Support for the Vulnerability Management Process Using Conversion CVSS Base Score 2.0 to 3.x.

COVID-19 forced a number of changes in many areas of life, which resulted in an increase in human activity in cyberspace. Furthermore, the number of cyberattacks has increased. In such circumstances, detection, accurate prioritisation, and timely removal of critical vulnerabilities is of key importance for ensuring the security of various organisations. One of the most-commonly used vulnerability assessment standards is the Common Vulnerability Scoring System (CVSS), which allows for assessing the degree of vulnerability criticality on a scale from 0 to 10. Unfortunately, not all detected vulnerabilities have defined CVSS base scores, or if they do, they are not always expressed using the latest standard (CVSS 3.x). In this work, we propose using machine learning algorithms to convert the CVSS vector from Version 2.0 to 3.x. We discuss in detail the individual steps of the conversion procedure, starting from data acquisition using vulnerability databases and Natural Language Processing (NLP) algorithms, to the vector mapping process based on the optimisation of ML algorithm parameters, and finally, the application of machine learning to calculate the CVSS 3.x vector components. The calculated example results showed the effectiveness of the proposed method for the conversion of the CVSS 2.0 vector to the CVSS 3.x standard.

Learning to Classify DWDM Optical Channels from Tiny and Imbalanced Data.

Applying machine learning algorithms for assessing the transmission quality in optical networks is associated with substantial challenges. Datasets that could provide training instances tend to be small and heavily imbalanced. This requires applying imbalanced compensation techniques when using binary classification algorithms, but it also makes one-class classification, learning only from instances of the majority class, a noteworthy alternative. This work examines the utility of both these approaches using a real dataset from a Dense Wavelength Division Multiplexing network operator, gathered through the network control plane. The dataset is indeed of a very small size and contains very few examples of "bad" paths that do not deliver the required level of transmission quality. Two binary classification algorithms, random forest and extreme gradient boosting, are used in combination with two imbalance handling methods, instance weighting and synthetic minority class instance generation. Their predictive performance is compared with that of four one-class classification algorithms: One-class SVM, one-class naive Bayes classifier, isolation forest, and maximum entropy modeling. The one-class approach turns out to be clearly superior, particularly with respect to the level of classification precision, making it possible to obtain more practically useful models.

Machine Learning Algorithms for Prediction of the Quality of Transmission in Optical Networks.

Increasing demand in the backbone Dense Wavelength Division (DWDM) Multiplexing network traffic prompts an introduction of new solutions that allow increasing the transmission speed without significant increase of the service cost. In order to achieve this objective simpler and faster, DWDM network reconfiguration procedures are needed. A key problem that is intrinsically related to network reconfiguration is that of the quality of transmission assessment. Thus, in this contribution a Machine Learning (ML) based method for an assessment of the quality of transmission is proposed. The proposed ML methods use a database, which was created only on the basis of information that is available to a DWDM network operator via the DWDM network control plane. Several types of ML classifiers are proposed and their performance is tested and compared for two real DWDM network topologies. The results obtained are promising and motivate further research.

Infrared Laser Application to Wood Cutting.

While lasers are widely used across various industries, including woodworking, few studies to date have addressed the issue of cutting fresh wood. In the present investigation, wood stemming from fresh tree branches was cut at different laser powers and beam travel speeds. A fiber laser and a CO2 laser were used for the research. The cellular structures of the cut surfaces were examined, with some of them found to be covered with a layer of compacted, charred cells. This may be a favorable phenomenon, preventing the invasion of pathogens via the wounds caused by laser beam branch cutting in nurseries, plantations, and orchards.

Experimental Investigation of Actively Q-Switched Er3+:ZBLAN Fiber Laser Operating at around 2.8 µm.

A diode-pumped Q-switched Er3+:ZBLAN double-clad, single-transverse mode fiber laser is practically realized. The Q-switched laser characteristics as a function of pump power, repetition rate, and fiber length are experimentally investigated. The results obtained show that the Q-switched operation with 46 µJ pulse energy, 56 ns long pulses, and 0.821 kW peak power is achieved at a pulse repetition rate of 10 kHz. To the best of our knowledge, this is the highest-ever demonstrated peak power emitted from an actively Q-switched, single-transverse mode Er3+:ZBLAN fiber laser operating near 2.8 µm.

Experimental photoluminescence and lifetimes at wavelengths including beyond 7 microns in Sm3+-doped selenide-chalcogenide glass fibers.

1000 ppmw Sm3+-doped Ge19.4Sb9.7Se67.9Ga3 atomic % chalcogenide bulk glass and unstructured fiber are prepared. Near- and mid-infrared absorption spectra of the bulk glass reveal Sm3+ electronic absorption bands, and extrinsic vibrational absorption bands, due to host impurities. Fiber photoluminescence, centred at 3.75 µm and 7.25 µm, is measured when pumping at either 1300 or 1470 nm. Pumping at 1470 nm enables the photoluminescent lifetime at 7.3 µm to be measured for the first time which was ∼100 µs. This is the longest to date, experimentally observed lifetime in the 6.5-9 µm wavelength-range of a lanthanide-doped chalcogenide glass fiber.

Experimental observation of gain in a resonantly pumped Pr3+-doped chalcogenide glass mid-infrared fibre amplifier notwithstanding the signal excited-state absorption.

