The present invention is directed to an optical fiber that includes a glass core region that has nano-sized structures configured to scatter light propagating in the glass core region. The glass core region has an average refractive index navg. The fiber includes an interior glass cladding region that has an interior cladding refractive index n2 that is less than navg. The fiber includes an outer cladding region that has an outer cladding refractive index n3 that is less than n2. A refractive index difference of n2−n3 corresponds to a bend uniformity diameter; the light exiting the outer cladding at a fiber bending location is substantially non-uniform when a bending diameter of the fiber bending location is less than the bend uniformity diameter.