Bending-resistant single-mode optical fiber with small outer diameter

Abstract

The present invention relates to a bending-resistant single-mode optical fiber with a small outer diameter. The optical fiber comprises a core layer and a cladding layer, characterized in that the relative refractive index difference △n1 of the core layer is 0.3% to 0.45%, and the radius R1 thereof is 5.5 μm to 7 μm; the cladding layer sequentially comprises, from inside to outside, a transition cladding layer, an inner cladding layer, a depressed cladding layer and an outer cladding layer; the relative refractive index of the transition cladding layer gradually decreases from inside to outside, and the radius R2 thereof is 8 μm to 12.6 μm; the relative refractive index difference △n3 of the inner cladding layer is -0.3% to -0.7%, and the radius R3 thereof is 8 μm to 14 μm; the relative refractive index difference △n4 of the depressed cladding layer is -0.6% to -0.75%, and the radius R4 thereof is 28 μm to 35 μm; the outer cladding layer is a pure silica glass layer, and the radius R5 thereof is 60.1 μm to 62.5 μm; the outer cladding layer is coated with a coating layer, and the outer diameter of the coating layer is 150 μm to 175 μm. By means of optimizing the cross-sectional structure of an optical fiber, and improving the performance of a coating layer, the present invention effectively ensures the bending performance and mechanical performance of the optical fiber while reducing a coating diameter, thereby reducing the breakage rate per hundred kilometers.

Description

A small outer diameter bend-resistant single-mode optical fiber Technical Field

[0001] This invention relates to a small-diameter, bend-resistant single-mode optical fiber, belonging to the field of optical communication technology. Background Technology

[0002] With the development of 5G, cloud computing, and artificial intelligence technologies, the demand for data traffic is exploding. To meet the ever-increasing demand for communication capacity, it is urgent to increase the fiber optic density within pipelines. However, in actual network construction projects, the deployment environment of the access and aggregation layers of the bearer network is complex, and existing cable pipeline resources are often limited, leading to increasingly strained fiber optic pipeline resources within the same area. The practical problem of how to utilize limited pipeline space to lay more optical fibers urgently needs to be solved. Against this backdrop, high-density, high-core-count optical cables have emerged, employing size-optimized small-diameter optical fibers to ensure that more optical fibers can be accommodated within a limited space.

[0003] Optical fiber consists of two main parts: the glass portion and the coating layer. The glass portion includes the core and the cladding. The cladding surrounds the core, which transmits optical signals. The cladding further confines the optical signals within the core. A coating is applied to the outside of the fiber cladding to protect the fiber from mechanical damage and enhance its flexibility for subsequent cabling and engineering applications. Therefore, to reduce the outer diameter of optical fibers, the three main approaches are to reduce the size of the glass portion, reduce the size of the coating layer, and simultaneously reduce both the glass portion and the coating layer.

[0004] To ensure the optical transmission performance of optical fibers, the common technical approach is to keep the outer diameter of the fiber glass portion constant at 125 micrometers and reduce the thickness of the fiber coating to achieve a smaller diameter. However, reducing the thickness of the fiber coating will affect the strength of the fiber to some extent, causing small-diameter optical fibers with conventional two-layer coatings to often face a high breakage rate over 100 kilometers. Summary of the Invention

[0005] The following are definitions and explanations of some terms used in this invention:

[0006] Starting from the fiber core axis, based on the change in refractive index, the layer closest to the axis is defined as the core layer, and the outermost layer of the fiber, namely the pure silica layer, is defined as the fiber cladding.

[0007] Relative refractive index difference between layers of optical fiber Defined by the following equation: ,

[0008] in, Let be the refractive index of the fiber core, and This is the refractive index of the outer cladding layer, i.e., the refractive index of pure silicon dioxide.

[0009] Optical cable cutoff wavelength λ cc In IEC 60793-1-44, the cutoff wavelength of an optical fiber is defined as the wavelength at which an optical signal ceases to propagate as a single-mode signal after traveling 22m in the optical fiber. During testing, a 22m long un-cablened optical fiber is used, with n loops of radius ≥ 14cm, and a 4cm loop added at each end to obtain data.

