A fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber

Abstract

This invention discloses a fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber, belonging to the field of optical fiber communication technology. The invention comprises a core layer and an outer cladding arranged sequentially from the inside out. The core layer includes a first recessed core layer and a second protruding core layer, with the second protruding core layer disposed outside the first recessed core layer. The outer cladding is a silica cladding. The refractive index of the core layer is higher than that of the outer cladding, and the refractive index profile of the core layer exhibits a step-like distribution. The relative refractive index difference ΔN1 of the first recessed core layer is smaller than the relative refractive index difference ΔN2 of the second protruding core layer. This invention, through a redesign of the optical fiber's refractive index profile, achieves a bend-insensitive optical fiber that still meets the standards in a fluorine-free state, satisfying the requirements of the G.657.A2 standard. This solves the technical problem of existing technologies using an outer fluorine cladding to reduce bending loss, which fails to meet safety and environmental protection requirements. The invention features a simple structure and excellent performance.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber communication technology, and more specifically, relates to fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber. Background Technology

[0002] With the advent of the 5G era, the Internet has become an indispensable part of people's lives, and the concept of fiber to the home has also received a lot of attention. In order to cope with complex application scenarios such as rooms, streets, and buildings, and to successfully complete the last mile of fiber optic network laying, the research and development of bend-insensitive optical fibers has also been emphasized.

[0003] Currently, the common method used in the market is to reduce the macro-bending loss of optical fibers by using an external fluorine cladding layer. Fluorine doping creates a camber in the waveguide structure, increasing the core-cladding refractive index difference and effectively improving the fiber's bending performance. However, the use of fluorinating agents such as CF4, SF6, and CCl2F2 during the production of optical fiber preforms generates large amounts of harmful fluorides, posing risks to human health and the natural environment. Therefore, the use of fluorinating agents should be avoided as much as possible during optical fiber fabrication.

[0004] To protect the ecological environment and human health and avoid the use of fluorinating agents, this invention improves the design of bend-insensitive optical fibers. Summary of the Invention

[0005] This invention addresses the deficiencies and improvement needs in existing technologies by providing a fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber. Its purpose is to achieve a bend-insensitive optical fiber that still meets the standards in a fluorine-free state by redesigning the fiber's refractive index profile, thus satisfying the requirements of the G.657.A2 standard. This solves the technical problem that existing technologies that use an external fluorine cladding layer to reduce bending loss cannot meet safety and environmental protection requirements.

[0006] To solve the above-mentioned technical problems, the present invention includes a core layer and an outer cladding layer arranged sequentially from the inside to the outside. The core layer includes a first recessed core layer and a second protruding core layer. The second protruding core layer is disposed outside the first recessed core layer. The outer cladding layer is provided with a silicon dioxide outer cladding layer. The refractive index of the core layer is higher than that of the outer cladding layer, and the refractive index profile of the core layer has a step-like distribution. The relative refractive index difference ΔN1 of the first recessed core layer is smaller than the relative refractive index difference ΔN2 of the second protruding core layer. The thickness ratio of the second protruding core layer to the first recessed core layer is 1.3-2.5.

[0007] Preferably, the refractive index of the first recessed core layer is distributed in a concave plane, and the refractive index of the second protruding core layer is distributed in a linearly increasing manner.

[0008] Preferably, the relative refractive index difference ΔN1 of the first indented core layer is 0.31%-0.38%, and the diameter d1 of the first indented core layer is 4.5-7.5μm.

[0009] Preferably, the relative refractive index difference ΔN2 of the second protruding core layer is 0.40%-0.48%, and the diameter d2 of the second protruding core layer is 7.5-8.5μm.

[0010] Preferably, the refractive index difference between the first recessed core layer and the second protruding core layer increases at an angle, and the refractive index difference between the second protruding core layer and the outer cladding layer exhibits a step-like distribution.

[0011] Preferably, neither the core layer nor the outer cladding layer is doped with fluorides, and the outer cladding layer is a pure silica glass layer.

[0012] Preferably, the diameter of the outer cladding layer is 124-126 μm.

[0013] Preferably, the finished optical fiber has a mode field diameter of 8.2-8.8 μm at a wavelength of 1310 nm, a cable cutoff wavelength of ≤1260 nm, and a zero-dispersion wavelength of 1300-1324 nm.

[0014] Preferably, the attenuation loss of the optical fiber at a wavelength of 1310 nm is less than or equal to 0.340 dB / km, the attenuation loss of the optical fiber at a wavelength of 1383 nm is less than or equal to 0.285 dB / km, the attenuation loss at a wavelength of 1550 nm is less than or equal to 0.197 dB / km, and the attenuation loss at a wavelength of 1625 nm is less than or equal to 0.214 dB / km.

