The optical fibers disclosed is a single mode optical fiber comprising a core region and a cladding region surrounding and directly adjacent to the core region. The core region can have a radius r1 in a range from 3 μm to 7 μm and a relative refractive index profile Δ1 having a maximum relative refractive index Δ1max in the range from 0.25% to 0.50%. The cladding region can include a first outer cladding region and a second outer cladding region surrounding and directly adjacent to the first outer cladding region. The first outer cladding region can have a radius r4a. The second outer cladding region can have a radius r4b less than or equal to 45 μm and comprising silica based glass doped with titania.