Analysis of bend loss in loaded fiber coil for a circular and an elliptical shape

Bending in the optical fiber can result in a loss of optical fiber. Bending causes the output light intensity smaller than the intensity of the light source. Bending can be utilized to a sensor based on optical fiber. This paper presents to know the correlation between the optical fiber sensor utilizing bending effect with rubber coil to a circular and an elliptical shape.

The principle of this sensor is a detecting change in the output voltage through an optical fiber. The output voltage then converted to transmittance with the program of a computer. The optical fiber is divided into two arms, that is one reference arm and one modulate arm. Fiber bending sensor was made by coiling optical fiber in modulating arm. The displacement loaded to the optical fiber coil in a rubber thread, so that occur of bending. Rubber threaded used to have a 1.0 cm diameter for the circular shape, and 1.1 cm mayor axis and 0.9 cm minor axis for the elliptical shape. Tests are taken from variations in a number of turns, that are 1, 2, 3, and 4 turns and displacement load from 0.0–10.0 mm.

The results can be concluded that the loss is greater with the more number of turns. The larger of displacement load has also resulted in the greater loss. The ratio of loss generated to both of the rubber shapes is visible. The circular shape shows that the loss is a very small firstly. But, after the cross section coil turned into an elliptical shape with a minor axis, the loss increased significantly. While for the elliptical shape shows that the loss increased significantly from the first displacement loaded. (paper)