Optical Fiber and Its Applications

Abstract

The present invention provides an optical fiber and its applications. The optical fiber sequentially includes a core layer, a transition layer, a depressed layer, and an outer cladding from inside to outside; the relative refractive index difference of the core layer material is Δ1, the maximum relative refractive index difference in the transition layer is Δ2max, the relative refractive index difference of the depressed layer material is Δ3, and Δ1 > Δ2max ≥ Δ3; r represents the radial distance from a certain position in the transition layer to the center of the optical fiber, Δ2(r) represents the relative refractive index difference of the material at a distance r from the center in the transition layer, and Δ2(r), Δ2max, and Δ3 satisfy the following relational expression (1), where R0 represents the radius of the core layer, and R1 represents the radial distance from the contact interface between the transition layer and the depressed layer to the center of the optical fiber; the outer cladding is a silica layer. By a specific design of the refractive index profile of the optical fiber, the attenuation coefficient of the optical fiber can be adjusted, the guided wave transmission of the optical fiber can be restricted, and the bending resistance of the optical fiber can be improved, so that the optical fiber can have a small macro-bending loss.

Description

Technical Field

[0001] The present invention relates to the technical field of optical communication, and more particularly, to an optical fiber and its application. Background Art

[0002] Due to the special nature of the marine environment, optical fiber is an important transmission medium for realizing high-speed real-time communication of deep-sea equipment and has been widely used in deep-sea equipment. Deep-sea exploration submersibles often use optical fiber microcables as communication carriers. However, during the release of optical fiber microcables, they are subjected to bending and winding, axial tension, and non-uniform lateral pressure, resulting in an increase in signal attenuation of ordinary single-mode optical fibers and the possibility of communication signal interruption. That is to say, when laying optical fibers in small spaces, local area networks, and data centers, a small bending radius or pulling of the optical fiber will cause an increase in additional loss of the optical fiber, and in severe cases, it may even cause communication anomalies, resulting in data loss.

[0003] Ordinary optical fibers have poor tension resistance performance, and their additional attenuation will increase significantly when the winding tension is greater than 100 g. However, the deep-sea exploration field has higher requirements for the tension resistance performance of optical fibers (the attenuation loss of the optical fiber is ≤ 0.1 dB under the condition of ≥ 300 g). On this basis, researching and developing an optical fiber with excellent tension resistance performance and low attenuation is of great significance for realizing real-time communication of deep-sea equipment. Summary of the Invention

[0004] The main object of the present invention is to provide an optical fiber and its application to solve the problem that the high macro-bending loss of the optical fiber or even the inability to transmit data caused by the poor tension resistance performance of the optical fiber in the prior art.

[0005] To achieve the above object, on the one hand, the present invention provides an optical fiber, which sequentially includes a core layer, a transition layer, a depression layer, and an outer cladding layer from the inside to the outside; the relative refractive index difference of the core layer material is △1, and the maximum relative refractive index difference in the transition layer is △2 max , the relative refractive index difference of the depression layer material is △3, and △1 > △2 max ≥ △3; r represents the radial distance from a certain position in the transition layer to the center of the optical fiber, and △2(r) represents the relative refractive index difference of the material at a distance r from the center in the transition layer. △2(r) and △2 max and △3 satisfy the following relational formula (1):

[0006]

[0007] wherein, R0 represents the radius of the core layer, and R1 represents the radial distance from the contact interface between the transition layer and the depression layer to the center of the optical fiber;

[0008] The outer cladding layer is a silica layer.

[0009] Furthermore, R0 is 4.0-4.5 μm, the ratio of R1 to R0 is (3.5-4.0):1, and the thickness of the recessed layer (30) is 5.5-6.5 μm.

[0010] Furthermore, △1 is 0.35% to 0.38%; △2 max It is -0.1% to 0; △3 is -0.45% to -0.35%.

[0011] Furthermore, the material of the core layer is selected from SiO2 doped with Ge, the material of the transition layer is selected from SiO2 doped with F, or SiO2 doped with Ge and F, and the recessed layer is SiO2 doped with F.

