<p>The invention provides an optical fiber having a first covering surrounding the optical fiber and a second covering surrounding the first covering. The first covering comprises a material having a Young's modulus at -30.degree.C which is not greater than ten times that at 23.degree.C. The fiber has a small increase of attenuation of light transmission at low temperatures and also has a small increase of attenuation of light transmission due to lateral pressures not only at room temperature but also at low temperatures.</p>
