A polarization maintaining radiation resistant erbium and ytterbium co-doped optical fiber and a preparation method thereof

Abstract

The application relates to a polarization-maintaining anti-radiation erbium-ytterbium co-doped optical fiber and a preparation method thereof. The optical fiber comprises an outer cladding and a core layer, and stress regions are symmetrically arranged on two sides of the core layer. The core layer is an erbium-ytterbium co-doped silica glass layer, the erbium-ytterbium co-doped silica glass layer is based on SiO2, and is doped with Er2O3, Yb2O3, P2O5, GeO2, Ce2O3 and F. The doping amount of each dopant in the core layer is as follows: Yb2O3 1.5-2.0 mol%, Er2O3 0.1-0.2 mol%, P2O5 13.0-15.0 mol%, GeO2 5-4.0 mol%, F 0.1-1.0 mol% and Ce2O3 0.05-0.3 mol%. The application improves the anti-radiation performance of the optical fiber by doping Ce, Ge and F in the core layer, and meets the application requirements of high-power amplifiers in space radiation environments. Through core-cladding structure design, the polarization-maintaining optical fiber has the characteristics of large mode field and low numerical aperture, can bear higher pump laser power and signal light output power.

Description

Technical Field

[0001] This invention belongs to the field of active optical fiber technology, specifically relating to a polarization-maintaining and radiation-resistant erbium-ytterbium co-doped optical fiber and its preparation method. Background Technology

[0002] In recent years, the construction of "Starlink" has become a hot topic of development both at home and abroad. Internationally, as early as 2015, SpaceX in the United States proposed the "Starlink Project" to build a satellite internet, which has already been commercially available in some regions, and European countries followed suit.

[0003] Radiation-hardened erbium-ytterbium co-doped fiber is an important gain medium for fiber amplifier devices in satellite communication. Currently, in conventional two-stage fiber amplifiers, the first-stage optical path uses radiation-hardened erbium-doped fiber, and the second-stage optical path uses 10 / 125 single-mode radiation-hardened erbium-ytterbium co-doped fiber. Communication can be achieved with a module output power of less than 5W. Further increasing the pump power and output power, exceeding the laser damage threshold of the fiber, can easily lead to fiber burnout. Therefore, to meet the needs of future high-power, high-capacity coherent optical communication, it is necessary to develop a large-mode-field polarization-maintaining radiation-hardened erbium-ytterbium co-doped fiber. This increases the fiber's mode field diameter, thereby improving the laser damage threshold, while simultaneously reducing the numerical aperture (NA) to ensure single-mode or few-mode transmission characteristics and improve beam quality.

[0004] In erbium-ytterbium co-doped optical fibers, each component plays a role. To improve the pump and output power of the fiber, the doping concentration of rare earth ions needs to be increased, and the amount of P2O5, acting as a "solvent," also needs to be increased accordingly to avoid clustering effects. However, this leads to a decrease in the fiber's radiation resistance and an increase in the core nanometer (NA). Therefore, it is essential to find ways to reduce the fiber core NA and improve the radiation resistance of erbium-ytterbium co-doped fibers. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a polarization-maintaining and radiation-resistant erbium-ytterbium co-doped optical fiber, a preform and its preparation method. Through the design of geometric structure and doping composition, the erbium-ytterbium co-doped optical fiber has a high laser damage threshold and polarization-maintaining performance, while also having good radiation resistance.

[0006] The optical fiber technology solution adopted by this invention to solve the above-mentioned problems includes an outer cladding layer and a core layer, with stress zones symmetrically arranged on both sides of the core layer. The core layer is characterized by being an erbium-ytterbium co-doped silica glass layer. This erbium-ytterbium co-doped silica glass layer uses SiO2 as a substrate and is doped with Er2O3, Yb2O3, P2O5, GeO2, Ce2O3, and F. The doping amounts of each dopant in the core layer are: Yb2O3 1.5–2.0 mol%, Er2O3 0.1–0.2 mol%, P2O5 13.0–15.0 mol%, GeO2 5–4.0 mol%, F 0.1–1.0 mol%, and Ce2O3 0.05–0.3 mol%.

[0007] According to the above scheme, the Yb2O3 doping amount in the core layer is 1.5-1.7 mol%, the Er2O3 doping amount is 0.1-0.15 mol%, and the Yb2O3 / Er2O3 ratio is controlled at 8-20.

