DBPapers
DOI: 10.5593/SGEM2014/B61/S24.028

TRENDS IN THE DEVELOPMENT OF MINIATURE OPTICAL ACCELEROMETERS

T. L. Grigorie, I. R. Edu, F. C. Adochiei
Wednesday 1 October 2014 by Libadmin2014

References: 14th International Multidisciplinary Scientific GeoConference SGEM 2014, www.sgem.org, SGEM2014 Conference Proceedings, ISBN 978-619-7105-20-9 / ISSN 1314-2704, June 19-25, 2014, Book 6, Vol. 1, 197-204 pp

ABSTRACT
The paper presents various structures conceived for acceleration detection based on optical principles. In this technological segment the efforts are usually concentrated on the development of fiber optic accelerometers and of fiber Bragg grating accelerometers. Principled, fiber optic accelerometers may encounter in different architectures. One of the most interesting is that the optical sensing element uses the principle of moiré fringes. In other architecture, the acceleration effect is manifested by changing the optical path travelled by a light wave in the free space between two mirrors, one of which is mobile, being rigidly attached to the proof mass of the accelerometer. In fact, the two mirrors form a Fabry-Perot interferometer as a resonant cavity having an optical resonant frequency dependent by the distance between them. It is also shown a fiber-optic accelerometer architecture, in which the light intensity is modulated by the position of the seismic mass. Optical accelerometer structure is similar to a Mach-Zender interferometer, optical path leading to changes in light intensity obtained by detecting the interference wave obtained directly from the light source and the optical path variable wave that propagates along the route: (light source) - (waveguide) - (seismic mass) - (waveguide) - photodetector (photodiode). The second category of optical accelerometers with a strong development is fiber Bragg grating accelerometers. The fiber Bragg transducer is an induced permanent filter in the middle of a piece of single-mode optical fiber, which reflects a narrowband signal. The filter is actually a diffraction grating formed by the periodic modulation of the refractive index of the fiber core. For different architectures the mathematical models and the resulted static characteristics are emphasized. Are also described and mathematically modelled some possible ways to optimize these input-output characteristics.

Keywords: inertial sensors, accelerometers, optical methods, mathematical models