Continuous arbitrary strain profile measurements with fiber Bragg gratings

Abstract

A new distributed strain sensing technique using a fiber optic Bragg grating has been developed and tested. This is the first 'true' distributed strain sensor, to the authors' knowledge, with a high spatial resolution of about 1 mm. Since gratings can be made with a length of tens of centimeters, this new fiber optic measurement technique could have broad applications to smart materials and structures where monitoring of a continuous strain profile over a length of millimeters to tens of centimeters is needed. In this paper three different demodulation approaches are reviewed indicating a trade-off between a relatively simple measurement process for selected types of strain profile and a more complete measurement process that is suitable for any strain profile. Experimental results with different approaches are presented.

Development of smart composite structures with small-diameter fiber Bragg grating sensors for damage detection: Quantitative evaluation of delamination length in CFRP laminates using Lamb wave sensing

“…When FBG sensors are applied to the detection of ultrasonic waves, the relation between the gage length L of FBG sensors and the wavelength k of ultrasonic waves is important [35], since FBG sensors are also sensitive to non-uniform strain in the grating region [36]. When the FBG sensor is under non-uniform strain, the reflection spectrum of the FBG is deformed because various wavelength components return from the FBG depending on the strain distribution.…”

Comparison of Bragg and Polarimetric Optical Fiber Sensors for Stress Monitoring in Composite Materials

“…The main advantages of fiber Bragg gratings (FBGs) over other optic sensor schemes are its low cost, good linearity, wavelength multiplexing capacity, resistance in harsh environments and transduction mechanism which eliminates the need for referencing as in interferometric sensors [1][2][3][4][5]. FBG sensor technology is now on the verge of maturity after almost three decades of active research and development in this field.…”

Polarimetric and Bragg Optical Fiber Sensors for Stress Distribution and Temperature Measurements in Composite Materials

“…The main advantages of fiber Bragg gratings (FBGs) over other optic sensor schemes are its low cost, good linearity, wavelength multiplexing capacity, resistance in harsh environments and transduction mechanism which eliminates the need for referencing as in interferometric sensors [4][5][6][7][8]. FBG sensor technology is now on the verge of maturity after almost three decades of active research and development in this field.…”