[0008] According to the above scheme, the P2O5 doping amount in the core layer is 13.0-14.0 mol%, the Ce2O3 doping amount is 0.1-0.25 mol%, and the F doping amount is 0.1-0.5 mol%.

[0009] According to the above scheme, the diameter of the core layer is 20-30 μm, and the refractive index difference between the core layer and pure quartz glass is 0.015-0.019.

[0010] According to the above scheme, the numerical aperture (NA) of the optical fiber is 0.07 to 0.09, and the mode field diameter is 17 to 25 μm.

[0011] According to the above scheme, the core layer is tightly wrapped with an inner cladding layer, which is a germanium-fluorine-phosphorus co-doped silica glass layer. The germanium-fluorine-phosphorus co-doped silica glass layer uses SiO2 as a matrix and is doped with GeO2, P2O5 and F. The doping amount of each dopant in the core layer is 8-14 mol% for GeO2, 1-4 mol% for P2O5 and 0.1-1.0 mol% for F.

[0012] According to the above scheme, the diameter of the inner cladding layer is 40-45 μm, and the refractive index difference between the inner cladding layer and pure quartz glass is 0.013-0.015.

[0013] According to the above scheme, the diameter of the stress zone is 60-90 μm, and the distance between the center of the stress zone and the center of the core layer is 70-90 μm.

[0014] According to the above scheme, the diameter of the stress zone is 65-75 μm, the distance between the center of the stress zone and the center of the core layer is 75-80 μm, and the relative refractive index difference of the stress zone is ≤-0.008.

[0015] According to the above scheme, the birefringence of the optical fiber is ≥1.0×10⁻⁶. -4 Radiation-induced gain change ≤ 0.01 dB / krad.

[0016] According to the above scheme, the outer coating layer has a diameter of 300±10μm, the outer coating layer is a pure silica glass layer, and the outer coating layer is covered with an inner resin coating layer and an outer resin coating layer. The inner resin coating layer has a diameter of 375±10μm, and the outer resin coating layer has a diameter of 450±20μm.

[0017] The technical solution for optical fiber fabrication in this invention is as follows:

[0018] Manufacture of core rod: The inner cladding and core layer are deposited sequentially in a quartz liner. After the deposition is completed, the doped deposition liner is melted down into a solid core rod.

[0019] Fabrication of solid preforms: Insert a solid core into a quartz sleeve and stretch it into a solid preform of a certain size through high-temperature melting and shrinking. Then, process a pair of through holes on both sides of the solid preform with the center of the end face as the symmetrical point.

[0020] Fabrication of stress bars: Doping is carried out in a quartz liner, and after deposition, the doped liner is melted down into a solid stress bar.

[0021] Fabrication of polarization-maintaining fiber preform: Insert solid stress rods into the through holes on both sides of the solid preform, and tape one end to form the polarization-maintaining fiber preform.

[0022] Drawing polarization-maintaining fiber: The polarization-maintaining fiber preform is clamped into a drawing furnace and drawn to obtain polarization-maintaining fiber.

[0023] According to the above scheme, the mandrel manufacturing process includes

[0024] A gas-phase process using MCVD combined with a chelate evaporation system (CDS) is employed, in which the reactants SiCl4, P2O5, GeO2 and F are loaded into a quartz liner tube via oxygen. The liner tube is heated to 1700-1750℃ to vitrify the reactants, and an inner cladding layer is repeatedly deposited on the inner wall of the quartz tube.

[0025] A gas-phase process using MCVD combined with a chelate evaporation system (CDS) is employed. The reactants SiCl4, P2O5, GeO2, and F are loaded into a quartz liner tube using oxygen. Yb chelate, Er chelate, and Ce chelate are loaded into the quartz liner tube using helium. The liner tube is heated to 1500–1600°C to vitrify the reactants. Rare earth doped core layers are repeatedly deposited on the inner wall of the quartz tube.

[0026] After the core layer is deposited, the quartz tube is heated to 1800-2100℃, and the surface tension of the glass is used to melt and shrink the quartz tube into a doped quartz rod.

