An optical guide comprising a core that has a entrance segment that is rectilinear in an entrance direction, an exit segment that is rectilinear in an exit direction, and a transition segment between the rectilinear entrance segment and the rectilinear exit segment. The exit direction is different from the entrance direction so that light propagates between the entrance segment and the exit segment in a propagation direction that has a bend having an interior side and an exterior side. The transition segment comprises a region with a pseudo-index gradient, this region having an interior edge on the interior side of the bend and an exterior edge on the exterior side of the bend. The region with the pseudo-index gradient comprises trenches formed in the core in order to make a refractive index decrease from the interior edge to the exterior edge.