[0015] Preferably, the macrobending loss of the optical fiber in the 1550nm window is less than or equal to 0.02dB and in the 1625nm window is less than or equal to 0.05dB in the R15mm-10 turns; the macrobending loss in the 1550nm window is less than or equal to 0.05dB and in the 1625nm window is less than or equal to 0.15dB in the R10mm-1 turn; and the macrobending loss in the 1550nm window is less than or equal to 0.4dB and in the 1625nm window is less than or equal to 0.9dB in the R7.5mm-1 turn.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] This invention provides a fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber with a simple and reasonable structure. By redesigning the refractive index profile of the fiber, it can still meet the G.657.A2 bend-insensitive fiber standard in a fluorine-free state, thereby solving the technical problem that the existing technology uses an external fluorine cladding layer to reduce bending loss but cannot meet the requirements of safety and environmental protection.

[0018] This invention employs a concave core refractive index distribution, defining the core diameter, refractive index, and depth to ensure bending insensitivity of single-mode fiber under fluorine-free conditions. A dual-core cross-sectional structure is used for the fiber core. VAD technology is employed to precisely adjust the torch position and flow parameters, redesigning the fiber waveguide structure. Optimization of the depth-to-width ratio of the concave core and the thickness ratio of the second protruding core to the first concave planar core achieves better macro-bending performance while maintaining low bending loss, thus improving the fiber's resistance to bending loss. The production process avoids the use of fluorides, ensuring safety and environmental protection, reducing production costs, and responding to the national low-carbon and environmentally friendly development concept. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the radial cross-sectional structure of the optical fiber of the present invention;

[0021] Figure 2 This is a schematic diagram of the refractive index profile of the optical fiber of the present invention. Detailed Implementation

[0022] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] See Figure 1 This invention provides a fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber, comprising a core layer and an outer cladding layer arranged sequentially from the inside out. The core layer includes a first recessed core layer and a second protruding core layer, with the second protruding core layer disposed outside the first recessed core layer. The outer cladding layer is provided with a silica outer cladding layer. The refractive index of the core layer is higher than that of the outer cladding layer, and the refractive index profile of the core layer exhibits a step-like distribution. The relative refractive index difference ΔN1 of the first recessed core layer is less than the relative refractive index difference ΔN2 of the second protruding core layer. The thickness ratio of the second protruding core layer to the first recessed core layer is 1.3-2.5.

[0024] Specifically, the first recessed core layer is located at the center of the fiber cross-section, close to the fiber core axis, and is the main light-guiding region of the fiber; the second protruding core layer covers the outside of the first recessed core layer and is the annular region of the fiber cross-section; the outer cladding layer covers the outside of the second protruding core layer. The diameter d1 of the first recessed core layer is 4.5-7.5 μm, the diameter d2 of the second protruding core layer is 7.5-8.5 μm, and the outer cladding layer is a pure silica glass layer with a diameter between 124-126 μm.

[0025] The refractive index of the first recessed core layer is distributed in a concave plane, and the relative refractive index difference ΔN1 of the first recessed core layer is 0.31%-0.38%; the refractive index of the second protruding core layer is distributed in a linearly increasing manner, and the relative refractive index difference ΔN2 of the second protruding core layer is 0.40%-0.48%.

[0026] The refractive index difference between the first recessed core layer and the second protruding core layer increases at an angle, while the refractive index difference between the second protruding core layer and the outer cladding layer exhibits a step-like distribution.

[0027] To reduce macrobending loss in optical fibers, this invention redesigns the waveguide structure of the optical fiber, creating a first concave core layer with a concave plane refractive index distribution, a second protruding core layer with an increased refractive index, and a silica cladding layer. The overall core waveguide structure is step-shaped, avoiding the use of fluorinating agents, reducing the impact on the natural environment and human health, and saving manufacturing costs.

[0028] The optical fiber of this invention is manufactured using a VAD+OVD method to prepare an optical fiber preform. The VAD process prepares a core rod corresponding to the first indented core layer, the second protruding core layer, and part of the outer cladding of the optical fiber. The core rod is prepared by stretching and fusion splicing. The optical fiber preform prepared by OVD process can then be drawn into a fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber that meets the G.657.A2 standard.

[0029] Moreover, the optical fiber of this invention does not use fluorides such as CF4, SF6, and CCl2F2 during the entire production process, and does not generate fluorides that are harmful to the human body and the natural environment, making the production process safe and environmentally friendly.

[0030] The fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber of this invention meets the G.657.A2 standard.

