Abstract: Optical waveguide of the type comprising a core (10) presenting a refractive index (n.sub.1), maximal at least at its center; an optical cladding (20) involving core (10) and presenting a refractive index (n.sub.2) constant along its diametral extension and lower than the maximum refractive index (n.sub.1) of core (10) and further including a region defined by at least a stress-relieving intermediate portion (30) disposed between core (10) and the optical cladding (20), said intermediate portion presenting: a refractive index (n.sub.3), maximal along its diametral extension, at the maximum equal to the refractive index (n.sub.1) of core (10) and at least equal to refractive index (n.sub.