  We verify the existence of scintillation enhancement by measuring the
scintillation index of a beam composed of two coherent Gaussian vortex beams
with $\pm 1$ topological charges propagating through thermally induced
turbulence. Further experimental research based on the reference wave
interferometric method demonstrates that this phenomenon is caused by the
combined effect of a screw dislocation and an infinitely extended edge
dislocation, namely the impact of an anisotropic dislocation. The experimental
results indicate that the anisotropic dislocation is more sensitive to weak
perturbations than an isotropic screw dislocation and an infinitely extended
edge dislocation, which means the anisotropic dislocation has potential for
weak perturbation measurement. This phenomenon is instructive in further phase
discontinuity research.
