Since larger Aeff can achieve smaller |DMD| in the 2-LP-mode operation region (2-LP-MOR), we set target of Aeff of LP01 mode at 110 μm2. If W/r1 changes, the 2-LP-MOR will shift and if W/r1 is <~0.5, DMD will decrease immediately. According to the above characteristics of core with TA-GIP, we selected three non-identical cores with the same Aeff at different W/r1 to make sure large Δneff of cores, so that the relative small threshold value of bending radius (Rpk) can be ensured.
We investigated the impact of DRS on the cable cutoff wavelength (λcc) of LP21 mode in the selected cores in order to make sure the 3898134a83c79e44e413" title="Click to view the MathML source">(λcc) would not be larger than 1530 nm, which is the lowest limit of C+L band. To optimize the core arrangement, we put the core with W/r1 of <0.5 at the outer layer, where (λcc) is not much influenced by the trenches.
TA-GIP is more suitable than trench-assisted multi-step-index profile (TA-MSIP) to obtain low |DMD|. Square lattice structure (SLS) and DRS are better than one-ring structure (ORS) to ensure small crosstalk. Additionally, DRS has less confinement degree on mode than SLS if cladding diameter and core pitch are fixed at similar values. Hence, DRS-FM-MCF with TA-GIP is proved as a more appropriate structure to achieve |DMD| of <100 ps/km, reach XT of <−30 dB/100km and guarantee 409b1386e3d64d80518f99" title="Click to view the MathML source">λcc is ≤1530 nm at the same time.
Finally, we compared the reported FM-MCFs and the proposed DRS-FM-MCF in this work. We found that TA-GIP is more suitable than trench-assisted multi-step-index profile (TA-MSIP) to obtain low |DMD| for FM-MCF. Square lattice structure (SLS) and DRS are better than one-ring structure (ORS) to ensure small inter-core crosstalk. Furthermore, DRS has less confinement degree on mode than SLS if cladding diameter and core pitch are fixed at similar values. Hence, DRS-FM-MCF with TA-GIP is proved as a more appropriate structure to achieve the lower |DMD| of , reach small XT of
and guarantee the maximum λcc is
at the same time.