Patent ID: 8634687

Claim:
A coated plastic cladding optical fiber constructed by forming a coating layer, which is formed of a thermosetting resin, on a plastic cladding optical fiber, in which a cladding layer formed of a resin whose refractive index is lower than core glass is formed on an outer periphery of the core glass formed of quartz glass, wherein a diameter of the core glass is set to 50 to 100 μm, a diameter of the cladding layer is 1.4 to 2.5 times the diameter of the core glass, a relative index difference of the core glass to the cladding layer is set to 3.7% or more, a breaking probability of the core glass is 10 −6 or less when a step that the plastic cladding optical fiber is wound around a mandrel of 2 mm radius by 10 turns and is held for one minute, then is unwound once, and then is wound once again and is held for one minute is repeated 100 times, and a difference between a transmission loss of a signal light having a wavelength of 850 nm which is caused after the plastic cladding optical fiber is wound around the mandrel whose radius is 2 mm by 10 turns as measured by applying a cutback technique, and a transmission loss caused before the plastic cladding optical fiber is wound, is 1 dB or less.