This PDF file contains the front matter associated with SPIE Proceedings Volume 11045, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

The paper is a digest of works presented during the 18th National Symposium on Optical Fibres and Their Applications. The Symposium has been organised since 1976, currently at one-and-a-half year intervals. The OFTA Symposium usually gathers around 120-150 participants and 100 technical presentations. OFTA 2018 was organized by Optical Fibre Laboratory of the Faculty of Chemistry at the University of Maria Curie Skłodowska (UMCS), and Institute of Electronics and Information Technology of the Lublin University of Technology (LUT), in Nałęczów on 19-23 November 2018. The 17th OFTA 2017 Symposium, was organized by the Technical University of Białystok in Supraśl in January 2017. The OFTA 2018 meeting gathered around 120 participants who presented 85 research and technical papers. The Symposium, organized every 18 months, is a good portrait of optical fibre technology development in Poland at university laboratories, governmental institutes, company R&D laboratories, etc. The topical tracks of the Symposium usually concern: optical and photonic materials, technology of classical, tailored and structural photonic optical fibres, light propagation physics in optical fibres, passive and active optical fibre components, optical fibre sensors, passive and active optical fibre networks, optical fibre amplifiers and lasers, optical fibre network issues – modulation, architectures, economy, teaching, etc.

In this paper we present the preliminary results of UV excimer laser application for optical fibers micromachining. We used a high power KrF laser to perform pulsed laser ablation of glass material at the end of single-mode optical fibers. By removing parts of the cladding we were able to change the light propagation conditions and therefore observe modified output beam distributions. The studies were undertaken for near infrared wavelength equal to 1550 nm. Based on the preliminary results we were able to determine the basic parameters influencing the modification of optical fibers’ geometry and the direction of further improvements to the micromachining setup. Although the focused spot was too large and energy density was too high to perform precise modifications of fibers’ geometry, we managed to prepare samples that indicate usability of proposed approach to micromachining. Obtained results of output beam distribution from modified samples were similar to the ones calculated by means of numerical simulations. By producing well characterized and repeatable micromachined structures we will be able to provide a new sensing platform for integrated measurements especially designed for applications in biological and chemical sensing.

Tilted fiber Bragg gratings (TFBG) are often used for refractive index (RI) measurements. Such measurements consist in monitoring changes in grating spectrum transmission in the range of cladding modes. The most popular method of TFBG transmission spectrum demodulation is to determine the area of the cladding mode envelope. Recently, a much simpler method has been proposed for this purpose, i.e. determining the length of the spectral contour. The contour length can be used directly as a parameter indicating the value of the refractive index measured. The paper proposes to develop the method of the spectral contour length to establish the cutoff wavelength and next indirectly discovering the refractive index. The algorithm consists in determining the curve of changes in contour length along with the wavelength for each spectrum measured with a given refractive index. The cutoff wavelength is defined as the intersection of individual curves with a line defining a certain level. This method is very simple, while at the same time being characterized by very high sensitivity.

The article presents the use of Eu³⁺ ions as a spectroscopic probe to measure changes in glass structure without interfering with the tested material. The aim of the work is to obtain bioactive glass-ceramics structure with increased mechanical properties. Examined 45S5 Bioglass® was annealed at 620°C for 8h. XRD measurements indicate the formation of the glass-ceramics structure with nanocrystals (Na₄CaSi₃O₉). Despite the additional heat treatment, the bioactivity of the glass has been preserved. The changes of luminescence profile of Eu3^{+ -} doped glass was determined. Decreasing value of fluorescence intensity radio parameter after annealing indicates symmetry around europium ions and thus the arrangement of the glass structure.

Optical layers produced from liquid phase are susceptible to the occurrence of refractive index inhomogeneity. The presented work involves the determination of refractive index inhomogeneity in waveguide layers, using the envelope of the recorded reflectance spectrum. Appropriate formulas and the calculation procedure have been demonstrated. The determined refractive indices are used to calculate theoretical reflectance characteristics which are compared with the experimental characteristics. In this way, the determination correctness of refractive indices on layer boundaries is verified. The calculations of theoretical reflectance characteristics were carried out with the use of the transfer matrix 2×2 formalism. Excellent agreement of both characteristics has been obtained.

The aim of the work is to apply the Auger Electron Spectroscopy to determine the chemical composition and uniformity of silica-titania SiO₂:TiO₂ waveguide films which were fabricated via sol-gel method. The SiO₂:TiO₂ waveguide layers are routinely produced on glass substrates, however, for the research presented in the paper, they were made on silicon substrates. We registered series of 50 Auger spectra on the different depths in the structure. The result show that the structure is chemically and structurally uniform through the whole depth.