[0010] The microbending test method is performed according to Method B specified in IEC TR62221-2012. Since longer wavelengths are more sensitive to bending and the bending increases exponentially, and the test wavelength range is 1250~1700nm, this invention focuses on examining microbending at longer wavelengths, and uses the microbending value at 1700nm to measure the microbending performance of the optical fiber.

[0011] The technical problem to be solved by this invention is to provide a small-diameter, bend-resistant single-mode optical fiber that addresses the shortcomings of the existing technology. By optimizing the fiber profile structure and improving the coating performance, it effectively ensures the bending and mechanical properties of the optical fiber while reducing the coating diameter, thereby reducing the breakage rate per 100 kilometers.

[0012] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows: It includes a core layer and a cladding layer. The core layer has a relative refractive index difference Δn1 of 0.3 ~ 0.45% and a radius R1 of 5.5 ~ 7 μm. The cladding layer, from the inside out, includes a transition cladding layer, an inner cladding layer, a recessed cladding layer, and an outer cladding layer. The transition cladding layer has a gradually decreasing relative refractive index from the inside out and a radius R2 of 8 ~ 12.6 μm. The inner cladding layer has a relative refractive index difference Δn3 of -0.3 ~ -0.7% and a radius R3 of 8 ~ 14 μm. The recessed cladding layer has a relative refractive index difference Δn4 of -0.6 ~ -0.75% and a radius R4 of 28 ~ 35 μm. The outer cladding layer is a pure silica glass layer with a radius R5 of 60.1 ~ 62.5 μm. The outer cladding layer is coated with a coating layer with an outer diameter of 150 ~ 175 μm.

[0013] According to the above scheme, the transition cladding is distributed in an α-parabolic shape, with a distribution index α ranging from 1.0 to 5.0.

[0014] According to the above scheme, the coating layer of the optical fiber is a single layer, and the coating layer is a polyacrylate polymer adhesive with an in-situ modulus of 0.7 to 1.0 GPa.

[0015] According to the above scheme, the curing rate of the coating layer of the optical fiber after drawing is 93%~96%. Under preferred conditions, the curing rate is higher than 96%.

[0016] According to the above scheme, after the optical fiber coating is fully cured, the tensile strength F15% ≥ 3.4 GPa and F50% ≥ 3.8 GPa. Under preferred conditions, the tensile strength F15% ≥ 4.0 GPa and F50% ≥ 4.5 GPa, and under more preferred conditions, the tensile strength F15% ≥ 5.0 GPa and F50% ≥ 5.0 GPa.

[0017] According to the above scheme, the average peeling force F of the optical fiber coating layer is... avg ≥0.4N, peak peel force F peak ≥0.6N; under preferred conditions, the average peel force F of the optical fiber coating avg ≥0.6N, peak peel force F peak ≥0.8N; more preferably, the average peel force F of the optical fiber coating. avg ≥1.0N, peak peel force F peak ≥1.3N.

[0018] According to the above scheme, the dynamic fatigue parameter n of the optical fiber d Greater than or equal to 20; under preferred conditions, n d Greater than or equal to 22; more preferably n d Greater than or equal to 23.

[0019] According to the above scheme, the breakage rate of the optical fiber is less than or equal to 5 times per 100 kilometers.

[0020] According to the above scheme, when the optical fiber is bent 10 times with a radius of 15mm, the macro-bending loss at a wavelength of 1550nm is less than or equal to 0.03dB, and the macro-bending loss at a wavelength of 1625nm is less than or equal to 0.1dB; when the optical fiber is bent once with a radius of 10mm, the macro-bending loss at a wavelength of 1550nm is less than or equal to 0.1dB, and the macro-bending loss at a wavelength of 1625nm is less than or equal to 0.2dB; when the optical fiber is bent once with a radius of 7.5mm, the macro-bending loss at a wavelength of 1550nm is less than or equal to 0.5dB, and the macro-bending loss at a wavelength of 1625nm is less than or equal to 1.0dB.

