Design of Uncoupled Three-Mode-Group Graded-Index Fiber with Low Bending Loss in C+L Band
Optical fiber is the most stable medium for signal transmission in modern communication networks.In-creasing the number of fiber modes is an effective way to meet the increasing demand for communication capacity.In this paper,a kind of uncoupled three-mode-group(LP01,LP1LP21)graded-index fiber with low bending loss is designed.The strict cut-off conditions of the mode groups in the graded-index optical fiber are obtained by using the stratified method.In addition,the effective mode area and bending losses are calculated by a finite element simulation software,and the design region of three-mode-group transmission in the C+L(1 530～1 625 nm)band with low bending loss is obtained.It is re-vealed that the combined effects of the concave refractive index at the core center and the trench layer can promote the cut-off of radial higher-order modes in the fiber.The simulation results show that the designed fiber has a large effective index difference between mode groups that is 3×10-3,and the maximum bending loss is 1.3 dB/km when the bending radius is 30 mm,which meets the low bending loss condition recommended by ITU-T.In addition,at the wavelength of 1 550 nm,the degenerate modes in the same mode group have a relatively small differential mode group delay(≈176 ps/km),and the crosstalk between degenerate modes can be compensated by 4×4 multi-input multi-output technique.This fiber can be used in the C+L band to realize uncoupled space-division multiplexing signal transmission.
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维普
