A longitudinal stress and strain sensor based on the multimode POF Bragg gratings was analyzed. Several fiber modes were propagating in this multimode fiber, but two fiber modes were chosen for the stress and strain sensing. Variations of the peak wavelengths for both modes were approximately linear, but eventual discrepancies may be attributed to a certain vis-coelasticity of the fiber and measurement errors. The stress and strain coefficient was estimated to be about 5.3nm/N and 11.8 nm/%, respectively. Furthermore, the effective strain-optic constant and the Young's modulus of POF were calculated to be about 0.248 and 3.367 GPa. All the results based on such multimode POF gratings sensor for the measurement of refractive index, strain, temperature, etc.
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