[0021] According to the above scheme, the microbending loss of the optical fiber at a wavelength of 1700nm is 0.7~4.0dB / km.

[0022] According to the above scheme, the optical fiber has an attenuation of less than or equal to 0.37 dB / km at a wavelength of 1310 nm, less than or equal to 0.38 dB / km at a wavelength of 1383 nm, less than or equal to 0.23 dB / km at a wavelength of 1550 nm, and less than or equal to 0.27 dB / km at a wavelength of 1625 nm. A more optimized optical fiber has an attenuation of less than or equal to 0.35 dB / km at a wavelength of 1310 nm, less than or equal to 0.30 dB / km at a wavelength of 1383 nm, less than or equal to 0.19 dB / km at a wavelength of 1550 nm, and less than or equal to 0.21 dB / km at a wavelength of 1625 nm.

[0023] According to the above scheme, the mode field diameter of the optical fiber at a wavelength of 1310nm is 8.0~9.5μm; under preferred conditions, the mode field diameter of the optical fiber at a wavelength of 1310nm is 8.2~9.2μm.

[0024] According to the above scheme, the optical fiber's cutoff wavelength is less than or equal to 1260nm; the zero-dispersion wavelength is 1300nm~1324nm.

[0025] The beneficial effects of this invention are as follows: 1. By optimizing the refractive index distribution of the optical fiber profile and reducing the thickness of the resin coating layer, the outer diameter of the optical fiber is reduced, which can effectively increase the fiber capacity per unit volume of the optical cable; 2. By optimizing the physicochemical properties of the resin coating and adopting a single-layer coating structure, not only is the diameter of the optical fiber resin coating reduced, with the outer diameter reduced by more than 30% compared to the 245μm outer diameter of conventional single-mode optical fiber, but the optical fiber also possesses excellent bending and mechanical properties, improves the optical fiber strength, and reduces the fiber breakage rate per 100 kilometers; 3. Setting a transition cladding with a gradually decreasing relative refractive index from the inside to the outside helps to reduce the internal stress between the core and cladding, reduce optical fiber profile defects, and further enhance the bending and mechanical properties of the optical fiber; 4. This invention simplifies the manufacturing process, improves production efficiency, reduces the manufacturing cost of optical fibers, and is suitable for large-scale production; it also reduces the amount of resin coating material used, which is beneficial to environmental protection. Attached Figure Description

[0026] Figure 1 is a schematic diagram of the relative refractive index difference of various cross sections according to an embodiment of the present invention.

[0027] Figure 2 is a schematic diagram of the microbending sensitivity of the coating layer in an embodiment of the present invention. Embodiments of the present invention

[0028] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0029] The bare optical fiber consists of a core and a cladding, with a coating layer outside the cladding. The core has a flat refractive index with a relative refractive index difference of Δn1 and a radius of R1. The cladding, from the inside out, includes a transition cladding, an inner cladding, a recessed cladding, and an outer cladding. The transition cladding has a gradually changing relative refractive index from the inside out, distributed in an α-order parabolic shape with a distribution index α of 1.0–5.0 and a radius of R2. The inner cladding is flat with a relative refractive index difference of Δn3 and a radius of R3. The recessed cladding is a concave cladding with a relative refractive index difference of Δn4 and a radius of R4. The outer cladding is a pure silica glass layer with a relative refractive index difference of Δn5 of 0 and a radius of R5 of 60.1–62.5 μm. Outside the outer cladding is a coating layer with an outer diameter of 150–175 μm, which is the outer diameter of the optical fiber.

[0030] Table 1 shows the refractive index profile parameters and in-situ modulus characteristics of the coating layer in various examples of the present invention, and Table 2 shows the optical and mechanical properties of the optical fiber in various examples of the present invention.

[0031] Table 1. Refractive index profile parameters and in-situ modulus of coating layer in the embodiments of the present invention.

