Ultra-small outside diameter low-loss bend-resistant single-mode optical fiber

Abstract

The application relates to an ultra-small-outer-diameter low-attenuation bending-resistant single-mode optical fiber, which comprises a core layer and a cladding layer, the relative refractive index difference Delta n1 of the core layer is 0.3-0.5%, and the diameter D1 is 7-9 mu m; the cladding layer 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, the relative refractive index difference decreases from inside to outside, the relative refractive index difference Delta n2 is -0.01-0.05%, and the diameter D2 is 14-18 mu m; the relative refractive index difference Delta n3 of the sunken cladding layer is -0.2--0.4%, and the diameter D3 is 28-34 mu m; the outer cladding layer is a pure silica glass layer, the relative refractive index difference Delta n4 is 0, and the diameter D4 is 79-81 mu m. The application can accommodate more fibers in the same volume of optical cable. Through optimization of the fiber profile design and the physicochemical properties of the coating layer, the bending performance, the mechanical performance and the optical transmission performance of the optical fiber can be effectively ensured, and the same communication performance as that of a 125 mu m conventional fiber can be achieved.

Description

Technical Field

[0001] This invention relates to an ultra-small outer diameter, low attenuation, and bend-resistant single-mode optical fiber, belonging to the field of optical communication technology. Background Technology

[0002] With the rapid 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: a glass portion and a coating. The glass portion includes a core and a cladding. The cladding surrounds the core, which transmits optical signals, while the cladding further confines the signals within the core. A coating is applied to the outside of the 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 current common approach is to maintain the outer diameter of the glass portion at 125 micrometers and reduce the thickness of the coating to achieve a smaller diameter. However, reducing the coating thickness can affect the fiber's strength to some extent, leading to a high breakage rate over 100 kilometers for small-diameter fibers using conventional two-layer coatings. Furthermore, when the fiber is bent, the transmitted light signal is easily refracted through the cladding, causing signal leakage. Generally, the smaller the bending radius, the more severe the leakage, leading to signal instability or even failure during transmission. Therefore, bending resistance is a crucial indicator for evaluating optical fiber performance. Summary of the Invention

[0004] The following are definitions and explanations of some terms used in this invention:

[0005] 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.

[0006] The relative refractive index difference Δn between the layers of the optical fiber i Defined by the following equation:

[0007]

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

[0009] The technical problem to be solved by this invention is to address the shortcomings of existing technologies by providing an ultra-small outer diameter, low attenuation, and bend-resistant single-mode optical fiber. This fiber not only reduces the fiber diameter but also effectively ensures the fiber's bending performance, mechanical properties, and transmission performance.

[0010] 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 0.3–0.5% and a diameter D1 of 7–9 μm. The cladding layer, from the inside out, includes an inner cladding layer, a recessed cladding layer, and an outer cladding layer. The inner cladding layer is a transition layer between the core layer and the recessed cladding layer, with a decreasing relative refractive index difference from the inside out. The relative refractive index difference Δn2 is -0.01–0.05%, and the diameter D2 is 14–18 μm. The recessed cladding layer has a relative refractive index difference Δn3 of -0.2–-0.4% and a diameter D3 of 28–34 μm. The outer cladding layer is a pure silica glass layer with a relative refractive index difference Δn4 of 0 and a diameter D4 of 79–81 μm.

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

[0012] According to the above scheme, the refractive index curve of the fiber core layer is concave at the top and sloping inward, resembling a crater.

[0013] According to the above scheme, the outer coating layer is covered 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 120-135 μm and an in-situ modulus of 0.3-0.9 MPa, and the outer resin coating layer has a diameter of 160-170 μm and an in-situ modulus of 0.9-1.3 GPa.

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

[0015] According to the above scheme, the average peel force F of the resin coating layer 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.

[0016] According to the above scheme, the dynamic fatigue parameter n of the optical fiber 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, at a wavelength of 1383nm is less than or equal to 0.36dB / km, at a wavelength of 1550nm is less than or equal to 0.23dB / km, and 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, at a wavelength of 1383nm is less than or equal to 0.29dB / km, at a wavelength of 1550nm is less than or equal to 0.20dB / km, and 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 1310nm is 8.2 to 9.5μm; under preferred conditions, the mode field diameter of the optical fiber at a wavelength of 1310nm is 8.4 to 9.2μm.

[0021] According to the above scheme, the optical fiber's cutoff wavelength is less than or equal to 1260nm; the zero-dispersion wavelength is 1300nm to 1324nm.

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

[0023] Under optimal conditions, when the optical fiber is bent once with a diameter of 20 mm, 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. When bent 10 times with a diameter of 30 mm, 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.

[0024] Under optimal conditions, when the optical fiber is bent once with a diameter of 20 mm, the macrobending loss at a wavelength of 1550 nm is less than or equal to 0.03 dB, and the macrobending loss at a wavelength of 1625 nm is less than or equal to 0.1 dB. When bent 10 times with a diameter of 30 mm, the macrobending loss at a wavelength of 1550 nm is less than or equal to 0.015 dB, and the macrobending loss at a wavelength of 1625 nm is less than or equal to 0.05 dB.