The paper considers the modelling of the finely-dispersed non-coherent material flowing from the conic unloading hopper hole under the vibration disturbance of the flow with the conical bottom. There was presented the method for bringing Navier-Stokes equations that describe the movement of the non-coherent material under vibration, to the Lorenz model, based on which there were received graphic dependences, which allow forecasting the behavior of non-coherent material at the equipment projecting stage and controlling it by means of vibration intensity change as well as the unloading hopper hole parameters.

An inscription of a Bragg grating on a typical telecommunications fibre is difficult to obtain. In inscribing a structure, special fibres with an increased germanium content or classic fibres subjected to the hydrogenation process are used. The following article analyses the dependence of the hydrogen pressure on the parameters of the structures produced, such as grating reflectivity, Bragg wavelength or full width at half maximum (FWHM). The article also verifies how the pressure in the hydrogenation process affects the time of inscribing structures. Two types of fibre were subjected to photosensitisation: the classic one and one with a higher content of germanium. The hydrogenation process was performed at three pressures of 50 bar, 100 bar and 190 bar. Hydrogenation took place under the ambient temperature conditions of the room in which the chamber was located.

This paper presents the results of experiment determining the dependence of shift in spectral characteristics of Bragg gratings as a function of energy supplied to the optical fibre in the process of producing optical fibre periodic structures. The experiment was performed in an excimer laser system for two optical fibres with different photosensitivity.

This paper presents the introduction about fiber periodic structures which have a ability to coupling light from fiber core to cladding, their principles and applications. Paper also presents the detail description of particular example of TFBG spectral response for changes of fiber bending in range of curvature radius from 30 to 7 mm. The area of observed cladding mode resonances is changing due to strengthening of fiber curve with simultaneous core mode independence for this quantity. The ghost mode which is resonance closest to Bragg mode wavelength also stands out with transmission loss dependency from fiber bending which is also described.

Synthesis and characterization of a new materials in form of polymeric blends are presented. For the synthesis the following chemical components were used: bisphenol A glycerolate diacrylate, Pluronic® F-127, methyl methacrylate and Irgacure as UV polymerization initiator. Five samples with different amounts of Pluronic® F-127 and one reference sample without of polymeric dopant were received. The correct course of the reaction polymerization was confirmed by spectroscopic analysis (ATR/FT-IR). The thermal resistance of the samples was examined by thermogravimetric analysis (TG/DTG). Moreover, using by Shore method, hardness of obtained blends was tested. The obtained materials may find potential application as a resistant coating materials.

Tapering technique is one of the most useful in the telecommunications as well as in sensing which offers up to now the best quality fused optical fiber elements such as couplers, splitters and combiners. It allows to fabricate various types of the tapers used as platforms of optical fiber transducers for chemical or biological sensors, as well. In the paper polarization properties of an optical biconical taper with liquid crystal cladding are presented. The optical fiber taper manufactured by mentioned above technique was sandwiched between parallel glass plates with ITO and alignment layers to form a tested optical element. Standard nematic liquid crystals E7 and 6CHBT were applied as claddings of the tapered fiber. Sufficient transmission losses of infrared radiation were observed when orientation layers of glass plates were perpendicular to the tapered fiber. The main contribution of this paper is calculation the polarization properties of the tested samples by the Lu-Chipman decomposition method based on measured Mueller matrices. Analysis of measurements show that the applied voltages have the strongest influence on transmission losses and dichroism. These effects will be carefully investigated towards the voltage sensor and emulators of polarization depended loss.

The paper presents the results of manufacturing and characterization of a broad band in-line hybrid device using a nematic liquid crystal as an active cladding for biconical tapered optical fiber. Two different liquid crystal mixtures denoted as 1550* and E7 were used for electric and temperature control in a broad wavelength range. An optical fiber tapers with a waist of 10±0.5 μm and losses lower than 0.5 dB in a whole broad band spectrum range were applied. Such taper waist diameter makes the whole waist as core for light propagation, where the surrounding air becomes the cladding. Additionally, such diameter enables an effective control of molecules orientation. Performance of a tuned cladding was studied in an electric field in the range between 0 V and 160 V in the room temperature equal to 20 °C. Influence of induced liquid crystal molecules reorientation was measured at a broad wavelength range (500-1700 nm).

