Patent ID: 8571372

Claim:
A colored optical fiber comprising: an optical fiber; and a colored layer which coats the optical fiber and which is formed by being applied to the optical fiber, wherein the optical fiber includes a glass fiber and at least a double-layered coating layer that coats the glass fiber, the double-layered coating layer including a soft layer and a hard layer, an elastic modulus of the colored layer is equal to or less than an elastic modulus of the hard layer, the double-layered coating layer and the colored layer are an ultraviolet curing resin, a ratio of thermal expansion coefficient of a first configuration of coating layers relative to the thermal expansion of coefficient of a second configuration of coating layers is greater than or equal to 1.00 and less than or equal to 1.05, the first configuration of coating layers including the soft layer, the hard layer, and the colored layer of the colored optical fiber, the second configuration of coating layers including the soft layer and the hard layer of the optical fiber in a state where the colored layer does not exist, and an increase in a transmission loss for the colored optical fiber in a wavelength of 1.55 μm having a length of 1 km is 0.00 dB/km when immersed in water heated to 60° C. for 90 days.