[0027] The beneficial effects of this invention are as follows: 1. By optimizing the core doping composition, three components—GeO2, Ce2O3, and F—are introduced into the fiber core to improve the radiation resistance of the optical fiber. GeO2 itself is relatively insensitive to radiation, and the electron and hole defects it generates can interact with radiation-induced defects generated by other components such as P2O5, playing a neutralizing role, thereby improving the radiation resistance of the optical fiber and meeting the application requirements of high-power amplifiers in radiation environments such as space. However, the introduction of GeO2 leads to an increase in the numerical aperture of the fiber core, so F needs to be introduced to reduce the refractive index of the core. Furthermore, F can combine with SiO2-related defects, replacing O ions in the structure to form stronger Si-F bonds, which also helps reduce the generation of SiO2-related radiation-induced defects. 2. This invention increases the mode field diameter of the optical fiber through core-cladding structure design, thereby increasing the laser damage threshold of the optical fiber and enabling it to withstand higher pump laser power and signal light output power. Simultaneously, the low numerical aperture design ensures that the signal light maintains single-mode or few-mode transmission characteristics in the optical fiber, improving beam quality. The optical fiber described in this invention has significant application value in the field of high-power communication amplifiers for terrestrial and low-orbit satellite communications. 3. The polarization-maintaining structure design of this invention can maintain good polarization mode transmission of the transmitted light in the optical fiber, and the large mode field diameter design reduces the nonlinear effects during high-power pump output. The optical fiber described has significant application value in high-power, long-distance correlation communications in space. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the radial structure of an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the optical fiber preform structure in one embodiment of the present invention.

[0030] Figure 3 This is a graph showing the radiation-induced gain variation of the large-mode-field polarization-maintaining radiation-resistant erbium-ytterbium co-doped fiber described in this invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0032] Examples of embodiments of the optical fiber of the present invention Figure 1As shown, it includes an outer cladding layer 4 and a core layer 1. Stress zones 3 are symmetrically arranged on both sides of the core layer. The core layer is an erbium-ytterbium co-doped silica glass layer. The erbium-ytterbium co-doped silica glass layer uses SiO2 as a matrix and is doped with Er2O3, Yb2O3, P2O5, GeO2, Ce2O3 and F. The core layer is tightly wrapped with an inner cladding layer 2. The inner cladding layer is a germanium-fluorine-phosphorus co-doped silica glass layer. The germanium-fluorine-phosphorus co-doped silica glass layer uses SiO2 as a matrix and is doped with GeO2, P2O5 and F. The diameter of the core layer is 20-30 μm, the diameter of the inner cladding layer is 40-45 μm, the diameter of the stress zone is 60-90 μm, and the distance between the center of the stress zone and the center of the core layer is 70-90 μm. The outer coating layer has a diameter of 300±10μm, and is covered with an inner resin coating layer 5 and an outer resin coating layer 6. The inner resin coating layer has a diameter of 375±10μm, and the outer resin coating layer has a diameter of 450±20μm.

[0033] The present invention will be further described below with reference to embodiments and comparative examples.

[0034] Comparative Example: In this comparative example, the core layer dopant of the large-mode-field polarization-maintaining radiation-resistant erbium-ytterbium co-doped fiber contains P2O5, Er2O3, and Yb2O3, with doping concentrations of Yb2O3 at 1.5 mol%, Er2O3 at 0.1 mol%, and P2O5 at 13.0 mol%. The inner cladding dopant of the fiber contains P2O5 and GeO2, with doping concentrations of approximately 2.0 mol% for P2O5 and approximately 13.0 mol% for GeO2, and the remaining matrix material is SiO2.

[0035] Its preparation method specifically includes the following steps:

[0036] S1: A gas-phase process using MCVD combined with a chelate evaporation system (CDS) is employed. The reactants SiCl4, P2O5, and GeO2 are introduced into a quartz liner via oxygen, with flow rates of 300 sccm, 100 sccm, and 500 sccm, respectively. The liner is heated to 1700–1750℃ to vitrify the reactants, and several inner cladding layers are repeatedly deposited on the inner wall of the quartz tube.

[0037] S2: A gas-phase process using MCVD combined with a chelate evaporation system (CDS) is employed. The reactants SiCl4 and P2O5 are loaded into a quartz liner using oxygen at flow rates of 100 sccm and 1000 sccm, respectively. The Yb chelate and Er chelate are loaded into the quartz liner using helium at flow rates of 500 sccm and 100 sccm, respectively. The liner is heated to 1500–1600℃ to vitrify the reactants, and several rare-earth-doped core layers are repeatedly deposited on the inner wall of the quartz tube.