[0012] Furthermore, in the optical fiber, when the material of the core layer is selected from SiO2 doped with GeO2, the doping amount of GeO2 is 2.5 to 4.5%, based on the total weight of the material of the core layer; when the material of the transition layer is selected from SiO2 doped with F element, the doping amount of F element is greater than 0 and ≤1.0wt% based on the total weight of the material of the transition layer; when the material of the transition layer is selected from SiO2 doped with GeO2 and F element, the doping amount of GeO2 and F element is 0.2 to 2.0wt%; and the doping amount of F element is 0.5 to 1.0wt% based on the total weight of the material of the recessed layer.

[0013] Furthermore, the stress difference between the core layer and the recessed layer is ≤20%, and the stress difference between the transition layer and the recessed layer is ≤2%.

[0014] Furthermore, the outer surface of the outer layer is also covered with a coating, and the material of the coating is selected from one or more of the group consisting of polyacrylic resin, epoxy acrylic resin and polyurethane acrylic resin; preferably, the coating includes an inner coating and an outer coating, and the elastic modulus of the inner coating is 0.3~0.8MPa; the elastic modulus of the outer coating is 600~900MPa.

[0015] Furthermore, under the conditions of a bending radius of 5 mm and one winding of the optical fiber, the macrobending loss at a wavelength of 1550 nm is ≤0.15 dB.

[0016] Furthermore, the mode field diameter MFD of the optical fiber at 1310 nm is 8.2-9.0 μm, the optical cable cutoff wavelength of the optical fiber is ≤1260 nm, the attenuation coefficient of the optical fiber at a wavelength of 1310 nm is ≤0.324 dB / km, and the attenuation coefficient of the optical fiber at a wavelength of 1550 nm is ≤0.184 dB / km.

[0017] In order to achieve the above-mentioned purpose, another aspect of the present invention further provides an application of the above-mentioned optical fiber provided in this application in the field of optical communications.

[0018] Applying the technical solution of the present invention, through a specific design of the fiber refractive index profile, a transition layer 20, a depressed layer 30, and a cladding layer 40 are sequentially arranged around the core layer 10, and the cladding layer 40 is a silica layer. Among them, the refractive index profile formed by the core layer 10 and the transition layer 20 can adjust the fiber attenuation coefficient; the setting of the depressed layer 30 can constrain the fiber guided wave transmission and improve the fiber bending resistance, so as to ensure that the fiber has a small macro-bending loss. Compared with other ranges, the relative refractive index differences of the above-mentioned core layer 10 and each outer cladding layer are limited within the above range and the relative refractive index differences change non-linearly (i.e., △2(r), △2 max and △3 satisfy the above specific relationship), which is beneficial to giving full play to the synergistic effect between layers, and further beneficial to reducing the macro-bending loss of the fiber, thereby improving its tensile resistance performance.

[0019] The above-mentioned optical fiber provided by this application is particularly suitable as a communication carrier and is applied to deep-sea exploration submersibles, which is of great significance for realizing real-time communication of deep-sea equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0021] Figure 1 Shows a schematic cross-sectional view of the structure of the optical fiber prepared in Example 1;

[0022] Figure 2 Shows a refractive index structure cross-sectional view of the optical fiber prepared in Example 1.

[0023] Among them, the above-mentioned drawings include the following reference numerals:

[0024] 10, core layer; 20, transition layer; 30, depressed layer; 40, cladding layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0026] As described in the background art, existing optical fibers have poor tensile resistance performance, resulting in high macro-bending loss of the optical fiber or even inability to transmit data. To solve the above technical problems, this application provides an optical fiber, which sequentially includes a core layer 10, a transition layer 20, a depressed layer 30, and a cladding layer 40 from the inside to the outside; the relative refractive index difference of the core layer 10 material is △1, and the maximum relative refractive index difference in the transition layer 20 is △2 max, the relative refractive index difference of the material of the depressed layer 30 is Δ3, and Δ1 > Δ2 max ≥Δ3; r represents the radial distance from the center of the optical fiber to a certain position in the transition layer 20, and Δ2(r) represents the relative refractive index difference of the material at a distance r from the center in the transition layer 20. Δ2(r) and Δ2 max and Δ3 satisfy the following relational expression (1):

[0027]

[0028] Among them, R0 represents the radius of the core layer 10, and R1 represents the radial distance from the center of the optical fiber to the contact interface between the transition layer 20 and the depressed layer 30; the outer cladding 40 is a silica layer.

