A resin composition comprises a base resin containing an urethane (meth)acrylate oligomer, a monomer having a phenoxy group, and a photopolymerization initiator, and hydrophobic inorganic oxide particles, wherein the viscosity is 300 mPa.Math.s or more and 4200 mPa.Math.s or less at 45° C. and the content of the monomer having a phenoxy group is 1% by mass or more and 30% by mass or less based on the total amount of the base resin.

Apparatus, systems, and methods that provide coats on a glass optical fiber including of an inner layer and an outer layer. The method includes two steps. First, a conductive polymer coating is applied to the optical fiber as it is being produced. Second, a protective coating is applied to that conductive polymer coating. The conductive polymer coating is applied immediately after the fiber is drawn from preform to fiber.

A method for manufacturing an optical fiber includes: a coating step of forming a first layer by applying a first ultraviolet ray curable resin composition onto a glass fiber, and then, of forming a second layer by applying a second ultraviolet ray curable resin composition onto the first layer; a first irradiation step of curing the first layer and the second layer by irradiating the first layer and the second layer with an ultraviolet ray, and of obtaining the optical fiber including a primary resin layer and a secondary resin layer; and a second irradiation step of irradiating the optical fiber with an ultraviolet ray at an illuminance of less than or equal to one tenth of an illuminance in the first irradiation step for an irradiation time of longer than or equal to 10 times an irradiation time in the first irradiation step.

A resin composition for secondary coating of an optical fiber is a resin composition comprising: a non-reactive urethane compound having a number average molecular weight of 10000 or more and 40000 or less, a photopolymerizable compound, and a photopolymerization initiator, wherein the content of the non-reactive urethane compound is 0.05 parts by mass or more and 10 parts by mass or less based on the total amount of the resin composition of 100 parts by mass, and the non-reactive urethane compound is a reaction product of a polyol having a number average molecular weight of 1800 or more and 4500 or less, a diisocyanate, and a compound having active hydrogen.

A resin composition for secondary coating of an optical fiber is a resin composition comprising: a non-reactive urethane compound having a number average molecular weight of 10000 or more and 40000 or less, a photopolymerizable compound, and a photopolymerization initiator, wherein the content of the non-reactive urethane compound is 0.05 parts by mass or more and 10 parts by mass or less based on the total amount of the resin composition of 100 parts by mass, and the non-reactive urethane compound is a reaction product of a polyol having a number average molecular weight of 1800 or more and 4500 or less, a diisocyanate, and a compound having active hydrogen.

An object is to obtain an optical fiber having a small diameter and suppressing the increase of a microbending loss of the optical fiber. The optical fiber includes: a core portion made of silica glass; a cladding portion made of silica glass, the cladding portion covering the outer periphery of the core portion and having a refractive index smaller than a maximum refractive index of the core portion; and a coating portion covering the outer periphery of the cladding portion. The outer diameter of the cladding portion is 100 μm or smaller, the relative refractive-index difference Δ1 of the core portion is 0.5% or smaller, and the thickness of the coating portion is 10 μm or larger.

A resin composition for the secondary coating of an optical fiber is a resin composition containing a non-reactive urethane compound having a number average molecular weight of 10000 or more and 50000 or less, a photopolymerizable compound, and a photopolymerization initiator, the content of the non-reactive urethane compound is 0.05 parts by mass or more and 5 parts by mass or less based on the total amount of the resin composition, and the non-reactive urethane compound is a reaction product of a polyol having a number average molecular weight of 8000 or more and 20000 or less, a diisocyanate, and a compound having active hydrogen.

A resin composition for the secondary coating of an optical fiber is a resin composition containing a non-reactive urethane compound having a number average molecular weight of 10000 or more and 50000 or less, a photopolymerizable compound, and a photopolymerization initiator, the content of the non-reactive urethane compound is 0.05 parts by mass or more and 5 parts by mass or less based on the total amount of the resin composition, and the non-reactive urethane compound is a reaction product of a polyol having a number average molecular weight of 8000 or more and 20000 or less, a diisocyanate, and a compound having active hydrogen.

The present disclosure provides optical fibers with an impact-resistant coating system. The fibers feature low attenuation. The coating system includes a primary coating and a secondary coating. The primary coating and secondary coating have reduced thickness to provide low-diameter fibers without sacrificing protection. The primary coating has high tear strength and is resistant to damage caused by mechanical force. The secondary coating has high puncture resistance. The outer diameter of the optical fiber is less than or equal to 190 μm.

A method for preparing optical fibers formed with high-particle-coated porous polymeric outer coating layer is provided. The method includes preparing a coating suspension solution by dispersing a plurality of particles into an organic solvent system, immersing one or more optical fibers into the coating suspension solution, removing the one or more optical fibers from the coating suspension solution to form high-particle-coated porous polymeric outer coating layer after drying. Concentrations and compositions of the particles in the coating suspension solution, concentrations and compositions of the organic solvent system, the period of time of immersing, or the external environment are adjusted such that the optical fibers is formed with high-particle-coated polymeric outer coating layers having desirable coating masses, coating thicknesses, or coating morphologies.