The invention relates to a bending-resistant multimode
fiber comprising a core layer and a cladding. The
refractive index profile of the core is in [alpha]
power exponent function distribution. The bending-resistant multimode
fiber is characterized in that the cladding successively comprises, from inside to outside, an inner cladding, a first sunk cladding, a second sunk cladding, and an outer cladding; the core layer has a distribution index [alpha] from 1.9 to 2.2, a
radius R1 from 23 to 27[mu]m, and a maximum
relative index of
refraction [
delta]1 from 0.9 to 1.2%; the inner cladding has a
radius R2, a unilateral radial thickness R2-R1 from 0 to 6.0[mu]m, a
relative index of
refraction difference [
delta]2 from -0.3 to 0.03%; the first sunk cladding has a
radium R3, a unilateral radial thickness R3-R2 from 2.5 to 6.0[mu]m, and a
relative index of
refraction difference [
delta]3 from -0.6 to -0.2%; the second sunk cladding has a
radium R4, a unilateral radial thickness R4-R3 from 6.0 to 10.0[mu]m, and a relative index of refraction difference [delta]4 from -0.3 to -0.2%; and the outer cladding is a pure
silicon dioxide glass layer. The bending-resistant multimode
fiber has excellent bending resistance and
broad bandwidth performance.