Reduced diameter optical fiber and manufacturing method
The invention relates to an optical fiber 1 comprising a core 2 and a cladding 3 surrounding the core 2 and having an outer diameter of 125 μm, the optical fiber 1 comprising a cured primary coating 4 directly surrounding the cladding 3 and a cured secondary coating 5 directly surrounding the cured primary coating 4 , said cured primary coating 4 having a thickness t 1 between 10 and 18 μm and an in-situ tensile modulus Emod 1 between 0.10 and 0.18 MPa, said cured secondary coating 5 having a thickness t 2 lower or equal to 18 μm and an in-situ tensile modulus Emod 2 between 700 and 1200 MPa, wherein said first and second thicknesses and said first and second in-situ tensile moduli satisfy the following equation: 4%<(t 1 ×t 2 ×Emod 1 ×Emod 2 3 )/(t 1_norm ×t 2_norm ×Emod 1_norm ×Emod 2_norm 3 )<50%.
1. An optical fiber ( 1 ) having an optical-fiber diameter of 180 microns or less, the optical fiber comprising a core ( 2 ) and a cladding ( 3 ) surrounding the core ( 2 ) and having an outer diameter of 125 μm, the optical fiber ( 1 ) comprising a cured primary coating ( 4 ) directly surrounding the cladding ( 3 ) and a cured secondary coating ( 5 ) directly surrounding the cured primary coating ( 4 ), said cured primary coating ( 4 ) having a thickness t 1 between 10 and 18 μm and an in-situ tensile modulus Emod 1 between 0.10 and 0.18 MPa, said cured secondary coating ( 5 ) having a thickness t 2 lower or equal to 18 μm and an in-situ tensile modulus Emod 2 between 700 and 1200 MPa, wherein said first and second thicknesses and said first and second in-situ tensile moduli satisfy the following equation:
4%<( t 1 ×t 2 ×E mod 1 ×E mod 2 3 )/( t 1_norm ×t 2_norm ×E mod 1_norm ×E mod 2_norm 3 )<50%
Where t 1_norm is the thickness of the cured primary coating of a standard 245 μm-diameter optical fiber, which is equal to 33.5 μm,
t 2_norm is the thickness of the cured secondary coating of a standard 245 μm-diameter optical fiber, which is equal to 25 μm,
Emod 1_norm is the in-situ tensile modulus of the cured primary coating of a standard 245 μm-diameter optical fiber, which is equal to 0.4 MPa, and
Emod 2_norm is the in-situ tensile modulus of the cured secondary coating of a standard 245 μm-diameter optical fiber, which is equal to 800 MPa.
2. The optical fiber ( 1 ) according to claim 1 , wherein both the core ( 2 ) and the cladding ( 3 ) are made of doped or un-doped silica.
3. The optical fiber ( 1 ) according to claim 1 , wherein the cured primary coating ( 4 ) has a cure rate yield after UV curing between 80 and 90% one week after draw.
4. The optical fiber ( 1 ) according to claim 1 , wherein the cured secondary coating ( 5 ) has a cure rate yield after UV curing between 94 and 98%.
5. The optical fiber ( 1 ) according to claim 1 , wherein the primary coating ( 4 ) has a thickness t 1 between 10 and 16 μm.
6. The optical fiber ( 1 ) according to claim 1 , wherein the secondary coating ( 5 ) has a tensile modulus Emod 2 higher than 1000 MPa.
7. The optical fiber ( 1 ) according to claim 1 , wherein the optical fiber ( 1 ) complies with the macro-bend losses specified in the ITU-T G.657.A1 (October 2012) recommendations.
