Strain detection and measurement using a matched fibre Bragg grating

Abstract

We present and describe a method to demodulate the incoming strain signal from sensors based on fibre Bragg gratings (FBGs). This demodulation is achieved by using a reference FBG with similar characteristics to those of the FBG sensor as a band-pass filter to recover the total power in the detected signal from the shift in the Bragg wavelength caused by the strain experienced by the FBG sensor. From the experimental data and the numerical simulation, the system static transfer characteristic curves are obtained and compared. Using this method, a linear measurement range of 227 pm (183 με), along with a precision of 0.8 με and a resolution of 1.6 με were achieved. This simple and inexpensive method is a practical alternative to conventional FBG interrogation units because few optical elements are used in the set-up, and the Bragg wavelength shifts are determined by the changes in the detected optical intensity. These intensity changes are caused by the mechanical axial strain experienced by the FBG sensor.

Keywords:

• Demodulation
• fibre Bragg grating
• interrogator
• sensor
• strain

Acknowledgements

M. A. Casas-Ramos is grateful to CONACYT for the financial support in the form of a scholarship for the Master’s and PhD Engineering Program through the Universidad Nacional Autónoma de México.