| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical fiber having a large photodetecting angle and high light condensing efficiently. SOLUTION: The clad materials of the optical fiber formed of a core material 1 and the clad materials covering the outside surface of the core material 1 and having the refractive index lower than the refractive index of the core material 1 is composed of plural layers of the clad materials 2a, 2b. The clad material 2b of the outermost layer among plural layers of these clad materials 2a, 2b is a silica aerogel consisting of the porous skeleton of silica having the refractive index of 1.0008 to 1.18. The silica aerogel is obtd. by subjecting alkoxysilane to hydrolysis polymn., then to supercritical drying. The silica aerogel is subjected to a hydrophobing treatment. The silica aerogel which is the clad material 2b of the outermost layer covers a part of the outside surface of the clad material 2a of the inner layer nearest the outermost layer. The outside surface of the silica aerogel 2b which is the clad material of the outermost layer is coated with a coating material 3. The coating material 3 and the clad material of the inner layer are preferably parted. |
