A single-mode optical fiber includes a central core, an intermediate cladding, a depressed trench, and an external optical cladding. The central core has a radius r1 and a positive refractive index difference Δn1 with the optical cladding. The intermediate cladding has a radius r2 and a refractive index difference Δn2 with the optical cladding, wherein Δn2 is less than the central core's refractive index difference Δn1. The depressed trench has a radius r3 and a negative index difference Δn3 with the optical cladding. The optical fiber has a nominal mode field diameter (MFD) between 8.6 microns and 9.5 microns at a wavelength of 1310 nanometers, and at a wavelength of 1550 nanometers, the optical fiber has bending losses less than 0.15 dB/turn for a radius of curvature of 5 millimeters and cable cut-off wavelengths of less than or equal to 1260 nanometers.