Periodyczne struktury światłowodowe w optoelektronicznych czujnikach do pomiaru wybranych wielkości nieelektrycznych

Abstract

This work describes periodic fiber optic structures used in optoelectronic sensors and proposes sensor system solutions for measuring selected nonelectrical quantities. The main section of the work presents methods and systems to reduce the problem of dependence of the sensor parameters on the variable temperature when measuring various physical quantities using fiber optic sensors. The work contains a description of the chirp generation method in the FBG section to measure the strain and temperature. The sensor system design is presented, and the validity of the selection of grating parameters that are subsequently used to determine the strain and temperature is demonstrated. A method of obtaining information on the quantities measured using the chirp generated in the FBG is described. The work presents an analysis of the sensor response during the variable temperature and strain tests, determining the nonlinearity errors and sensitivity of the individual LPG parameters to the force. A method is described to enable simultaneous measurement of the temperature and two force components using sensors with fiber Bragg gratings. The advantages of this method when compared to the existing solutions for the force and temperature sensors are indicated. The next section describes a method for measuring the temperature and maximum value of the heterogeneous linear stress distribution, clearly stating the assumptions of the method. It also presents an algorithm for determining the uniform stress under a variable temperature, using a sensor model constructed for this purpose and the conjugate gradients method. The final section contains an interpretation of the Fredholm integral equation of the first type used to reconstruct the temperature and stress distribution; a proprietary method is proposed to determine the variable stress distribution at a variable ambient temperature. In summary, this work presents a comprehensive approach to the problems associated with measurements of selected non-electrical quantities using optoelectronic sensors with a closed optical path and fiber optic segments on which periodic changes in the refractive index have been induced in the form of Bragg gratings. The dependence of the sensor parameters on temperature is also considered. The work describes systems and methods allowing for temperatureindependent measurements or simultaneous measurements of a given nonelectrical quantity and temperature.