Interferometric optical fiber inclinometer with dynamic FBG based interrogation

Abstract

The development of an interferometric optical fiber inclinometer is described in this paper. A weak tapered region is induced in a standard single mode fiber in the vicinity of the cleaved fiber tip, using a standard fusion splicer. In this situation an in-fiber Michelson interferometer is constructed that is sensitive to curvature applied in the tapered region. It is shown that depending on the angular range, fringe visibility and/or peak position depend strongly on the applied curvature enabling low cost dielectric inclinometer to be setup that is suitable for high voltage applications. It is presented an analysis of the sensor response by means of experimental measurements and manipulation of these experimental data through computational simulations. The results coming from the numerical simulations indicate a good performance of the sensor within range of angular variation between 3 and 6 degrees and 10 and 14 degrees. A low cost strategy to interrogate the response of sensor using electrically modulated fiber Bragg gratings, a photodetector and frequency analysis is described. The results presented by this electric interrogation technique show a good sensitivity in the range 3.5 to 5.5 degrees.

Interferometric Interrogation of the Inclination and Displacement of Tapered Fiber Mach-Zehnder Interferometers

“…The measurement spectral resolutions for the inclination, wavelength shift over θ , and displacement, wavelength shift over displacement, are 1.275 nm per degree and 0.1 nm/μm, respectively. The inclination sensing resolution is at least one order of magnitude better than the aforementioned methods [4], [9], which use a single abrupt taper.…”

“…Moreover, the AT-MZIs contain two abrupt tapers; one of them serves as the reference point while the other acts as the sensing point. This design leads to better extinction ratios and higher sensitivity when compared with the references in [4], [9], [15], [16] based on reflection-type interferometric sensing. In this work, tunable AT-MZIs demonstrate an extinction ratio higher than 30.4 dB by introducing two adjacent abrupt tapers [5]- [10], in a short length of EYDF (Fibercore: DY1500Y), as shown in Fig.…”

“…1(a). The precision of measuring the inclination angle in this work is at least one order of magnitude higher than other sensors using abrupt tapers [4], [9]. This AT-MZI is a fiber comprised of two abrupt tapers, serving as a 3-dB fiber coupler, connected by a short span of untapered fiber, which serves as a monolithic phase shifter.…”