Anti-radiation ultra-low-loss single-mode optical fiber having dual-pedestal waveguide guiding structure

Abstract

Disclosed in the present invention is an anti-radiation ultra-low-loss single-mode optical fiber having a dual-pedestal waveguide guiding structure. The anti-radiation ultra-low-loss single-mode optical fiber comprises a fiber core layer, an inner cladding layer, a first graded layer, a first transition layer, a near-core pedestal, a pedestal interlayer, a second graded layer, a far-core pedestal, a recessed layer, a second transition layer and an outer cladding layer, which are sequentially arranged from the center to the outside. In the present invention, a waveguide guiding structure is formed between a near-core pedestal and a far-core pedestal, and an optical signal is reflected multiple times in the waveguide guiding structure, thus realizing a longer propagation path, reducing the degree of attenuation of the optical signal, and improving the transmission efficiency and signal quality of an optical fiber; at 1550 nm, the attenuation coefficient is less than or equal to 0.15 dB / km, the dispersion coefficient is less than or equal to 21 ps / (nm·km), the dispersion slope is less than or equal to 0.06 ps / (nm2·km), and the zero-dispersion wavelength is less than or equal to 1270 nm; and additional attenuation at 1550 nm under 10 rad irradiation intensity for 25 years is less than or equal to 0.001 dB / km, such that the requirements of a high-speed optical communication system for dispersion compensation can be better met.

Description

A radiation-resistant ultra-low-loss single-mode optical fiber with a double-table waveguide guiding structure Technical Field

[0001] The present invention belongs to the technical field of optical communications, and in particular relates to a radiation-resistant ultra-low-loss single-mode optical fiber with a double-mesa waveguide guiding structure. Background Art

[0002] Ultra-low-loss fiber is a common single-mode fiber used in optical communications. Its cladding structure has a significant impact on fiber performance and transmission characteristics. Existing ultra-low-loss fiber designs utilize a single-plane cladding structure, which presents several drawbacks and shortcomings. Furthermore, most current designs employ a step-type profile between the fiber core and the different cladding layers. Rapid changes in doping concentration can easily cause sudden stress changes, leading to additional attenuation.

[0003] In terms of transmission loss, existing single-unit cladding structures can cause significant transmission loss during optical fiber transmission, impacting transmission efficiency and signal quality. Regarding dispersion characteristics, existing single-unit cladding structures have limited adjustment capabilities and cannot meet the dispersion compensation requirements of high-speed optical communication systems. In terms of resistance to external interference, existing single-unit cladding structures offer weak shielding against external light and electromagnetic interference, making them susceptible to external interference and reducing optical fiber reliability, particularly in submarine cable communications.

[0004] A Chinese invention patent, publication number CN109839694A, discloses a cutoff wavelength-shifted single-mode optical fiber. Through a rational fiber structural design, this design further reduces optical loss while simultaneously meeting ultra-low loss requirements for parameters such as mode field diameter, cutoff wavelength, and bending loss. However, the patent's waveguide structure fails to significantly improve transmission loss and dispersion, nor does it effectively protect the fiber from the effects of external radiation interference.

[0005] Summary of the Invention

[0006] In order to solve the technical problems existing in the prior art, the purpose of the present invention is to provide a radiation-resistant ultra-low-loss single-mode optical fiber with a double-table waveguide guiding structure, which can reduce transmission loss, improve dispersion characteristics and enhance radiation resistance.

[0007] In order to achieve the above-mentioned purpose and the above-mentioned technical effect, the technical solution adopted by the present invention is:

[0008] A radiation-resistant ultra-low-loss single-mode optical fiber with a double-mesa waveguide guiding structure, comprising a core layer, an inner cladding, a first gradient layer, a first transition layer, a near-core mesa, a mesa sandwich, a second gradient layer, a far-core mesa, a depressed layer, a second transition layer, and an outer cladding, which are arranged in sequence from the center to the outside;

[0009] The radius R1 of the core layer is 3 to 9 μm, and the relative refractive index difference Δn1 is 0 to 0.27%;

[0010] The radius of the inner cladding is R2, the thickness R2-R1 thereof is in the range of 1 to 5 μm, and the relative refractive index difference Δn2 of the inner cladding is -0.12 to -0.32%;

