| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a fiber type optical element capable of obtaining required characteristics and minimizing the influence of ununiformity in the rise of a refractive index in an optical fiber obtained by adding a photosensitive substance to a core and a clad. SOLUTION: In Fig. 2 (a), a symbol 1 is a core, a symbol 2 is a clad, a symbol (a) is the radius of the core, and ncore and nclad are the refractive indexes of the core and the clad. In Fig. 2 (b), RGe is the radius of the outermost frame of a layer having photosensitivity and Pcore and Pclad are the photosensitivity of the core and the clad. The diameter 2RGe of the outermost frame of the layer having photosensitivity of the optical fiber is formed so as to be twice or more the diameter of a mode field, preferably 2.5 times or more. The optical fiber is irradiated with ultraviolet rays so that the refractive index variation of the core and the clad caused by ultraviolet irradiation on the outgoing side of irradiated ultraviolet rays out of the cross section of the optical fiber is less than 0.002 in a 674.9 nm wavelength band.</p> |
