Patent ID: 7429138

Claim:
An optical connection method for connecting a light emission device and a light receiving device via a graded index plastic optical fiber, wherein a light beam from a light emission device enters one end of a graded index type plastic optical fiber, exits from the other end of the plastic optical fiber and enters the light receiving device, the method comprising: providing the plastic optical fiber with a core, a first clad and a second clad, the core being in the shape of an approximately circular cross section and having the refractive index profile in which the refractive index increases toward the center, the first clad being formed outside of the core and having a refractive index equal to or smaller than the core, the second clad being formed outside of the first clad and having a refractive index smaller than the first clad, the plastic optical fiber satisfying the following conditions: 100(μm)≦ d 1≦700(μm) 200(μm)≦ d 2≦1000(μm) d1<d2 wherein d 1 indicates the diameter of the core, and d 2 indicates the outer diameter of the first clad.