Optical fiber capable of controlling attenuation losses caused by microbending on the signal transmitted thereby. The optical fiber comprises: a) an internal glass portion; b) a first coating layer of a first polymeric material surrounding said glass portion; and c) a second coating layer of a second polymeric material surrounding said first coating layer, wherein said first polymeric material has a hardening temperature lower than -10.degree. C., an equilibrium tensile modulus lower than 1.5 MPa, wherein said first coating layer has a thickness of from 18 .mu.m to 28 .mu.m and wherein said second coating layer has a thickness of from 10 .mu.m to 20 .mu.m.