[0038] S3: After the core layer deposition is completed, the quartz tube is heated to 1800-2100℃, and the surface tension of the glass is used to melt and shrink the quartz tube into a doped quartz rod.

[0039] S4: The doped quartz rod and quartz sleeve are combined into a preform using the tube-rod method, and then stretched into a solid preform with a certain outer diameter in a stretching tower.

[0040] S5: Process two through holes in the solid preform at a position symmetrical about the fiber core center.

[0041] S6: After cleaning the two stress rods and the solid preform rod with the holes processed above, assemble them into a polarization-maintaining fiber preform rod.

[0042] S7: The above polarization-maintaining fiber preform is heated to 1800-2100℃ in a drawing furnace to soften and draw it into a polarization-maintaining fiber.

[0043] The radiation-resistant erbium-ytterbium co-doped optical fiber prepared by the above method has a cladding diameter of 300 μm, an inner cladding diameter of 43 μm, a refractive index difference of 0.013 between the inner cladding and pure quartz glass, a core diameter of 25 μm, a core NA of 0.08, an inner coating diameter of approximately 375 μm, and an outer coating diameter of approximately 450 μm.

[0044] Example 1: In this example, the core layer dopant of the large-mode-field polarization-maintaining radiation-resistant erbium-ytterbium co-doped fiber includes P2O5, Er2O3, Yb2O3, GeO2, Ce2O3, and F, with doping concentrations of Yb2O3 at 1.7 mol%, Er2O3 at 0.12 mol%, P2O5 at 14.0 mol%, GeO2 at 2.0 mol%, Ce2O3 at 0.2 mol%, and F at approximately 0.3 mol%. The inner cladding dopant of the fiber includes P2O5, GeO2, and F, with doping concentrations of P2O5 at approximately 4.0 mol%, GeO2 at approximately 13.0 mol%, F at approximately 0.2 mol%, and the remaining matrix material is SiO2.

[0045] Its preparation method specifically includes the following steps:

[0046] S1: A gas-phase process using MCVD combined with a chelate evaporation system (CDS) is employed. The reactants SiCl4, P2O5, GeO2, and SiF4 are introduced into a quartz liner via oxygen, with flow rates of 300 sccm, 200 sccm, 500 sccm, and 5 sccm, respectively. The liner is heated to 1700–1750℃ to vitrify the reactants, and several inner cladding layers are repeatedly deposited on the inner wall of the quartz tube.

[0047] S2: A gas-phase process using MCVD combined with a chelate evaporation system (CDS) is employed. The reactants SiCl4, P2O5, GeO2, and SiF4 are loaded into a quartz liner using oxygen at flow rates of 100 sccm, 1200 sccm, 50 sccm, and 7 sccm, respectively. Yb chelates, Er chelates, and Ce chelates are loaded into the quartz liner using helium at flow rates of 550 sccm, 150 sccm, and 200 sccm, respectively. The liner is heated to 1500–1600℃ to vitrify the reactants, and several rare-earth-doped core layers are repeatedly deposited on the inner wall of the quartz tube.

[0048] S3: After the core layer deposition is completed, the quartz tube is heated to 1800-2100℃, and the surface tension of the glass is used to melt and shrink the quartz tube into a doped quartz rod.

[0049] S4: The doped quartz rod and quartz sleeve are combined into a preform using the tube-rod method, and then stretched into a solid preform with a certain outer diameter in a stretching tower.

[0050] S5: Two through holes 7 are machined in the solid preform at a position symmetrical about the fiber core center.

[0051] S6: After cleaning the two stress rods and the solid preform rod with the holes processed above, assemble them into a polarization-maintaining fiber preform rod.

[0052] S7: The above polarization-maintaining fiber preform is heated to 1800-2100℃ in a drawing furnace to soften and draw it into a polarization-maintaining fiber.

[0053] The radiation-resistant erbium-ytterbium co-doped optical fiber prepared by the above method has a cladding diameter of 300 μm, an inner cladding diameter of 41 μm, a refractive index difference of 0.0149 between the inner cladding and pure quartz glass, a core diameter of 25 μm, a core NA of 0.09, an inner coating diameter of approximately 375 μm, and an outer coating diameter of approximately 450 μm.