[0011] The radius of the first gradient layer is R3, the thickness thereof R3-R2 is in the range of 0.5 to 3 μm, and the relative refractive index difference of the first gradient layer is Δn2 to Δn4;

[0012] The radius of the first transition layer is R4, the thickness thereof is R4-R3, which is 1 to 2.5 μm, and the relative refractive index difference Δn4 of the first transition layer is -0.35 to -0.5%;

[0013] The radius of the near-core mesa is R5, the thickness R5-R4 thereof is in the range of 5 to 12 μm, and the relative refractive index difference Δn5 of the near-core mesa is -0.25 to -0.4%;

[0014] The radius of the mesa interlayer is R6, the thickness thereof is R6-R5, which is 1 to 2.5 μm, and the relative refractive index difference of the mesa interlayer is -0.65 to -0.75%;

[0015] The radius of the second gradient layer is R7, the thickness thereof R7-R6 is in the range of 0.5 to 3 μm, and the relative refractive index difference of the second gradient layer is Δn6 to Δn7;

[0016] The radius of the remote core mesa is R8, the thickness thereof is 5 to 12 μm, and the relative refractive index difference Δn8 of the remote core mesa is -0.75 to -0.85%;

[0017] The radius of the recessed layer is R9, the thickness thereof is 3 to 8 μm, and the relative refractive index difference Δn9 of the recessed layer is -0.8 to -1.0%;

[0018] The radius of the second transition layer is R10, the thickness thereof is 1 to 2.5 μm, and the relative refractive index difference of the second transition layer is -0.05 to -0.15%.

[0019] Furthermore, the molar concentration of potassium doped in the core layer is in the range of 0.2-0.4%, and the molar concentration of germanium dioxide doped in the core layer is in the range of 0.05-0.3%.

[0020] Furthermore, the molar concentration of fluorine doped in the inner cladding is 0 to 0.3%.

[0021] Furthermore, the molar concentration of fluorine doped in the first gradient layer and the second gradient layer is 0.1-2%.

[0022] Furthermore, the molar concentration of fluorine doped on the near-core mesa is 0.2-0.5%.

[0023] Furthermore, the molar concentration of thulium doped in the mesa interlayer is 0.5-2%.

[0024] Furthermore, the molar concentration of fluorine doped on the remote core mesa is 0.4-0.8%.

[0025] Furthermore, the molar concentration of fluorine doped in the recessed layer is 1-3%.

[0026] Furthermore, the radius of the outer cladding is 50 to 65 μm, and the outer cladding is pure silica or silica glass doped with metal ions, and the metal ions are a combination of one or more of Fe, Ni, Co, and Tm.

[0027] Furthermore, the application wavelength range of the optical fiber is 1530-1625 nm, the attenuation coefficient at 1550 nm is ≤0.15 dB / km, the dispersion coefficient at 1550 nm is ≤21 ps / (nm·km), and the dispersion slope at 1550 nm is ≤0.06 ps / (nm·km). 2 ·km), zero dispersion wavelength ≤ 1270nm, additional attenuation at 1550nm under 10rad irradiation intensity for 25 years ≤ 0.001dB / km.

[0028] The present invention also discloses a method for preparing a radiation-resistant ultra-low-loss single-mode optical fiber with a double-table waveguide guiding structure, wherein the optical fiber is prepared by a PCVD or MCVD process;

[0029] The steps of preparing the optical fiber using the PCVD process include:

[0030] 1) Using a pure silicon liner or a liner doped with metal ions, after acid washing, placing it on a drying rack for drying, and passing Ar into the tube at a temperature of 60°C for 12 to 24 hours. This step mainly reduces the hydroxyl content in the liner. The metal ions are one or more combinations of metal ions such as Fe, Ni, Co, and Tm.

