Intrusion Detection System Based on Speckle Pattern Analysis

Advances in Optical Fiber Speckle Sensing: A Comprehensive Review

“…In Section 3, we mentioned two main problems of FSSs: the quasi-random and nonlinear transfer function (changing under drifting environmental conditions) and, as a result, signal fading. The first problem does not allow precise measurement of EFPs; rather, the sensor can detect some events disturbing the fiber, for example, heartbeats in medical applications [68,69] or intrusion into a secured territory in perimeter surveillance applications [70]. If the interferometric signal is detected using one PD (or camera pixel), the second problem, signal fading, does not allow reliable measurement of the perturbation amplitude.…”

“…It should be mentioned that the use of the absolute value of the alternating signal (e.g., sine shape) leads to the doubling of signal spectrum width [37]. In works [69,70,75], authors applied a time differentiation of the camera pixel's signal. The work [76] demonstrates the results of the application of various image processing algorithms (both intensity-based and correlation-based) for speckle pattern processing.…”

“…Further, the scope of potential applications expanded towards vibration measurement [37] and perimeter surveillance [104]. These applications as well as new directions have also been investigated in the following years: vibration [105], intrusion detection [70], security of museum collections [72], temperature sensors [106][107][108], strain [109,110], force sensors [111,112], tactile sensors for human-system interaction applications [111,113], monitoring of gas leakage along the pipelines [114], current sensors [115], displacement sensors [116][117][118][119], and bending sensors [120].…”

Machine Learning for Turning Optical Fiber Specklegram Sensor into a Spatially-Resolved Sensing System. Proof of Concept

“…At the other end of the fiber, a granular pattern is generated, called specklegram [6]. This specklegram (speckle pattern) is highly sensitive to external perturbations such as vibrations, temperature, or strain [1][2][3][4][5][6]. A multimode optical fiber carries many different optical paths.…”

“…In particular, the use of interferometers can provide exceptional vibration-sensing capabilities. Interferometric optical fiber sensors, like the fiber specklegram sensor (FSSs), exhibit remarkably good sensitivity to external vibrations which can be used as a sensing tool for applications such as non-contact patient monitoring [2,3] or surveillance [4,5]. The speckle phenomenon in optical fibers was described by Spillman et al who first realized about its utility as a sensing tool [6].…”