Laser-frequency locking techniques for high-sensitivity strain measurements by high-birefringence fiber Bragg gratings and resonators

M. Salza; G. Gagliardi; A. Di Maio; P. Ferraro; P. De Natale; E. Chehura; R. Tatam

doi:10.1117/12.738379

2 July 2007 Laser-frequency locking techniques for high-sensitivity strain measurements by high-birefringence fiber Bragg gratings and resonators

M. Salza, G. Gagliardi, A. Di Maio, P. Ferraro, P. De Natale, E. Chehura, R. Tatam

Author Affiliations +

Proceedings Volume 6619, Third European Workshop on Optical Fibre Sensors; 661915 (2007) https://doi.org/10.1117/12.738379
Event: Third European Workshop on Optical Fibre Sensors, 2007, Napoli, Italy

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..

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M. Salza, G. Gagliardi, A. Di Maio, P. Ferraro, P. De Natale, E. Chehura, and R. Tatam "Laser-frequency locking techniques for high-sensitivity strain measurements by high-birefringence fiber Bragg gratings and resonators", Proc. SPIE 6619, Third European Workshop on Optical Fibre Sensors, 661915 (2 July 2007); https://doi.org/10.1117/12.738379

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