[0054] Example 2: In this example, the core layer dopant of the large-mode-field polarization-maintaining radiation-resistant erbium-ytterbium co-doped fiber includes P2O5, Er2O3, Yb2O3, GeO2, Ce2O3, and F, with doping concentrations of Yb2O3 at 1.8 mol%, Er2O3 at 0.15 mol%, P2O5 at 15.0 mol%, GeO2 at 3.0 mol%, Ce2O3 at 0.2 mol%, and F at approximately 0.5 mol%. The inner cladding dopant of the fiber includes P2O5, GeO2, and F, with doping concentrations of P2O5 at approximately 4.0 mol%, GeO2 at approximately 13.0 mol%, F at approximately 0.2 mol%, and the remaining matrix material is SiO2.

[0055] Its preparation method specifically includes the following steps:

[0056] S1: A gas-phase process using MCVD combined with a chelate evaporation system (CDS) is employed. The reactants SiCl4, P2O5, GeO2, and SiF4 are introduced into a quartz liner via oxygen, with flow rates of 300 sccm, 200 sccm, 500 sccm, and 5 sccm, respectively. The liner is heated to 1700–1750℃ to vitrify the reactants, and several inner cladding layers are repeatedly deposited on the inner wall of the quartz tube.

[0057] S2: A gas-phase process using MCVD combined with a chelate evaporation system (CDS) is employed. The reactants SiCl4, P2O5, GeO2, and SiF4 are loaded into a quartz liner using oxygen at flow rates of 100 sccm, 1500 sccm, 75 sccm, and 10.0 sccm, respectively. Yb chelates, Er chelates, and Ce chelates are loaded into the quartz liner using helium at flow rates of 580 sccm, 180 sccm, and 200 sccm, respectively. The liner is heated to 1500–1600℃ to vitrify the reactants, and several rare-earth-doped core layers are repeatedly deposited on the inner wall of the quartz tube.

[0058] S3: After the core layer deposition is completed, the quartz tube is heated to 1800-2100℃, and the surface tension of the glass is used to melt and shrink the quartz tube into a doped quartz rod.

[0059] S4: The doped quartz rod and quartz sleeve are combined into a preform using the tube-rod method, and then stretched into a solid preform with a certain outer diameter in a stretching tower.

[0060] S5: Process two through holes in the solid preform at a position symmetrical about the fiber core center.

[0061] S6: After cleaning the two stress rods and the solid preform rod with the holes processed above, assemble them into a polarization-maintaining fiber preform rod.

[0062] S7: The above polarization-maintaining fiber preform is heated to 1800-2100℃ in a drawing furnace to soften and draw it into a polarization-maintaining fiber.

[0063] The radiation-resistant erbium-ytterbium co-doped optical fiber prepared by the above method has a cladding diameter of 300 μm, an inner cladding diameter of 45 μm, a refractive index difference of 0.0146 between the inner cladding and pure quartz glass, a core diameter of 25 μm, a core NA of 0.07, an inner coating diameter of approximately 375 μm, and an outer coating diameter of approximately 450 μm.

[0064] Example 3: In this example, the core layer dopant of the large-mode-field polarization-maintaining radiation-resistant erbium-ytterbium co-doped fiber includes P2O5, Er2O3, Yb2O3, GeO2, Ce2O3, and F, with doping concentrations of Yb2O3 at 2.0 mol%, Er2O3 at 0.15 mol%, P2O5 at 15.0 mol%, GeO2 at 4.0 mol%, Ce2O3 at 0.3 mol%, and F at approximately 0.8 mol%. The inner cladding dopant of the fiber includes P2O5, GeO2, and F, with doping concentrations of P2O5 at approximately 4.0 mol%, GeO2 at approximately 14.0 mol%, F at approximately 0.1 mol%, and the remaining matrix material is SiO2.

[0065] Its preparation method specifically includes the following steps:

[0066] S1: A gas-phase process using MCVD combined with a chelate evaporation system (CDS) is employed. The reactants SiCl4, P2O5, GeO2, and SiF4 are introduced into a quartz liner via oxygen, with flow rates of 300 sccm, 200 sccm, 600 sccm, and 3 sccm, respectively. The liner is heated to 1700–1750℃ to vitrify the reactants, and several inner cladding layers are repeatedly deposited on the inner wall of the quartz tube.

