This PDF file contains the front matter associated with SPIE Proceedings Volume 11456, including the Title Page, Copyright information, and Table of Contents.

The conference series on Optical Fibres and Their Applications (OFTA) is held in Poland since 1976, now every 18 months. It is organized alternately by two national optical fibre technological centres in Białystok (Technical University od Białystok) and Lublin (UMCS University and Technical University of Lublin). The conference gathers photonics experts from academic communities, technological, application, research and development, industrial, business, and administration ones. The Conference summarizes research, technical and application achievements of the involved national laboratories and enterprises, with participation of international guests. Since 1986, the conference is supported by SPIE via publications of the Proceedings. The conference gathers 100- 150 participants and 100 technical presentations. The XIX^th OFTA 2020, organized by Technical University of Białystok, was held in January 2020, and gathered similar number of persons and quality papers. Topical area of the optical fibre photonics conference embraces technology of active and passive optical fibres, active and passive components, sources and detectors, sensors, photonic devices, circuits and systems, photonic signal transmission, processing and networking. A digest of chosen OFTA 2020 research and technical works is presented.

New multicomponent titanate-germanate glasses were synthesized and their luminescence properties have been studied. The intense near-infrared luminescence bands are observed in titanate-germanate glass, which correspond to main laser transitions ⁴F_3/2 → ⁴I_11/2 (Nd³⁺), ⁴I_13/2 → ⁴I_15/2 (Er³⁺) and ⁵I₇ → ⁵I₈ (Ho³⁺) of rare earth ions. In particular, luminescence linewidths have been examined in relation to potential broadband near-infrared laser applications.

In the article, the effect of samarium ions doping on the spectroscopic and biological properties of 45S5 Bioglass® was presented. The luminescence spectra of doped glasses have been analyzed in the visible range under 405 nm laser excitation. The in vitro method for testing the apatite-forming ability of bioactive glasses was used. Crushed to 100μm fractions bioactive glasses were immersed in Simulated Body Fluid (SBF) prepared by the Kokubo method. The material was incubated at 37°C for 3 days and then the measurements of ions (Ca, Na, Si) release in SBF were carried out. The bioactivity test indicated that Sm³⁺ ions affect not only on the luminescent properties of the bioactive glasses but also their capability of creating the hydroxycarbonate-apatite (HCA) layer.

(Ga_0.4In_0.6)₂Se₃ thin films were deposited by thermal evaporation technique. Refractive index and extinction coefficient dispersions were obtained from the spectral ellipsometry measurements. The dispersion of refractive index is described in the framework of Wemple-DiDomenico model. The energy pseudogap and Urbach energy were determined from the optical absorption spectrum of (Ga_0.4In_0.6)₂Se₃ thin film. Optical parameters of (Ga_0.4In_0.6)₂Se₃ thin film and single crystal were compared.

The given data on the optical arrangement, in which the coordinate distributions of the real and imaginary component of the elements of the Jones matrix of optically thin polycrystalline layers are determined. Algorithms are presented and an experimental method for measuring the real and imaginary component of Jones-matrix images is analyzed. The experimental results of the study of statistical, correlation, and fractal parameters, which characterize the real component of the Jones-matrix image of polycrystalline networks of flat layers of the main types of human amino acids, are presented.

Hollow core, anti-resonant fiber with 65 μm core diameter is used for transmission of ultrashort laser pulses under 100 fs at a central wavelength of 1560 nm from a mode-locked laser. Meter-scale lengths of the fiber (up to 3 m) and bend radii down to 6 cm are considered. Cross-correlation frequency-resolved optical gating is used for investigation of performance of the fiber in this application. Achieved results on dispersive stretching of the pulse up to around 200 fs are compared with nonlinear propagation simulations, performed using the generalized nonlinear Schrödinger equation parametrized with measured characteristics of the fiber. Dechirping of the pulse to its original shape in the fiber under bending is observed and related to suppression of higher-order modes. As shown, the proposed fiber can be used to transmit sub-100 fs long laser pulses without spectral or temporal distortions providing a 6 cm radius loop.

The paper deals with a design method of multi-order diffractive intraocular lenses (IOL) that we have developed in order to correct chromatic aberration. It is shown that in order to prevent a color halo around the focused image the phasematching number is selected to attend at each point of the image three color components to get quality image. A computer simulation of multi-order diffractive lens (MODL) in a schematic model of the human eye was carried out. The calculated MODL focuses white light into a segment on an optical axis with high diffractive efficiency. More research needed to study an aberration analysis of lenses of this type.

Among the various characteristics of infrared radiation, the degree of polarization is not often used in radiation analysis. The main reason is that polarization is less informative characteristic compared to others for most practical tasks. Also obtaining polarized radiation in infrared spectrum is relative complex and expensive act. In some cases, such as remote sensing, the improvement of spatial, radiometric and spectral resolution approaches it’s physical limit. It becomes relevant to obtain additional information of a different nature, such as polarization information. Modern infrared radiation polarizers based on diffraction gratings are quite expensive. The article explores the possibility of creating infrared polarizers based on a planeparallel plate, to which radiation falls at an Brewster angle. It is shown that the polarizer operating on transmittance will be more efficient than reflecting radiation polarizer, since it does not deviate the optical axis by a significant angle. Such a polarizer provides a polarization degree of 90% and a transmittance of about 50%.