[0029] Through a specific design of the refractive index profile of the optical fiber, a transition layer 20, a depressed layer 30, and an outer cladding 40 are sequentially arranged around the core layer 10, and the outer cladding 40 is a silica layer. Among them, the refractive index profile formed by the core layer 10 and the transition layer 20 can adjust the attenuation coefficient of the optical fiber; the setting of the depressed layer 30 can constrain the optical waveguide transmission of the optical fiber and improve the bending resistance of the optical fiber, so as to ensure that the optical fiber has a small macro-bending loss. Compared with other ranges, limiting the relative refractive index differences of the above-mentioned core layer 10 and each outer cladding within the above range and making the relative refractive index differences change non-linearly (that is, limiting that Δ2(r), Δ2 max and Δ3 satisfy the above specific relationship) is beneficial to giving full play to the synergistic effect between layers, and further beneficial to reducing the macro-bending loss of the optical fiber, thereby improving its tensile resistance performance.

[0030] The optical fiber provided by this application is particularly suitable as a communication carrier and is applied to deep-sea exploration submersibles, which is of great significance for realizing real-time communication of deep-sea equipment.

[0031] In a preferred embodiment, R0 is 4.0 - 4.5 μm, the ratio of R1 to R0 is (3.5 - 4.0):1, and the thickness of the depressed layer 30 is 5.5 - 6.5 μm. The radius R0 of the core layer 10, the ratio of R1 to R0, and the thickness of the depressed layer 30 include but are not limited to the above range. Limiting them within the above range is beneficial to giving full play to the synergistic effect between layers, beneficial to adjusting the attenuation coefficient of the optical fiber, thereby beneficial to reducing the macro-bending loss of the optical fiber and improving the tensile resistance performance of the optical fiber.

[0032] In a preferred embodiment, Δ1 is 0.35% - 0.38%; Δ2 max is -0.1% - 0; Δ3 is -0.45% - -0.35%. Compared with other ranges, the relative refractive index differences Δ1, Δ2 maxThe limitation of [specific parameters] within the above ranges is beneficial for restricting the optical fiber waveguide transmission. Meanwhile, it is also conducive to adjusting the fiber attenuation coefficient, thereby reducing the macro-bending loss of the optical fiber and improving its tensile resistance performance.

[0033] In a preferred embodiment, the material of the core layer 10 includes but is not limited to SiO2 doped with Ge element, and the material of the transition layer 20 includes but is not limited to SiO2 doped with F element, or SiO2 doped with Ge element and F element. The depressed layer 30 is SiO2 doped with F element. Compared with other materials, using the quartz materials doped with the above-mentioned elements as the materials of the transition layer 20 and the depressed layer 30 is beneficial for adjusting the refractive index difference of each cladding layer to meet the above-mentioned specific optical fiber refractive index profile design.

[0034] In a preferred embodiment, in the optical fiber, based on the total weight of the material of the core layer 10, when the material of the core layer 10 includes but is not limited to SiO2 doped with GeO2, the doping amount of GeO2 is 2.5 - 4.5%; based on the total weight of the material of the transition layer 20, when the material of the transition layer 20 includes but is not limited to SiO2 doped with F element, the doping amount of F element is >0 and ≤1.0 wt%; when the material of the transition layer 20 includes but is not limited to SiO2 doped with GeO2 and F element, the doping amounts of GeO2 and F element are 0.2 - 2 wt%. The doping amounts of the above doping elements include but are not limited to the above ranges. Limiting them within the above ranges is beneficial for further reducing the macro-bending loss of the optical fiber, thereby improving its tensile resistance performance.

[0035] In a preferred embodiment, based on the total weight of the depressed layer 30, the doping amount of F element is 0.5 - 1.0 wt%. The doping amount of F element includes but is not limited to the above range. Limiting it within the above range is beneficial for further reducing the macro-bending loss of the optical fiber, thereby improving its tensile resistance performance.

[0036] In a preferred embodiment, the stress difference between the core layer 10 and the depressed layer 30 ≤ 20%, and the stress difference between the transition layer 20 and the depressed layer 30 ≤ 2%. Compared with other ranges, limiting the stress difference between the core layer 10 and the depressed layer 30 and the stress difference between the transition layer 20 and the depressed layer 30 within the above ranges is beneficial for reducing the micro-bending loss, thereby reducing the macro-bending loss of the optical fiber and improving the tensile resistance performance of the optical fiber.

