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

Abstract

The invention relates to a bending-resistant single-mode optical fiber with a small outer diameter, which comprises a core layer and a cladding layer, and is characterized in that the relative refractive index difference n1 of the core layer is 0.3-0.45%, the radius R1 of the core layer is 5.5-7 microns, the cladding layer sequentially comprises a transition cladding layer, an inner cladding layer, a sunken cladding layer and an outer cladding layer from inside to outside, the relative refractive index of the transition cladding layer is gradually reduced from inside to outside, and the inner cladding layer is a concave cladding layer. The relative refractive index difference n3 of the inner cladding layer is-0.3% to-0.7%, the radius R3 of the inner cladding layer is 8-14 [mu] m, the relative refractive index difference n4 of the sunken cladding layer is-0.6% to-0.75%, the radius R4 of the sunken cladding layer is 28-35 [mu] m, the outer cladding layer is a pure silica glass layer, the radius R5 of the outer cladding layer is 60.1-62.5 [mu] m, a coating layer is coated outside the outer cladding layer, and the outer diameter of the coating layer is 150-175 [mu] m. By optimizing the section structure of the optical fiber and improving the performance of the coating layer, the bending performance and the mechanical performance of the optical fiber are effectively ensured on the premise of reducing the coating diameter, and the fracture rate per 100 kilometers is reduced.

Description

Technical Field

[0001] The invention relates to a small outer diameter bending-resistant single-mode optical fiber, belonging to the technical field of optical communication. Background Art

[0002] With the development of 5G, cloud computing and artificial intelligence technologies, the demand for data traffic has exploded. In order to meet the growing demand for communication capacity, it is urgent to increase the density of optical fibers in the pipeline. However, in actual network construction projects, the deployment environment of the access layer and aggregation layer of the bearer network is complex, the existing cable pipeline resources are often limited, and the fiber pipeline resources in the same area are becoming increasingly tight. How to use the limited pipeline space to lay more optical fibers needs to be solved urgently. In this context, high-density, large-core optical cables came into being, which use small outer diameter optical fibers with optimized size to ensure that more optical fibers can be accommodated in a limited space.

[0003] Optical fiber consists of two parts: the glass part and the coating. The glass part includes the core layer and the cladding. The cladding surrounds the core layer. The core layer is used to transmit optical signals. The cladding further confines the optical signal to the core layer. The coating is applied to the outer surface of the optical fiber cladding to protect the optical fiber from mechanical damage while enhancing the flexibility of the optical fiber for subsequent cabling and engineering use. Therefore, to reduce the outer diameter of the optical fiber, the three main ideas are to reduce the size of the glass part, reduce the size of the coating layer, and reduce the size of the glass part and the coating layer at the same time.

[0004] In order to ensure the optical transmission performance of optical fiber, the commonly used technical path is to keep the outer diameter of the optical fiber glass part unchanged at 125 microns, and to achieve a small diameter of the optical fiber by reducing the thickness of the optical fiber coating. However, reducing the thickness of the optical fiber coating will affect the strength of the optical fiber to a certain extent, making the small outer diameter optical fiber using conventional two-layer coating often face the problem of high breakage rate per 100 kilometers. Summary of the invention

[0005] The following are definitions and explanations of some terms involved in the present invention:

[0006] Starting from the axis of the optical fiber core, according to the change of refractive index, the layer closest to the axis is defined as the core layer, and the outermost layer of the optical fiber, that is, the pure silica layer, is defined as the optical fiber cladding.

[0007] Relative refractive index difference of each layer of optical fiber Δn i It is defined by the following equation:

[0008] Among them, n i is the refractive index of the fiber core, and n c is the refractive index of the outer cladding, that is, the refractive index of pure silica.

[0009] Optical cable cut-off wavelength λcc IEC 60793-1-44 defines the optical cable cutoff wavelength as the wavelength at which the optical signal no longer propagates as a single-mode signal after propagating 22m in the optical fiber. During the test, a 22m long uncabled optical fiber was used, and n circles with a radius greater than or equal to 14cm were wound around it, with a circle of 4cm radius added at each end as the test condition to obtain data.