This paper investigates the relationship between the integral equation and Kirchhoff approximation in the diffraction theory of coherent radiance. The spectrum of the reflected wave is formed in the far field (Fraunhofer zone) and the solution is to Fourier transform of effective reflectance coefficient of a surface. In the paper, the analytical relationship between the method of solving an integral equation and the Kirchhoff approximation has been proven. It helps to define the structure of the field of diffracted waves in a Fraunhofer zone for coherent scattered light. The analytical equations for calculation of the average value of intensity scattering field and the mirror reflection coefficient of a rough surface have been obtained. Analysis of the components of the scattering coherent light coming from a metal surface has been improved. It helps to specify the data processing algorithms for evaluation of statistical characteristics of rough surfaces.

A prototype of the optical fiber current sensor with external conversion has been developed at the Department of Optoelectronics of Silesian University of Technology. The prototype which has been extensively tested will be applied to measure electric currents at voltages of magnitude 30 kV. Therefore, voltage strength tests were carried out as part of this work. The results presented in this work show good insulating properties of the tested prototype sensor. Our studies also allowed determination of the impact of lightning impulses on the metrological properties of the sensor.

A very important problem in modern medicine is the identification of atherosclerotic lesions within human tubular vessels. Current methods such as OCT and intravascular ultrasonography are very expensive and do not provide conclusive information about the formation of atherosclerotic plaques, especially within the human thoracic aorta. This paper presents a new solution to the identification of atherosclerotic lesions based on a specially constructed endoscope that uses CCD cameras. The endoscope analyses the condition of the walls of the blood vessels (side analysis) and represents a step towards an in vivo investigation of part of the human body. The remaining problem is the exact identification of the places where changes occur in the human tubular vessels. Research using the fluorescence phenomenon gives a summary result from an area whose location can be determined with an accuracy of millimetres. For pipes with sufficiently large internal diameter CCD cameras can be used to produce images of the examined tissues. It is possible for doctors to use the images so obtained to identify diseased areas with high accuracy. An alternative approach for identifying atherosclerosis is to use a neural network method to analyse the received pictures. Popular methods such as Machine Learning and Deep Learning can also be used to identify features in medical images. Creating a ‘learning’ database of endoscopic images in which a doctor identifies regions of healthy and atherosclerotic tissue is time consuming. However, after creating the database, the image identification algorithm works much faster than known numerical methods. It can significantly contribute to improving the effectiveness of atherosclerosis diagnostics. This paper presents initial results that confirm the effectiveness of a Machine Learning approach in identifying atherosclerotic lesions from the analysis of endoscope images obtained with a black and white camera following fluorescence stimulation and with a colour CCD camera using white light illumination. These findings are important since histological tests are not possible in in vivo investigations.

New modifications of the Cook-Torrance and Ward models are proposed, which differ from the known uses when calculating only one function and smaller degrees of polynomials, which makes it possible to improve the performance of three-dimensional image formation taking into account the offset properties of surfaces.

The article investigated the optical-frequency gas flow meter based on a transistor structure with negative differential resistance (NDR). A schematic diagram and design of an optical-frequency gas flow transducer that operates in the microwave range (0.85 to 1.5 GHz), which consists of a bipolar and field-effect transistor with a Schottky barrier, is proposed as a photosensitive element using a photoresistor. A mathematical model of an optical-frequency gas flow meter based on a transistor structure with negative differential resistance has been developed, which allows one to obtain the main characteristics of the transducer in a wide frequency range. Theoretically and experimentally, the possibility of controlling both the reactive component and the negative differential resistance from changes in control voltage and power is shown, it extends the functionality of optical transducers and allows linearization of the conversion function within (0.1 - 0.2)%. Experimental studies have shown that the greatest sensitivity and linearity of the conversion function of an opticalfrequency gas flow transducer lies in the range from 3 V to 3.5 V. The sensitivity of the developed optical-frequency gas flow transducer based on a transistor structure with NDR is 146 kHz/liter/hour, and the measurement error is ± 1.5%.

The possibilities of optical capillaroscopy to determine microcirculatory disorders are considered. Methods for evaluating microcirculation by measuring the size of a pillar and its departments, as well as the speed of capillary blood flow, which may indicate a state of microcirculation in general are proposed. The physical model of the capillary is considered, as well as the classification of the stages of microcirculation disturbance, which is used to form a medical conclusion about the severity of hemodynamic disorders. Also, for the system of computer capillaroscopy, methods for calibrating and segmenting images of microvessels are proposed.

The work is devoted to the modern method of diagnosing skin diseases - video dermoscopy in the ultraviolet spectrum. The main features of the method are considered. The features of image processing and analysis for HC-video dermatoscopy are proposed for consideration. The main stages of processing HC-video dermoscopic images are considered. The main emphasis is placed on the methods of automated segmentation of HC-videodermoscopic images and the analysis of the errors that arise in this case. The stages of preliminary and post-processing of UVvideodermoscopic images are examined in detail. The main aspects of the automated analysis of dermoscopic image processing and the prospects of using such systems in medical practice are considered.