[0031] 2) Install the purged pure silicon liner or the liner doped with special metal ions on the deposition machine of the PCVD process to perform ultra-low loss core rod deposition:

[0032] 21) Outer cladding, reactants containing Ni, Si, and F are introduced into the liner, and the carrier gas is high-purity O2;

[0033] 22) Deposition of the second transition layer: Si and F-containing reactants are introduced into the outer cladding using high-purity O2 as the carrier gas, so that the relative refractive index difference of the second transition layer reaches -0.05 to -0.15%;

[0034] 23) Deposition of the depressed layer: introducing reactants containing Si and F into the second transition layer, using high-purity O2 as the carrier gas, so that the relative refractive index difference Δn9 of the depressed layer reaches -0.8 to -1.0%, and the molar concentration of F is 1 to 3%;

[0035] 24) Deposition of the remote mesa: introducing reactants containing Si and F into the recessed layer, using high-purity O2 as the carrier gas, such that the relative refractive index difference Δn8 of the remote mesa reaches -0.75 to -0.85%, and the molar concentration of fluorine doping in the remote mesa is 0.4 to 0.8%;

[0036] 25) Deposition of the second graded layer: introducing reactants containing Si and F into the distal mesa layer, using high-purity O2 as the carrier gas, the relative refractive index difference of the second graded layer being Δn6 to Δn7, and the molar concentration of fluorine doping in the second graded layer being 0.1 to 2%;

[0037] 26) Deposition of the mesa interlayer: introducing reactants containing Tm, Si, and F into the second graded layer using high-purity O2 as the carrier gas, such that the relative refractive index difference of the mesa interlayer reaches -0.65 to -0.75%, and the molar concentration of thulium doped in the mesa interlayer is 0.5 to 2%;

[0038] 27) Deposition of the mesa: Si and F-containing reactants are introduced into the mesa interlayer, with high-purity O2 as the carrier gas, so that the relative refractive index difference Δn5 of the mesa reaches -0.25 to -0.4%, and the molar concentration of fluorine doping in the mesa is 0.2 to 0.5%;

[0039] 28) Deposition of the first transition layer: Si and F-containing reactants are introduced into the near-core mesa layer using high-purity O2 as the carrier gas, so that the relative refractive index difference Δn4 of the first transition layer reaches -0.35 to -0.5%;

[0040] 29) Deposition of the first gradient layer: introducing reactants containing Si and F into the first transition layer, using high-purity O2 as the carrier gas, such that the relative refractive index difference of the first gradient layer reaches Δn2 to Δn4, and the molar concentration of fluorine doping in the first gradient layer is 0.1 to 2%;

[0041] 30) Deposition of the inner cladding: introducing reactants containing Si and F into the first graded layer, using high-purity O2 as the carrier gas, such that the relative refractive index difference Δn2 of the inner cladding reaches -0.12 to -0.32% and the molar concentration of fluorine doping in the inner cladding is 0 to 0.3%;

[0042] 31) Deposition of the core layer: Reactants containing K, Ge, Si, and F are introduced into the inner cladding, with high-purity O2 as the carrier gas, so that the relative refractive index difference Δn1 reaches 0-0.27%, the molar concentration of K doping in the core layer is in the range of 0.2-0.4%, and the molar concentration of Ge doping is in the range of 0.05-0.3%;

[0043] 3) After the liner is deposited, caps must be placed on both ends of the liner before the rod is moved to prevent air from entering and ensure the ultra-low attenuation performance of the core rod. After the tube is quickly moved and installed in the melt-shrink bed, it must be purged with high-purity O2 to reduce the hydroxyl content in the liner during the installation of the deposition tube. The O2 flow rate is 1000-2000 sccm and the purge time is 1-5 minutes.

[0044] 4) Melting and shrinking the deposited liner into a solid core rod at a melting temperature of 1800-2200°C. During the melting and shrinking process, high-purity O2 is introduced at a flow rate of 1000-2000 sccm. The internal pressure of the melting and shrinking tube is controlled at 0-10 Pa.

[0045] 5) According to the design size of the core rod, match the corresponding sleeve so that the optical fiber meets the design thickness requirements of R1 to R10.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1. Reducing transmission loss: This invention provides a radiation-resistant, ultra-low-loss single-mode optical fiber with a dual-mesa waveguide structure and a preparation method. A mesa layer of a certain width is formed between the near-core and distal mesa surfaces in this optical fiber. The interlayer region between the two mesas forms a waveguide guiding structure, allowing optical signals to be reflected multiple times within the layer, thereby increasing the propagation distance of the optical signal and achieving a longer propagation path. This reduces the attenuation of the optical signal, improving the transmission efficiency and signal quality of the optical fiber, and achieving an attenuation coefficient of ≤0.15dB / km at 1550nm.

