Dual-Wavelength Speckle-Based SI-POF Sensor for Cost-Effective Detection of Microvibrations

In this work, a novel method for cost-effective remote sensing of microvibrations is presented. The proposed technique detects periodical changes in the spatial distribution of energy on the speckle pattern at the endface of a SI-POF. By employing a dual-wavelength approach it is possible to increase the system sensitivity without changing its maximum mean squared error, which increases the system accuracy as well as its resolution. The system operates in reflective configuration providing a centralized interrogation scheme. The speckle pattern of both wavelengths is demultiplexed at the fiber end before being directly recorded by an off-the-shelf and a cost-effective webcam. The changes in the intensity distribution are processed at the remote interrogation unit. The proposed system is able to detect instantaneous and periodic microvibrations (with amplitudes ranging from 1 to 6 μm) localized farther than 9 m from the remote interrogation unit.