A single-mode optical fiber includes a central core surrounded by an outer cladding. The optical fiber includes at least first and second depressed claddings positioned between the central core and the outer cladding. The central core typically has a radius of between about 3.5 microns and 5.5 microns and a refractive-index difference with the outer cladding of between about −1×10−3 and 3×10−3. The first depressed cladding typically has an outer radius of between about 9 microns and 15 microns and a refractive-index difference with the outer cladding of between about −5.5×10−3 and −2.5×10−3. The second depressed cladding typically has an outer radius of between about 38 microns and 42 microns and a refractive-index difference with the first depressed cladding of between about −0.5×10−3 and 0.5×10−3.