[0048] 2. Improved dispersion characteristics: The present invention provides a radiation-resistant ultra-low-loss single-mode optical fiber with a double-table waveguide guiding structure and a preparation method. A certain distance and refractive index difference are formed between the near-core table and the far-core table in the optical fiber. This refractive index difference can adjust the propagation mode of the light guided by the waveguide, affecting the propagation speed and dispersion characteristics of the optical signal. By reasonably designing the double-table spacing and refractive index difference, the dispersion characteristics of the optical fiber can be adjusted and optimized, so that the optical fiber meets the dispersion compensation requirements of high-speed optical communication systems. The dispersion coefficient at 1550nm is ≤21ps / (nm·km), and the dispersion slope at 1550nm is ≤0.06ps / (nm 2 km), zero dispersion wavelength ≤ 1270 nm;

[0049] 3. Improved resistance to external radiation: Due to the difference in refractive index, external radiation incident on the double-table structure will be refracted and reflected. This refraction and reflection changes the propagation path of the radiation energy, reducing the possibility of the radiation energy entering the fiber core. The design of the refractive index difference can affect the degree to which external radiation enters the fiber core, thereby further improving the radiation resistance of the optical fiber; using silica doped with metal ions with high radiation resistance as the cladding material can reduce or absorb the damage caused by external radiation. Through appropriate material selection and optimization, the radiation resistance of the optical fiber can be further enhanced. Under the irradiation intensity of 10rad for 25 years, the additional attenuation at 1550nm is ≤0.001dB / km, which is more suitable for transmission lines passing through scenes such as the seabed, mines, and hot springs. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] FIG1 is a schematic diagram of the relative refractive index of a radiation-resistant ultra-low-loss single-mode optical fiber with a double-mesa waveguide guiding structure according to the present invention. DETAILED DESCRIPTION

[0051] The present invention is described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0052] The following is a brief summary of one or more aspects to provide a basic understanding of these aspects. This summary is not an exhaustive overview of all conceivable aspects and is neither intended to identify key or critical elements of all aspects nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that will be provided later.

[0053] As shown in Figure 1, the present invention discloses a radiation-resistant ultra-low-loss single-mode optical fiber with a double-table waveguide guiding structure. By adopting the double-table waveguide guiding structure, the radiation resistance and transmission characteristics of the optical fiber are improved. The optical fiber specifically includes a core layer, an inner cladding, a first gradient layer, a first transition layer, a near-core table, a table interlayer, a second gradient layer, a far-core table, a depressed layer, a second transition layer and an outer cladding, which are arranged in sequence from the center to the outside.

[0054] In the present invention, the radius R1 of the core layer is 3 to 9 μm, the relative refractive index difference Δn1 is 0 to 0.27%, the molar concentration of potassium doped in the core layer is in the range of 0.2 to 0.4%, and the molar concentration of germanium dioxide doped in the core layer is in the range of 0.05 to 0.3%; the radius of the inner cladding is R2, the thickness R2-R1 is in the range of 1 to 5 μm, the relative refractive index difference Δn2 of the inner cladding is -0.12 to -0.32%, and the molar concentration of fluorine doped in the inner cladding is 0 to 0.3%; the radius of the first graded layer is R3, the thickness R3-R2 is in the range of 0.5 to 3 μm, and the first The relative refractive index difference of the gradient layer is Δn2~Δn4; the radius of the first transition layer is R4, its thickness R4-R3 is 1~2.5μm, and the relative refractive index difference Δn4 of the first transition layer is -0.35~-0.5%; the radius of the near-core table is R5, its thickness R5-R4 ranges from 5~12μm, the relative refractive index difference Δn5 of the near-core table is -0.25~-0.4%, and the molar concentration of fluorine doped in the near-core table is 0.2~0.5%; the radius of the table interlayer is R6, and its thickness R6-R5 ranges from 1~2.5μm The relative refractive index difference of the mesa interlayer is -0.65 to -0.75%, and the molar concentration of thulium doped in the mesa interlayer is 0.5 to 2%. The radius of the second graded layer is R7, and its thickness R7-R6 ranges from 0.5 to 3 μm. The relative refractive index difference of the second graded layer is Δn6 to Δn7, and the molar concentration of fluorine doped in the first and second graded layers are 0.1 to 2%, respectively. The radius of the tele-core mesa is R8, and its thickness is 5 to 12 μm. The relative refractive index difference of the tele-core mesa is Δn8, which is -0.75 to -0.85%, and the molar concentration of fluorine doped in the tele-core mesa is 0. The radius of the depressed layer is R9, the thickness is 3-8 μm, the relative refractive index difference of the depressed layer is Δn9, which is -0.8 to -1.0%, and the molar concentration of fluorine doped in the depressed layer is 1 to 3%; the radius of the second transition layer is R10, the thickness is 1 to 2.5 μm, and the relative refractive index difference of the second transition layer is -0.05 to -0.15%; the radius of the outer cladding is 50 to 65 μm, and the outer cladding is pure silica or silica glass doped with metal ions, and the metal ions are a combination of one or more metal ions such as Fe, Ni, Co, and Tm.