[0037] In a preferred embodiment, the outer surface of the outer cladding layer 40 is further coated with a coating, and the materials of the coating include, but are not limited to, one or more of the group consisting of polyacrylic resin, epoxy acrylate resin, and polyurethane acrylate resin. The setting of the coating is beneficial to improving the comprehensive performance such as the flexibility of the optical fiber. Compared with the coatings of other materials, using the above types of coatings is beneficial to reducing the elastic modulus of the coating, thereby being beneficial to improving the flexibility of the optical fiber.

[0038] In order to further improve the flexibility of the optical fiber, preferably, the coating includes an inner coating layer and an outer coating layer. The elastic modulus of the inner coating layer is 0.3 - 0.8 MPa; the elastic modulus of the outer coating layer is 600 - 900 MPa.

[0039] In a preferred embodiment, when the optical fiber is under the conditions of a bending radius of 5 mm and being wound 1 circle, the macro-bending loss at a wavelength of 1550 nm ≤ 0.15 dB. The macro-bending loss of the optical fiber provided by this application at a wavelength of 1550 nm is very small, and it is particularly suitable for being used as a communication carrier and applied to deep-sea exploration submersibles.

[0040] In a preferred embodiment, the mode field diameter MFD of the optical fiber at 1310 nm is 8.2 - 9.0 μm, the cut-off wavelength of the optical fiber cable ≤ 1260 nm, the attenuation coefficient of the optical fiber at a wavelength of 1310 nm ≤ 0.324 dB / km, and the attenuation coefficient at a wavelength of 1550 nm ≤ 0.184 dB / km. The cut-off wavelength of the above optical fiber cable is lower than 1260 nm, meeting the single-mode transmission requirements, and the attenuation coefficients at wavelengths of 1310 nm and 1550 nm are respectively lower than 0.324 dB / km and 0.184 dB / km, meeting the application scenarios of communication carriers in deep-sea exploration submersibles.

[0041] Through the refractive index structure design parameters of the core layer 10, transition layer 20, depressed layer 30, and outer cladding layer 40 of the optical fiber, by controlling the content of doped GeO2 or F element, the relative refractive index difference and width of the corresponding layer can be adjusted.

[0042] The second aspect of the present application also provides a method for preparing an optical fiber, which comprises: (1) preparing a preform: in a gas reactor, depositing a basic gas and a doping gas by a deposition method, and introducing an inert gas into a reaction chamber as a carrier gas, wherein the basic gas comprises SiCl4, H2 and O2, and the doping gas comprises but is not limited to a fluoride, or a combination of GeCl4 gas and a fluoride, and sintering at 1600-1800°C after deposition to obtain an optical fiber preform; (2) drawing the preform: melting the optical fiber preform at 1800-2100°C, drawing a bare quartz optical fiber after softening, cooling and annealing to 900-1200°C to remove thermal stress, and then cooling the quartz optical fiber to room temperature, controlling the drawing tension to 50-150g, and then coating and curing the surface of the quartz optical fiber, winding the fiber into a coil to obtain an optical fiber.

[0043] In a preferred embodiment, the deposition method includes but is not limited to one or more of modified chemical vapor deposition (MCVD), plasma chemical vapor deposition (PCVD), axial vapor deposition (VAD), and outside vapor deposition (OVD).

[0044] In a preferred embodiment, the fluoride includes but is not limited to one or more of CF4, C2F6, SF6 and SiF4.

[0045] In a preferred embodiment, the deposition process temperature is 1300-1600°C, and the deposition time is 6-8 hours. The temperature and time of the deposition process include, but are not limited to, the above ranges. Limiting them to the above ranges is beneficial for controlling the diffusion of the dopant gas in the deposited layer and improving the accuracy of the refractive index profile.

[0046] A third aspect of the present application further provides an application of the optical fiber provided herein in the field of optical communications. The optical fiber provided herein has low macrobending losses and excellent tensile strength, making it particularly suitable for use as a communication carrier in deep-sea exploration submersibles, and is of great significance for enabling real-time communication in deep-sea equipment.

[0047] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0048] Example 1

[0049] A method for preparing an optical fiber, comprising:

[0050] (1) Preform preparation: In a reaction furnace, the MCVD deposition method is used to deposit basic gases and doping gases. The basic gases SiCl4, H2, and O2 are introduced, and an inert gas Ar or He is used as the carrier gas to introduce into the reaction chamber. GeCl4 gas and CF4 are introduced. The temperature during the deposition process is 1360 °C. After depositing for 8 h, it is sintered at 1750 °C for 4 h to obtain an optical fiber preform;

[0051] (2) Preform drawing: The optical fiber preform is melted at 1910 °C, and after softening, it is drawn to obtain a bare silica optical fiber. It is cooled and annealed to 50 °C to remove thermal stress. The drawing tension is 130 g. Then, an inner coating and an outer coating are coated on the surface of the silica optical fiber, and after curing, it is traction-wound into a coil to obtain an optical fiber.

