An optical fiber comprising: (i) a core; (ii) a cladding surrounding the core; wherein the cladding comprises a cladding ring that: (a) has a width W equal to or less than 10 microns; (b) includes at least 50 airlines, each airline having a maximum diameter or a maximum width of not more than 2 microns and more than 50% of said airlines have a length of more than 20 m; (c) has an air fill fraction of 0.1% to 10%, and (d) has an inner radius Rin and an outer radius Rout, wherein 6 μm≦Rin≦14 μm, and 8 μm≦Rout≦14 μm; and (iii) an outer cladding surrounding said cladding ring.