A chromatic-dispersion photonic crystal fiber having a negative chromatic dispersion the absolute value of which is large in a wide band and small confinement loss. The chromatic-dispersion photonic crystal fiber is provided with a core part positioned at the center and a clad part provided around the core part and comprising cavities extending in the axial direction of the optical fiber. The cavities are arranged in layers into a hexagon coaxial with the core part, and form a triangular array structure centering the core part. The chromatic-dispersion photonic crystal fiber is characterized by comprising two or more clad part configuration regions each of which is composed of one or more layers where cavities having a diameter d1 [μm] are arranged outside the core part and one or more layers provided next to and outside the one or more layers composed of the cavities having the diameter d1 where cavities having the diameter d (dd1) [μm] are arranged.
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