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This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).

An experimental and numerical investigation is performed into the power loss induced in grooved polymer optical fibers (POFs) subjected to combined bending and elongation deformations. The power loss is examined as a function of both the groove depth and the bend radius. An elastic-plastic three-dimensional finite element model is constructed to simulate the deformation in the grooved region of the deformed specimens. The results indicate that the power loss increases significantly with an increasing bending displacement or groove depth. Specifically, the power loss increases to as much as 12% given a groove depth of 1.1 mm and a bending displacement of 10 mm. Based on the experimental results, an empirical expression is formulated to relate the power loss with the bending displacement for a given groove depth. It is shown that the difference between the estimated power loss and the actual power loss is less than 2%.

Compared to conventional glass fibers, polymer optical fibers (POFs) have a larger core diameter, greater flexibility, lighter weight, and a lower cost [

In all of the above studies, the sensitivity of the proposed POF sensors was enhanced by making the POFs imperfect in some way. In previous studies [

_{co}_{cl}

The groove-like features in the POF specimens were produced using a grinding wheel (diamond grain size: #120) and therefore had a curved profile. _{1}_{1}

In this study, an elastic-plastic finite element model is employed to evaluate the deformation and stress distributions in the core diameter as the POF specimen is subjected to bent and elongated deformation. The simulations are performed using the commercial finite element package ABAQUS. The finite element mesh of the tested POF specimen is shown in

The disc is modeled as an analytical surface rigid body and the fiber model is constructed using four-node, three-dimensional tetrahedron elements. In performing the simulations, the contact behavior between the disc and the POF is modeled using surface-to-surface contact. Due to the symmetry of the POF geometry, only one half of the model needs be considered in the finite element analysis. Various finite element mesh sizes are performed for the convergence test of the von-Mises stress computed at the center point of the grooved POF specimen. The exact number of elements used in the simulations depends on the depth of groove. However, in general, the simulations involve approximately 246,484 elements and 61,706 nodes. In the finite element analysis, both ends of the specimen is considered to be fixed, while a displacement of

In the experimental tests, POF specimens with groove depths of _{in}_{in}_{out}_{in}_{out}_{in}

The initial power ratio (_{out}_{in}_{o}_{out}_{in}_{δ=0}_{out}_{in}_{δ=0}_{out}_{in}

_{o}_{o}_{o}_{o}

As shown in

In [

Applying a nonlinear least squares fitting procedure to the experimental data shown in

The predicted results obtained from

This study has performed an experimental and numerical investigation into the power loss in grooved POFs subject to combined bending and elongation deformation. The investigations have considered groove depths ranging from 0∼1.1 mm and bending radii of 5, 10, 15 and 20 mm. The deformation-induced stress within the various POF specimens has been examined using an elastic-plastic FE model. The results have shown that the power loss increases significantly with an increasing bending displacement or groove depth, but is insensitive to the bending radius. The power loss reaches a value as high as 12% given a groove depth of

The authors gratefully acknowledge the financial support provided to this study by the National Science Council, under Grant No. NSC 100-2221-E-020-013.

Experimental setup used to measure power loss in grooved POF specimens under combined bending and elongation loading.

Geometrical model of grooved POF specimen. (

Finite element model of grooved POF specimen.

Variation of normalized power ratio

von-Mises stress contours near grooved region at

Variation of normalized power ratio

Ray paths in deformed POF specimens at various groove depths. (

Mechanical properties of POF materials [

3000 | 200 | 100 | |

_{y} |
56 | 11.3 | 9.8 |

_{ult} |
72.4 | 55 | 17.15 |

0.4 | 0.46 | 0.49 |