Multi-core optical fiber and multi-core optical fiber cable
This MCF ensures sufficient manufacturing tolerance, is excellent in mass productivity, and is also capable of suppressing degradation of splice loss. The MCF includes four cores and a common cladding. Each core has adjacent relationships with two cores of remaining cores, an adjacent core interval Λ is from Λ nominal −0.9 μm to Λ nominal +0.9 μm, a common cladding diameter is from 124 μm to 126 μm, an MFD, λ cc and d coat at a wavelength of 1310 nm satisfy a predetermined relationship, the MFD is from a MFD-reference-value−0.4 μm to the MFD-reference-value+0.4 μm with the MFD-reference-value of from 8.6 μm to 9.2 μm, a zero-dispersion wavelength is from a wavelength-reference-value−12 nm to the wavelength-reference-value+12 nm with the wavelength-reference-value of from 1312 nm to 1340 nm, a dispersion slope at a zero-dispersion wavelength is 0.092 ps/(nm 2 ·km) or less, λ cc is 1260 nm or less, and a predetermined structural condition and an optical condition are satisfied.
1. A multi-core optical fiber comprising:
four cores extending along a central axis; and
a common cladding covering each of the four cores, wherein
the four cores each have an adjacent relationship with two cores of remaining cores,
a center-to-center interval A between the cores having the adjacent relationship among the four cores falls within a range of a value of Λ nominal −0.9 μm or more and a value of Λ nominal +0.9 μm or less with a predetermined core-interval nominal value Λ nominal used as a basis,
on a cross-section of the four cores, the four cores are respectively allocated to four vertexes of a 3-sides equal trapezoid, in which three sides of the 3-sides equal trapezoid have an equal length of Λ nominal , and a length of Λ nominal of the remaining one side of the 3-sides equal trapezoid is longer than the equal length of Λ nominal of the three sides of the 3-sides equal trapezoid,
an outer diameter of the common cladding falls within a range of 124 μm or more and 126 μm or less with 125 μm used as a basis,
in each of the four cores, a mode field diameter MFD at a wavelength of 1310 nm, a cable cutoff wavelength λ cc measured on a 22 m length of fiber, and a shortest distance d coat of distances from centers of the four cores to an outer periphery of the common cladding satisfy a relationship in a following Formula (1), in any of the four cores:
a numerical value of the shortest distance d coat ≥a numerical value of (2.88MFD/λ cc +5.36) (1),
in each of the four cores, the mode field diameter MFD falls within a range of a value of an MFD reference value−0.4 μm or more and a value of the MFD reference value+0.4 μm or less, with a value of 8.6 μm or more and 9.2 μm or less used as the MFD reference value,
in each of the four cores, a zero-dispersion wavelength falls within a range of a value of a wavelength reference value−12 nm or more and a value of the wavelength reference value+12 nm or less with a value of 1312 nm or more and 1340 nm or less used as the wavelength reference value,
in each of the four cores, a dispersion slope at the zero-dispersion wavelength is 0.092 ps/(nm 2 ·km) or less,
in each of the four cores, the cable cutoff wavelength λ cc is 1260 nm or less,
either a first condition or a second condition is satisfied and either a third condition or a fourth condition is satisfied,
the first condition is defined that each of the four cores is in direct contact with the common cladding,
the second condition relates to each of the four cores, each of the four cores further including an optical cladding provided between each of the four cores and the common cladding, and is defined that a relative refractive index difference Δ2 of the optical cladding with respect to the common cladding satisfies a relationship that −0.1%≤Δ2≤0.1%,
the third condition is defined that a crosstalk between the cores having the adjacent relationship for a fiber length of 10 km at a wavelength of 1360 nm is −10 dB or less, and in each of the four cores, MFD/λ cc and a center-to-center interval Λ a between the cores having the adjacent relationship satisfy a following Formula (2):
7.2≤a numerical value of (MFD/λ cc )≤10.2≤a numerical value of (0.443Λ a −5.33) (2), and
the fourth condition is defined that the crosstalk between the cores having the adjacent relationship for the fiber length of 10 km at the wavelength of 1360 nm is −20 dB or less, and in each of the four cores, MFD/λ cc and the center-to-center interval Λ a between the cores having the adjacent relationship satisfy a following Formula (3):
7.2≤the numerical value of (MFD/λ cc )≤10.2≤a numerical value of (0.392Λ a −4.88) (3).
