In this study, a high sensitivity and easy fabricated plastic optical fiber (POF) displacement sensor is proposed. A POF specimen subjected to dual cyclic bending is used to improve the sensitivity of the POF displacement sensor. The effects of interval between rollers, relative displacement and number of rollers on the sensitivity of the displacement sensor are analyzed both experimentally and numerically. A good agreement between the experimental measurements and numerical calculations is obtained. The results show that the interval between rollers affects sensitivity most significantly than the other design parameters. Based on the experimental data, a linear equation is derived to estimate the relationship between the power loss and the relative displacement. The difference between the estimated results and the experimental results is found to be less than 8%. The results also show that the proposed POF displacement sensor based on dual cyclic bending can be used to detect displacement accurately.

The combined effects of bending and elongation on fiber losses as rays propagate along deformed polymer optical fibers (POFs) are investigated. The variations in power attenuation for various curvature radii and elongations are studied. The experimental results indicate that the combination of bending and elongation significantly affects the power loss of POF. From the results an equation is proposed to predict the power losses for different bent radii and elongations. The maximum difference between the proposed equation and the experimental results is less than 5%.

We investigate the effect of fiber elongation on power loss as rays propagate along deformed polymer optical fibers (POFs). Variations in core diameter, incident angle, stress and strain distributions, and necking of the POFs during fiber elongation are studied. The power losses in the deformed POFs are analyzed both experimentally and numerically. Theoretical analysis based on an elastic-plastic finite-element model and a planar waveguide assumption is proposed. It is found that fiber elongation significantly affects the power loss in POFs, particularly at higher values of elongation. Good agreement between the measured results and the results simulated from the proposed model is obtained. The maximum difference is less than 5%. Results indicate that the proposed theoretical analysis based on an elastic-plastic finite-element model and a planar waveguide assumption is feasible to predict the power loss variation introduced by elongated deformations. A curve-fitted equation is also proposed to estimate the power loss of POFs under different fiber elongation conditions.

The excess loss and output optical power ratio of symmetrical and asymmetrical Y-branch couplers for plastic optical fibers (POFs) are studied in this work. A ray-tracing model for the Y-branch coupler is derived to investigate the effect of coupling parameters on its optical performance. The coupling parameters, namely coupling angle, axial displacement, and refractive index of filling medium between the emitting-end and receiving-end POFs, are studied. The simulated and measured results indicate that the coupling efficiency is sensitive to all these coupling parameters. A minimum excess loss of approximately 0.83 dB is observed for the symmetrical Y-branch coupler. It is found that both the excess loss and the output power ratio are increased with the increase of the refractive index of the filling medium and the total coupling angle (α+β) for the asymmetrical Y-branch coupler. The experimental results indicate that the maximum output power ratio P1∶P2 is found to be 3.8∶1 for excess loss of less than 2.8 dB for the asymmetrical Y-branch coupler.

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