair simultaneously constructs an image of the internal structure of soft tissue and measures its elasticity, temperature, refractive index, and the pressure it exerts on the tissue itself. Several such probes were interrogated by a single optoelectronic module. This allows for obtaining a volumetric image without mechanically moving the probe. Research supported By the Russian Science Foundation.
Today, an endoscopist has to choose between devices: one constructs an image, another measures the physical parameters of the tissue. Meanwhile, it is precisely the combination of the morphological picture with numbers — how dense the tissue is, how warm it is, its optical density — that is critical in diagnosing neoplasms and vascular plaques, as well as during endoscopic surgeries. Using multiple instruments reduces measurement reliability and can increase the trauma of the procedure. Scientists from St. Petersburg proposed combining all these functions into a single optical fiber.
The platform is based on optical coherence tomography (OCT) — a method that allows you to see beneath the tissue surface to a depth of several millimeters and distinguish details as small as a few micrometers.
Optical coherence tomography is an optical analogue of ultrasound: instead of sound, it uses infrared light, and the depth at which reflection occurs is determined by measuring the reflected radiation spectrum. The depth of view is less than that of ultrasound, only a few millimeters, but details as small as a few micrometers can be distinguished. An optical fiber about the thickness of a human hair is used to deliver infrared light to the studied tissue. In this same fiber, we placed sensors for temperature, pressure, and refractive index, which will allow better differentiation between diseased and healthy tissues,
The second key result is multiplexing. Scientists have learned to interrogate multiple probes with a single optoelectronic module and process their signals jointly, applying approaches known from phased array antenna technology. After recording the signals, it is possible to programmatically select the region of space from which the image is formed and obtain a more detailed picture than that provided by a single probe. Thus, a three-dimensional distribution of tissue parameters is constructed without a single mechanical movement.
The achieved characteristics are measured in micrometers and fractions of a degree. The system distinguishes inhomogeneities with a transverse size of 20 µm and a longitudinal size of about 7 µm. The measurement error of the refractive index was up to 2·10⁻⁵, temperature — 0.15 °C, force — about 1 nN. The resolution of pressure in a single fiber-optic sensor based on a microsphere reached 0.001 Pa. Such sensitivity allows detecting slight deviations of the tissue’s mechanical properties from normal, enabling observation of changes at the earliest stage.
Tests were conducted on artificial models of biological tissues made of gelatin and albumin with added scattering microparticles, simulating the walls of the esophagus, respiratory tract, and skin. These were used to develop structural imaging, measurement of elastic properties, and assessment of the diffusion rate of liquid agents through the sample. The latter opens the way to drug delivery control: by combining OCT with a fiber optic refractive index sensor, the researchers were able to simultaneously monitor the penetration of water and glycerin into the sample.
The platform also has a second, non-biological area of application — metrology in the optical and semiconductor industries. Scientists demonstrated the measurement of thin film thicknesses (less than 1 µm) with an accuracy of a few nanometers and visualization of the core of an optical fiber with a resolution better than 1 µm. This is in demand for non-destructive testing of semiconductor wafers, fiber components, and welded joints.
OCT itself is a fairly mature technology, it has been developing since the early 1990s, and endoscopic OCT has been actively developing for more than ten years. Unfortunately, at the moment there is no production of OCT systems in Russia, all studies conducted by the medical community are performed on Western devices. The main novelty of our project lies in the integration of OCT probes with fiber-optic sensors and the ability to simultaneously record signals from several probes using one device without significant modification of the hardware. The prototype is assembled from standard telecommunications components using conventional fiber splicing, so it can be reproduced in any fiber-optic laboratory in the country and will be quite simple to manufacture,
Additionally, the team proposed a method to suppress signals from parasitic back-reflections of light within the studied object — using quantum-inspired second-order interferometry. This required generating radiation with a special thermal photon statistics, in a way easily compatible with standard single-mode fibers. The scientists’ near-term plans include transitioning to fully contactless optical coherence elastography, where acoustic waves in the object are excited by a sequence of short laser pulses; improving depth resolution to 1–2 microns by registering signals in two spectral windows; and creating a probe on a multicore fiber with electronic beam control — scanning without moving parts. A separate goal set by the team is to enable serial production of optical coherence tomography systems in Russia.
The research was carried out with the support of Russian Science Foundation grant No. 23-72-10095 (2023–2026) within the framework of the Presidential Research Projects Program. The work will continue as part of the project extension for 2026–2028. The project involves Associate Professors A. A. Markvart and A. V. Petrov, Professor L. B. Liokumovich, and graduate students L. D. Zavalishina and U. A. Makarenko. The results have been published in the “Optical Journal”, the journals “Instruments and Experimental Techniques”, “Scientific and Technical Gazette of SPbPU. Physical and Mathematical Sciences”, as well as in SPIE proceedings and the EExPolytech conference.
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