Presented article shows the effect of using ZnS:Mn nanoparticles in the solution of higher alkanes on the light wave propagation in a biconical, adiabatic optical fiber taper. The used mixture of alkanes with nanoparticles forms a special cladding surrounding a fiber taper. Described studies show change of beam intensity depending on mixture temperature and its state of aggregation. Tests were carried out in a wide spectral range from the visible up to infrared wavelengths. The taper was made of a standard single-mode telecom fiber, pulled out to a length of 20.0 ± 0.5 mm and the diameter of the taper waist is 14.0 ± 0.2 μm. Such taper causes the beam to leak out of a waist structure and allows to add an external beam-controlling cladding material. The built-in sensor containing nanoparticles operates on the on-off principle. Nanoparticles added to the alkanes cause increase of hysteresis in a heating and cooling process. Such mixture makes also a significant shift of temperature characteristic in a heating process in which mixture change their physical state with a simultaneous slight shifting of the characteristics during cooling. Depending on the source used, weakening or amplification of the signal was obtained after switching to the liquid state.

The main aim of this paper is to present a geometry shaping of a polymer microtip manufactured on the end of different multi-mode optical fibers by using UV radiation. Used fabrication process is based on a photopolymerization where the microtip grows on one end of the optical fiber when light is launched to its other end. Two different types of the photopolymerizable mixtures and two typical multi-mode optical fibers with different core sizes and refractive index profiles were used for tested microtips. In order to assess their geometries scanning electron microscopy images were used. These images have showed that the influence on the microtip geometry has optical power and spectral characteristics of the UV light. The sensor’s transducer properties were evaluated on the basis of backscatter measurements when a refractive index of a surrounded medium of the microtip changes. Dynamic ranges of tested optical fibers with selected microtips have reached 25-28 dB for the gradient-index multi-mode optical fiber while for the step-index one were around 14 dB. Future research will be focused on increase of dynamic range for the sensor’s application and will be tested as micro-lens.

The research is based on properties of a tapered optical fiber, ability to influence external factors on the propagating light beam in the fiber and anisotropic properties of the liquid crystal (LC) mixture that surrounds a tapered region. The combination of these elements is possible by creating a liquid crystal cell consisting of a layer orientating a liquid crystal (LC) between conductive layers. In that type of a sandwich construction, we can change the orientation of LC molecules under influence of the applied electrical voltage. The second interesting feature of LC is change in a structure that results from the degree of molecules’ alignment. When temperature rises, structure of LC changes from smectic through nematic to an isotropic liquid. Both the molecules orientation as well as the LC structure changes modified a refractive index of structure, which directly affects the propagating light beam in a tapered optical fiber. The spectral characteristics in the 500 -1100 nm range for a LC cell filled with a mixture of 1550* oriented orthogonally to the cross section of the tapered optical fiber are presented. Changes on spectral characteristics depended on manipulation of such parameters as: electrical voltage (0-200 V), frequency (1-10 Hz), shape of electrical signal, and time course for different voltage in the range 20-180 V.

This study presents the influence of temperature and electric field on optical power spectrum of an optical fiber taper device coated with nematic liquid crystal. The fiber-optic device consists tapered fiber placed between two glass electrodes covered with alignment layer and ITO. The tapering process caused the elongation of the optical fiber equal to 20.20 ± 0.16 mm and the taper waist diameter equal to 12 ± 0.5 μm. The applied tapered fiber is characterized by losses lower than 0.5 dB in the whole investigated spectrum range. The device was filled with nematic liquid crystal mixture E7 which is designed for an electric as well as temperature control of electromagnetic wave propagation. The measurements were performed for three kinds of initial liquid crystal molecules’ orientation (parallel, orthogonal and twist) in relation to the light beam propagating in the taper as well as axis of fiber. The induced reorientation of liquid crystal molecules was measured for visible and near infrared wavelength range [500-900 nm] at electric field range of 0–160 V and the temperature range of 20-60 °C. The relation between temperature and optical power spectrum of investigated fibers has been established.

The work presents theoretical analysis of applicability of a waveguide current sensors with external conversion (OFCSEC) in a power protection system. In such case the OFCS-EC sensor serves as a current transformer. Therefore due to its functionality it can be called an optical fiber current transformer. The considerations presented in this work are focused on potential for simultaneous application of many wavelengths. This concept renders the OFCS-EC sensor tunable depending on needs. It opens new possibilities for application of OFCS-EC sensors in power systems.

