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Proceedings Paper

Laser-frequency locking techniques for high-sensitivity strain measurements by high-birefringence fiber Bragg gratings and resonators
Author(s): M. Salza; G. Gagliardi; A. Di Maio; P. Ferraro; P. De Natale; E. Chehura; R. Tatam
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Paper Abstract

A new approach to simultaneously interrogate orthogonal axes of single Fiber-Bragg-Gratings (FBGs) and FBG-Fabry Perot resonator sensors fabricated in linearly highly birefringent (HiBi) fibre is presented. Novel interrogation techniques of single Fiber-Bragg-Gratings (FBGs) and FBG-resonator sensors are presented. For a single FBG, we combined a laser-modulation technique to an electronic feedback loop that keeps the source always frequency locked to one peak of the sensor's reflected spectrum. Two different lasers, with orthogonally-polarized states, were adopted to monitor simultaneously both the "fast" and "slow" FBG peaks. The corresponding correction signals from the servo-loop outputs can be interpreted as strain or temperature induced on the FBG. Detection limits ranging from 1 n&Vegr;/&sqrt;Hz to 100 n&Vegr;/&sqrt;Hz, for axial dynamic and static deformations, respectively, and of 0.025 °C/&sqrt;Hz for temperature variations, are expected. A similar approach was developed for sub-pε resolution interrogation of an optical resonator made of a high-reflectivity FBG-pair, using the Pound-Drever-Hall (PDH) stabilization method..

Paper Details

Date Published: 2 July 2007
PDF: 4 pages
Proc. SPIE 6619, Third European Workshop on Optical Fibre Sensors, 661915 (2 July 2007); doi: 10.1117/12.738379
Show Author Affiliations
M. Salza, Istituto Nazionale di Ottica Applicata-CNR (Italy)
G. Gagliardi, Istituto Nazionale di Ottica Applicata-CNR (Italy)
A. Di Maio, Istituto Nazionale di Ottica Applicata-CNR (Italy)
P. Ferraro, Istituto Nazionale di Ottica Applicata-CNR (Italy)
P. De Natale, Istituto Nazionale di Ottica Applicata-CNR (Italy)
E. Chehura, Cranfield Univ. (United Kingdom)
R. Tatam, Cranfield Univ. (United Kingdom)


Published in SPIE Proceedings Vol. 6619:
Third European Workshop on Optical Fibre Sensors

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