A method and system for suppressing attenuation of a single-mode optical fiber in an irradiation environment

Abstract

The application relates to a single-mode optical fiber attenuation inhibition processing method and system in an irradiation environment, and relates to the technical field of single-mode optical fibers, and comprises the following steps: obtaining a fiber core doping parameter of a single-mode optical fiber to be processed, and determining a target hydrogen concentration required for inhibiting radiation-induced attenuation according to the fiber core doping parameter; generating double-stage hydrogen loading process parameters and ladder annealing process parameters according to the target hydrogen concentration, and forming a customized processing strategy; sequentially performing double-stage hydrogen loading, pre-irradiation and ladder annealing processing on the single-mode optical fiber, so as to excite and passivate color center defects and remove free hydrogen; and finally coating a solidified sealing layer on the surface of the optical fiber to obtain an attenuation inhibition type anti-radiation single-mode optical fiber, so that the technical problem of how to reasonably determine matched processing conditions according to the material characteristics of the single-mode optical fiber to be processed and simultaneously consider radiation defect inhibition and background transmission loss control is solved.

Description

Technical Field

[0001] This invention relates to the field of single-mode optical fiber technology, and in particular to a method and system for attenuation suppression of single-mode optical fiber under irradiation environment. Background Technology

[0002] Single-mode optical fiber is widely used in environments with ionizing radiation, such as nuclear facility monitoring, spacecraft communications, particle physics experiments, and radiation medicine equipment. When optical fibers are irradiated by gamma rays, X-rays, or high-energy particles, the defect precursors in the fiber core and cladding glass network may transform into color centers with light absorption, causing radiation-induced additional attenuation in the fiber's operating wavelength range. Existing technologies typically employ methods such as material composition optimization, hydrogen loading of the fiber, pre-irradiation, heat treatment, or surface protection to reduce radiation-induced transmission loss. Furthermore, by setting appropriate pressure, temperature, processing time, and irradiation dose, the internal defect state and hydrogen-related absorption of the fiber can be controlled to improve the transmission stability of the optical fiber in radiation environments.

[0003] However, different batches of single-mode fibers exhibit variations in doping composition, defect precursor content, glass network structure, and hydrogen diffusion capabilities. Existing processing techniques often employ fixed or empirical parameters, making it difficult to match the processing intensity with the actual material properties of the fiber to be processed. When the processing intensity is insufficient, some radiation-sensitive defects cannot be effectively suppressed; when the processing intensity is too high, problems such as hydrogen-related background absorption, insufficient structural relaxation, or subsequent hydrogen escape may be introduced, leading to insufficient consistency in attenuation performance and long-term stability of the processed fiber. Therefore, how to rationally determine suitable processing conditions based on the material properties of the single-mode fiber to be processed, while balancing radiation defect suppression and background transmission loss control, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to at least partially solve one of the technical problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides a method for attenuation suppression of single-mode optical fiber under irradiation conditions, comprising: Obtain the core doping parameters of the single-mode fiber to be processed; calculate the target hydrogen concentration of the single-mode fiber to suppress radiation-induced attenuation based on the core doping parameters. Based on the target hydrogen loading concentration, the two-stage hydrogen loading process parameters for hydrogen permeation into the optical fiber and the stepped annealing process parameters for removing free hydrogen from the optical fiber to eliminate hydrogen loss and background attenuation are calculated, resulting in a customized treatment strategy. According to the customized processing strategy, the single-mode fiber is subjected to a two-stage hydrogen loading operation, a pre-irradiation operation to excite and passivate color center defects, and a stepped annealing operation in sequence. After the stepped annealing operation is completed, a curing sealing layer is coated on the surface of the single-mode fiber to obtain an attenuation-suppressed radiation-resistant single-mode fiber.

