Ultra-small-outer-diameter low-attenuation bending-resistant single-mode optical fiber

Abstract

The invention relates to an ultra-small-outer-diameter low-attenuation bending-resistant single-mode optical fiber which comprises a core layer and cladding layers, the relative refractive index difference n1 of the core layer ranges from 0.3% to 0.5%, the diameter D1 of the core layer ranges from 7 micrometers to 9 micrometers, the cladding layer sequentially comprises an inner cladding layer, a sunken cladding layer and an outer cladding layer from inside to outside, the inner cladding layer is a transition layer between the core layer and the sunken cladding layer, and the outer cladding layer is a transition layer between the core layer and the sunken cladding layer. The relative refractive index difference is gradually decreased from inside to outside, the relative refractive index difference n2 is-0.01-0.05%, the diameter D2 is 14-18 [mu] m, the relative refractive index difference n3 of the sunken cladding layer is-0.2--0.4%, the diameter D3 is 28-34 [mu] m, the outer cladding layer is a pure silica glass layer, the relative refractive index difference n4 is 0, and the diameter D4 is 79-81 [mu] m. According to the invention, the optical cable with the same volume can accommodate more fibers. By optimizing the section design of the optical fiber and the physicochemical properties of the coating layer, the bending performance, mechanical performance and optical transmission performance of the optical fiber can be effectively ensured, and the same communication performance as that of a fiber with a conventional wire diameter of 125 microns can be achieved.

Description

Technical Field

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

[0002] With the rapid 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 layer. The glass part includes the core layer and the cladding layer. The cladding layer surrounds the core layer. The core layer is used to transmit optical signals. The cladding layer further confines the optical signal to the core layer. The coating layer is applied to the outer surface of the optical fiber cladding layer to protect the optical fiber from mechanical damage while enhancing the flexibility of the optical fiber for subsequent cabling and engineering use. Therefore, in order to reduce the outer diameter of the optical fiber, the technical path currently used is to keep the outer diameter of the optical fiber glass part unchanged at 125 microns and achieve a small diameter of the optical fiber by reducing the thickness of the optical fiber coating layer. However, reducing the thickness of the optical fiber coating layer will affect the strength of the optical fiber to a certain extent, so that the small outer diameter optical fiber using conventional two-layer coating layers often faces the problem of a high breakage rate per 100 kilometers. On the other hand, when the optical fiber is bent, the optical transmission signal is easy to refract out of the optical fiber cladding, causing the optical signal to leak out. Generally speaking, the smaller the bending radius, the more serious the light leakage, and the optical signal will cause a series of problems such as signal instability or even failure during transmission, so the bending resistance is an important indicator for evaluating the performance of optical fiber. Summary of the invention

[0004] The following are definitions and explanations of some terms involved in the present invention:

[0005] 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.

[0006] Relative refractive index difference of each layer of optical fiber Δn i It is defined by the following equation:

[0007]

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

[0009] The technical problem to be solved by the present invention is to provide an ultra-small outer diameter low-attenuation anti-bending single-mode optical fiber in view of the shortcomings of the prior art, which not only reduces the diameter of the optical fiber, but also can effectively ensure the bending performance, mechanical performance and transmission performance of the optical fiber.

[0010] 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 0.3~0.5%, and the diameter D1 is 7~9μm. The cladding includes an inner cladding, a sunken cladding and an outer cladding from the inside to the outside. The inner cladding is a transition layer between the core layer and the sunken cladding. The relative refractive index difference decreases from the inside to the outside, the relative refractive index difference △n2 is -0.01~0.05%, and the diameter D2 is 14~18μm. The relative refractive index difference △n3 of the sunken cladding is -0.2~-0.4%, and the diameter D3 is 28~34μm. The outer cladding is a pure silica glass layer, the relative refractive index difference △n4 is 0, and the diameter D4 is 79~81μm.

[0011] According to the above scheme, the relative refractive index difference of the core layer is flat or concave.

