A photonic crystal fiber (12) according to the present invention has a plurality of holes (11) arranged in the optical fiber along a longitudinal direction, in which the holes (11) are arranged such that, in a cross section, a hole ratio which is an area of the holes per unit area is larger in a central side than in an outer side in a portion corresponding to a cladding and that a wide core area can be obtained while the number of modes that can be propagated is limited to several. Moreover, in a high-power optical transmission system (81) according to the present invention, the amount of axis misalignment between the central axis of a laser oscillator (92) and the central axis of the photonic crystal fiber (91) is less than or equal to a certain amount.
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