Name: Ingrid Andrade Reis
Type: MSc dissertation
Publication date: 22/10/2021

Namesort descending Role
Evandro Ottoni Teatini Salles Advisor *

Examining board:

Namesort descending Role
Evandro Ottoni Teatini Salles Advisor *
Maria Jose Pontes Internal Examiner *
Shirley Peroni Neves Cani External Examiner *

Summary: In multimode optical fibers, a speckle pattern, or specklegram, appears at the output of the fiber when illuminated by coherent light. In this case, the phenomenon responsible for generating the specklegram is the interference between the different modes propagating in the fiber. Considering the sensitivity of this pattern to changes in the optical fiber, sensors capable of detecting different types of disturbances, such as vibrations, stress and displacements, have been developed. Previous works show that there is a correlation between the distance at which a disturbance is generated in an optical fiber and the changes that occur in its speckle pattern. Due to its granular appearance, it is proposed in this work a speckle pattern image classification system using neural networks based on features extracted by texture descriptors, in order to assess whether such aspects can also represent
the specklegram. For this, two datasets containing images obtained by experiments with polymeric optical fibers were used and, for each one, the results of accuracy for different sets of characteristics were compared. They were extracted by two texture extractors, the Local Binary Pattern (LBP) and the Gray Level Co-occurrence Matrix (GLCM). The results showed that it was possible to classify the location of the perturbations, especially when using the uniform and rotation-invariant LBP operator applied to the images when
divided into 25 blocks.
Keywords: Feature Extraction, Texture Analysis, Speckle, LBP, GLCM, Neural Network.

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