Light propagating through optical fibers always leaks to the edge of the
cladding in principle, although this leakage can be made negligible by
proper design. This leakage is often significant in new types of optical
fibers called photonic crystal fibers and has significant practical
as well as theoretical implications for the behavior of these waveguides.
This is a simluation shows light propagation in a W-type waveguide.
Light is injected into the W-type waveguide at z = 0.
The black dash-dotted lines and black dashed lines indicate x = ±a and x = ±b, respectively.
The movie shows the real part of the electric field.