PHOTONIC CRYSTAL FIBER
The present disclosure is a photonic crystal fiber in which a plurality of holes are formed in a cladding, having a uniform light refractive index, capable of propagating three modes of a fundamental mode, a first higher-order mode, and a second higher-order mode, wherein the plurality of holes are disposed in a triangular lattice pattern so as to surround a center of the photonic crystal fiber with no hole disposed at the center of the photonic crystal fiber, and the photonic crystal fiber has a ratio d/A of a diameter d of each of the holes to a pitch A between the holes such that a confinement loss of a third higher-order mode at a minimum wavelength within a used wavelength range is 1.0 dB/m or more and a confinement loss at a maximum wavelength is 0.001 dB/km or less.
1 . A photonic crystal fiber in which a plurality of holes are formed in a cladding, having a uniform light refractive index, capable of propagating three modes of a fundamental mode, a first higher-order mode, and a second higher-order mode, wherein
the plurality of holes are disposed in a triangular lattice pattern so as to surround a center of the photonic crystal fiber with no hole disposed at the center of the photonic crystal fiber, and
the photonic crystal fiber has a uniform ratio d/λ of a diameter d of each of the holes to a pitch ∧ between the holes such that a confinement loss of a third higher-order mode at a minimum wavelength within a used wavelength range is 1.0 dB/m or more and a confinement loss at a maximum wavelength is 0.001 dB/km or less.
2 . The photonic crystal fiber according to claim 1 , wherein
the number of holes of the plurality of holes is 36,
the plurality of holes are three layers of holes surrounding the center of the photonic crystal fiber,
the d/∧ is between 0.62 and 0.69 inclusive, and
the ∧ is between 18.0 and 21.5 inclusive.
3 . The photonic crystal fiber according to claim 1 , wherein
the number of holes of the plurality of holes is 36,
the plurality of holes are three layers of holes surrounding the center of the photonic crystal fiber,
the d/∧ is between 0.58 and 0.72 inclusive, and
the ∧ is between 8.0 and 18.0 inclusive.
4 . The photonic crystal fiber according to claim 1 , wherein
the number of holes of the plurality of holes is 18,
the plurality of holes are two layers of holes surrounding the center of the photonic crystal fiber,
the d/∧ is between 0.67 and 0.72 inclusive, and
the ∧ is between 18.0 and 22.5 inclusive.
5 . The photonic crystal fiber according to claim 1 , wherein
the number of holes of the plurality of holes is 18,
the plurality of holes are two layers of holes surrounding the center of the photonic crystal fiber,
the d/∧ is between 0.67 and 0.73 inclusive, and
the ∧ is between 10.0 and 22.5 inclusive.
6 . The photonic crystal fiber according to claim 1 , wherein
the photonic crystal fiber has the d/∧ such that a bending loss at the minimum wavelength within the used wavelength range is 0.5 dB/100 turns or less at a bending radius of 30 mm.