Sensor de diâmetro de fibra óptica de baixo custo

Abstract

The optical fiber has characteristics that favor the propagation of electromagnetic signals from one point to another, when compared to other waveguides. In addition, it can be used for small, medium and long distance communications. For each type of situation, different types of fibers may be used. In terms of manufacturing, control of the absolute diameter of the fiber in its two manufacturing steps (obtaining preform and pulling) is of paramount importance to ensure the standards and the transmission capacity in an optical communications system. For this control, the optical methods are among the most used, among which the diffraction method stands out. This process consists in identifying the minimum or maximum diffraction pattern when light interacts transversely with the fiber. In this sense, geometric parameters such as the distance between the fiber and the observation screen (detector), the amount of light maxima / minima and the wavelength of the laser light source, must be optimized in order to increase sensitivity to fiber diameter changes. Some usual methods in the pull step for the recording and recording of the pattern use a matrix of photodiodes or CCD (charge-coupled device). In addition, the data processing is performed through electronic circuit blocks or through an algorithm for the calculation of FFT (Fast Fourier Transform), which insert costs and processing capacity to the methods. In this context, this work presents a study for the optimization of the aforementioned geometric parameters, using diffraction patterns and image processing. The diffraction patterns were collected for the case of a stationary fiber using a digital camera and the image processing was performed in MATLAB, in order to verify the sensitivity of this low cost system.