An extrinsic fiber Fabry-Perot interferometer for dynamic displacement measurement

Abstract

A versatile fiber interferometer was proposed for high precision measurement. The sensor exploited a double-cavity within the unique sensing arm of an extrinsic-type fiber Fabry-Perot interferometer to produce the quadrature phase-shifted interference fringes. Interference signal processing was carried out using a modified zero-crossing (fringe) counting technique to demodulate two sets of fringes. The fiber interferometer has been successfully employed for dynamic displacement measurement under different displacement profiles over a range of 0.7 µm to 140 µm. A dedicated computer incorporating the demodulation algorithm was next used to interpret these detected data as well as plot the displacement information with a resolution of λ/64. A commercial displacement sensor was employed for comparison purposes with the experimental data obtained from the fiber interferometer as well as to gauge its performance, resulting in the maximum error of 2.8% over the entire displacement range studied.

A High Sensitivity of Vital Signs Detector using Fiber Optic-based Fabry-Perot Interferometer

“…Consequently, the 96% light beam is to be reflected back to the fiber as the "sensing signal ". The interference signal is, ultimately, generated when the two light beams are superpositioned, with the intensity of the modulated signal (I) depicted by [8][9]:…”

“…Coincidentally, ∆φ is related to the displacement length from the fiber cave-end to the sensing target (∆d), along with the number of fringes (N f ). These could be mathematically described as [8][9], [15]:…”

“…high sensitivity & precision, electromagnetic immunity [8][9]. Consequently, there are many medical instruments that have, recently, adopted FOS to improve their performance [10].…”

“…Particularly, the interesting parameters of HR, systolic blood pressure (SBP), and also diastolic blood pressure (DBP) are measured via the FFPI sensing principles. Furthermore, signal demodulation has been completed by applying the deflection of material and fringe counting techniques [8][9].…”

In-Fiber Collimator-Based Fabry-Perot Interferometer with Enhanced Vibration Sensitivity

“…The optic fiber sensors based on Fabry-Perot interferometers (FPIs) [1,2,3,4,5,6,7] have been attracting significant attention into broad range of physical [8], chemical [9,10], and biomedical [1,3,11,12] fields in recent years, due to their unique advantages, such as compact size [8,9,13], easiness for integration [6,14], immunity to electromagnetic interference [7], and resistance to high temperatures [8]. The intensity changes in their interference spectra, caused by small spatial displacements [6,15,16], makes these sensors ideal for detecting vibrations with high accuracy.…”