[0012] According to the above scheme, the refractive index curve of the core layer is in the shape of a crater, with the lower side concave and inclined inward under the top arc.

[0013] According to the above scheme, the outer cladding is coated with a resin coating layer, and the resin coating layer includes an inner resin coating layer coating1 and an outer resin coating layer coating2 from the inside to the outside. The inner resin coating layer has a diameter of 120 to 135 μm and an in-situ modulus of 0.3 to 0.9 MPa. The inner resin coating layer has a diameter of 160 to 170 μm and an in-situ modulus of 0.9 to 1.3 GPa.

[0014] According to the above scheme, after the resin coating layer is completely cured, the tensile strength F50% is ≥3.8 GPa; under preferred conditions, the tensile strength F50% is ≥4.5 GPa; under more preferred conditions, the tensile strength F50% is ≥5.0 GPa.

[0015] According to the above scheme, the average peeling force F of the resin coating layer is avg ≥0.4N, peak peel force F peak ≥0.6N; Average stripping force of optical fiber coating under optimal conditions F avg ≥0.6N, peak peel force F peak ≥0.8N; the average stripping force of the optical fiber coating under more preferred conditions F avg ≥1.0N, peak peel force F peak ≥1.3N.

[0016] According to the above scheme, the dynamic fatigue parameter n of the optical fiber is d ≥20.

[0017] According to the above scheme, the attenuation of the optical fiber at a wavelength of 1310nm is less than or equal to 0.36dB / km, the attenuation at a wavelength of 1383nm is less than or equal to 0.36dB / 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.

[0018] According to the above scheme, the attenuation of the optical fiber at a wavelength of 1310nm is less than or equal to 0.34dB / km, the attenuation at a wavelength of 1383nm is less than or equal to 0.29dB / km, the attenuation at a wavelength of 1550nm is less than or equal to 0.20dB / km, and the attenuation at a wavelength of 1625nm is less than or equal to 0.22dB / km.

[0019] According to the above scheme, the microbending loss of the optical fiber at a wavelength of 1700nm is 1.7dB / km.

[0020] According to the above scheme, the mode field diameter of the optical fiber at a wavelength of 1310 nm is 8.2-9.5 μm; under preferred conditions, the mode field diameter of the optical fiber at a wavelength of 1310 nm is 8.4-9.2 μm.

[0021] 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.

[0022] According to the above scheme, the optical fiber is bent once with a diameter of 20 mm, and the macro-bending loss at a wavelength of 1550 nm is less than or equal to 0.05 dB, and the macro-bending loss at a wavelength of 1625 nm is less than or equal to 0.15 dB. The optical fiber is bent 10 times with a diameter of 30 mm, and the macro-bending loss at a wavelength of 1550 nm is less than or equal to 0.025 dB, and the macro-bending loss at a wavelength of 1625 nm is less than or equal to 0.09 dB.

[0023] Under more optimal conditions, the optical fiber is bent once with a diameter of 20 mm, and the macro-bending loss at a wavelength of 1550 nm is less than or equal to 0.04 dB, and the macro-bending loss at a wavelength of 1625 nm is less than or equal to 0.12 dB; the optical fiber is bent 10 times with a diameter of 30 mm, and the macro-bending loss at a wavelength of 1550 nm is less than or equal to 0.02 dB, and the macro-bending loss at a wavelength of 1625 nm is less than or equal to 0.07 dB.

[0024] Under more optimal conditions, the optical fiber is bent once with a diameter of 20 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 10 times with a diameter of 30 mm, and the macro-bending loss at a wavelength of 1550 nm is less than or equal to 0.015 dB, and the macro-bending loss at a wavelength of 1625 nm is less than or equal to 0.05 dB.

