FIBER-OPTIC ACCELEROMETER FOR CONTROL OF PIPELINE LEAKAGES BASED ON TWO COMBINED ADDRESSABLE FIBER BRAGG STRUCTURES WITH WAVE AND PHASE-WAVE COMPONENTS. MATHEMATICAL MODELS

Abstract

Pipeline leakage detection remains an important issue, especially for the development of smart energy. Various non-destructive testing methods for pipeline leak detection have been actively developing since the end of the last century. However, research needs and technological problems still remain, especially at the stage of their implementation in practice of thermal and nuclear power plants. Researchers have shown great interest in the vibration method of leak detection. The signal of the natural frequency of pipe vibrations is monitored using an accelerometer, the parameters of which change when leaks appear. Recently, such accelerometers are based on fiber-optic technologies using one or more fiber Bragg gratings (FBG) with well-known advantages and disadvantages. The latter are mainly associated with the need to use an expensive optical spectral device for their interrogation - an interrogator. The emerging way to eliminate this drawback is the transition to budget radio-photonic interrogators operating in the radio frequency range and sensitive elements adapted to them - addressable fiber Bragg structures (AFBS). In the simplest case, AFBS are two FBGs, spectrally separated by a unique frequency that does not change under any conditions, also lying in the radio frequency range. The article consistently considers the issues of synthesis of the functional optoelectronic circuit of the microwave photonic accelerometer, based on two combined AFBS with wave and phase-wave components operating on reflection, a mathematical model of the process of adjusting the accelerometer in the region of its operating point, as well as a mathematical model of the process of measuring vibrations using their frequency localization on a known scale of an optical filter with an inclined linear characteristic through the difference in the components of two AFBS, wherein the relative position of the components inside the AFBS is known in advance.