2. The multi-core optical fiber according to claim 1 , further comprising
a coating surrounding the common cladding, wherein
a leakage loss from at least any of the four cores to the coating at a wavelength of 1550 nm or a wavelength of 1625 nm is 0.05 dB/km or more, a transmission loss of at least one of the four cores at the wavelength of 1550 nm is 0.25 dB/km or more, or a transmission loss at the wavelength of 1625 nm is 0.25 dB/km or more.
3. The multi-core optical fiber according to claim 1 , wherein
the third condition is satisfied, and
the crosstalk between the cores having the adjacent relationship at a wavelength of 1550 nm for the fiber length of 10 km is −10 dB or more.
4. The multi-core optical fiber according to claim 1 , wherein
the fourth condition is satisfied, and
the crosstalk between the cores having the adjacent relationship at a wavelength of 1550 nm for the fiber length of 10 km is −20 dB or more.
5. A multi-core optical fiber cable comprising a plurality of multi-core optical fibers including the multi-core optical fiber defined in claim 1 .
6. The multi-core optical fiber cable according to claim 5 , wherein the multi-core optical fiber has an average bending radius of 0.03 m or more and 0.14 m or less, or 0.14 m or more and 0.3 m or less in a fiber longitudinal direction.
7. A multi-core optical fiber cable incorporating a multi-core optical fiber ribbon in which a plurality of multi-core optical fibers including the multi-core optical fiber defined in claim 1 are intermittently bonded.
8. The multi-core optical fiber cable according to claim 7 , wherein the multi-core optical fiber ribbon is incorporated with spirally twisted.
9. The multi-core optical fiber cable according to claim 7 , wherein the multi-core optical fiber has an average bending radius of 0.03 m or more and 0.14 m or less, or 0.14 m or more and 0.3 m or less in a fiber longitudinal direction.
10. A multi-core optical fiber comprising:
four cores extending along a central axis; and
a common cladding covering each of the four cores, wherein
the four cores each have an adjacent relationship with two cores of remaining cores,
a center-to-center interval A between the cores having the adjacent relationship among the four cores falls within a range of a value of Λ nominal −0.9 μm or more and a value of Λ nominal +0.9 μm or less with a predetermined core-interval nominal value Λ nominal used as a basis,
on a cross-section of the four cores, the four cores are respectively allocated to four vertexes of a 3-sides equal trapezoid, in which three sides of the 3-sides equal trapezoid have an equal length of Λ nominal , and a length of Λ nominal of the remaining one side of the 3-sides equal trapezoid is longer than the equal length of Λ nominal of the three sides of the 3-sides equal trapezoid,
a diameter CD of the common cladding falls within a range of a value of CD nominal −1 μm or more and a value of CD nominal +1 μm or less with a predetermined cladding diameter nominal value CD nominal [μm] of less than 125 μm used as a basis,
in each of the four cores, a mode field diameter MFD at a wavelength of 1310 nm, a cable cutoff wavelength λ cc measured on a 22 m length of fiber, and a shortest distance d coat of distances from centers of the four cores to an outer periphery of the common cladding satisfy a following Formula (4), in any of the four cores:
a numerical value of the shortest distance d coat ≥a numerical value of (2.88MFD/λ cc +5.36) (4),
in each of the four cores, the mode field diameter MFD falls within a range of a value of an MFD reference value−0.4 μm or more and a value of the MFD reference value+0.4 μm or less with a value of 8.6 μm or more and 9.2 μm or less used as the MFD reference value,
in each of the four cores, a zero-dispersion wavelength falls within a range of a value a wavelength reference value−12 nm or more and a value of the wavelength reference value+12 nm or less with a value of 1312 nm or more and 1340 nm or less used as the wavelength reference value,