[0025] The beneficial effects of the present invention are: 1. The diameter of the outer cladding of the optical fiber is reduced, so that the outer pure silicon layer in the optical fiber section is thinner than the conventional section, and the use of pure silicon glass is reduced, so that the optical fiber can reduce the outer diameter while meeting the transmission requirements, and save glass material resources, and the optical cable of the same volume can accommodate more fibers. 2. The proportion of the cross-sectional area of ​​the optical fiber glass part occupied by the pure silicon layer of the outer cladding of the conventional diameter 125μm G657 optical fiber is 94%, and the MFD of the optical fiber is below 9.2μm. It can be seen that the optical power of G657 is concentrated in the core layer, and part of it occupies the sunken cladding. The pure silicon layer outside the sunken cladding has no obvious effect on optical communication. By reducing the thickness of the pure silicon layer, glass materials can be saved, the drawing length of the preform per unit volume can be increased, and the drawing efficiency can be improved. 3. After the thickness of the pure silica glass layer is reduced, the microbending performance of the optical fiber will deteriorate. The present invention can significantly reduce the impact on the microbending performance by adjusting the optical fiber sinking depth to about -0.30. In addition, the modulus and thickness of the coating layer have a great influence on the performance of the optical fiber. The present invention selects a reasonable coating thickness to not only enhance the mechanical properties of the optical fiber, but also improve the stripping force of the optical fiber coating layer, which can enhance the cabling performance and significantly reduce the additional attenuation of high and low temperatures after cabling. 4. By optimizing the optical fiber profile design and the physical and chemical properties of the coating layer, the bending performance, mechanical performance and optical transmission performance of the optical fiber can be effectively guaranteed under the premise of reducing the diameter of the optical fiber outer cladding, and the same communication performance as the conventional 125μm wire diameter fiber can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 FIG. 4 is a cross-sectional diagram of the refractive index of an optical fiber according to an embodiment of the present invention.

[0027] Figure 2 FIG. 4 is a radial cross-sectional view of an optical fiber according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] It includes a core layer, a cladding layer and a coating layer. The relative refractive index difference of the core layer is △n1, the diameter is D1, and the refractive index curve of the core layer is step-type (straight line) or concave at the top arc and inclined inward, forming a crater shape. The cladding includes an inner cladding, a depressed cladding and an outer cladding from the inside to the outside. The inner cladding is a transition layer between the core layer and the depressed cladding. The relative refractive index difference decreases from the inside to the outside. The relative refractive index difference of the inner cladding is △n2 and the diameter is D2. The relative refractive index difference of the depressed cladding is △n3 and the diameter is D3. The outer cladding is a pure silica glass layer with △n4 of 0 and a diameter D4 of 79 to 81 μm. The outer cladding is covered with a coating layer, which includes an inner coating layer (coating1) and an outer coating layer (coating2). The diameter of the inner coating layer is 120 to 130 μm, and the diameter of the outer coating layer, i.e., the outer diameter of the optical fiber, is 160 to 170 μm.

[0029] Table 1 shows the refractive index profile parameters and coating layer parameters in the examples of the present invention.

[0030] Table 2 shows the optical and mechanical properties of the optical fiber in the example of the present invention.

[0031] Table 1

[0032]

[0033] Table 2

[0034]

[0035]

Claims

1. An ultra-small outer diameter, low attenuation, bend-resistant single-mode optical fiber, comprising a core layer and a cladding layer, characterized in that The core layer has a relative refractive index difference △n1 of 0.3 to 0.5%, and a diameter D1 of 7 to 9 μm. The cladding includes an inner cladding, a sunken cladding and an outer cladding from the inside to the outside. The inner cladding is a transition layer between the core layer and the sunken cladding. The relative refractive index difference decreases from the inside to the outside. The relative refractive index difference △n2 is -0.01 to 0.05%, and the diameter D2 is 14 to 18 μm. The sunken cladding has a relative refractive index difference △n3 of -0.2 to -0.4%, and a diameter D3 of 28 to 34 μm. The outer cladding is a pure silica glass layer, with a relative refractive index difference △n4 of 0 and a diameter D4 of 79 to 81 μm.