The paper specifies the achievable Bragg wave shift generated by pre-stressing the optical fibre in the phase mask writing process. The maximum possible shift results from the mechanical strength of the optical fibre to axial stress. Two methods are also proposed for the production of Bragg gratings with a controlled Bragg wavelength. The experiment was performed for the SMF28 fibre subjected to the hydrogenation process. The FBG fabrication was carried out in the excimer laser system using the phase mask method.

The method of resolving power enhancement of analog-digital conversion path of jitter analyzers in fiber-optical networks is suggested in the research. The analog-digital path is designed on the basis of the principle of phase-plane correction of dynamic errors and is characterized by high resolving power.

The paper presents methods for combining single and multi-channel fiber-optic links. On this basis, the architecture of the current and next generations of mobile communication systems, which should be strongly supported by all-optical networks, is presented. An example of a mobile system based on the EON/OTN/TSON backbone and edge optical networks operating in active and passive modes is presented. The current and future needs of mobile systems and networks were analyzed in terms of the quality of service parameters. Requirements for optical links used in separate networks of mobile systems such as NGC, BH, FH, and MH are presented. Calculations of the optical spectral efficiency of single-channel optical links used in the mobile systems were made. The calculations include the coherent modulations of single-carrier and multi-carrier OFDM formats, as well as D-RoF and A-RoF formats used in optical FH and MH. The results of the calculations are presented in diagrams. Application scenarios of the proposed network architecture and spectral effective modulation formats were discussed.

The paper presents a comparative classification of reference models used in IoT technology. The layers that directly determine the effectiveness of providing information at a distance are indicated. Examples of the construction of cores used in telecommunications silica-fibers are presented. Exemplary simulation models of SM-MCF and FM-MCF modal structures has been presented. Attention was paid to the need to construct MCFs, which can be used in local access networks as well as in distribution and indoor networks. Applications of MCFs in the networks operating in FTTH, FTTA and FTTS configurations are presented. During the presentation of the network solutions, proposal for the construction of a hybrid fiber-optic cable consisting of MCFs, SCFs, and TMCs are described. The proposed cable construction has been also used in the presented FTTH/FTTA network solutions.

The paper discusses uncertainty in estimation of sign of accumulated chromatic dispersion in an optical fiber communication link where the estimation is based on fitting a model of chromatic dispersion affected optical intensity waveforms to intensity measurement data. The uncertainty is characterized by probability of false readout of accumulated chromatic dispersion sign. Through extensive computations it is shown that despite the sign estimation in the method in question is in general ambiguous the chance for erroneous readout can be engineered to a desired level provided certain conditions are met. For the purpose of the characterization a theoretical model of sign false readout was developed and validated through combined measurements and simulations.

The process of providing a telecommunications monitoring system for gas leaks at the level of the queuing system is proposed. Based on the features of this type of system and considering the requirements, a simulation model was developed that allows to optimize the process of data exchange between sensors – wireless modules providing control of gas leaks from gas mains and electronic computers for collection, processing, storage, analysis of various kinds of information, as well as the adoption of management decisions.

Photorefractive quantum wells are nonlinear materials characterised by high sensitivity and a fairly fast response (≈ μs) at relatively low densities of optical power (μW/cm²). For structures working in the Franz-Keldysh geometry (with the electric field parallel to quantum wells) observed phenomena are related to the nonlinearity of electrons transport, i.e. the dependence of electron mobility on electric field intensity. This phenomenon plays an important role in photorefractive two-wave mixing, causing the shift of the space-charge field relative to the interference pattern, which allows obtaining high photorefractive gain, reaching 1000 cm^-1 for E=10 kV/cm. One of the parameters of SI-MQW structures that affects nonlinear transport is the electron and hole trapping coefficient. In the literature describing the processes taking place in GaAs/AlGaAs quantum wells that value is presented as constant. In article, the authors describe experiments testing the effect of strong electric field on the electron and hole trapping coefficients for bulk GaAs. An analysis of how the electric field-dependent trapping coefficient affects the process of two-wave mixing in MQW structures is discussed in. The results presented therein relate only to the stationary interference pattern. However in some studies the shift of the electric field distribution relative to the distribution of light intensity is obtained by using a moving interference pattern. We present the results of a numerical analysis of the impact of the electric field-dependent carriers trapping coefficients on the space-charge field formation under a moving grating.

