| 摘要 |
<p>A POF (12) comprises a core (65) having a radius of R1, an outer shell (66) and an outermost shell (67). The core (65) includes concentric layers. A first layer (61) is at the periphery side and an nth layer (64) is at the center of the core (65). The refractive index increases from the first layer (61) to the nth layer (64). The refractive index N(r) at a position where a distance r apart in a radius direction from the center of the core (65) having a radius of R1 is satisfied following equations (1) and (2) when the center of a cross-sectional circle of the core (65) has the refractive index of N1, the outermost part of the core (65) has the refractive index of N2, and a refractive index distribution coefficient is shown as g: [Equation (1)] N(r) = N1[1-2?(r/R1)<SUP>g</SUP>]<SUP>1/2</SUP> [Equation (2)] ?= (N1<SUP>2</SUP>-N2<SUP>2</SUP>)/(2N1<SUP>2</SUP>)</p> |