We demonstrate a maximum gain of 4.6 dB at a signal wavelength of 5.28 µm in a 4.1 µm resonantly pumped Pr3+-doped selenide-based chalcogenide glass fibre amplifier of length 109 mm, as well as a new signal excited-stated absorption (ESA) at signal wavelengths around 5.5 µm. This work to the best of our knowledge is the first experimental demonstration of gain at mid-infrared (MIR) wavelengths in a Pr3+-doped chalcogenide fibre amplifier. The signal ESA of the fibre is attributed to the transition 3H6 → (3F4, 3F3) after the pump ESA (3H5 → 3H6) at a pump wavelength of 4.1 µm, which absorbs the MIR signal at wavelengths of 5.37, 5.51 and 5.57 µm, and so spoils the amplifier's performance at these wavelengths. Thus, this signal ESA should be suppressed in a resonantly pumped Pr3+-doped selenide-based chalcogenide fibre amplifier.

Mid-infrared supercontinuum generation to 12.5µm in large NA chalcogenide step-index fibres pumped at 4.5µm.

We present numerical modeling of mid-infrared (MIR) supercontinuum generation (SCG) in dispersion-optimized chalcogenide (CHALC) step-index fibres (SIFs) with exceptionally high numerical aperture (NA) around one, pumped with mode-locked praseodymium-doped (Pr(3+)) chalcogenide fibre lasers. The 4.5um laser is assumed to have a repetition rate of 4MHz with 50ps long pulses having a peak power of 4.7kW. A thorough fibre design optimisation was conducted using measured material dispersion (As-Se/Ge-As-Se) and measured fibre loss obtained in fabricated fibre of the same materials. The loss was below 2.5dB/m in the 3.3-9.4µm region. Fibres with 8 and 10µm core diameters generated an SC out to 12.5 and 10.7µm in less than 2m of fibre when pumped with 0.75 and 1kW, respectively. Larger core fibres with 20µm core diameters for potential higher power handling generated an SC out to 10.6µm for the highest NA considered but required pumping at 4.7kW as well as up to 3m of fibre to compensate for the lower nonlinearities. The amount of power converted into the 8-10µm band was 7.5 and 8.8mW for the 8 and 10µm fibres, respectively. For the 20µm core fibres up to 46mW was converted.

Progress in rare-earth-doped mid-infrared fiber lasers.

The progress, and current challenges, in fabricating rare-earth-doped chalcogenide-glass fibers for developing mid-infrared (IR) fiber lasers are reviewed. For the first time a coherent explanation is forwarded for the failure to date to develop a gallium-lanthanum-sulfide glass mid-IR fiber laser. For the more covalent chalcogenide glasses, the importance of optimizing the glass host and glass processing routes in order to minimize non-radiative decay and to avoid rare earth ion clustering and glass devitrification is discussed. For the first time a new idea is explored to explain an additional method of non-radiative depopulation of the excited state in the mid-IR that has not been properly recognized before: that of impurity multiphonon relaxation. Practical characterization of candidate selenide glasses is presented. Potential applications of mid-infrared fiber lasers are suggested.

Arbitrary truncation order three-point finite difference method for optical waveguides with stepwise refractive index discontinuities.

An exact finite difference (FD) representation of the second-order derivative on three nodes is presented and used to obtain an FD algorithm that allows achieving an arbitrary truncation order. The FD weights are calculated analytically using the series that expresses the field value at a given FD node in terms of the field value and its derivatives at a neighboring node, when a stepwise discontinuity in the refractive index distribution is present between the nodes. The results obtained confirm that the proposed algorithm is accurate, efficient, and achieves the predicted improved performance.

Ligand recognition processes in the formation of homochiral C3-symmetric LnL3 complexes of a chiral alkoxide.

The reaction of a chiral racemic bidentate ligand HL1 (tBu2P(O)CH2CH(tBu)OH) with mid to late trivalent lanthanide cations affords predominantly homochiral lanthanide complexes (RRR)-[Ln(L1)3] and (SSS)-[Ln(L1)3]. A series of reactions are reported that demonstrate that the syntheses are under thermodynamic control, and driven by a ligand 'self-recognition' process, in which the large asymmetric bidentate L1 ligands pack most favourably in a C3 geometry around the lanthanide cation. The synthesis of bis(L1) adducts [Ln(L1)2X] (X=N(SiMe3)2, OC6H3tBu-2,6) is also reported. Analysis of the diastereomer mixtures shows that homochiral (L1)2 complexes are favoured but to a lesser extent. The complexes Ln(L1)3 and [Ln(L1)2(OC6H3tBu-2,6)] have been studied as initiators for the polymerization of epsilon-caprolactone and its copolymer with lactide, glycolide and its copolymer with lactide, and epsilon-caprolactam.

Generalized rectangular finite difference beam propagation method.

A method is proposed that allows for significant improvement of the numerical efficiency of the standard finite difference beam propagation algorithm. The advantages of the proposed method derive from the fact that it allows for an arbitrary selection of the preferred direction of propagation. It is demonstrated that such flexibility is particularly useful when studying the properties of obliquely propagating optical beams. The results obtained show that the proposed method achieves the same level of accuracy as the standard finite difference beam propagation method but with lower order Padé approximations and a coarser finite difference mesh.

Wide-angle, finite-difference beam propagation in oblique coordinate system.

The one-way wave equation in the oblique coordinate system in terms of the square root operator is derived. This equation forms the basis for the development of efficient algorithms using the beam propagation method for the design and optimization of integrated optical devices. In an illustrative example, using the derived one-way wave equation, Anada's very-wide-angle algorithm is generalized to the oblique coordinate system. Since in the oblique coordinate system the direction of propagation can be selected freely to follow the path of the optical beam and to minimize the stair-casing errors, the algorithm is expected to show superior performance, which is confirmed by the results obtained.