[0052] As Figure 1 shown in the structural cross-sectional schematic diagram, the above-mentioned optical fiber prepared in Example 1 includes a core layer 10, a transition layer 20, a depression layer 30, and an outer cladding layer 40 from the inside to the outside. Among them, the radius R0 of the core layer 10 is 4.3 μm, the radial distance R1 from the contact interface between the transition layer 20 and the depression layer 30 to the center of the optical fiber is 15.1 μm, that is, the thickness of the transition layer 20 is 10.8 μm; the thickness of the depression layer 30 is 5.6 μm; the material of the core layer 10 is Ge-doped SiO2, and the doping amount of GeO2 is 2.6 wt%, the material of the transition layer 20 is SiO2 doped with F element, and the doping amount of F element at the interface between the transition layer 20 and the core layer 10 is 0.17 wt%, the depression layer 30 is SiO2 doped with F element, and the doping amount of F element is 0.9 wt%.

[0053] As Figure 2 shown in the refractive index structural cross-sectional diagram, in the above-mentioned prepared optical fiber, the relative refractive index difference △1 of the core layer 10 material is 0.364%, and the maximum relative refractive index difference △2 max in the transition layer 20 is -0.1%, and the relative refractive index difference △3 of the depression layer 30 material is -0.4%. The stress difference between the core layer 10 and the depression layer 20 is measured to be 15.2% by the optical fiber birefringence stress measurement method, and the stress difference between the transition layer 20 and the depression layer 30 is 1%; the elastic modulus of the inner coating is measured to be 0.35 MPa and the elastic modulus of the outer coating is 820 MPa by the tensile method or the bending method.

[0054] Example 2

[0055] An optical fiber is prepared by using the same preparation method as in Example 1. The difference from Example 1 is that the drawing tension is 130 g; the doping amount of F element in the depression layer 30 material is 0.5 wt%.

[0056] In the optical fiber prepared above, the radial distance R1 from the contact interface between the transition layer 20 and the depression layer 30 to the center of the optical fiber is 15.05 μm, the relative refractive index difference △1 of the core layer 10 material is 0.38%, and the maximum relative refractive index difference △2 in the transition layer 20 max is 0, the relative refractive index difference △3 of the depression layer 30 material is -0.35%, and the stress difference between the transition layer 20 and the depression layer 30 is 0.3%.

[0057] Example 3

[0058] An optical fiber is prepared by using the same preparation method as in Example 1. The differences from Example 1 are as follows: the drawing tension is 50 g; the doping amount of F element at the interface between the transition layer 20 and the core layer 10 is 0.08 wt%, and the doping amount of F element in the depression layer 30 material is 0.9 wt%.

[0059] In the optical fiber prepared above, the radial distance R1 from the contact interface between the transition layer 20 and the depression layer 30 to the center of the optical fiber is 17.6 μm, the relative refractive index difference △1 of the core layer 10 material is 0.35%, and the maximum relative refractive index difference △2 in the transition layer 20 max is -0.05%, the relative refractive index difference △3 of the depression layer 30 material is -0.42%, and the stress difference between the transition layer 20 and the depression layer 30 is 1.8%.

[0060] Example 4

[0061] An optical fiber is prepared by using the same preparation method as in Example 1. The differences from Example 1 are as follows: R0 is 4.0 μm, R1 is 14 μm, and the thickness of the depression layer 30 is 6.5 μm.

[0062] Example 5

[0063] An optical fiber is prepared by using the same preparation method as in Example 1. The differences from Example 1 are as follows: R0 is 4.5 μm, R1 is 18 μm, and the thickness of the depression layer 30 is 5.5 μm.

[0064] Example 6

[0065] An optical fiber is prepared by using the same preparation method as in Example 1. The difference from Example 1 is that R1 is 20 μm.

[0066] Example 7

[0067] An optical fiber is prepared by using the same preparation method as in Example 1. The differences from Example 1 are as follows: △1 is 0.35%; △2 max is -0.1%; △3 is -0.35%.

