Design and optimization of 3-mode x 12-core dual-ring structured few-mode multi-core fiber

We adopt dual-ring structure (DRS) for the core arrangement of 3-mode (LP01, LP11a and LP11b) x 12-core few-mode multi-core fiber (FM-MCF) and then introduce the design method for this DRS-FM-MCF. After investigating the characteristics such as differential mode delay (DMD), inter-core crosstalk (XT), threshold value of bending radius (Roc), relative core multiplicity factor (RCMF) and cable cutoff wavelength (lambda(cc)), we present an optimized scheme for this DRS-FM-MCF. For the optimized DRS-FM-MCF, IDMDI is <= 100 ps/km over C+L band, the maximum XT at wavelength (lambda) of 1625 nm achieves -33 dB/ 100 km, maximum R-pk is 11.03 cm, RCMF (LP01, LP11a and LP11b) reaches 25.49 and maximum lambda(cc), is <= 1530 nm. Compared with one-ring structure (ORS), DRS has much more space to enlarge core pitch (Lambda) so that lower XT can be achieved. Furthermore, DRS has less confinement degree on mode than square lattice structure (SLS) if A and cladding diameter (D-cl) are set at similar values. It means that it is easier for DRS to make sure lambda(cc) would not be larger than the lower limit of bands. In this paper, DRS is proved as a suitable core arrangement for 3-mode x 12-core FM-MCF. (C) 2016 Elsevier B.V. All rights reserved.