Optical fiber

An optical fiber comprising a glass fiber and a coating resin layer coating the glass fiber,

• wherein, in a differential molecular weight distribution curve obtained by gel permeation chromatography for an extraction liquid obtained by extracting the optical fiber using tetrahydrofuran with a horizontal axis being a logarithmic value log M of a molecular weight M and a vertical axis being dw/d log M obtained by differentiating a concentration fraction w with the logarithmic value log M of the molecular weight, when an extremum satisfying both of conditions (A) and (B) is defined as a satisfying extremum, a number of satisfying extrema is 4 or less:
• (A) the extremum is in a molecular weight range of 3.5≤log M≤5.5;
• and
• (B) when a maximum value of dw/d log M in the molecular weight range is 1, a difference in dw/d log M between the extremum and another extremum adjacent to the extremum is 0.15 or more.