Hole-assisted holey fiber and a low bending loss multimode holey fiber

Low bending loss The core portion having a refractive index higher than the clad part (11), a clad portion surrounding (12), a plurality of formed by a pore hole-assisted holey fiber provided in the clad portion surrounding the core portion in an empty hole is provided in two inner and outer layers, a pore number of the inner holes layer and the outer holes layer are the same, the outer holes (17) inside the holes are viewed from the core unit center (16) There is disposed at a position not disposed, the pores and constituting each cavity layer is the same size, the distance lambda