[0010] The microbend test method is tested according to Method B specified in IEC TR62221-2012. Since long wavelengths are more sensitive to bending and increase exponentially, and the test wavelength range is 1250-1700nm, the microbend at long wavelengths is focused on in the present invention, and the microbend value at 1700nm is used to measure the microbend performance of the optical fiber.

[0011] The technical problem to be solved by the present invention is to provide a small outer diameter bending-resistant single-mode optical fiber to address the deficiencies in the above-mentioned prior art. It optimizes the optical fiber profile structure and improves the coating performance to effectively ensure the bending performance 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: it includes a core layer and a cladding, characterized in that the relative refractive index difference △n1 of the core layer is 0.3~0.45%, the radius R1 is 5.5~7μm, the cladding includes a transition cladding, an inner cladding, a depressed cladding and an outer cladding from the inside to the outside, the relative refractive index of the transition cladding is gradually decreasing from the inside to the outside, the radius R2 is 8~12.6μm, the relative refractive index difference △n3 of the inner cladding is -0.3~-0.7%, the radius R3 is 8~14μm, the relative refractive index difference △n4 of the depressed cladding is -0.6~-0.75%, the radius R4 is 28~35μm, the outer cladding is a pure silica glass layer, the radius R5 is 60.1~62.5μm, and the outer cladding is coated with a coating layer, and the outer diameter of the coating layer is 150~175μm.

[0013] According to the above scheme, the transition cladding is distributed in an α-order parabola, and the distribution index α is 1.0 to 5.0.

[0014] According to the above solution, 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% to 96%. Under preferred conditions, the curing rate is higher than 96%.

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

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

[0018] According to the above scheme, the dynamic fatigue parameter n of the optical fiber is d Greater than or equal to 20; preferably 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, the optical fiber is bent 10 times with a radius of 15 mm, and the macro-bending loss at a wavelength of 1550 nm is less than or equal to 0.03 dB, and the macro-bending loss at a wavelength of 1625 nm is less than or equal to 0.1 dB; the optical fiber is bent 1 time with a radius of 10 mm, and the macro-bending loss at a wavelength of 1550 nm is less than or equal to 0.1 dB, and the macro-bending loss at a wavelength of 1625 nm is less than or equal to 0.2 dB; the optical fiber is bent 1 time with a radius of 7.5 mm, and the macro-bending loss at a wavelength of 1550 nm is less than or equal to 0.5 dB, and the macro-bending loss at a wavelength of 1625 nm is less than or equal to 1.0 dB.

[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 attenuation of the optical fiber at a wavelength of 1310nm is less than or equal to 0.37dB / km, the attenuation at a wavelength of 1383nm is less than or equal to 0.38dB / km, the attenuation at a wavelength of 1550nm is less than or equal to 0.23dB / km, and the attenuation at a wavelength of 1625nm is less than or equal to 0.27dB / km. The attenuation of a more preferred optical fiber at a wavelength of 1310nm is less than or equal to 0.35dB / km, the attenuation at a wavelength of 1383nm is less than or equal to 0.30dB / km, the attenuation at a wavelength of 1550nm is less than or equal to 0.19dB / km, and the attenuation at a wavelength of 1625nm is less than or equal to 0.21dB / km.

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

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

[0025] The beneficial effects of the present invention are as follows: 1. By optimizing the refractive index distribution of the optical fiber section and reducing the thickness of the resin coating layer, the outer diameter of the optical fiber is reduced, which can effectively improve the fiber capacity per unit volume of the optical cable; 2. By optimizing the physical and chemical properties of the resin coating and adopting a coating layer structure, not only the diameter of the optical fiber resin coating is reduced, the outer diameter is reduced by more than 30% compared with the outer diameter of 245μm of the conventional single-mode optical fiber, but also the optical fiber has excellent bending performance and mechanical properties, improves the optical fiber strength, and reduces the optical fiber breakage rate per 100 kilometers; 3. Providing 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 cladding, reduce the optical fiber sectioning defects, and further enhance the bending performance and mechanical properties of the optical fiber; 4. The present invention simplifies the preparation process, improves production efficiency, reduces the preparation cost of the optical fiber, and is suitable for large-scale production; at the same time, it also reduces the use of resin coating materials, which is beneficial to green environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the relative refractive index difference of each cross section of an embodiment of the present invention.