It is well known that a homogeneous sensitivity of a single-layer slab waveguide, for given polarization, is maximized for a certain thickness of a waveguide film. Transition from a slab waveguide, referred to as a parent-slab, to a rib waveguide consist in partial constraint of the waveguide film in the direction parallel to its interfaces and perpendicular to the direction of propagation. Therefore it is appropriate to normalize the rib waveguides homogeneous sensitivity, which depends on the two additional parameters: rib width and height, to the sensitivity of the optimized slab waveguide. The article discuss dependence of rib waveguides normalized, homogeneous sensitivity on a parent slab thickness, rib width and rib height. High aspect ratio rib waveguides, whose rib width is several times longer than the parent slab thickness, are considered. It is shown, using the film mode matching method, that the sensitivity of a rib waveguide can exceed the sensitivity of the optimized slab waveguide and that sensitivity characteristics as a function of rib height may have maximum like it is in the case of a homogeneous sensitivity of the slab waveguide as a function of its thickness. Analysis of a principal electric field component spatial distribution, carried out for the fundamental EH mode, showed that for the optimized rib waveguide, its sidewalls are the place where changes of the ambient refractive index affect the guided mode to greatest extent.

We present rate equation model of a modified vertical surface-emitting laser with two optical-coupled active cavities (СС-VSCEL) and external optical channel. The model allows to determine all the relevant parameters – carrier densities, gains, and output powers – starting from two input parameters: the injection currents in each cavity taking into account the additional external photonic injection. The system of rate equations is solved for different operating regimes of the modified laser device. The results provided by the model shown that operating characteristics of CC-VCSEL greatly depend on the number of photons of the external injection.

In this paper the construction and technology of the dual-band UV-VIS photodetector has been shown. The designed and manufactured device allows for parallel monitoring of a single signal path in two different optical bands. The presented device consists of two independent photodiodes, the first of them is developed silicon carbide diode working in UV range, and the other one can be any VIS photodiode available commercially.

In this article, we research the physic and mathematical model of a digital coherent optical spectrum analyzer, which made it possible to obtain an analytical expression for calculating the spatial spectral resolution of the spectrum analyzer depending on the parameters of the spatial light modulator, the Fourier lens, and the matrix detector. To determine the spatial resolution of the aberrational Fourier lens, it is proposed to use a criterion similar to the Rayleigh criterion. Obtained the formula for determining the dependence of the spectral resolution of the processor on the aberration parameter of the Fourier lens, the research of which showed that for small pixel sizes of the detectors the resolution is determined by the size of the modulator matrix, and for large pixels by the pixel size.

The work is aimed to research the process of synthesis and analysis of musical compositions. The main goal is to increase speed and quality of this process. This is done by combining sound analysis algorithms with music synthesis technologies. By this method music taken by the device microphone is processed by the mobile application and then transformed to the note sequence which could be edited by the user.

Free forms synthesized by means of the perturbation functions are proposed. the problem of mapping a two-dimensional texture array to curved surfaces defined by perturbation functions is considered. surface patterns are created by interactions between texture and surface. the synthesis a 2d and 3d texture array onto curvilinear surfaces is solved. For shape creating, we propose a set of algorithms and software based on function-defined surfaces that perform an interactive rate and enable intuitive operations.

Extraction method is still the most waste-free in oil recovery technologies, and in the case of low-soybean seeds, the most convenient. Therefore, with the impulse intensification of this process, it is possible not only to increase its efficiency, but also to achieve compactness of equipment, to reduce energy costs and to improve the quality of extraction oils. The methods of intensification of the extraction process from plant raw materials, which can be divided into mechanical, thermal, biochemical and electrophysical, are analyzed, generalized and classified. The hypothesis is confirmed according to which the intensification of the extraction process of oil with an increased content of tocopherols occurs due to the use of a pressure diffusion flux from the capillary-porous structure of plant raw materials under the action of a microwave field. It is proved that the proposed number of energy effects successfully correlates the effect of the pulsed microwave field on the mass-transfer rate when extracting oil from rapeseed and soybean seeds. Using the developed mathematical model of the extraction process with pulse intensification, it is possible to deduce the dependences of the mass transfer coefficient on the number of energy effects, the dependence of the mass transfer coefficient on the microwave power and other dependences of the dimensionless criterial complexes characterizing the investigated process with means of its intensification. A determining effect on the mass transfer coefficient microwave power is defined. Burdo (Bu) vaporization number, showing the ratio of the microwave power and power needed to convert the liquid into vapor, corrects and coordinates the experimental data with an error of 8-16.5%.