in each of the four cores, a dispersion slope at the zero-dispersion wavelength is 0.092 ps/(nm 2 ·km) or less,
in each of the four cores, the cable cutoff wavelength λ cc is 1260 nm or less,
either a first condition or a second condition is satisfied and either a fifth condition or a sixth condition is satisfied,
the first condition is defined that each of the four cores is in direct contact with the common cladding,
the second condition relates to each of the four cores, each of the four cores further including an optical cladding provided between each of the four cores and the common cladding, and is defined that a relative refractive index difference Δ2 of the optical cladding with respect to the common cladding satisfies a relationship that −0.1%≤Δ2≤0.1%,
the fifth condition is defined that a crosstalk between the cores having the adjacent relationship for a fiber length of 10 km at a wavelength of 1360 nm is −10 dB or less, in each of the four cores, a following Formula (5):
a numerical value of the predetermined cladding diameter nominal value CD nominal ≥a numerical value of (13.31MFD/λ cc +24.47) (5)
is satisfied,
and in each of the four cores, MFD/λ cc and a center-to-center interval Λ a between the cores having the adjacent relationship satisfy a following Formula (6):
6.5≤a numerical value of (MFD/λ cc )≤9.5≤a numerical value of (0.443Λ a −5.33) (6), and
the sixth condition is defined that the crosstalk between the cores having the adjacent relationship for the fiber length of 10 km at the wavelength of 1360 nm is −20 dB or less, in each of the four cores, a following Formula (7):
the numerical value of the predetermined cladding diameter nominal value CD nominal ≥a numerical value of (9.37MFD/λ cc +31.73) (7)
is satisfied,
and in each of the four cores, MFD/λ cc and the center-to-center interval Λ a between the cores having the adjacent relationship satisfy a following Formula (8):
6.5≤the numerical value of (MFD/λ cc )≤9.5≤a numerical value of (0.392Λ a −4.88) (8).
11. The multi-core optical fiber according to claim 10 , further comprising
a coating surrounding the common cladding, wherein
a leakage loss from at least any of the four cores to the coating at a wavelength of 1550 nm or a wavelength of 1625 nm is 0.05 dB/km or more, a transmission loss of at least one of the four cores at the wavelength of 1550 nm is 0.25 dB/km or more, or a transmission loss at the wavelength of 1625 nm is 0.25 dB/km or more.
12. The multi-core optical fiber according to claim 10 , wherein
the fifth condition is satisfied, and
the crosstalk between the cores having the adjacent relationship at a wavelength of 1550 nm for the fiber length of 10 km is −10 dB or more.
13. The multi-core optical fiber according to claim 10 , wherein
the sixth condition is satisfied, and
the crosstalk between the cores having the adjacent relationship at a wavelength of 1550 nm for the fiber length of 10 km is −20 dB or more.
14. A multi-core optical fiber cable comprising a plurality of multi-core optical fibers including the multi-core optical fiber defined in claim 10 .
15. The multi-core optical fiber cable according to claim 14 , wherein the multi-core optical fiber has an average bending radius of 0.03 m or more and 0.14 m or less, or 0.14 m or more and 0.3 m or less in a fiber longitudinal direction.
16. A multi-core optical fiber cable incorporating a multi-core optical fiber ribbon in which a plurality of multi-core optical fibers including the multi-core optical fiber defined in claim 10 are intermittently bonded.
17. The multi-core optical fiber cable according to claim 16 , wherein the multi-core optical fiber ribbon is incorporated with spirally twisted.
18. The multi-core optical fiber cable according to claim 16 , wherein the multi-core optical fiber has an average bending radius of 0.03 m or more and 0.14 m or less, or 0.14 m or more and 0.3 m or less in a fiber longitudinal direction.