According to some embodiments a single mode fiber includes: a germania doped central core region having outer radius r1 and relative refractive index Δ1; and a cladding region comprising (i) a first inner cladding region having an outer radius r2>6 microns and relative refractive index Δ2 and 0.3≦r1/r2≦0.85; and (ii) a second inner cladding region having an outer radius r3>9 microns and comprising a minimum relative refractive index Δ3, wherein said second inner cladding region has at least one region with a relative refractive index delta that becomes more negative with increasing radius; and (iii) an outer cladding region surrounding the second inner cladding region and comprising relative refractive index Δ4, wherein Δ1>Δ2>Δ3, Δ3