Instead , especially in single - mode fibers , a significant fraction of the energy in the bound mode travels in the cladding as an evanescent wave .
The waveguide analysis shows that the light energy in the fiber is not completely confined in the core .
Especially in single - mode fibers , a significant fraction of the energy in the bound mode travels in the cladding as an evanescent wave .
The waveguide analysis shows that the light energy in the fiber is not completely confined in the core .