[0032] Parameter Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 R1 (μm) 6.2 5.8 6.9 6.3 6.5 6.6 5.8 6.3 5.8 Δn1 (%) 0.31 0.34 0.36 0.42 0.44 0.36 0.43 0.32 0.45 R2 (μm) 8.11 0.61 0.41 1.81 0.71 2.11 2.61 2.21 1.9 α 1.0 2.1 4.2 3.55 2.5 3.6 4.25 R3 (μm) 8.11 2.61 1.61 3.41 2.51 3.91 3.81 4 13.7 Δn3 (%) -0.55 -0.42 -0.36 -0.64 -0.68 -0.42 -0.51 -0.47 -0.33 R4 (μm) 30.23 1.62 9.73 0.92 8.53 2.53 4.13 3.63 1.9 Δn4 (%) -1.23 -1.05 -1.34 -1.27 -1.38 -1.21 -1.43 -1.25 1.43 In-situ modulus of coating layer (GPa) 0.70 0.72 0.86 0.95 0.87 0.93 0.94 0.97 0.99 Fiber outer diameter (μm) 156.6 161.1 168.5 171.3 172.5 175.4 169.5 161.6 172.6

[0033] Table 2 Optical and mechanical properties of the optical fibers in the embodiments of the present invention

[0034] Fiber Characteristics Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Mode Field Diameter (MFD) @ 1310 nm (μm) 8.57 8.46 8.72 8.82 8.63 8.71 8.86 8.52 8.91 Zero Dispersion Wavelength (nm) 1309 1310 1311 1310 1310 1312 1310 1311 1310 Optical Cable Cutoff Wavelength (nm) 1235 1240 125 11243 1240 1230 1228 1236 1242 Attenuation Coefficient @ 1310 (dB / km) 0.328 0.343 0.355 0.319 0.334 0.340 0.327 0.326 0.342 Attenuation coefficient @1383 (dB / km) 0.301 0.293 0.270 0.271 0.289 0.297 0.281 0.272 0.270 Attenuation coefficient @1550 (dB / km) 0.188 0.189 0.187 0.188 0.188 0.186 0.191 0.190 0.185 Attenuation coefficient @1625 (dB / km) 0.198 0.195 0.196 0.197 0.197 0.194 0.197 0.199 0.193 Macro bending loss Bending radius R15mm 10 cycles @ 1550nm (dB) 0.021 0.023 0.024 0.020 0.016 0.019 0.023 0.026 0.021 Macro bending loss Bending radius R15mm 10 cycles @ 1625nm (dB) 0.01 0.06 0.03 0.04 0.07 0.02 0.01 0.03 0.07 Macro bending loss Bending radius R10mm 1 cycle @ 1550nm (dB) 0.02 0.02 0.02 0.05 0.06 0.04 0.01 0.08 0.05 Macro bending loss Bending radius R10mm 1 cycle @ 1625nm (dB) 0.09 0.11 0.12 0.11 0.10 0.07 0.08 0.15 0.16 Macro bending loss Bending radius R7.5mm 1 revolution @ 1550nm (dB) 0.210.210.210.210.210.210.210.21 Macro bending loss Bending radius R 7.5mm 1 loop @ 1625nm (dB) 0.2 0.52 0.24 0.65 0.32 0.15 0.25 0.28 0.46 Microbending sensitivity 1.5 1.92 2.0 2.1 2.0 2.2 2.4 2.0 2.0 Microbending loss @ 1700nm (dB / km) 0.72 0.95 0.94 1.6 1.79 2.74 3.2 2.96 3.68 Fiber strength F15% (GPa) 4.12 3.94 4.03 4.10 5.10 5.01 4.85 4.76 4.85 Fiber strength F50% (GPa) 4.65 4.36 4.42 4.25 5.26 5.125.044.965.08 Average peel force of coating Favg (N) 0.6 0.7 0.7 0.6 0.8 0.6 0.7 0.8 0.7 Peak peel force of coating Fpeak (N) 0.9 1.0 1.0 0.9 1.1 1.2 1.0 1.0 0.9 Breaking rate / 100km 453 455 445.

