Fiber Bragg-grating strain sensor interrogation using laser radio-frequency modulation

Year: 2005

Authors: Gagliardi G., Salza M., Ferraro P., De Natale P.

Autors Affiliation: Istituto Nazionale di Ottica Applicata and European Laboratory for Non-Linear Spectroscopy, Comprensorio “A. Olivetti”, Via Campi Flegrei 34, 80078 Pozzuoli (NA), Italy

Abstract: We demonstrate the possibility of using radio-frequency modulation spectroscopic techniques for interrogation of fiber Bragg-grating (FBG) structures. Sidebands at 2 GHz are superimposed onto the output spectrum of a 1560-nm DFB diode laser. The power reflected by an FBG is demodulated at multiples of the sideband frequency. The sideband-to-carrier beat signal is shown to be extremely sensitive to Bragg wavelength shifts due to mechanical stress. Using this method, both static and dynamic strain measurements can be performed, with a noise-equivalent sensitivity of the order of 150 n epsilon/root Hz, in the quasi-static domain ( 2 Hz), and 1.6 n epsilon/root Hz at higher frequencies ( 1 kHz). The measured frequency response is presently limited at 20 kHz only by the test device bandwidth. A long-term reproducibility in strain measurements within 100 n epsilon is estimated from laser frequency drift referred to molecular absorption lines. (C) 2005 Optical Society of America.

Journal/Review: OPTICS EXPRESS

Volume: 13 (7)      Pages from: 2377  to: 2384

KeyWords: Bandwidth; Fiber optics; Frequency modulation; Laser beams; Semiconductor lasers; Spectroscopic analysis; Strain measurement; Tensors, Mechanical stress; Radio-frequency; Sideband frequency; Strain tensor, Fiber Bragg gratings
DOI: 10.1364/OPEX.13.002377

Citations: 65
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