Effect of Single-Mode and Hetero-core Macrobend Fiber Optics

Fiber optic sensors can function well if they have good sensitivity. A hetero-core structure is one of the choices to increase the sensitivity of fiber optics. Usually, the structure of a hetero-core fiber consists of a transmission line and an inner fiber segment, which is usually used as a sensing portion. The core diameters of the transmission line and the sensing region are different, and they can be set up depending on the type of sensor. A periodic macro bending hetero-core fiber optic has been designed with core diameters of 9 and 4 μm for hetero-core sensing region. A 9 μm single-mode fiber, 50-9-50 μm and 50-4-50 μm hetero-core fibers were investigated and the bend loss due to the number of turns, wavelength and types of fiber configurations were measured. Experimental results showed that the sensitivity of the proposed macro bending constructed using hetero-core optical fiber was considerably higher than that of the standard single mode fiber optic. The sensitivity of the configuration increased as the number of loops increased. On the other hand, a significant bend loss was obtained at a long wavelength of 1550 nm. Moreover, the 50-9-50 structure was less sensitive compared with the 50-4-50 structure and this finding can be explained in terms of coupling loss at the hetero-core interfaces. The outcomes of this research enable the development of bending sensors based on preliminary data.