We present a new class of optical fibers: silica chiral multicore microstructured optical fibers (MOFs) characterized by twisting induced during the drawing process and the use of supporting elements made of GeO2-doped silica glass. Technological aspects of core preform manufacturing, as well as specific features of the implementation of drawing the lengths of twisted MOFs, are considered. The technical feasibility of the described complex fiber-optic structure is confirmed. Extended (50 m long) pilot samples of silica six-core MOFs with step- and graded-index profiles of the cores and different twisting degrees from 50 to 500 rpm are manufactured for the first time, and the results of measuring their basic characteristics are presented.

This work introduces first time fabricated spun silica microstructured optical fiber (MOF) with inclusion of seven GeO2-doped capillaries, placed in the central part of MOF cross-section, and induced twisting up to 730 revolutions per meter. Part I discusses technological issues for manufacturing of described complicated twisted fiber optic structure, while Part II presents some results of test series, performed for successfully manufactured twisted MOF pilot samples with typical hexagonal geometry under hole radius 4.40 μm and pitch 9.80 μm, outer “telecommunication” diameter 125 μm, and center part, formed by seven hollow GeO2-doped ring cores with inner radius 2.50 μm, pitch 8.80 μm and refractive index difference Δn=0.030. Following measurements were performed: measurements of transmission spectra under various twisting order, far-field laser beam profiles, some attempts of fusion splicing of typical telecommunication optical fibers and fabricated MOF with insertion loss estimation, and spectral response measurements of both single and group WDM (Wavelength Division Multiplexing)-channels of commercially available telecom WDM-system under inclusion of 2 m length MOF into various spans of short-range lab fiber optic link.

This work presents the first instance of a silica few-mode microstructured optical fiber (MOF) being successfully fabricated with a hollow GeO2-doped ring core and by strongly inducing twisting up to 790 revolutions per meter. Some technological issues that occurred during the manufacturing of the GeO2-doped supporting elements for the large hollow cores are also described, which complicated the spinning of the MOFs discussed above. We also provide the results of the tests performed for the pilot samples—designed and manufactured using the untwisted and twisted MOFs described above—which were characterized by an outer diameter of 65 µm, a hollow ring core with an inner diameter of 30.5 µm, under a wall thickness of 1.7 µm, and a refractive index difference of Δn = 0.030. Moreover, their geometrical parameters, basic transmission characteristics, and the measurements of the far-field laser beam profile patterns are also provided.

This work presents results of test series, performed for earlier on designed and successfully fabricated twisted silica fewmode microstructured optical fibers (MOF) with six GeO2-doped cores. While Part I introduces results of differential mode delay map measurements, Part II is focused on researches of spectral responses, measured for fiber Bragg gratings, recorded in these multi-core MOFs with core graded refractive index profiles and induced twisting 100 revolutions per meter. Specially setup for spectral response measurement for described complicated fiber optic element was developed, that provides selected alignment of matching singlemode optical fiber with particular single core of MOF via free space and reducing of reflection by precision 8 angle cleaving. Comparing analysis of measured spectral responses confirmed written FBGs in 2 of 6 cores, and demonstrated potentiality of fabricated complicated structure, containing multi-core MOF with FBG, for applications in multichannel fiber optic sensors with spatial division multiplexing technique.

We developed and characterized luminescent temperature sensors with a simple construction based on YAG:Ln(3+) (Ln = Nd, Yb, Ce) nanocrystals and silica multimode optical fibers. Lanthanide-doped nanocrystals 40 to 60 nm in size were synthesized in the form of powders using the modified Pechini method. The obtained materials exhibited high sensitivity of luminescence intensity to temperature variations at wavelengths of 550 nm (YAG:Ce3+), 1030 nm (YAG:Yb3+), and 1064 nm (YAG:Nd3+) in the temperature range 50 degrees C to 600 degrees C. Additionally, we offered a method to eliminate influence of vibration on accuracy of temperature measurements by adding SiO2 sol to powders after their synthesis in sensitive elements. (c) 2023 Society of Photo-Optical Instrumentation Engineers (SPIE)

This work presents a fabricated silica few-mode microstructured optical fiber (MOF) with a special six GeO2-doped core geometry, an outer diameter of 125 µm (that corresponds to conventional commercially available telecommunication optical fibers), and improved induced twisting up to 500 revolutions per 1 m (under a rotation speed of 1000 revolutions per meter with a drawing speed of ~2 m per minute). The article discusses some technological aspects and issues of manufacturing the above-described twisted MOFs with complicated structures and geometry as GeO2-doped silica supporting elements for them. We present results of some measurements performed for fabricated samples of chiral silica six-GeO2-doped-core few-mode MOFs with various orders of twisting and both step and graded refractive indexes of “cores”. These tests contain research on MOF geometrical parameters, attenuation, and measurements of the far-field laser beam profile.