[0068] Example 8

[0069] The optical fiber was prepared by the same preparation method as in Example 1. The difference from Example 1 is that: △1 is 0.38%; △2 max is 0; △3 is -0.45%.

[0070] Example 9

[0071] The optical fiber was prepared by the same preparation method as in Example 1. The difference from Example 1 is that: △1 is 0.4%; △2 max is 0; △3 is -0.3%.

[0072] Example 10

[0073] The difference from Example 1 is that: a coating is wrapped around the outer periphery of the outer cladding 40, and the coating includes an inner coating and an outer coating. The elastic modulus of the inner coating is 0.3 MPa; the elastic modulus of the outer coating is 900 MPa.

[0074] Example 11

[0075] The difference from Example 10 is that: the elastic modulus of the inner coating is 0.8 MPa; the elastic modulus of the outer coating is 600 MPa.

[0076] Example 12

[0077] The difference from Example 10 is that: the elastic modulus of the inner coating is 0.9 MPa; the elastic modulus of the outer coating is 500 MPa.

[0078] Comparative Example 1

[0079] The difference from Example 1 is that: the optical fiber sequentially includes a core layer 10, a transition layer 20, and an outer cladding 40 from the inside to the outside, that is, the depression layer 30 is not provided.

[0080] Comparative Example 2

[0081] The difference from Example 1 is that: the optical fiber sequentially includes a core layer 10, a depression layer 30, and an outer cladding 40 from the inside to the outside, that is, the transition layer 20 is not provided.

[0082] Comparative Example 3

[0083] The difference from Example 1 is that: the relative refractive index difference △1 of the core layer 10 material is 0.45%; the maximum relative refractive index difference in the transition layer 20 is △2 max is -0.2%; the relative refractive index difference △3 of the depression layer 30 material is -0.2%.

[0084] Measure the mode field diameter of the optical fibers prepared in all the above-mentioned examples and comparative examples at a wavelength of 1310 nm; measure the macro-bending loss at a wavelength of 1550 nm under the conditions of a bending radius of 5 mm and one winding; measure the additional attenuation coefficient of the optical fiber at a wavelength of 1550 nm under a winding tension of 300 g; and measure the Weibull distributions of the tensile strength E15% and E50% with a gauge length of 0.5 m. The test results are shown in Table 1.

[0085] Table 1

[0086]

[0087] From the above description, it can be seen that the above-mentioned examples of the present invention achieve the following technical effects:

[0088] Comparing Examples 1 to 3 and Comparative Examples 1 to 3, it can be seen that through a specific optical fiber refractive index profile design, a transition layer 20, a depression layer 30, and an outer cladding layer 30 are sequentially arranged around the core layer 10, and the outer cladding layer 30 is a silica layer. Among them, the refractive index profile formed by the core layer 10 and the transition layer 20 can adjust the attenuation coefficient of the optical fiber; the setting of the depression layer 30 can constrain the optical fiber waveguide transmission and improve the bending resistance of the optical fiber, thereby ensuring that the optical fiber has a small macro-bending loss. Compared with other ranges, limiting the relative refractive index differences between the above-mentioned core layer 10 and each outer cladding layer within the preferred range of the present application and making the relative refractive index differences change non-linearly (i.e., limiting that △2(r), △2 max and △3 satisfy the above specific relationship) is beneficial to giving full play to the synergistic effect between layers, and further beneficial to reducing the macro-bending loss of the optical fiber, thereby improving its tension resistance performance.

[0089] Comparing Examples 1, 4 to 6, it can be seen that the radius R0 of the core layer 10, the ratio of R1 to R0, and the thickness of the depression layer 30 are not limited to the preferred range of the present application. Limiting them within the preferred range of the present application is beneficial to giving full play to the synergistic effect between layers, beneficial to adjusting the attenuation coefficient of the optical fiber, thereby beneficial to reducing the macro-bending loss of the optical fiber and improving the tension resistance performance of the optical fiber.

[0090] Comparing Examples 1, 7 to 9, it can be seen that compared with other ranges, limiting the relative refractive index differences between the above-mentioned core layer 10, transition layer 20, and depression layer 30 within the preferred range of the present application is beneficial to constraining the optical fiber waveguide transmission, and at the same time is also beneficial to adjusting the attenuation coefficient of the optical fiber, thereby beneficial to reducing the macro-bending loss of the optical fiber, and thus improving its tension resistance performance.