The known methods for defining the parameters of interaction between different abstract objects, as technological or biological origin, do not reflect the full influence of environmental factors. This leads to errors in the measurement of the mechanical and physical properties of the quality of the manufacture of precision parts, as well as to errors in the diagnostics of the fluid state of objects. This article discusses the method of determining the interaction of objects on the basis of determining the processes that affect the creation of a zone of the presence of objects, that is, the abstract object always has spatial-temporal properties, that is, it notifies about its presence, as well as features of the life of the mass of object within its Pandan zone. The assumption is made that the Pandan zone is a force factor in a limited space, to determine the influence of factors of the environment.

This paper presents research on the use of discrete Fourier transform algorithm to limit the amount of data without losing information. Such preprocessing of registered optical spectra is necessary in order to shorten the execution time of the complex spectral deconvolution algorithms. It was shown that the spectral reduction coefficient with the noise component is sensitive to the noise level and decreases asymptotically to the hardware signal oversampling ratio.

The article presents the results of multifractal and statistical analysis changes in the characteristics of the multifractal spectra of a burner flame luminosity waveforms in industrial boilers at different loads and air supply levels to obtain a characteristic space for solving classification problems.

Glitches appear in digital-to-analog converters and lead to significant limitations of conversion accuracy and speed, which is critical for DAC and limits their usage, especially in the direct digital synthesis systems. This paper researches the causes, the specificity of the appearance of glitches in DAC and the possibility of using weight redundancy in order to reduce glitches in DAC. There had been suggested and analyzed the mathematical model of glitches in DAC with weight redundancy. There had also been proved that glitch amplitude is significantly influenced by the value of the voltage control of the DAC and the parasitic capacities of the digital keys. There had been shown that the attenuation time (duration) of the glitch is significantly influenced by the value of load resistance. The paper shows the expediency of using the DAC based on redundant positional number systems including Fibonacci p-codes. The simulation results prove that with the increase of the parameter p, the characteristics of glitch are significantly improved in comparison with the classical binary system, namely the amplitude and the attenuation time of glitch decrease.

In recent years, a tendency is established to reduce the size of orbital spacecrafts while preserving their functional capabilities. The modern element base allows to create inexpensive Earth-sensing satellites having 1U-2U form factor, which are capable to form images of the Earth's surface with the medium spatial resolution. To perform synthesis of such optoelectronic remote sensing equipment, a relatively simple calculation technique is required. In this article, a technique has been developed to estimate an information system "Earth’s surface – atmosphere – television camera". It allows to determine the basic parameters of a lens and a matrix detector of the television camera, based on harmonization of their resolution and providing a given spatial resolution on the surface of the Earth. By using the proposed technique, a lens and a matrix detector have been selected. They provide geometric resolution of 25 m at the orbit with a height of 600 km. The resulting technical solution enables to fulfil applied tasks, for example, in agriculture, and can be implemented in a nanosatellite with the 1U-2U form factor.

A GPU-based method of multi-volume rendering is described. the analytic results are supported by simulations of volume rendering on a number of scenes with function-based surfaces. our method supports a large number of volumes, complex translucent functional objects as well as constructive solid geometry intersections of volumes and function-based surfaces.

The results of experimental and theoretical studies are presented for the case when the vessel with water performs periodic reciprocating and oscillatory movements. The problem was solved in the linear approximation using the potential equation. From the results of experiments and an analytical analysis of the problem it follows that the first resonance frequency of the oscillation of a liquid in a vessel plays an important role in the character of the motion. At the same time, bifurcation occurs in the region of resonant frequencies, i.e. transitions from the plane motion of the liquid to the rotational motion and vice versa.

This article contains a more accurate method for estimating the minimum necessary order of a passive low pass filter using untunnable SMD components. To design analog filters of the VHF band, parasitic effects can lead to appreciable differences in the experimental characteristics from the modeling results obtained by the AFC approximation method. An compensation attempt for the components selection may take a long time and require topology changes, for example, to increase order.

The method for determining the absolute spectral sensitivity of fiber-optic spectrophotometers by brightness based on the use of a standard tungsten incandescent lamp is described. The reasons for the observed nonlinearity of the light characteristics of the AvaSpec 2048 spectrometer in the short-wave region of the spectrum are discussed. An example of the practical use of a fiber-optic spectrophotometer for recording spectra in the laser treatment of metals is given.

The results of an experimental study of obtaining approximate solutions of the multidimensional knapsack problem are presented in the paper. Three methods for obtaining these solutions are considered, based on branch-end-bound algorithms with a one-sided branching. One hundred test tasks of different dimensions have been solved for each method. The estimation of the approximation of the solutions obtained in relation to the best solution is provided, as well as the estimation of the computational complexity.