Patent ID: 7068908

Claim:
A resin liquid for an optical fiber coating layer for improving long-period transmission properties of an optical fiber which comprises a naked optical fiber and a coating layer, wherein the coating layer comprises a first coating layer which is directly coated onto the naked optical fiber and a second coating layer which is coated onto the first coating layer, the resin liquid containing at least one resin, wherein the resin liquid contains less than 500 pieces of extraneous material per 1 ml of the resin liquid, the extraneous material has a minimum length of 0.5 μm or more and a hardness greater than a hardness of the resin liquid after curing, and the resin liquid is used for forming at least the first coating layer, and wherein the first coating layer has a Young's modulus in a range from 0.3 to 10 MPa and contains less than 500 pieces of extraneous material per 1 ml of the resin liquid, and the extraneous material has a minimum length of 0.5 μm or more and a hardness greater than a hardness of the first coating layer.