Claims

1. A small-diameter, bend-resistant single-mode optical fiber, comprising a core and a cladding, characterized in that... The core layer has a relative refractive index difference Δn1 of 0.3 to 0.45% and a radius R1 of 5.5 to 7 μm. The cladding consists of a transition cladding, an inner cladding, a recessed cladding, and an outer cladding, from the inside out. The transition cladding has a gradually decreasing relative refractive index from the inside out and a radius R2 of 8 to 12.6 μm. The inner cladding has a relative refractive index difference Δn3 of -0.3 to -0.7% and a radius R3 of 8 to 14 μm. The recessed cladding has a relative refractive index difference Δn4 of -0.6 to -0.75% and a radius R4 of 28 to 35 μm. The outer cladding is a pure silica glass layer with a radius R5 of 60.1 to 62.5 μm. The outer cladding is coated with a coating layer with an outer diameter of 150 to 175 μm.

2. The small outer diameter bend-resistant single-mode optical fiber according to claim 1, characterized in that... The transition cladding is distributed in an α-parabolic shape, with a distribution index α ranging from 1.0 to 5.

0.

3. The small-diameter, bend-resistant single-mode optical fiber according to claim 1 or 2, characterized in that... The optical fiber has a single-layer coating, which is a polyacrylate polymer adhesive with an in-situ modulus of 0.7–1.0 GPa.

4. The small outer diameter bend-resistant single-mode optical fiber according to claim 3, characterized in that... The coating of the optical fiber has a curing rate of 93% to 96% after drawing.

5. The small outer diameter bend-resistant single-mode optical fiber according to claim 4, characterized in that... After the optical fiber coating is fully cured, the tensile strength F15%≥3.4GPa and F50%≥3.8GPa.

6. The small outer diameter bend-resistant single-mode optical fiber according to claim 4, characterized in that... Average peel force F of optical fiber coating avg ≥0.4N, peak peel force F peak ≥0.6N.

7. The small outer diameter bend-resistant single-mode optical fiber according to claim 4, characterized in that... The dynamic fatigue parameter n of the optical fiber d Greater than or equal to 20.

8. The small outer diameter bend-resistant single-mode optical fiber according to claim 4, characterized in that... The fiber optic cable has a breakage rate of less than or equal to 5 times per 100 kilometers.

9. The small outer diameter bend-resistant single-mode optical fiber according to claim 1 or 2, characterized in that... The optical fiber bent 10 times with a radius of 15 mm has a macro-bending loss of less than or equal to 0.03 dB at a wavelength of 1550 nm and less than or equal to 0.1 dB at a wavelength of 1625 nm; the optical fiber bent once with a radius of 10 mm has a macro-bending loss of less than or equal to 0.1 dB at a wavelength of 1550 nm and less than or equal to 0.2 dB at a wavelength of 1625 nm; the optical fiber bent once with a radius of 7.5 mm has a macro-bending loss of less than or equal to 0.5 dB at a wavelength of 1550 nm and less than or equal to 1.0 dB at a wavelength of 1625 nm.

10. The small-diameter, bend-resistant single-mode optical fiber according to claim 1 or 2, characterized in that... The optical fiber has a microbending loss of 0.7~4.0 dB / km at a wavelength of 1700 nm.

11. The small-diameter, bend-resistant single-mode optical fiber according to claim 1 or 2, characterized in that... The optical fiber has an attenuation of less than or equal to 0.37 dB / km at a wavelength of 1310 nm, less than or equal to 0.38 dB / km at a wavelength of 1383 nm, less than or equal to 0.23 dB / km at a wavelength of 1550 nm, and less than or equal to 0.27 dB / km at a wavelength of 1625 nm.

12. The small-diameter, bend-resistant single-mode optical fiber according to claim 1 or 2, characterized in that... The optical fiber has a mode field diameter of 8.0~9.5μm at a wavelength of 1310nm.

13. The small-diameter, bend-resistant single-mode optical fiber according to claim 1 or 2, characterized in that... The optical fiber has a cutoff wavelength of less than or equal to 1260nm and a zero-dispersion wavelength of 1300nm~1324nm.

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