Numerical design and analysis of multimode fiber with high bend tolerance and bandwidth using refractive index optimization

This paper presents a multimode optical fiber design that has high tolerance to bending. The fiber is designed by increasing refractive index difference between core and cladding and by the introduction of low index rod in the core. Average bending loss per mode for a standard 50 μm graded index multimode fiber is 1.58E+08 dB/km for a bending radius of 1.25 mm and particularly for fundamental mode it is 3.793E+05 dB/km. Whereas, simulation results show that average bending loss per mode in the case of the proposed bend insensitive multimode fiber for a bending radius of 1.25 mm is about 7.409E−09 dB/km and particularly for the fundamental mode it is 4.985E−22 dB/km only. Selective mode launch phenomenon is used to excite only the bend insensitive modes of the proposed fiber. It is also observed that the proposed design is consistent with standard 50 μm graded index multimode fiber in terms of bandwidth and interconnectivity. Thus both standard 50 μm fiber and proposed fiber can be spliced with the proposed fiber in the bending section.