[0067] S2: A gas-phase process using MCVD combined with a chelate evaporation system (CDS) is employed. The reactants SiCl4, P2O5, GeO2, and SiF4 are loaded into a quartz liner using oxygen at flow rates of 100 sccm, 1500 sccm, 90 sccm, and 14.0 sccm, respectively. Yb chelates, Er chelates, and Ce chelates are loaded into the quartz liner using helium at flow rates of 600 sccm, 200 sccm, and 250 sccm, respectively. The liner is heated to 1500–1600℃ to vitrify the reactants, and several rare-earth-doped core layers are repeatedly deposited on the inner wall of the quartz tube.

[0068] S3: After the core layer deposition is completed, the quartz tube is heated to 1800-2100℃, and the surface tension of the glass is used to melt and shrink the quartz tube into a doped quartz rod.

[0069] S4: The doped quartz rod and quartz sleeve are combined into a preform using the tube-rod method, and then stretched into a solid preform with a certain outer diameter in a stretching tower.

[0070] S5: Process two through holes in the solid preform at a position symmetrical about the fiber core center.

[0071] S6: After cleaning the two stress rods and the solid preform rod with the holes processed above, assemble them into a polarization-maintaining fiber preform rod.

[0072] S7: The above polarization-maintaining fiber preform is heated to 1800-2100℃ in a drawing furnace to soften and draw it into a polarization-maintaining fiber.

[0073] The radiation-resistant erbium-ytterbium co-doped optical fiber prepared by the above method has a cladding diameter of 300 μm, an inner cladding diameter of 42 μm, a refractive index difference of 0.014 between the inner cladding and pure quartz glass, a core diameter of 25 μm, a core NA of 0.08, an inner coating diameter of approximately 375 μm, and an outer coating diameter of approximately 450 μm.

[0074] For the large-mode-field polarization-maintaining and radiation-resistant erbium-ytterbium co-doped optical fibers in comparative examples and specific embodiments 1-3, the changes in doped materials and radiation-induced gain in different parts are summarized as follows:

[0075]

[0076] The test results of radiation-induced gain changes in the examples and comparative examples show that the fiber doping composition provided by this invention can significantly improve the radiation resistance of the fiber. Furthermore, the radiation resistance of the fiber also improves with the increase of GeO2, Ce2O3, and F in the core layer. The large-mode-field polarization-maintaining radiation-resistant erbium-ytterbium co-doped fiber of this invention, through optimized fiber geometry and doping design, improves the radiation resistance and laser damage threshold of the erbium-ytterbium co-doped fiber. This ensures that the gain medium, such as the erbium-ytterbium co-doped fiber, maintains good optical amplification performance in radiation-filled environments such as space, and has significant application value in high-power amplification modules in space communication and integrated space-air-ground optical communication.

[0077] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A polarization-maintaining, radiation-resistant erbium-ytterbium co-doped optical fiber, comprising an outer cladding and a core layer, wherein stress regions are symmetrically arranged on both sides of the core layer, characterized in that... The core layer is an erbium-ytterbium co-doped silica glass layer. The erbium-ytterbium co-doped silica glass layer uses SiO2 as a matrix and is doped with Er2O3, Yb2O3, P2O5, GeO2, Ce2O3 and F. The doping amount of each dopant in the core layer is 1.5-2.0 mol% Yb2O3, 0.1-0.2 mol% Er2O3, 13.0-15.0 mol% P2O5, 5-4.0 mol% GeO2, 0.1-1.0 mol% F, and 0.05-0.3 mol% Ce2O3. The diameter of the core layer is 20-30 μm, and the refractive index difference between the core layer and pure quartz glass is 0.015-0.

019.

2. The polarization-maintaining and radiation-resistant erbium-ytterbium co-doped optical fiber according to claim 1, characterized in that... The core layer contains 13.0–14.0 mol% P2O5, 0.1–0.25 mol% Ce2O3, and 0.1–0.5 mol% F.

3. The polarization-maintaining, radiation-resistant erbium-ytterbium co-doped optical fiber according to claim 1 or 2, characterized in that... The optical fiber has a numerical aperture (NA) of 0.07–0.09 and a mode field diameter of 17–25 μm.