[0091] Comparing Examples 1, 10 to 12, it can be seen that the setting of the coating is beneficial to improving the comprehensive performance of the optical fiber. Compared with coatings made of other materials, using the above-mentioned type of coating is beneficial to reducing the elastic modulus of the coating, thereby beneficial to improving the flexibility of the optical fiber.

[0092] It should be noted that the terms "first", "second", etc. in the description and claims of this application are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of this application described here can be implemented, for example, in an order other than those described here.

[0093] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, various modifications and changes can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An optical fiber, characterized in that, The optical fiber sequentially includes a core layer (10), a transition layer (20), a depressed layer (30), and an outer cladding layer (40) from the inside to the outside; the relative refractive index difference of the material of the core layer (10) is △1, and the maximum relative refractive index difference in the transition layer (20) is △2 max , the relative refractive index difference of the material of the depressed layer (30) is △3, and △1 > △2 max ≥ △3; r represents the radial distance from a certain position in the transition layer (20) to the center of the optical fiber, △2(r) represents the relative refractive index difference of the material at a distance r from the center in the transition layer (20), and the △2(r) and the △2 max and the △3 satisfy the following relational expression (1): （1）； Among them, R 0 represents the radius of the core layer (10), R 1 represents the radial distance from the contact interface between the transition layer (20) and the recessed layer (30) to the center of the optical fiber; The outer cladding layer (40) is a silica layer.

2. The optical fiber according to claim 1, characterized in that, The R 0 is 4.0 to 4.5 μm, and the R 1 ratio to the R 0 is (3.5 to 4.0):1, and the thickness of the recessed layer (30) is 5.5 to 6.5 μm.

3. The optical fiber according to claim 2, wherein The said △1 is 0.35% to 0.38%; the said △2 max is -0.1% to 0; the said △3 is -0.45% to -0.35%.

4. The optical fiber according to any one of claims 1 to 3, characterized in that, The material of the core layer (10) is selected from SiO2 doped with Ge element, the material of the transition layer (20) is selected from SiO2 doped with F element, or SiO2 doped with Ge element and F element, and the recessed layer (30) is SiO2 doped with F element.

5. The optical fiber according to claim 4, wherein, In the optical fiber, based on the total weight of the material of the core layer (10), when the material of the core layer (10) is selected from SiO2 doped with GeO2, the doping amount of GeO2 is 2.5 - 4.5%; based on the total weight of the material of the transition layer (20), when the material of the transition layer (20) is selected from SiO2 doped with F element, the doping amount of F element > 0 and ≤ 1.0 wt%; when the material of the transition layer (20) is selected from SiO2 doped with GeO2 and F element, the doping amounts of GeO2 and F element are 0.2 - 2.0 wt%; based on the total weight of the recessed layer (30), the doping amount of F element is 0.5 - 1.0 wt%.

6. The optical fiber according to claim 1, wherein The stress difference between the core layer (10) and the recessed layer (30) ≤ 20%, and the stress difference between the transition layer (20) and the recessed layer (30) ≤ 2%.

7. The optical fiber according to claim 6, characterized in that, The outer surface of the outer cladding layer (40) is further coated with a coating, and the material of the coating is selected from one or more of the group consisting of polyacrylic resin, epoxy acrylate resin, and polyurethane acrylate resin.

8. The optical fiber according to claim 7, characterized in that, The coating includes an inner coating and an outer coating. The elastic modulus of the inner coating is 0.3 - 0.8 MPa; the elastic modulus of the outer coating is 600 - 900 MPa.

9. The optical fiber according to claim 1, characterized in that, Under the condition of a bending radius of 5 mm and one winding, the macro-bending loss of the optical fiber at a wavelength of 1550 nm ≤ 0.15 dB.

10. The optical fiber according to claim 9, characterized in that, The mode field diameter MFD of the optical fiber at 1310 nm is 8.2 - 9.0 μm, the cable cut-off wavelength of the optical fiber ≤ 1260 nm, the attenuation coefficient of the optical fiber at a wavelength of 1310 nm ≤ 0.324 dB / km, and the attenuation coefficient at a wavelength of 1550 nm ≤ 0.184 dB / km.

11. Application of the optical fiber according to any one of claims 1 to 9 in the field of optical communication.

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