[0025] The beneficial effects of this invention are as follows: 1. By reducing the diameter of the fiber cladding, the outer pure silicon layer in the fiber cross-section is thinner compared to the conventional cross-section, reducing the use of pure silicon glass. This allows the fiber to meet transmission requirements while reducing its outer diameter, saving glass material resources, and enabling the same volume of optical cable to accommodate more fibers. 2. In a conventional 125μm diameter G657 fiber, the pure silicon layer occupies 94% of the cross-sectional area of ​​the fiber glass portion, and the fiber's MFD is below 9.2μm. This indicates that the optical power of G657 is concentrated in the core layer, partially occupying the recessed cladding. The pure silicon layer outside the recessed cladding has no significant impact on optical communication. By reducing the thickness of the pure silicon layer, glass material can be saved, the drawing length of the preform per unit volume can be increased, and the drawing efficiency can be improved. 3. Reducing the thickness of the pure silica glass layer will worsen the microbending performance of the fiber. This invention significantly reduces the impact on microbending performance by adjusting the fiber recess depth to approximately -0.30. Furthermore, the modulus and thickness of the coating layer have a significant impact on optical fiber performance. This invention selects a reasonable coating thickness, which not only enhances the mechanical properties of the optical fiber but also improves the peeling force of the coating layer, thus enhancing cabling performance and significantly reducing the additional attenuation caused by high and low temperatures after cabling. 4. By optimizing the optical fiber profile design and the physicochemical properties of the coating layer, the bending performance, mechanical properties, and optical transmission performance of the optical fiber can be effectively guaranteed while reducing the diameter of the outer cladding layer, achieving the same communication performance as a conventional 125μm diameter fiber. Attached Figure Description

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

[0027] Figure 2 This is a radial cross-sectional view of an optical fiber according to an embodiment of the present invention. Detailed Implementation

[0028] It includes a core layer, a cladding layer, and a coating layer. The core layer has a relative refractive index difference of Δn1 and a diameter of D1. The refractive index curve of the core layer is either step-type (linear) or concave at the top and sloping inward, resembling a crater. The cladding consists of an inner cladding, a recessed cladding, and an outer cladding from the inside out. The inner cladding is a transition layer between the core layer and the recessed cladding, with a decreasing relative refractive index difference from the inside out. The relative refractive index difference of the inner cladding is Δn2, and its diameter is D2. The relative refractive index difference of the recessed cladding is Δn3, and its diameter is D3. The outer cladding is a pure silica glass layer with Δn4 of 0 and a diameter of D4 of 79–81 μm. The outer cladding is surrounded by a coating layer, which includes an inner coating layer (coating1) and an outer coating layer (coating2). The inner coating layer has a diameter of 120–130 μm, and the outer coating layer, i.e., the outer diameter of the optical fiber, has a diameter of 160–170 μm.

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

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

[0031] Table 1

[0032]

[0033] Table 2

[0034]

[0035]

Claims

1. A low-attenuation, bend-resistant single-mode optical fiber with ultra-small outer diameter, comprising a core and a cladding, characterized in that... The core layer has a relative refractive index difference Δn1 of 0.3~0.439% and a diameter D1 of 7~9 μm. The cladding, from the inside out, includes an inner cladding, a recessed cladding, and an outer cladding. The inner cladding is a transition layer between the core layer and the recessed cladding, with a decreasing relative refractive index difference from the inside out. The relative refractive index difference Δn2 is -0.01~0.05%, and the diameter D2 is 14~18 μm. The recessed cladding has a relative refractive index difference Δn3 of -0.2~-0.4% and a diameter D3 of 28~34 μm. The outer cladding is a pure silica glass layer with a relative refractive index difference Δn4 of 0 and a diameter D4 of 79~81 μm. The outer cladding is covered with a resin coating layer, which, from the inside out, includes... The optical fiber has an inner resin coating layer (coating1) and an outer resin coating layer (coating2). The inner resin coating layer has a diameter of 120-130 μm and an in-situ modulus of 0.3-0.9 MPa. The outer resin coating layer has a diameter of 160-170 μm and an in-situ modulus of 0.9-1.3 GPa. When the optical fiber is bent once with a diameter of 20 mm, 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. When bent 10 times with a diameter of 30 mm, 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.

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

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

4. The ultra-small outer diameter, low attenuation, and bend-resistant single-mode optical fiber according to claim 1, characterized in that... After the resin coating is fully cured, the tensile strength F50% ≥ 3.8 GPa.

5. The ultra-small outer diameter, low attenuation, and bend-resistant single-mode optical fiber according to claim 1, characterized in that... The average peel force of the resin coating is Favg≥0.4N, and the peak peel force is Fpeak≥0.6N.

6. 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 an attenuation of less than or equal to 0.36 dB / km at a wavelength of 1310 nm, less than or equal to 0.36 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.

7. 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 an attenuation of less than or equal to 0.34 dB / km at a wavelength of 1310 nm, less than or equal to 0.29 dB / km at a wavelength of 1383 nm, less than or equal to 0.20 dB / km at a wavelength of 1550 nm, and less than or equal to 0.22 dB / km at a wavelength of 1625 nm.

8. 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.

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 mode field diameter of 8.2~9.5μm at a wavelength of 1310nm.

10. 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 cutoff wavelength of less than or equal to 1260nm and a zero-dispersion wavelength of 1300nm~1324nm.

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 fiber has a macro-bending loss of less than or equal to 0.04dB at a wavelength of 1550nm when bent once with a diameter of 20mm, and less than or equal to 0.12dB at a wavelength of 1625nm. When bent 10 times with a diameter of 30mm, the macro-bending loss is less than or equal to 0.02dB at a wavelength of 1550nm and less than or equal to 0.07dB at a wavelength of 1625nm.

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