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Magnetometric measurements are widely used to solve problems in geology, navigation, and a number of other areas. Currently, there is a tendency to miniaturize and reduce the cost of magnetometers. However, the readings of inexpensive magnetometers are distorted by errors, which requires a calibration procedure. The article describes mathematical error models that are used in most well-known scientific research and adopted in this work. Mathematical modeling of the measuring signals of the magnetometer is carried out, and the principle of calibration of the magnetometric sensor, based on the accurate measurement of changes in its spatial position in a constant magnetic field, is proposed and researched. Estimates are given of the accuracy of restoration of calibrated parameters and the signal restoration errors achievable when performing the calibration operations proposed in the study.

The paper studies the possibility of using a long short-term memory (LSTM) neural network to simulate the operation of a PID controller. A PID regulator has been implemented to control a heater with a temperature sensor by using the Arduino framework. An LSTM model trained on the controller data has been developed. It is shown that the neural network model quite accurately reproduces the regulator operation and can completely replace it. In addition, the applicability of this model as a detector of abnormal operation of the PID controller is shown.

The problem of traffic control is solved using a model-oriented method. To develop a mathematical model, an automaton formalism is proposed. In strict accordance with the problem conditions, the states of a deterministic finite automaton (DFA) and predicates of directed transitions are defined. To implement the DFA, a transition is made to the Harel diagram (statechart), which is a unified mathematical and software support for modern global modeling tools. The solution to the problem posed is proved constructively by a table of states with the corresponding dynamics and computational experiments of the selected scenario in advanced domestic and foreign instrumental environments for modeling the designated class of event systems. Computational experiments show complete agreement with constructive analysis.

Recent results on continuous-wave bismuth-doped fiber lasers for a wavelength region of 1.3 - 1.5 μm pumped with laser diodes (multimode semiconductor laser diodes) are presented. A concept of the development of such devices by an example of the laser level scheme is considered. The main features of operation of cladding-pumped bismuth-doped fiber lasers and their performance characteristics (efficiency, output power, stability) are discussed. In addition, the possibility of optimizing the parameters of these devices by changing the geometry of the inner cladding and dual-wavelength pumping is considered.

Generation of ultrashort mid-infrared pulses in Raman gas fiber lasers is investigated. Using a hollow-core revolver fiber filled with a mixture of molecular deuterium and hydrogen gases, Raman generation of ultrashort pulses at λ = 3.9 μm is realized for the first time. The pulse duration of 4.6 ps is obtained, and the pulse energy as high as 10 μJ is achieved at λ = 3.9 μm.

Quantum squeezed states of light, characterized by a reduced quantum uncertainty in one of the quadrature variables below the uncertainty of the vacuum state (below the standard quantum limit), play an important role in modern fundamental and applied research. This paper provides basic information about the properties and manifestations of squeezed states. A brief review of methods for obtaining and detecting quantum squeezed light is given, with special attention paid to fiber systems. The Kerr mechanism for generating squeezed states, which is implemented in various variants of fiber systems, is considered in detail. An experimental scheme for generating polarization-squeezed states based on a polarization-maintaining nonlinear fiber is presented. Various factors limiting squeezing are considered.

The paper overviews new means of photonics based on the use of stimulated Brillouin scattering (SBS) in optical fibers. The main attention is paid to the original configurations of narrow-band low-noise lasers and their potential applications for distributed fiber-based measurements.

A review of major noise processes affecting the operation of phase-sensitive coherent reflectometers is given. The overview may be useful for educational purposes. The measurement results obtained using modified single-mode fibers with artificial scatterers distributed along the fiber length are presented. The advantages of such fibers over the standard single mode fibers are demonstrated and analyzed. The relationship between the phase noise of the reflectometer signal and that of the probing laser is shown.

In this work, spectral and phase properties of dynamic population gratings in various samples of ytterbium fibers are studied at various powers of recording and pumping radiation. It turned out that, despite differences between the samples, power dependences have a similar character, which is determined by the gain in the fiber and the saturation power in it. It is shown that the phase of the dynamic grating takes on a constant value, changing it only at the instant of the transition from the absorption grating to the gain grating. Significant influence of the phase component in dynamic population gratings in ytterbium doped fibers is experimentally shown.

Under the action of light in plasmon resonance conditions, metal nanoparticles induce heat at the nanoscale. This effect forms the basis for thermoplasmon probing of phase changes occurring in nanoscale systems, the study of which is a key task in modern material science. Despite the obvious simplicity of this approach, enhanced absorption of light by resonant nanostructures does not guarantee the desired optical heating in cases where the thermal conductivity of the medium significantly exceeds the thermal conductivity of the plasmonic nanostructure. We propose an approach for creating controlled heating of plasmonic nanostructures by nanostructuring the surface of a thermostat, which is demonstrated using a thermoplasmonic metasurface, which is an array of TiN:Si voxels - a vertical system of titanium nitride (TiN) and silicon (Si) nanostructures on a silicon substrate. Plasmonic TiN nanostructures play the role of nanoheaters, and varying the height of silicon heat conductor makes it possible to control the temperature of heating of voxels at a fixed value of the pump intensity by controlling heat localization. A possibility of probing phase transitions in nanoscale systems is demonstrated by an example of thin polymer films using a thermoplasmonic metasurface and Raman spectroscopy.