[0055] The radiation-resistant ultra-low-loss single-mode optical fiber with a double-table waveguide guiding structure provided by the present invention has an application wavelength range of 1530 to 1625 nm. A table layer of a certain width is formed between the near-core table and the far-core table. The sandwich area between the two tables forms a waveguide guiding structure, in which the optical signal is reflected multiple times to achieve a longer propagation path, reduce the attenuation of the optical signal, and improve the transmission efficiency and signal quality of the optical fiber. The attenuation coefficient of the optical fiber at 1550 nm is ≤0.15 dB / km; at the same time, the optical fiber has better dispersion characteristics, with a dispersion coefficient of ≤21 ps / (nm·km) at 1550 nm and a dispersion slope of ≤0.06 ps / (nm·km) at 1550 nm. 2 ·km), with a zero-dispersion wavelength ≤ 1270nm, which is suitable for the dispersion compensation requirements of high-speed optical communication systems; the optical fiber has better radiation resistance, with an additional attenuation of ≤0.001dB / km at 1550nm under 10rad irradiation intensity for 25 years, making it more suitable for transmission lines passing through scenarios such as the seabed, mines, and hot springs.

[0056] The waveguide guiding structure of the present invention is more complex than that of conventional single-mode optical fibers. Therefore, the in-tube method (PCVD or MCVD) is recommended for fabrication, although other processes are not limited. Compared to out-of-tube methods (OVD or VAD), the in-tube method (PCVD or MCVD), particularly the PCVD process, can more conveniently fabricate optical fiber core rods with complex waveguide structures. In particular, the present invention relates to a deep fluorine doping process, and the PCVD fluorine doping can achieve a relative refractive index difference of up to -1.2%.

[0057] The present invention also discloses a method for preparing a radiation-resistant ultra-low-loss single-mode optical fiber with a double-table waveguide guiding structure, which is prepared using a PCVD (plasma chemical vapor deposition) process. The main steps include:

[0058] 1) Use pure silicon liner or liner doped with special metal ions, after acid washing, place on a drying rack for drying, and introduce Ar into the tube at 60°C for 12 to 24 hours. This step mainly reduces the hydroxyl content in the liner. The metal ions are one or more combinations of metal ions such as Fe, Ni, Co, and Tm.

[0059] 2) Install the purged pure silicon liner or the liner doped with special metal ions on the deposition machine of the PCVD process to perform ultra-low loss core rod deposition:

[0060] 21) Outer cladding, reactants containing Ni, Si, and F are introduced into the liner, and the carrier gas is high-purity O2;

[0061] 22) Deposition of the second transition layer: Si and F-containing reactants are introduced into the outer cladding using high-purity O2 as the carrier gas, so that the relative refractive index difference of the second transition layer reaches -0.05 to -0.15%;

[0062] 23) Deposition of the depressed layer: introducing reactants containing Si and F into the second transition layer, using high-purity O2 as the carrier gas, so that the relative refractive index difference Δn9 of the depressed layer reaches -0.8 to -1.0%, and the molar concentration of F is 1 to 3%;