[0006] Furthermore, calculating the target hydrogen concentration of the single-mode fiber used to suppress radiation-induced attenuation based on the fiber core doping parameters includes: The molar percentage of fluorine and the residual percentage of chlorine in the single-mode fiber to be processed are obtained as the core doping parameters. The molar percentage of fluorine and the residual percentage of chlorine are multiplied by the corresponding first defect conversion coefficient and second defect conversion coefficient, respectively, to calculate the fluorine-induced defect density base and the chlorine-induced defect density base. The product of the molar percentage of fluorine and the residual percentage of chlorine is calculated, and combined with the preset lattice distortion constant, the dihalogen synergistic additional defect density is calculated. The density of the non-bridging oxygen hole center precursor is obtained by summing the base values ​​of the fluorine-induced defect density, the base values ​​of the chlorine-induced defect density, and the dihalogen-synergistic additional defect density. The stoichiometric multiplier is calculated based on the theoretical molar ratio of the hydrogen molecule to the non-bridged oxygen hole center precursor during the bonding and passivation reaction, and the preset hydrogen molecule thermal diffusion escape compensation coefficient. The target hydrogen concentration of the single-mode fiber used to suppress radiation-induced attenuation is calculated by multiplying the density of the non-bridged oxygen hole center precursor by the stoichiometric multiplier.

[0007] Furthermore, based on the target hydrogen loading concentration, the two-stage hydrogen loading process parameters for hydrogen permeation into the optical fiber and the stepped annealing process parameters for removing free hydrogen from the optical fiber to eliminate hydrogen loss background attenuation are calculated, resulting in a customized treatment strategy, including: Based on the target hydrogen loading concentration and the cladding diameter of the single-mode optical fiber, the first-order low-pressure permeation pressure and time for establishing the permeation channel, and the second-order high-pressure solid solution pressure and time for achieving concentration saturation are calculated and combined to generate the dual-order hydrogen loading process parameters. Based on the target hydrogen concentration, the first-order low-temperature desorption temperature and time for removing interstitial free hydrogen and the second-order high-temperature relaxation temperature and time for releasing lattice stress are calculated and combined to generate the stepped annealing process parameters for removing free hydrogen inside the optical fiber to eliminate hydrogen loss and background attenuation. The two-stage hydrogen loading process parameters and the stepped annealing process parameters are sequentially spliced ​​together to obtain a customized processing strategy.

[0008] Furthermore, according to the customized processing strategy, the single-mode fiber is sequentially subjected to a two-stage hydrogen loading operation, a pre-irradiation operation for exciting and passivating color center defects, and a stepped annealing operation, including: According to the customized processing strategy, the single-mode optical fiber is subjected to the dual-stage hydrogen loading operation in a temperature-controlled autoclave with the first-stage low-pressure permeation pressure and the second-stage high-pressure solid solution pressure. After the two-stage hydrogen loading operation is completed, the single-mode fiber is subjected to the pre-irradiation operation for exciting and passivating color center defects using a pulsed gamma-ray source, wherein the pulse interval time of the pulsed gamma-ray source is controlled to be greater than the preset local heat dissipation threshold of the fiber to prevent the internal bound hydrogen from escaping due to heat. After the pre-irradiation operation is completed, the stepped annealing operation is performed in a dynamic vacuum furnace at the first low-temperature desorption temperature and the second high-temperature relaxation temperature.

[0009] Furthermore, according to the customized processing strategy, the dual-stage hydrogen loading operation is performed on the single-mode optical fiber in a temperature-controlled autoclave sequentially with the first-stage low-pressure permeation pressure and the second-stage high-pressure solid solution pressure, including: The customized processing strategy is analyzed to obtain the first-order low-pressure permeation pressure and the second-order high-pressure solid solution pressure; Hydrogen gas is introduced into the temperature-controlled high-pressure autoclave to the first-stage low-pressure permeation pressure to perform the first-stage hydrogen permeation on the single-mode optical fiber. After the first stage of hydrogen permeation is completed, an inert buffer gas is injected into the temperature-controlled high-pressure vessel to absorb the adiabatic heat generated by gas compression. After injecting the inert buffer gas, hydrogen is continuously introduced into the temperature-controlled autoclave to the second-stage high-pressure solid solution pressure to perform the second-stage hydrogen permeation on the single-mode optical fiber, thus completing the two-stage hydrogen loading operation.

