Fig. 2.

Spatio-temporal correlations in MMF with strong random mode mixing. a Intensity correlations $C\left(\mathrm{\Delta }r,t\right)\equiv C\left(\mid \mathbf{\Delta }\mathbf{r}\mid ,t,t\prime =t\right)$, revealing a short-range component C₁(t) ≈ 1 at spatial distance within one speckle ($\mathrm{\Delta }r\lesssim 3$ μm) and a long-range component C₂(t) that persists at large distance. b Two cross sections of C(Δr, t) at arrival times t = −17.3 ps and t = 3.7 ps. c Time dependence of the long-range component C₂(t), averaging over Δr for Δr > 5 μm. The error bars represent the standard deviation among four measurements of the fiber in different bending configurations. d Long-range correlations C₂(t, t′) between spatio-temporal speckle grains at different arrival times t and t′. e Cross sections of C₂(t, t′) at t′ = −17.3 ps, 3.7 ps and 16.1 ps (marked by white dashed lines in d)