Estimation of the nonlinear dependence of the indications of a fiber Bragg grating on temperature and strain from experimental data

The readings of the Bragg grating are determined based on the optical radiation reflected from it. A quantitative characteristic of this radiation is the wavelength at which the maximum power of the optical signal is achieved. This characteristic is called the central wavelength of the grating. The central wavelength shift depends on temperature and strain. As a rule, a linear approximation of this dependence is used. However, from the available literature it is known that, the grating wavelength shift demonstrates a strong nonlinear dependence on temperature at 5<T<200K and a weak quadratic dependence close to room temperature. Thus far, the authors have not found studies that consider all terms in the quadratic expansion of the central wavelength of the Bragg grating as a function of temperature and strain at near-room temperatures. Our work is intended to fill this gap. The article describes an experiment in which an optical fiber with Bragg grating was subjected to loading using three different weights. A step-wise temperature change from 5 to 100 0С was realized for each weight. Based on these data, all terms of the quadratic expansion of the desired function are determined. The contribution of each term is estimated

Control of surface subsidence based on building deformation monitoring data

This paper presents an approach to the estimation of ground surface distortion based on the data from the online deformation monitoring systems mounted on the foundations of the group of buildings located in the area of ground instability. The local monitoring systems provide control of building foundation settlements using the hydrostatic level measurement technique. These data are used to calculate the inclination foundation angles which reflect the distortion of the earth's surface at local points. The hydrostatic level system allows one to perform measurements with the desired space and time sampling and to obtain a quite detailed picture of the changes in the deformation parameters over time. A set of such local monitoring units forms a distributed system that allows monitoring the state of the earth's surface over a large area. Here, we present long-term results obtained using such system located in the city area above mining. The evolution of the inclination angles of the group of overlying buildings is shown. We discuss the validity of this approach, and estimate the accuracy of the measuring method and the factors that influence it. Finally, we assess the possibility of making short-term predictions of deformation processes inside the rock massif

Control of surface subsidence based on building deformation monitoring data

This paper presents an approach to the estimation of ground surface distortion based on the data from the online deformation monitoring systems mounted on the foundations of the group of buildings located in the area of ground instability. The local monitoring systems provide control of building foundation settlements using the hydrostatic level measurement technique. These data are used to calculate the inclination foundation angles which reflect the distortion of the earth's surface at local points. The hydrostatic level system allows one to perform measurements with the desired space and time sampling and to obtain a quite detailed picture of the changes in the deformation parameters over time. A set of such local monitoring units forms a distributed system that allows monitoring the state of the earth's surface over a large area. Here, we present long-term results obtained using such system located in the city area above mining. The evolution of the inclination angles of the group of overlying buildings is shown. We discuss the validity of this approach, and estimate the accuracy of the measuring method and the factors that influence it. Finally, we assess the possibility of making short-term predictions of deformation processes inside the rock massif