DFB fiber laser sensor for simultaneous strain and temperature measurements in concrete structures

Richards, D. J., Hadeler, O. and Dakin, J.P. (1999) DFB fiber laser sensor for simultaneous strain and temperature measurements in concrete structures. Claus, Richard O. and Spillman, William B. (eds.) In Proceedings of Smart Structures and Materials 1999: Sensory Phenomena and Measurement Instrumentation for Smart Structures and Materials. vol. 3670, SPIE - The International Society for Optical Engineering. pp. 332-341 . (doi:10.1117/12.349744).

Abstract

A distributed feedback (DFB) fiber laser sensor for simultaneously measuring strain and temperature has been developed. The DFB fiber laser consists of a single fiber Bragg grating written in a low birefringent rare-earth doped fiber. By measuring the rf beat frequency between the two orthogonal polarized lasing modes and the absolute wavelength of one mode, both strain and temperature can be determined simultaneously to an accuracy of ± 3με and ± 0.04 degrees Celsius. Multiplexing capabilities make this sensor ideal for monitoring several locations within a civil engineering structure. Three gauge protection systems were developed to prevent damage to the fiber during embedment and insulate it from the high alkaline environment of the concrete. This sensor is easy to install, provides excellent strain transfer from the concrete to the optical fiber and is thin enough not to degrade the concrete structure.

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