FIBRE OPTIC BRAGG STRUCTURES WITH MONOTONIC APODISATION CHARACTERISTICS

The article discusses the principle of operation and the structure of chirped and uniform gratings. It presents the method of producing gratings with monotonic apodisation characteristics, and compares the spectral features of produced gratings with the those obtained by mathematical modelling.

Microwave Bragg structures in a half-open coaxial line

Bragg microwave structures in a coaxial line have found application as converting elements in devices for dielectric control of liquid and bulk medias. A feature of the measuring conversion of the complex dielectric constant in coaxial structures is the introduction of the substance under study into the inner space of the line. The latter circumstance imposes certain restrictions on the design of the external conductor for express control. In this regard, the consideration of half-open coaxial lines based on an external conductor in the form of longitudinal conducting rods is an urgent problem. The article proposes a method for calculating the wave impedance of a half-open coaxial line using a numerical calculation of electromagnetic fields. Based on the results of modeling Bragg microwave structures in a half-open coaxial line, recommendations are made for the construction of conversion elements based on them.

Повышение мощности и улучшение направленности излучения широкоапертурных гетеролазеров при оптимизации размеров брэгговской решетки

We investigate the dynamics of heterolasers with finite-length planar Bragg structures. Based on the analysis of the dispersion equation describing the eigenwaves propagation in a Bragg structure, we present a physical interpretation of selection of modes with frequencies higher than the stopband. We demonstrate the improvement of stability by using the Bragg structures with transverse dimensions lower than the width of the active area of DFB heterolasers. As a result, the single-mode oscillation regime is sustained over a wider range of pump levels, and, correspondingly, of the output radiation power.

Addressed Fiber Bragg Sensors for Vibration Diagnostics of Complex Objects

The paper presents the results of a study of the concept of address fiber Bragg structures in the problem of vibration control. The mathematical model of measuring transformation is presented; the experimental study of a vibration diagnostics system based on Address Fiber Bragg Gratings is carried out; the quantitative and qualitative comparative assessment with electronic accelerometers is made; the gain by an order of magnitude in some parameters is shown.

Addressed Fiber Bragg Structures in Load-Sensing Wheel Hub Bearings

The work presents an approach to instrument the load-sensing bearings for automotive applications for estimation of the loads acting on the wheels. The system comprises fiber-optic sensors based on addressed fiber Bragg structures (AFBS) with two symmetrical phase shifts. A mathematical model for load–deformation relation is presented, and the AFBS interrogation principle is described. The simulation includes (i) modeling of vehicle dynamics in a split-mu braking test, during which the longitudinal wheel loads are obtained, (ii) the subsequent estimation of bearing outer ring deformation using a beam model with simply supported boundary conditions, (iii) the conversion of strain into central frequency shift of AFBS, and (iv) modeling of the beating signal at the photodetector. The simulation results show that the estimation error of the longitudinal wheel force from the strain data acquired from a single measurement point was 5.44% with a root-mean-square error of 113.64 N. A prototype load-sensing bearing was instrumented with a single AFBS sensor and mounted in a front right wheel hub of an experimental vehicle. The experimental setup demonstrated comparable results with the simulation during the braking test. The proposed system with load-sensing bearings is aimed at estimation of the loads acting on the wheels, which serve as input parameters for active safety systems, such as automatic braking, adaptive cruise control, or fully automated driving, in order to enhance their effectiveness and the safety of the vehicle.

Addressed Fiber Bragg Structures in Load Sensing Wheel Hub Bearings

The work presents an approach to instrument the load sensing bearings for automotive applications for estimation of the loads acting on the wheels. The system comprises fiber-optic sensors based on addressed fiber Bragg structures (AFBS) with two symmetrical phase shifts. A mathematical model for load-deformation relation is presented, and the AFBS interrogation principle is described. The simulation includes (i) modeling of vehicle dynamics in a split-mu braking test, during which the longitudinal wheel loads are obtained, (ii) the subsequent estimation of bearing outer ring deformation using a beam model with simply supported boundary conditions, (iii) the conversion of strain into central wavelength shift of AFBS, and (iv) modeling of the beating signal at the photodetector. The simulation results show that the estimation error of the longitudinal wheel force from the strain data acquired from a single measurement point was 5.44% with root-mean-square error of 113.64 N. A prototype load sensing bearing was instrumented with a single AFBS sensor and mounted in a front right wheel hub of an experimental vehicle. The experimental setup demonstrated comparable results with the simulation during the braking test. The proposed system with load-sensing bearings is aimed at estimation of the loads acting on the wheels, which serve as input parameters for active safety systems, such as automatic braking, adaptive cruise control, or fully automated driving, in order to enhance their effectiveness and safety of the vehicle.