The single mode optical fiber disclosed herein has a core, an inner cladding, a trench and an outer cladding, along with a non-glass protective coating. The refractive index profile of the optical fiber is such that the optical fiber has relatively low bend loss at both small and large bend diameters. The relative refractive indices of the inner cladding, trench and outer cladding are such that a tunneling point that arises during bending is pushed out beyond the trench and thus sufficiently far away from the core so that bending losses for both small and large radius bends are relatively small.