8. The optical fiber ( 1 ) according to claim 7 , wherein the cladding ( 3 ) comprises a depressed area.
9. An optical cable ( 6 ) comprising at least one optical fiber ( 1 ) according to claim 1 .
10. A method ( 12 ) for manufacturing an optical fiber ( 1 ) having an optical-fiber diameter of 180 microns or less from a core ( 2 ) and a cladding ( 3 ) surrounding the core ( 2 ) and having an outer diameter of 125 μm, the method ( 12 ) comprising:
Applying (S 1 ) a primary coating directly on the cladding ( 3 ), with a thickness t 1 between 10 and 18 μm,
Curing (S 2 ) the primary coating to obtain a cured primary coating ( 4 ) with an in-situ tensile modulus Emod 1 between 0.10 and 0.18 MPa,
Applying (S 3 ) a secondary coating directly on the cured primary coating ( 4 ), with a thickness t 2 lower or equal to 18 μm,
Curing (S 4 ) the secondary coating ( 5 ) to obtain a cured secondary coating ( 5 ) with an in-situ tensile modulus Emod 2 between 700 and 1200 MPa,
The preceding steps being performed so that said first and second thicknesses and said first and second in-situ tensile moduli satisfy the following equation:
4%<( t 1 ×t 2 ×E mod 1 ×E mod 2 3 )/( t 1_norm ×t 2_norm ×E mod 1_norm ×E mod 2_norm 3 )<50%
Where t 1_norm is the thickness of the cured primary coating of a standard 245 μm-diameter optical fiber, which is equal to 33.5 μm,
t 2_norm is the thickness of the cured secondary coating of a standard 245 μm-diameter optical fiber, which is equal to 25 μm,
Emod 1_norm is the in-situ tensile modulus of the cured primary coating of a standard 245 μm-diameter optical fiber, which is equal to 0.4 MPa, and
Emod 2_norm is the in-situ tensile modulus of the cured secondary coating of a standard 245 μm-diameter optical fiber, which is equal to 800 MPa.
11. An optical fiber ( 1 ) having an optical-fiber diameter of 180 microns or less, the optical fiber comprising a core ( 2 ) and a cladding ( 3 ) surrounding the core ( 2 ) and having an outer diameter of 125 μm, the optical fiber ( 1 ) comprising a cured primary coating ( 4 ) directly surrounding the cladding ( 3 ) and a cured secondary coating ( 5 ) directly surrounding the cured primary coating ( 4 ), said cured primary coating ( 4 ) having a thickness t 1 between 10 and 18 μm, an in-situ tensile modulus Emod 1 between 0.10 and 0.18 MPa, and a cure rate yield after UV curing between 80 and 90% one week after draw, said cured secondary coating ( 5 ) having a thickness t 2 lower or equal to 18 μm, an in-situ tensile modulus Emod 2 between 700 and 1200 MPa, and a cure rate yield after UV curing between 94 and 98%, wherein said first and second thicknesses and said first and second in-situ tensile moduli satisfy the following equation:
4%<( t 1 ×t 2 ×E mod 1 ×E mod 2 3 )/( t 1_norm ×t 2_norm ×E mod 1_norm ×E mod 2_norm 3 )<50%
where t 1_norm is the thickness of the cured primary coating of a standard 245 μm-diameter optical fiber, which is equal to 33.5 μm,
t 2-norm is the thickness of the cured secondary coating of a standard 245 μm-diameter optical fiber, which is equal to 25 μm,
Emod 1-norm is the in-situ tensile modulus of the cured primary coating of a standard 245 μm-diameter optical fiber, which is equal to 0.4 MPa, and
Emod 2_norm is the in-situ tensile modulus of the cured secondary coating of a standard 245 μm-diameter optical fiber, which is equal to 800 MPa.
12. The optical fiber ( 1 ) according to claim 11 , wherein the cured primary coating ( 4 ) has a cure rate yield after UV curing between 82 and 87% one week after draw.
13. The optical fiber ( 1 ) according to claim 11 , wherein the cured secondary coating ( 5 ) has a cure rate yield after UV curing between 95 and 97%.
14. The optical fiber ( 1 ) according to claim 11 , wherein the primary coating ( 4 ) has a thickness t 1 between 10 and 16 μm.
15. The optical fiber ( 1 ) according to claim 11 , wherein the secondary coating ( 5 ) has a tensile modulus Emod 2 higher than 1000 MPa.
16. The optical fiber ( 1 ) according to claim 11 , wherein the cladding ( 3 ) comprises a trench.
17. The optical fiber ( 1 ) according to claim 11 , wherein the optical fiber has a cable cut-off wavelength less than or equal to 1260 nm.
18. The optical fiber ( 1 ) according to claim 11 , wherein, at a wavelength 1310 nm, the optical fiber has a Mode Field Diameter (MFD) between 8.6 and 9.5 μm.
19. The optical fiber ( 1 ) according to claim 11 , wherein the optical fiber has a zero-dispersion wavelength between 1300 and 1324 nm.
20. An optical cable ( 6 ) comprising at least one optical fiber ( 1 ) according to claim 11 .