The method of mapping the ellipticity of the polarization image of blood plasma films and the analysis of the statistical moments of the obtained distributions underlies the evaluation of the mammary gland condition is considered in the article. Indicators of sensitivity and specificity of this method were evaluated and graphs of ROC curves for control group, malignant group and benign group were constructed.

The article describes the foundations of using method of using laser Doppler flowmetry in evaluation of the state of blood microcirculation system in students, future software engineers. By the method of laser Doppler flowmetry (LDF) individually-typological features of indicators of tissue blood flow in conventionally healthy adolescent students aged 17-20 years have been studied. Due to the results of research 3 types of LDF-grams have been defined: aperiodic, monotonous low amplitude, sinusoidal type with high perfusion. Among the examined students, future engineersprogrammers different frequency of appearing microcirculatory types with predominance of normoemic type with characteristic “aperiodic” LDF-gram has been found.

The article deals with changes in the amplitude-frequency spectrum of blood flow fluctuations in the perioperative period in patients with adhesive intestinal obstruction using computer diagnostics. To study the state of the microcirculatory bed and the mechanisms of its regulation, laser Doppler flowmetry was performed. Available results indicate significant changes at the level of the microcirculation system. Violation of blood circulation of tissues and decrease in body temperature at the end of surgery leads to hypoxia of organs and systems of the body, their dysfunction, and subsequently, insufficient functioning of the parenchymal organs and the development of complications.

Nowadays, the medical infrared thermal imaging (MITI) techniques can provide good quality images in real-time for monitoring and pre-clinical diagnostic of the diseases caused by inflammatory processes by showing the thermal abnormalities present in the body. MITI allows specify of the functional changes in the normal temperature distribution on the surface of the body, as well as enables refinement the localization of functional changes, the activity of the process, its prevalence and the nature of the changes – inflammation, stagnation, malignancy, etc. Due to its non-contact, non-invasive and non-destructive way of using, this technology has a distinct advantage among other diagnostic methods. Therefore, the main objectives of this research work were automated steps of feature extraction and analysis MTIs, i.e. to develop novel algorithm for quantitative interpretation of thermal images database, to improve the experimental protocol of obtaining thermal images and to perform an extensive field measurement in the selected cohort of patients, in our case, with spinal diseases, in order to provide an immediate high-quality solutions in real time clinical validation of the proposed method.

The current state of poultry farming requires the development and application of modern technologies for daily young fledge. Young fledge of high quality guarantees the maximum profit of the production in case of its further growth. It is known that to obtain a healthy, high-immunity young fledge it is necessary to implement an effective process of the eggshell surface disinfection. Therefore, the search and development of highly efficient hatching egg disinfection technologies is an urgent task.

The paper presents basics of the C-RAN network architecture, based on fiber-optic networks, for solutions targeted at 5G mobile systems. Service aspects of work the optical fronthaul (FH) and optical midhaul (MH) are presented. Such networks will constitute main component connecting the virtual baseband unit (vBBU) cloud and the physical active antenna (AAU)/ optical remote radio head (O-RRH) nodes. Calculations were made to indicate the impact of optical fiber path/link delay parameters on the functioning of a interface using D-RoF or A-RoF formats. Simulations of 5GRFoF signal transmission over the fiber-optic FH path up to 20km in length were carried out. During the simulation, the 5G-NR signal according to Rel-15/16, i.e. CP-OFDM with the maximum number of subcarriers supported by 4096-point DFT/FFT was used in the radio channel. Selected simulation results have been summarized in tabular form and in the form of visualization of the 256-QAM constellation. The summary indicates the need to consider the static parameters of the FH/MH fiber-optic link when synchronizing signals delivered to gNB-DU as a remote AAU/O-RRH group.

The paper presents the need to introduce new network solutions that will be able to significantly increase the efficiency of product manufacturing and delivery in the near future. Under Industry 4.0, so-called private networks based on 5G and IoT technologies will be introduced in an increasing number of industrial plants around the world. The combination of private and public network resources will significantly increase the potential of IoT solutions, as this will enable the combination of production, analytical and logistics processes. Fast decision-making systems, efficient transmission of massive data can be realized only thanks to fast and capacious fiber-optic networks. The paper suggests that fiber networks, also based on multi-core fibers, be introduced where copper cabling is still used for communication. It was also indicated that in order to increase the security and capacity of links in the radio domain, part of the link should be replaced by an optical wireless interface working in the future Li-Fi standard or its evolutionary version based on invisible light communication (inVLC) mode.

Currently, most operators are developing two separate fiber access networks: FTTH and Mobile, with its own rules of designing, cables dimensioning, redundancy etc. 5G at its later stage of development will enforce the aggregation of these two fiber networks in different planes that means technical aspects, regulators, security etc. The paper deals with this elements in order to predict different scenarios of future convergence and taking into account the operators perspective, for whom such issues as competition, security, technological compatibility, costs, etc. are of key importance.