Abstract
Since Nye and Berry$^{(1)}$ showed that in free space the electromagnetic field could contain stable, propagating phase singularities termed "dislocations", optical dislocations have been extensively investigated in nonlinear optics and laser physics. As the wave propagates, the lines of constant phase surrounding a dislocation trace out a spiral in space or in time. So these phase singularities are now usually referred to as optical vortices. Baranova and her co-workers$^{(2)}$ have shown that in fully developed speckle patterns, there is, one optical vortex accompanying each speckle spot on average. Among these vortices there are networks in phasemap because only one phase is to be assigned in one point except optical dislocations having zero amplitude. Freund et al.$^{(3)}$ have been studied optical dislocation networks and simulations are compared with experimental results. (omitted)