Multipoint temperature-independent fiber-Bragg-grating strain-sensing system employing an optical-power-detection scheme.

A temperature-independent fiber-Bragg-grating strains-sensing system, based on a novel optical-power-detection scheme, is developed and analyzed. In this system a pair of fiber Bragg gratings with reflection spectra either partially or substantially overlapping is placed side by side to form a temperature-independent strain-sensor unit. Conventional wavelength-interrogation techniques are not used here, and instead an optical-power-detection scheme is proposed to directly calibrate the measurand, i.e., the strain. Unlike the conventional approach in a multiplexed sensing system, the presented power-detection-based interrogation method does not need the fiber-Bragg-grating sensors to be spectrally separate. The only requirement is that the spectra of the two fiber Bragg gratings of each sensor unit in a multiplexed system be identical or slightly separate (slightly overlapping spectra would also work in the sensing scheme) and the source's optical power be sufficient for sensitive measurement. Based on a three-sensor-unit system, we demonstrate simple strain measurements of high linearity (+/- 0.4%), good sensitivity [2 microstrains (microS)], high thermal stability (+/- 0.8%), and zero cross talk. The effects of light source spectral flatness and fiber bending loss on measurement accuracy are also discussed.

[1]  Martin A. Putnam,et al.  Interrogation of 60 fibre Bragg grating sensors with microstrain resolution capability , 1996 .

[2]  Vincent A. Handerek,et al.  High resolution fibre Bragg grating sensor demodulation using a diffraction grating spectrometer and CCD detection , 1997 .

[3]  G. Johnson,et al.  Fiber Bragg grating interrogation and multiplexing with a 3/spl times/3 coupler and a scanning filter , 2000, Journal of Lightwave Technology.

[4]  H. Tam,et al.  Fiber Bragg grating cavity sensor for simultaneous measurement of strain and temperature , 1999 .

[5]  Moshe Tur,et al.  Static fiber-Bragg grating strain sensing using frequency-locked lasers , 1999 .

[6]  Michael A. Davis,et al.  Fiber grating sensors , 1997 .

[7]  D. Jackson,et al.  Simple multiplexing scheme for a fiber-optic grating sensor network. , 1993 .

[8]  Hwa-Yaw Tam,et al.  Simultaneous strain and temperature measurement using a superstructure fiber Bragg grating , 2000 .

[9]  John P. Dakin,et al.  Discrimination between strain and temperature effects using dual-wavelength fibre grating sensors , 1994 .

[10]  A. Kersey,et al.  Bragg grating-based laser sensors systems with interferometric interrogation and wavelength division multiplexing , 1995 .

[11]  Byoungho Lee,et al.  Temperature-independent strain sensor using a chirped grating partially embedded in a glass tube , 2000 .

[12]  I. Bennion,et al.  Multiplexed identical broad-band-chirped grating interrogation system for large-strain sensing applications , 1997, IEEE Photonics Technology Letters.

[13]  J. Mora,et al.  A magnetostrictive sensor interrogated by fiber gratings for DC-current and temperature discrimination , 2000, IEEE Photonics Technology Letters.

[14]  Faramarz Farahi,et al.  Frequency-modulated multimode laser diode for fiber Bragg grating sensors , 1998 .

[15]  A. Kersey,et al.  High-resolution fibre-grating based strain sensor with interferometric wavelength-shift detection , 1992 .