4. The polarization-maintaining, radiation-resistant erbium-ytterbium co-doped optical fiber according to claim 1 or 2, characterized in that... The core layer is tightly wrapped with an inner cladding layer, which is a germanium-fluorine-phosphorus co-doped silica glass layer. The germanium-fluorine-phosphorus co-doped silica glass layer is based on SiO2 and doped with GeO2, P2O5 and F. The doping amount of each dopant in the core layer is 8-14 mol% for GeO2, 1-4 mol% for P2O5 and 0.1-1.0 mol% for F.

5. The polarization-maintaining and radiation-resistant erbium-ytterbium co-doped optical fiber according to claim 4, characterized in that... The inner cladding has a diameter of 40–45 μm, and the refractive index difference between the inner cladding and pure quartz glass is 0.013–0.

015.

6. The polarization-maintaining, radiation-resistant erbium-ytterbium co-doped optical fiber according to claim 1 or 2, characterized in that... The stress zone has a diameter of 60–90 μm, the distance between the center of the stress zone and the center of the core layer is 70–90 μm, and the refractive index difference between the stress zone and pure quartz glass is ≤-0.

008.

7. The polarization-maintaining and radiation-resistant erbium-ytterbium co-doped optical fiber according to claim 6, characterized in that... The diameter of the stress zone is 65-75 μm, and the distance between the center of the stress zone and the center of the core layer is 75-80 μm.

8. The polarization-maintaining, radiation-resistant erbium-ytterbium co-doped optical fiber according to claim 1 or 2, characterized in that... The optical fiber has a birefringence ≥ 1.0 × 10⁻⁴ and a radiation-induced gain variation ≤ 0.01 dB / krad.

9. The polarization-maintaining, radiation-resistant erbium-ytterbium co-doped optical fiber according to claim 1 or 2, characterized in that... The outer coating layer has a diameter of 300±10μm, and is covered with an inner resin coating layer and an outer resin coating layer. The inner resin coating layer has a diameter of 375±10μm, and the outer resin coating layer has a diameter of 450±20μm.

10. A method for preparing polarization-maintaining radiation-resistant erbium-ytterbium co-doped optical fiber, used to prepare the polarization-maintaining radiation-resistant erbium-ytterbium co-doped optical fiber as described in any one of claims 1 to 9, characterized in that... Manufacture of core rod: The inner cladding and core layer are deposited sequentially in a quartz liner. After the deposition is completed, the doped deposition liner is melted down into a solid core rod. Fabrication of solid preforms: Insert a solid core into a quartz sleeve and stretch it into a solid preform of a certain size through high-temperature melting and shrinking. Then, process a pair of through holes on both sides of the solid preform with the center of the end face as the symmetrical point. Fabrication of stress bars: Doping is carried out in a quartz liner, and after deposition, the doped liner is melted down into a solid stress bar. Fabrication of polarization-maintaining fiber preform: Insert solid stress rods into the through holes on both sides of the solid preform, and tape one end to form the polarization-maintaining fiber preform. Drawing polarization-maintaining fiber: The polarization-maintaining fiber preform is clamped into a drawing furnace and drawn to obtain polarization-maintaining fiber.

11. The method for fabricating polarization-maintaining and radiation-resistant erbium-ytterbium co-doped optical fiber according to claim 10, characterized in that... The aforementioned mandrel manufacturing process includes A gas-phase process using MCVD combined with a CDS chelate evaporation system is employed, in which the reactants SiCl4, P2O5, GeO2 and F are loaded into a quartz liner tube via oxygen. The liner tube is heated to 1700-1750℃ to vitrify the reactants, and an inner cladding layer is repeatedly deposited on the inner wall of the quartz tube. A gas-phase process using MCVD combined with a CDS chelate evaporation system is employed. The reactants SiCl4, P2O5, GeO2, and F are loaded into a quartz liner tube using oxygen, while Yb chelate, Er chelate, and Ce chelate are loaded into the quartz liner tube using helium. The liner tube is heated to 1500–1600°C to vitrify the reactants, and rare earth doped core layers are repeatedly deposited on the inner wall of the quartz tube. After the core layer is deposited, the quartz tube is heated to 1800-2100℃, and the surface tension of the glass is used to melt and shrink the quartz tube into a doped quartz rod.

Images