This work presents overview of technological issues concerned with drawing of twisted silica microstructured optical fibers. We present results of drawing tower modifications with developed and verified technological modes, that provide fabrication of silica microstructured optical fibers with induced chirality up to extremely high twisting order of 800 revolutions per meter (rpm). Thus, a work package using the original designer technical solutions for upgrade the adapter for supplying overpressure to the cane holes of the microstructured optical fiber (MOF) was carried out. Hence, the target increase in the twisting speed in the cane feed unit to 2000 rpm is ensured while simultaneously target overpressure feeding to the cane holes, which prevents the hole collapsing in the process of MOF drawing. The reliability of the adapter design and the high reproducibility of the specified cross section structure for the MOF at lengths of more than 50 meters with a twist period of 500 rpm have been experimentally confirmed. For the first time in the Russian Federation, prototypes of "stable" chiral MOF lengths (more than 50 m) of a different configuration with a maximum induced twisting of 500 rpm and MOFs prototypes with structure stability at lengths of less than 50 m with a strongly induced chirality of up to 790 rpm were fabricated. The geometric patterns of these fibers are also presented in this work.

We suggested an alternative to technically complex CVD processes method for producing thin films containing highly luminescent YAG nanocrystals activated with Nd 3+ ions inside channels of microstructured optical fibers by the liquid polymer-salt method. As a result of studying structural and spectral properties of the obtained optical elements, the formation of highly luminescent in the near-IR region nanocrystals was determined, which defines the potential of their application in sensor technologies. We studied temperature sensitivity of YAG:Nd 3 + nanocrystals synthesized in channels of a microstructured optical fiber and compared it with YAG:Nd 3 + nanocrystals having the form of powder. It was found out that luminescence intensity of these materials decreases exponentially in the temperature range from 50 to 600 °C.

Two types of simple and inexpensive fiber optic sensors for detection ultraviolet A-band radiation have been developed and manufactured. The first sensor is a capillary made of quartz, which contains phosphor of organics, solvent and epoxyacrylate, as well as a fiber of multimode optical brought inside the capillary. The design of the second sensor is a multimode optical fiber coated on one edge with a photoactive compound. With a properly selected concentration of substances in the photoactive composition, it is possible to obtain the optical signal for the wavelength in range from 425 to 440 nm, which corresponds to the wavelength of the photoluminescence emission of selected phosphor. The prospects of using the developed structures as sensors for ultraviolet radiation of the A range are confirmed by the presence of photoluminescence at the output end upon excitation with a wavelength in the range of 365–390 nm and a linear dependence of the output amplitude of optical signal at optical power launched to the fiber input.

This work presents designed and fabricated silica few-mode optical fiber (FMF) with induced twisting 10 and 66 revolutions per meter, core diameter 11 µm, typical "telecommunication" cladding diameter 125 µm, improved height of quasi-step refractive index profile and numerical aperture 0.22. Proposed FMF supports 4 guided modes over "C"-band. We discussed selection of specified optical fiber parameters to provide desired limited mode number over mentioned wavelength range. Some results of tests, performed with pilot samples of manufactured FMF, are represented, including experimentally measured spectral responses of laser-excited optical signals, that comprise researches and analysis of few-mode effects, occurring after fiber Bragg grating writing.

We report the development of a group of luminescent fibre-optic temperature sensors that use Ce3+-, Dy3+-, and Yb3+- doped yttrium aluminium garnet (YAG) nanophosphors as thermosensitive materials. The nanophosphors have been prepared in the form of powders with a crystallite size from 19 to 27 nm by a polymer – salt method and exhibit bright luminescence at 550 (YAG : Ce3+), 400, 480 (YAG : Dy3+), and 1030 nm (YAG : Yb3+). The sensor design includes a silica capillary, partially filled with a nanophosphor, and two large-aperture multimode optical fibres located in the capillary, which deliver excitation light and receive and transmit the photoluminescence signal. The photoluminescence signal amplitude of all the sensors decreases exponentially with increasing temperature, pointing to characteristic thermal quenching of photoluminescence and adequate operation of the devices up to 500 °C. The highest temperature sensitivity among the fibre-optic sensors is offered by the YAG : Ce3+ nanophosphor-based devices.

The problems of river pollution with various hazardous elements on the example of the Volkovka river are considered. A study of water from various regions of the Volkovka river was carried out for the presence of various chemical compounds and elements in them. A relationship has been established between the location of the river bed in the city and the level of pollution by various compounds. The comparison of the measurement results with the previously obtained data is carried out and the tendency of changes in pollution is established.

This work presents fabricated silica microstructured optical fiber with special equiangular spiral six-ray geometry, an outer diameter of 125 µm (that corresponds to conventional commercially available telecommunication optical fibers of ratified ITU-T recommendations), and induced chirality with twisting of 200 revolutions per minute (or e.g., under a drawing speed of 3 m per minute, 66 revolutions per 1 m). We discuss the fabrication of twisted microstructured optical fibers. Some results of tests, performed with pilot samples of designed and manufactured stellar chiral silica microstructured optical fiber, including basic transmission parameters, as well as measurements of near-field laser beam profile and spectral and pulse responses, are represented.

The construction structure of microstructured fibers is considered. A research scheme of the mode composition and defects control in optical fibers is developed. A microstructured fiber for studying optical vortex fields has been developed and manufactured. The results of studies of the same fiber structure and the distribution of optical radiation depending on the parameters of the technological cycle of its production are presented.