IMPROVING OPTICAL FIBER SENSING BY MIMO SIGNAL PROCESSING
Andreas Ahrens
andreas.ahrens@hs-wismar.deHochschule Wismar, Philipp-Müller Straße 14, 23966 Wismar, Germany (Germany)
André Sandmann
Hochschule Wismar, Philipp-Müller Straße 14, 23966 Wismar, Germany (Germany)
Kort Bremer
Leibniz University Hannover, Nienburger Strasse 17, 30167 Hannover, Germany (Germany)
Bernhard Roth
Leibniz University Hannover, Nienburger Strasse 17, 30167 Hannover, Germany (Germany)
Steffen Lochmann
Hochschule Wismar, Philipp-Müller Straße 14, 23966 Wismar, Germany (Germany)
Abstract
Optical fiber sensors have reached a high state of maturity. Besides the high number of sensor groups, multi-mode fiber evanescent field sensors can be found in a lot of applications. Here, the signal source commonly excites many optical modes under steady-state conditions. Perturbations of the fiber then produce leaky modes. Thus, a simple intensity detector measures the degree of perturbation. In some cases also restricted mode launching conditions have been applied. They resulted in higher sensitivity but showed a narrower measurement range. Considering the individual modes as carriers of information we adapted multiple-input multiple-output (MIMO) signal processing which is well studied in the telecommunications community, for improvements on both the sensor sensitivity and its measurement range. In this paper MIMO signal processing is investigated for fiber optic sensor applications. A (2x2) MIMO implementation is realized by using lower-order and higher-order mode groups of a gradient-index multi-mode fiber as separate transmission channels. A micro-bending pressure sensor changes these separate transmission characteristics and introduces additional crosstalk. By observing the layer specific weight-factors of the MIMO system the amount of load applied was determined. Experiments verified a good correlation between the change of the MIMO weight coefficients and the load applied to the sensor and thus verified that MIMO signal processing can beneficially be used for fiber optic sensor applications. The experimental results also verified the superior sensitivity and measurement range when MIMO signal processing is utilized.
Keywords:
MIMO, optical fiber sensorsReferences
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Authors
Andreas Ahrensandreas.ahrens@hs-wismar.de
Hochschule Wismar, Philipp-Müller Straße 14, 23966 Wismar, Germany Germany
Authors
André SandmannHochschule Wismar, Philipp-Müller Straße 14, 23966 Wismar, Germany Germany
Authors
Kort BremerLeibniz University Hannover, Nienburger Strasse 17, 30167 Hannover, Germany Germany
Authors
Bernhard RothLeibniz University Hannover, Nienburger Strasse 17, 30167 Hannover, Germany Germany
Authors
Steffen LochmannHochschule Wismar, Philipp-Müller Straße 14, 23966 Wismar, Germany Germany
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