| 摘要 |
PURPOSE: A method of winding optical fiber on reel is provided to prevent breakage when letting out the optical fiber from the reel to form it into a cable with no-loosening of the winding occurs due to vibration during transportation, and the like, without increasing the transmission loss. CONSTITUTION: The refractive index distribution structure has a first annular region(22) and a second annular region(23) between a central region(21) constituting the core and a clad(24). The refractive index of the central region(21) and the refractive index of the second annular region(23) are higher than the refractive index of the clad(24), and the refractive index of the first annular region(22) is lower than the refractive index of the clad(24). While the refractive index of the first annular region(22) is lower than the refractive index of the clad(24), it is also possible for the refractive index of the first annular region(22) to be approximately the same as the refractive index of the clad(24). |
