Sensing and detecting changes due to displacement, pressure, or dynamic vibration in an optical fiber, based on fiber Specklegram

In the field of electronic warfare, acquiring information, detecting, localization, and tracking the target is one of the most important topics in the support sector. Concealment and anti-jamming are significant needs in this sector. This research, by designing and analyzing the radiation-free structure of optical fiber sensing, took advantage of the property of the formation of speckle light spots in the output of the multi-mode optical fiber, and in addition to detecting the deformation of the optical fiber, which can be due to pressure or displacement, By processing the output signal of a photodiode placed at a suitable distance from the end of the fiber, the dynamic changes caused by mechanical vibration was detected and measured. In addition to the frequency, the vibration amplitude is also extracted. In this research, dynamic change was applied to a part of the optical fiber length by using a shaker drive device that can be controlled in terms of amplitude and frequency, and the signal output after amplification and filtering was detected and identified. The frequency range from 5 to 91 Hz and the displacement range of the fiber from 50 μm to above were tested. The frequency and amplitude of the shaker correspond to the output electrical signal, and the sensitivity was studied based on the fiber Specklegram. The detection and extraction of the frequency parameter of the mechanical stimulus and the displacement of the fiber through the processing of the speckle spots at the end of the optical fiber along with the sensitivity measurement towards the amplitude and low frequency are reported in this article.