2. The ultra-small outer diameter low attenuation bend-resistant single-mode optical fiber according to claim 1, characterized in that The relative refractive index difference of the core layer of the ultra-small outer diameter low-attenuation bending-resistant single-mode optical fiber is straight or concave.

3. The ultra-small outer diameter, low attenuation, bend-resistant single-mode optical fiber according to claim 1, characterized in that The refractive index curve of the core layer is in the shape of a crater, with the top arc concave and inclining inward.

4. The ultra-small outer diameter, low attenuation, bend-resistant single-mode optical fiber according to claim 2 or 3, characterized in that The outer cladding is coated with a resin coating layer, and the resin coating layer includes an inner resin coating layer coating1 and an outer resin coating layer coating2 from the inside to the outside. The inner resin coating layer has a diameter of 120 to 130 μm and an in-situ modulus of 0.3 to 0.9 MPa. The inner resin coating layer has a diameter of 160 to 170 μm and an in-situ modulus of 0.9 to 1.3 GPa.

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

6. The ultra-small outer diameter low attenuation bend-resistant single-mode optical fiber according to claim 4, characterized in that The average peeling force F of the resin coating layer avg ≥0.4N, peak peel force F peak ≥0.6N.

7. The ultra-small outer diameter, low attenuation, bend-resistant single-mode optical fiber according to claim 2 or 3, characterized in that The attenuation of the optical fiber at a wavelength of 1310 nm is less than or equal to 0.36 dB / km, the attenuation at a wavelength of 1383 nm is less than or equal to 0.36 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.

8. The ultra-small outer diameter, low attenuation, bend-resistant single-mode optical fiber according to claim 2 or 3, characterized in that The attenuation of the optical fiber at a wavelength of 1310 nm is less than or equal to 0.34 dB / km, the attenuation at a wavelength of 1383 nm is less than or equal to 0.29 dB / km, the attenuation at a wavelength of 1550 nm is less than or equal to 0.20 dB / km, and the attenuation at a wavelength of 1625 nm is less than or equal to 0.22 dB / km.

9. The ultra-small outer diameter, low attenuation, bend-resistant single-mode optical fiber according to claim 2 or 3, characterized in that The optical fiber has a microbending loss of 1.7 dB / km at a wavelength of 1700 nm.

10. The ultra-small outer diameter, low attenuation, bend-resistant single-mode optical fiber according to claim 2 or 3, characterized in that The mode field diameter of the optical fiber at a wavelength of 1310 nm is 8.2-9.5 μm.

11. The ultra-small outer diameter, low attenuation, bend-resistant single-mode optical fiber according to claim 2 or 3, 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.

12. The ultra-small outer diameter, low attenuation, bend-resistant single-mode optical fiber according to claim 2 or 3, characterized in that The optical fiber is bent once with a diameter of 20 mm, and the macrobending loss at a wavelength of 1550 nm is less than or equal to 0.05 dB, and the macrobending loss at a wavelength of 1625 nm is less than or equal to 0.15 dB. The optical fiber is bent 10 times with a diameter of 30 mm, and the macrobending loss at a wavelength of 1550 nm is less than or equal to 0.025 dB, and the macrobending loss at a wavelength of 1625 nm is less than or equal to 0.09 dB.

13. The ultra-small outer diameter, low attenuation, bend-resistant single-mode optical fiber according to claim 2 or 3, characterized in that The optical fiber is bent once with a diameter of 20 mm, and the macrobending loss at a wavelength of 1550 nm is less than or equal to 0.04 dB, and the macrobending loss at a wavelength of 1625 nm is less than or equal to 0.12 dB. The optical fiber is bent 10 times with a diameter of 30 mm, and the macrobending loss at a wavelength of 1550 nm is less than or equal to 0.02 dB, and the macrobending loss at a wavelength of 1625 nm is less than or equal to 0.07 dB.

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