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Published on: September 30, 2019
In-fiber directional coupler for high-sensitivity curvature measurement
J R Guzman-Sepulveda1, D A May-Arrioja
1Fiber and Integrated Optics Laboratory, UAM Reynosa-Rodhe, Universidad Autónoma de Tamaulipas, Carr Reynosa-San Fernando S/N, Reynosa, Tamaulipas 88779, México.
Abstract:
A curvature fiber optic sensor using a two-core fiber (TCF) is proposed and demonstrated. The TCF is designed to operate as a directional coupler with one core located exactly at the center of the fiber and the other off-axis, but close to the center of the fiber. This design allows straightforward splicing of the TCF to single mode fibers (SMF), and alignment of the off-axis core is not strictly required for optimum operation. The sensor is fabricated by simply splicing a 5 cm long section of TCF between two SMF sections, which provides a sinusoidal spectral response. When the fiber is bent, the coupling parameters are modified due to stress-optic and effective length effects, effectively blue-shifting the sinusoidal spectral response of the sensor and allowing for the measurement of curvature. The sensor exhibits linear response and a sensitivity of -137.87 nm/m(-1) for curvature ranging from 0 to 0.27 m(-1), making it suitable to measure small curvatures with high sensitivity.