[0063] 24) Deposition of the remote mesa: introducing reactants containing Si and F into the recessed layer, using high-purity O2 as the carrier gas, such that the relative refractive index difference Δn8 of the remote mesa reaches -0.75 to -0.85%, and the molar concentration of fluorine doping in the remote mesa is 0.4 to 0.8%;

[0064] 25) Deposition of the second graded layer: introducing reactants containing Si and F into the distal mesa layer, using high-purity O2 as the carrier gas, the relative refractive index difference of the second graded layer being Δn6 to Δn7, and the molar concentration of fluorine doping in the second graded layer being 0.1 to 2%;

[0065] 26) Deposition of the mesa interlayer: introducing reactants containing Tm, Si, and F into the second graded layer using high-purity O2 as the carrier gas, such that the relative refractive index difference of the mesa interlayer reaches -0.65 to -0.75%, and the molar concentration of thulium doped in the mesa interlayer is 0.5 to 2%;

[0066] 27) Deposition of the mesa: Si and F-containing reactants are introduced into the mesa interlayer, with high-purity O2 as the carrier gas, so that the relative refractive index difference Δn5 of the mesa reaches -0.25 to -0.4%, and the molar concentration of fluorine doping in the mesa is 0.2 to 0.5%;

[0067] 28) Deposition of the first transition layer: Si and F-containing reactants are introduced into the near-core mesa layer using high-purity O2 as the carrier gas, so that the relative refractive index difference Δn4 of the first transition layer reaches -0.35 to -0.5%;

[0068] 29) Deposition of the first gradient layer: introducing reactants containing Si and F into the first transition layer, using high-purity O2 as the carrier gas, such that the relative refractive index difference of the first gradient layer reaches Δn2 to Δn4, and the molar concentration of fluorine doping in the first gradient layer is 0.1 to 2%;

[0069] 30) Deposition of the inner cladding: introducing reactants containing Si and F into the first graded layer, using high-purity O2 as the carrier gas, such that the relative refractive index difference Δn2 of the inner cladding reaches -0.12 to -0.32% and the molar concentration of fluorine doping in the inner cladding is 0 to 0.3%;

[0070] 31) Deposition of the core layer: Reactants containing K, Ge, Si, and F are introduced into the inner cladding, with high-purity O2 as the carrier gas, so that the relative refractive index difference Δn1 reaches 0-0.27%, the molar concentration of K doping in the core layer is in the range of 0.2-0.4%, and the molar concentration of Ge doping is in the range of 0.05-0.3%;

[0071] 3) After the liner is deposited, caps must be placed on both ends of the liner before the rod is moved to prevent air from entering and ensure the ultra-low attenuation performance of the core rod. After the tube is quickly moved and installed in the melt-shrink bed, it must be purged with high-purity O2 to reduce the hydroxyl content in the liner during the installation of the deposition tube. The O2 flow rate is 1000-2000 sccm and the purge time is 1-5 minutes.

[0072] 4) Melting and shrinking the deposited liner into a solid core rod at a melting temperature of 1800-2200°C. During the melting and shrinking process, high-purity O2 is introduced at a flow rate of 1000-2000 sccm. The internal pressure of the melting and shrinking tube is controlled at 0-10 Pa.

[0073] 5) According to the design size of the core rod, match the corresponding sleeve so that the optical fiber meets the design thickness requirements of R1 to R10.

[0074] Parts or structures not specifically described in the present invention may adopt existing technologies or existing products and will not be described in detail here.

