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Combined Bending and Torsion Sensing by Induced Birefringence in Distributed Bragg Reflector Laser

Rodriguez, C. ; LEAL-JUNIOR, A. ; Marques, C. ; Leitão, C. Leitão ; André, P.S ; Antunes, P. ; Pontes, M. J. ; Frizera-Neto, A. Frizera-Neto ; R. N. Ribeiro, M. R. N. Ribeiro

IEEE/OSA Journal of Lightwave Technology Vol. 37, Nº 3, pp. 861 - 867, February, 2019.

ISSN (print): 0733-8724
ISSN (online): 0733-8724

Journal Impact Factor: 2,567 (in 2015)

Digital Object Identifier: 10.1109/JLT.2018.2882137

Abstract
Measurement of torque or twist angle, and mechanical bending is important in several fields such as structural health monitoring, movement analysis, robotics instrumentation and mechanical systems in general. Several optical fiber sensors have
been already proposed to measure these parameters separately. However, their high cost interrogation systems are the main
drawback for their large commercial application. Distributed Bragg reflector (DBR) allows to overcome this issue, since its inherent heterodyne behavior leads to interrogation schemes in the frequency domain instead optical domain reducing significantly the interrogation systems cost. In this context, this paper presents a DBR to measure twist angle. The enhancement
of twist sensitivity by bending-induced birefringence is analytically and experimentally demonstrated achieving a value
of -51.63 kHz/bending angle. With a constant bending angle of 20◦ a twist sensitivity of 571.4 kHz/twist angle is achieved, which represents a enhancing sensitivity by a factor of ∼15, when compared to some DBR sensor configurations reported in literature.