An optical transmission fiber comprises a central core having an index difference ”n 1 with an outer optical cladding; a first inner cladding having an index difference ”n 2 with the outer cladding; and a second buried inner cladding having an index difference ”n 3 with the outer cladding of less than -3.10 -3 . The second buried inner cladding moreover contains Germanium in a weight concentration of between 0.5 % and 7 %. The fiber shows reduced bending and microbending losses whilst exhibiting the optical performances of a standard single-mode fiber (SSMF).