[0075] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A radiation-resistant ultra-low-loss single-mode optical fiber with a double-table waveguide guiding structure, characterized in that: It includes a core layer, an inner cladding, a first gradient layer, a first transition layer, a near-core table, a table sandwich, a second gradient layer, a far-core table, a recessed layer, a second transition layer and an outer cladding arranged in sequence from the center to the outside; The radius R1 of the core layer is 3 to 9 μm, and the relative refractive index difference Δn1 is 0 to 0.27%; The radius of the inner cladding is R2, the thickness R2-R1 thereof is in the range of 1 to 5 μm, and the relative refractive index difference Δn2 of the inner cladding is -0.12 to -0.32%; The radius of the first gradient layer is R3, the thickness R3-R2 thereof is in the range of 0.5 to 3 μm, and the relative refractive index difference of the first gradient layer is Δn2 to Δn4; The radius of the first transition layer is R4, the thickness thereof is R4-R3, which is 1 to 2.5 μm, and the relative refractive index difference Δn4 of the first transition layer is -0.35 to -0.5%; The radius of the near-core table is R5, the thickness R5-R4 thereof is in the range of 5 to 12 μm, and the relative refractive index difference Δn5 of the near-core table is -0.25 to -0.4%; The radius of the mesa interlayer is R6, the thickness thereof is R6-R5, which is 1 to 2.5 μm, and the relative refractive index difference of the mesa interlayer is -0.65 to -0.75%; The radius of the second gradient layer is R7, the thickness R7-R6 thereof is in the range of 0.5 to 3 μm, and the relative refractive index difference of the second gradient layer is Δn6 to Δn7; The radius of the remote core table is R8, the thickness thereof is 5 to 12 μm, and the relative refractive index difference Δn8 of the remote core table is -0.75 to -0.85%; The radius of the concave layer is R9, the thickness thereof is 3 to 8 μm, and the relative refractive index difference Δn9 of the concave layer is -0.8 to -1.0%; The radius of the second transition layer is R10, the thickness thereof is 1 to 2.5 μm, and the relative refractive index difference of the second transition layer is -0.05 to -0.15%.

2. The radiation-resistant ultra-low-loss single-mode optical fiber with a double-table waveguide guiding structure according to claim 1, characterized in that: The molar concentration of potassium doped in the fiber core layer is in the range of 0.2-0.4%, and the molar concentration of germanium dioxide doped in the fiber core layer is in the range of 0.05-0.3%.

3. The radiation-resistant ultra-low-loss single-mode optical fiber with a double-table waveguide guiding structure according to claim 1, characterized in that: The molar concentration of fluorine doped in the inner cladding is 0-0.3%.

4. The radiation-resistant ultra-low-loss single-mode optical fiber with a double-table waveguide guiding structure according to claim 1, characterized in that: The molar concentration of fluorine doped in the first gradient layer and the second gradient layer is 0.1-2%.

5. The radiation-resistant ultra-low-loss single-mode optical fiber with a double-mesa waveguide guiding structure according to claim 1, characterized in that: The molar concentration of fluorine doped on the near-core mesa is 0.2-0.5%; the molar concentration of fluorine doped on the far-core mesa is 0.4-0.8%.

6. The radiation-resistant ultra-low-loss single-mode optical fiber with a double-mesa waveguide guiding structure according to claim 1, characterized in that: The molar concentration of thulium doped in the mesa interlayer is 0.5-2%.

7. The radiation-resistant ultra-low-loss single-mode optical fiber with a double-mesa waveguide guiding structure according to claim 1, characterized in that: The molar concentration of fluorine doped in the recessed layer is 1-3%.

8. The radiation-resistant ultra-low-loss single-mode optical fiber with a double-mesa waveguide guiding structure according to claim 1, characterized in that: The radius of the outer cladding is 50-65 μm. The outer cladding is pure silicon dioxide or silicon dioxide glass doped with metal ions. The metal ions are a combination of one or more of Fe, Ni, Co, and Tm.

9. The radiation-resistant ultra-low-loss single-mode optical fiber with a double-mesa waveguide guiding structure according to claim 1, characterized in that: The application wavelength range of the optical fiber is 1530-1625nm, the attenuation coefficient at 1550nm is ≤0.15dB / km, the dispersion coefficient at 1550nm is ≤21ps / (nm·km), and the dispersion slope at 1550nm is ≤0.06ps / (nm 2 ·km), zero dispersion wavelength ≤1270nm, additional attenuation at 1550nm under 10rad irradiation intensity for 25 years ≤0.001dB / km.

