Influence of shear strains on the phase of light transmitted through single-mode fiber optic strain sensors

David W. Jensen; Suresh P. Pai

doi:10.1117/12.207764

20 April 1995 Influence of shear strains on the phase of light transmitted through single-mode fiber optic strain sensors

David W. Jensen, Suresh P. Pai

Author Affiliations +

Proceedings Volume 2574, Pacific Northwest Fiber Optic Sensor Workshop; (1995) https://doi.org/10.1117/12.207764
Event: Pacific Northwest Fiber Optic Sensor Workshop, 1995, Troutdale, OR, United States

Abstract

Since the well-known demonstration of a fiber-optic strain gage by Butter and Hocker in 1978, significant refinements have been made in the area of fiber optic sensing, enabling the measurement of many different physical quantities, including strain, displacement, linear and circular acceleration, temperature, degree of cure in plastics, chemical compositions, pressure, acoustic waves, and fluid flow rates. Both analytical and experimental efforts have contributed to our current understanding of the relationship between the elongation of a host medium and phase changes in the light passing through an optical fiber. This paper describes research which partially fills in the remaining gap by quantifying the influence of shear strains on the phase change of light passing through an embedded optical fiber. In this experiment, optical fibers were embedded in 18-inch long by 2.25-inch diameter composite tubes. Three tubes were fabricated with axial fibers and one with a helical fiber, using a hand layup fabrication technique. These tubes were also instrumented with two strain gage rosettes. The tubes were subjected to pure torsional loads while the surface strains and the fiber-optic phase changes were measured. A modified all-fiber Mach-Zehnder interferometer with active homodyne feedback was used to determine the phase changes in the optical fibers due to the applied strains. The phase changes were also predicted using fundamental concepts of structural mechanics and existing phase-strain models.

Citation Download Citation

David W. Jensen and Suresh P. Pai "Influence of shear strains on the phase of light transmitted through single-mode fiber optic strain sensors", Proc. SPIE 2574, Pacific Northwest Fiber Optic Sensor Workshop, (20 April 1995); https://doi.org/10.1117/12.207764

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