Resin composition, secondary coating material for optical fiber, optical fiber, and method for manufacturing optical fiber

An optical fiber comprising:

• a glass fiber comprising a core and a cladding;
• a primary resin layer being in contact with the glass fiber and coating the glass fiber;
• and
• a secondary resin layer coating the primary resin layer,
• wherein the secondary resin layer comprises a cured product of a resin composition comprising a base resin containing a photopolymerizable compound and a photopolymerization initiator;
• and surface-modified silica particles,
• wherein the surface-modified silica particles have, as a silicone structural unit, a T unit in which three oxygen atoms are bonded to a silicon atom, and a proportion of a T1 unit, in which one oxygen atom is bonded to another silicon atom, contained in the T unit is 29 mol % or less, and
• wherein the proportion of the T1 unit contained in the T unit is 10 mol % or more.