10. A method for preparing a radiation-resistant ultra-low-loss single-mode optical fiber with a double-table waveguide guiding structure, characterized in that: The optical fiber is prepared by PCVD or MCVD process; The steps of preparing the optical fiber by PCVD process include: 1) A pure silicon liner or a liner doped with metal ions is used, which is acid-washed and then placed on a drying rack for drying. Ar is introduced into the tube at a temperature of 60° C. for 12 to 24 hours. This step mainly reduces the hydroxyl content in the liner. The metal ions are a combination of one or more metal ions such as Fe, Ni, Co, and Tm; 2) Install the purged pure silicon liner or the liner doped with special metal ions on the deposition machine of the PCVD process to perform ultra-low loss core rod deposition: 21) Outer cladding, reactants containing Ni, Si, and F are introduced into the liner, and the carrier gas is high-purity O2; 22) Deposition of the second transition layer: introducing reactants containing Si and F into the outer cladding, with high-purity O2 as the carrier gas, so that the relative refractive index difference of the second transition layer reaches -0.05 to -0.15%; 23) Deposition of the depressed layer, introducing reactants containing Si and F into the second transition layer, with high-purity O2 as the carrier gas, so that the relative refractive index difference of the depressed layer reaches Δn9 of -0.8 to -1.0%, and the molar concentration of F is 1 to 3%; 24) Deposition of the remote core table: Si and F-containing reactants are introduced into the recessed layer, and the carrier gas is high-purity O2. The relative refractive index difference of the table reaches Δn8 of -0.75 to -0.85%, and the molar concentration of fluorine doped on the remote core table is 0.4 to 0.8%; 25) Deposition of the second gradient layer: introducing reactants containing Si and F into the remote core mesa layer, the carrier gas is high-purity O2, the relative refractive index difference of the second gradient layer is Δn6-Δn7, and the molar concentration of fluorine doped in the second gradient layer is 0.1-2%; 26) Deposition of the mesa interlayer: introducing reactants containing Tm, Si and F into the second graded layer, with high-purity O2 as the carrier gas, so that the relative refractive index difference of the mesa interlayer reaches -0.65 to -0.75%, and the molar concentration of thulium doped in the mesa interlayer is 0.5 to 2%; 27) Deposition of the near-core mesa: introducing reactants containing Si and F into the mesa interlayer, with high-purity O2 as the carrier gas, so that the relative refractive index difference of the near-core mesa reaches Δn5 of -0.25 to -0.4%, and the molar concentration of fluorine doped in the near-core mesa is 0.2 to 0.5%; 28) Deposition of the first transition layer: introducing reactants containing Si and F into the near-core mesa layer, with high-purity O2 as the carrier gas, so that the relative refractive index difference of the first transition layer reaches Δn4 of -0.35 to -0.5%; 29) Deposition of the first gradient layer: introducing reactants containing Si and F into the first transition layer, with high-purity O2 as the carrier gas, so that the relative refractive index difference of the first gradient layer reaches Δn2 to Δn4, and the molar concentration of fluorine doped in the first gradient layer is 0.1 to 2%; 30) Deposition of the inner cladding: introducing reactants containing Si and F into the first gradient layer, with high-purity O2 as the carrier gas, so that the relative refractive index difference Δn2 of the inner cladding reaches -0.12 to -0.32%, and the molar concentration of fluorine doped in the inner cladding is 0 to 0.3%; 31) Deposition of the core layer: introducing reactants containing K, Ge, Si, and F into the inner cladding, with high-purity O2 as the carrier gas, so that the relative refractive index difference Δn1 reaches 0-0.27%, the molar concentration of K doped in the core layer ranges from 0.2-0.4%, and the molar concentration of Ge doped is 0.05-0.3%; 3) After the liner tube is deposited, caps need to be placed on both ends of the liner tube before the rod is moved to prevent air from entering and ensure the ultra-low attenuation performance of the core rod. After the tube is quickly moved and installed on the melting bed, it needs to be purged with high-purity O2 to reduce the hydroxyl content in the liner tube during the installation of the deposition tube. The O2 flow rate is 1000-2000sccm and the purging time is 1-5min. 4) Melt and shrink the deposited liner into a solid core rod at a melting temperature of 1800-2200°C. During the melting process, high-purity O2 is introduced at a flow rate of 1000-2000 sccm. The internal pressure of the melting tube is controlled at 0-10 Pa. 5) According to the design size of the core rod, match the corresponding sleeve so that the optical fiber meets the design thickness requirements of R1~R10.

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