Inter-core crosstalk in weakly coupled MCFs with arbitrary core layout and the effect of bending and twisting on the coupling coefficient

Abstract

We investigate the bending and twisting-induced longitudinal variation of the inter-core coupling coefficient (ICCC) and its effect on inter-core crosstalk (ICXT) in weakly coupled multi-core fibers (MCFs) with an arbitrary core layout. An analytical discrete changes model (DCM) for ICXT field propagation under those conditions is proposed for the first time, providing very fast and rather accurate mean ICXT power estimates. The analytical mean ICXT power estimates are validated through numerical simulation. It is predicted that the mean ICXT power between adjacent cores of the outer ring of the 19-core MCF can be more than 10 dB higher than the one between adjacent cores of the inner ring. It is also predicted that the difference between the mean ICXT power of cores in the inner and outer rings can be much smaller by decreasing the core pitch and increasing the bending radius. This behavior is attributed to the ICXT dependence on the bending and twisting-induced longitudinal variation of the ICCCs. In particular, larger bending and twisting-induced fluctuations of the ICCCs along the longitudinal coordinate are observed in the cores of the outer ring, but the fluctuations become smaller for smaller core pitches and larger bending radii. Furthermore, it is shown that, if the ICCCs' longitudinal variation is neglected, the mean ICXT power estimates between two adjacent cores are very similar despite the location of those cores. This means that neglecting the longitudinal variation of the ICCCs can lead to misleading estimates of the mean ICXT power, with an error exceeding 15 dB.

Correlation and Power Distribution of Intercore Crosstalk Field Components of Polarization-Coupled Weakly Coupled Single-Mode Multicore Fibres

“…Figure 1 shows a schematic illustration of the two-core WC-MCF cross section representing the interfering core m (blue) with radius a m , the interfered core n (red) with radius a n , the corresponding core pitch Λ mn , and the cladding of the MCF with diameter d c . The usual range of values for the WC-MCF size parameters are the following: (i) core radius [3.8 µm, 4.7 µm] [17,20,28,29]; (ii) core pith [30 µm, 45 µm] [8,17,20,[28][29][30]; and (iii) core cladding diameter [125 µm, 260 µm] [5] (p. 22), [8,20,25,[29][30][31][32].…”

Distributed radiofrequency signal processing based on space-division multiplexing fibers

“…Twists produce a continuous-varying rotation of the fiber and can be understood as a random phase function that affects the core locations on the cross-sectional area of the fiber, [127]. With the inclusion of these perturbations, the CMEs for MCFs are written as, [127,128], where and thus the crosstalk can be estimated as, [110],…”