[0027] Figure 2 Schematic diagram of microbending sensitivity of a coating layer according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with embodiments and drawings.

[0029] The bare optical fiber part includes a core layer and a cladding layer, and the outer layer of the cladding is a coating layer. The refractive index of the core layer is flat, and the corresponding relative refractive index difference is △n1, and the radius is R1. The cladding includes a transition cladding, an inner cladding, a depressed cladding and an outer cladding from the inside to the outside. The relative refractive index of the transition cladding from the inside to the outside is gradual, distributed in an α-parabola shape, and the distribution index α is 1.0-5.0, and the radius is R2. The inner cladding is flat, and the corresponding relative refractive index difference is △n3, and the radius is R3. The depressed cladding is a depressed cladding, and the corresponding relative refractive index difference is △n4, and the radius is R4. The outer cladding is a pure silica glass layer, and the corresponding relative refractive index difference △n5 is 0, and the radius R5 is 60.1-62.5μm. The outer cladding is a coating layer, and there is a coating layer. The outer diameter of the coating layer is 150-175μm, that is, the outer diameter of the optical fiber.

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

[0032]

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

[0034]

[0035]

Claims

1. A small outer diameter bending-resistant single-mode optical fiber, comprising a core layer and a cladding layer, characterized in that The relative refractive index difference △n1 of the core layer is 0.3~0.45%, and the radius R1 is 5.5~7μm. The cladding includes a transition cladding, an inner cladding, a depressed cladding and an outer cladding from the inside to the outside. The relative refractive index of the transition cladding is gradually decreasing from the inside to the outside, and the radius R2 is 8~12.6μm. The relative refractive index difference △n3 of the inner cladding is -0.3~-0.7%, and the radius R3 is 8~14μm. The relative refractive index difference △n4 of the depressed cladding is -0.6~-0.75%, and the radius R4 is 28~35μm. The outer cladding is a pure silica glass layer, and the radius R5 is 60.1~62.5μm. The outer cladding is coated with a coating layer, and the outer diameter of the coating layer is 150~175μm.

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-order parabola, and the distribution index α is 1.0-5.

0.

3. The small outer diameter bend-resistant single-mode optical fiber according to claim 1 or 2, characterized in that 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 0.7-1.0 GPa.

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

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

6. The small outer diameter bend-resistant single-mode optical fiber according to claim 4, characterized in that Average stripping force F of the optical fiber coating avg ≥0.4N, peak peeling 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 breakage rate of the optical fiber is 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 is bent 10 times with a radius of 15 mm, and the macro-bending loss at a wavelength of 1550 nm is less than or equal to 0.03 dB, and the macro-bending loss at a wavelength of 1625 nm is less than or equal to 0.1 dB; the optical fiber is bent once with a radius of 10 mm, and the macro-bending loss at a wavelength of 1550 nm is less than or equal to 0.1 dB, and the macro-bending loss at a wavelength of 1625 nm is less than or equal to 0.2 dB; the optical fiber is bent once with a radius of 7.5 mm, and the macro-bending loss at a wavelength of 1550 nm is less than or equal to 0.5 dB, and the macro-bending loss at a wavelength of 1625 nm is less than or equal to 1.0 dB.

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

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

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

13. The small outer diameter bend-resistant single-mode optical fiber according to claim 1 or 2, characterized in that The optical cable cut-off wavelength of the optical fiber is less than or equal to 1260nm; the zero dispersion wavelength is 1300nm to 1324nm.

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