[0031] The refractive index profile of the fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber of this invention is shown in the figure below. Figure 2 As shown.

[0032] Furthermore, in this invention, the finished optical fiber has a mode field diameter of 8.2-8.8 μm at a wavelength of 1310 nm, a cable cutoff wavelength of ≤1260 nm, and a zero-dispersion wavelength of 1300-1324 nm.

[0033] The present invention will be described in detail below with reference to five specific embodiments to further evaluate the reliability of optical fibers.

[0034] Example 1:

[0035] In this embodiment, the first recessed core layer has a value of ΔN1 of 0.31% and a value of d1 of 4.50 μm, the second protruding core layer has a value of ΔN2 of 0.48% and a value of d2 of 7.50 μm, and the outer cladding layer is a pure silicon dioxide layer with a diameter of 125.0 μm.

[0036] The main parameters of the optical fiber are shown in Table 1, and the macrobending performance of the optical fiber is shown in Table 2.

[0037] Table 1. Main parameters of the optical fiber in Example 1

[0038]

[0039] Table 2. Fiber macrobending performance in Example 1

[0040]

[0041] Example 2:

[0042] In this embodiment, the first recessed core layer has a value of ΔN1 of 0.32% and a value of d1 of 5.51 μm, the second protruding core layer has a value of ΔN2 of 0.40% and a value of d2 of 8.50 μm, and the outer cladding layer is a pure silicon dioxide layer with a diameter of 125.2 μm.

[0043] The main parameters of the optical fiber are shown in Table 3, and the macrobending performance of the optical fiber is shown in Table 4.

[0044] Table 3. Main parameters of optical fiber in Example 2

[0045]

[0046] Table 4. Fiber macrobending performance in Example 2

[0047]

[0048] Example 3:

[0049] In this embodiment, the first recessed core layer has a value of ΔN1 of 0.34% and a value of d1 of 5.6 μm, the second protruding core layer has a value of ΔN2 of 0.43% and a value of d2 of 8.20 μm, and the outer cladding layer is a pure silicon dioxide layer with a diameter of 124.9 μm.

[0050] The main parameters of the optical fiber are shown in Table 5, and the macrobending performance of the optical fiber is shown in Table 6.

[0051] Table 5. Main parameters of optical fiber in Example 3

[0052]

[0053] Table 6. Fiber macrobending performance in Example 3

[0054]

[0055] Example 4:

[0056] In this embodiment, the first recessed core layer has a value of ΔN1 of 0.37% and a value of d1 of 7.01 μm, the second protruding core layer has a value of ΔN2 of 0.46% and a value of d2 of 8.05 μm, and the outer cladding layer is a pure silicon dioxide layer with a diameter of 125.1 μm.

[0057] The main parameters of the optical fiber are shown in Table 7, and the macrobending performance of the optical fiber is shown in Table 8.

[0058] Table 7. Main parameters of optical fiber in Example 4

[0059]

[0060] Table 8. Fiber macrobending performance in Example 4

[0061]

[0062] Example 5:

[0063] In this embodiment, the first recessed core layer has a value of ΔN1 of 0.38% and a value of d1 of 7.50 μm, the second protruding core layer has a value of ΔN2 of 0.45% and a value of d2 of 8.12 μm, and the outer cladding layer is a pure silicon dioxide layer with a diameter of 125.3 μm.

[0064] The main parameters of the optical fiber are shown in Table 9, and the macrobending performance of the optical fiber is shown in Table 10.

[0065] Table 9. Main parameters of optical fiber in Example 5

[0066]

[0067] Table 10. Fiber macrobending performance in Example 5

[0068]

[0069] The attenuation loss of the optical fiber at a wavelength of 1310 nm is less than or equal to 0.340 dB / km, the attenuation loss of the optical fiber at a wavelength of 1383 nm is less than or equal to 0.285 dB / km, the attenuation loss at a wavelength of 1550 nm is less than or equal to 0.197 dB / km, and the attenuation loss at a wavelength of 1625 nm is less than or equal to 0.214 dB / km.

[0070] Furthermore, the macro-bending loss of this optical fiber is less than or equal to 0.02dB in the 1550nm window and less than or equal to 0.05dB in the 1625nm window at a radius of 15mm-10 turns; less than or equal to 0.05dB in the 1550nm window and less than or equal to 0.15dB in the 1625nm window at a radius of 10mm-1 turn; and less than or equal to 0.4dB in the 1550nm window and less than or equal to 0.9dB in the 1625nm window at a radius of 7.5mm-1 turn. This optical fiber exhibits good bend insensitivity and a small mode field diameter, making it suitable for network access transmission.

