Papers by Author: Oleg B. Vitrik

Abstract: A reflectometric approach is proposed for interrogation of multiple fiber Bragg grating (FBG) sensors recorded in a single fiber optic line, based on the differential registration FBGs’ response to a short probing laser pulse using conventional OTDR. A special optical layout has been developed allowing transformation of FBG’s spectrally modulated signals into intensity modulated signals and at the same time eliminating the susceptibility of the system to light power fluctuations. Threshold sensitivity of the method amounted to ~50 μstrain within the measurement range of ~4000 μstrain. The maximum number of FBGs interrogated by the proposed technique is estimated at several hundred, which by far surpasses the requirements of most practical applications. Due to its simplicity, efficiency and usage of conventional OTDR equipment the proposed FBG interrogation technique can find a wide range of applications, in particular in structural health monitoring.

Abstract: Correlation method for processing dynamic light scattering patterns observed when laser radiation passes through liquid media was developed. The method is based on procedure of spatial averaging of the data contained measured values of correlation functions of intensity of light scattered by moving small particles. The method allows one to measure particles diameters from 30 to 750 nm with measurement error less then 10%. The method makes it possible to decrease correlation functions measurement time down to 1 ms and provides opportunity to carry out measurements for different scattering angles simultaneously. The method offers a way of recognizing speckle pattern transformations caused by harmonic, translatory and Brownian motions of particles, and allows one to register influence of uncontrolled forces such as monochromatic and wideband acoustic fields upon particles size measurements results.

Abstract: Possibilities of obtaining quantitative information about the deformation influence on the SFMI with a small number of excited modes by using a correlation method are investigated. It was shown that usage of diffusive scatterer allows us to transform the radiation of SFMI to a speckle field which can easily be processed. The working range of the SFMI deformation measurements is 0 – 160 µm with precision up to 10 µm.