[0071] This invention provides a fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber with a simple and reasonable structure. By redesigning the refractive index profile of the fiber, it can still meet the G.657.A2 bend-insensitive fiber standard in a fluorine-free state, thereby solving the technical problem that the existing technology uses an external fluorine cladding layer to reduce bending loss but cannot meet the requirements of safety and environmental protection.

[0072] This invention employs a concave core refractive index distribution, defining the core diameter, refractive index, and depth to ensure bending insensitivity of single-mode fiber under fluorine-free conditions. A dual-core cross-sectional structure is used for the fiber core. VAD technology is employed to precisely adjust the torch position and flow parameters, redesigning the fiber waveguide structure. Optimization of the depth-to-width ratio of the concave core and the thickness ratio of the second protruding core to the first concave planar core achieves better macro-bending performance while maintaining low bending loss, thus improving the fiber's resistance to bending loss. The production process avoids the use of fluorides, ensuring safety and environmental protection, reducing production costs, and responding to the national low-carbon and environmentally friendly development concept.

[0073] The calculation formulas involved in this invention are as follows:

[0074] The relative refractive index difference between the layers of the optical fiber:

[0075]

[0076] Where, n i Let n be the refractive index at various locations in the optical fiber, and n0 be the refractive index of pure silicon dioxide.

[0077] The terminology used in this invention is explained as follows:

[0078] VAD is an abbreviation for Vapor Axial Deposition.

[0079] OVD is an abbreviation for Outside Vapor Deposition.

[0080] The preform is a wire drawing preform made by depositing and sintering a core layer and cladding layer designed according to the waveguide structure.

[0081] In the description of this invention, it should be understood that terms such as “length”, “width”, “upper”, “lower”, “front”, “rear”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, and “outer” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0082] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber, comprising a core layer and an outer cladding arranged sequentially from the inside out, characterized in that, The core layer includes a first recessed core layer and a second protruding core layer, the second protruding core layer being disposed outside the first recessed core layer. The outer cladding layer is provided with a silicon dioxide outer cladding layer. The refractive index of the core layer is higher than that of the outer cladding layer, and the refractive index profile of the core layer has a step-type distribution. The relative refractive index difference ΔN1 of the first recessed core layer is smaller than the relative refractive index difference ΔN2 of the second protruding core layer. The thickness ratio of the second protruding core layer to the first recessed core layer is 1.3-2.

5. Neither the core layer nor the outer cladding layer is doped with fluoride. The relative refractive index difference ΔN1 of the first recessed core layer is 0.31%-0.38%, and the relative refractive index difference ΔN2 of the second protruding core layer is 0.40%-0.48%. The refractive index of the first recessed core layer is distributed in a concave plane, and the refractive index of the second protruding core layer is distributed in a linearly increasing manner. The refractive index difference between the first recessed core layer and the second protruding core layer increases on a sloping plane, and the refractive index difference between the second protruding core layer and the outer cladding layer is distributed in a step-like manner.

2. The fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber according to claim 1, characterized in that, The diameter d1 of the first indented core layer is 4.5-7.5 μm.

3. The fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber according to claim 1, characterized in that, The diameter d2 of the second protruding core layer is 7.5-8.5 μm.

4. The fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber according to claim 1, characterized in that, Furthermore, the outer cladding layer is a pure silicon dioxide glass layer.

5. A fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber according to claim 1 or 4, characterized in that, The diameter of the outer cladding layer is 124-126 μm.

6. The fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber according to claim 1, characterized in that, The finished optical fiber has a mode field diameter of 8.2-8.8μm at a wavelength of 1310nm, a cutoff wavelength of ≤1260nm for cabling, and a zero-dispersion wavelength of 1300~1324nm.

7. The fluorine-free, environmentally friendly, bend-insensitive single-mode optical fiber according to claim 1, characterized in that, The optical fiber has an attenuation loss of less than or equal to 0.340 dB / km at a wavelength of 1310 nm, an attenuation loss of less than or equal to 0.285 dB / km at a wavelength of 1383 nm, an attenuation loss of less than or equal to 0.197 dB / km at a wavelength of 1550 nm, and an attenuation loss of less than or equal to 0.214 dB / km at a wavelength of 1625 nm. The macrobending loss of the optical fiber is less than or equal to 0.02dB in the 1550nm window and less than or equal to 0.05dB in the 1625nm window at R15mm-10 turns; less than or equal to 0.05dB in the 1550nm window and less than or equal to 0.15dB in the 1625nm window at R10mm-1 turn; and less than or equal to 0.4dB in the 1550nm window and less than or equal to 0.9dB in the 1625nm window at R7.5mm-1 turn.

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