[0010] Furthermore, after the two-stage hydrogen loading operation is completed, the pre-irradiation operation for exciting and passivating color center defects is performed on the single-mode fiber using a pulsed gamma-ray source, including: After the two-stage hydrogen loading operation is completed, the single-mode optical fiber is fixed in a grounded conductive clamp. The single-mode optical fiber is pulsed with the pulsed gamma ray source, and the Compton transient charge excited in the silica matrix of the optical fiber by the pulsed irradiation is simultaneously extracted through the grounded conductive clamp. In an electrostatic-free environment that derives the Compton transient charge, hydrogen molecules inside the optical fiber are induced to combine with the excited defects, thus completing the pre-irradiation operation used to excite and passivate color center defects.

[0011] Furthermore, after the stepped annealing operation is completed, a curing sealing layer is coated onto the surface of the single-mode fiber to obtain an attenuation-suppressed radiation-resistant single-mode fiber, comprising: After the stepped annealing operation is completed, a silicon carbide-carbon transition film with a gradient carbon-silicon ratio is deposited on the bare surface of the single-mode optical fiber by chemical vapor deposition as the first anti-seepage layer of the curing and sealing layer. A fluorinated polyimide resin is coated on the outside of the first impermeable layer and thermally cured at a preset curing temperature to form the second radiation-resistant layer of the cured sealing layer, thereby obtaining an attenuation-suppressed radiation-resistant single-mode optical fiber.

[0012] Furthermore, after the stepped annealing operation is completed, a silicon carbide-carbon transition film with a gradient carbon-silicon ratio is deposited on the bare surface of the single-mode optical fiber using chemical vapor deposition as the first impermeable layer of the cured sealing layer, comprising: After the stepped annealing operation is completed, the single-mode optical fiber is placed in a chemical vapor deposition reaction chamber, and a mixed precursor gas containing silane and methane is introduced into the reaction chamber. During the chemical vapor deposition process, the flow rate ratio of silane in the mixed precursor gas is continuously reduced and the flow rate ratio of methane is simultaneously increased according to a preset time function. By continuously adjusting the flow ratio, a silicon carbide-carbon transition film with a gradient carbon-silicon ratio, rich in silicon on the inner side and rich in carbon on the outer side, is deposited on the bare surface of the single-mode optical fiber, and serves as the first anti-seepage layer of the curing and sealing layer.

[0013] Furthermore, the second radiation-resistant layer, formed by coating the outer side of the first impermeable layer with fluorinated polyimide resin and thermally curing it at a preset curing temperature to form the cured sealing layer, yields an attenuation-suppressed radiation-resistant single-mode optical fiber, comprising: The liquid fluorinated polyimide resin is uniformly coated on the outside of the first impermeable layer; The coated resin surface is pre-crosslinked using an ultraviolet light source to form a microporous closed membrane on the outer surface of the resin. After the microporous sealing membrane is formed, the thermal curing is carried out at the preset curing temperature with a gradient increase, so that the solvent inside the resin can be slowly diffused out through the gaps between molecules, forming a dense, pinhole-free second radiation-resistant layer of the cured sealing layer, thus obtaining an attenuation-suppressed radiation-resistant single-mode optical fiber.

[0014] This invention also provides an attenuation suppression system for single-mode optical fiber under irradiation conditions, comprising: The acquisition module is used to acquire the core doping parameters of the single-mode fiber to be processed; and to calculate the target hydrogen concentration of the single-mode fiber for suppressing radiation-induced attenuation based on the core doping parameters. The calculation module is used to calculate, based on the target hydrogen loading concentration, the two-stage hydrogen loading process parameters for hydrogen permeation into the optical fiber, and the stepped annealing process parameters for removing free hydrogen from the optical fiber to eliminate hydrogen loss background attenuation, so as to obtain a customized processing strategy. The operation module is used to sequentially perform a two-stage hydrogen loading operation, a pre-irradiation operation for exciting and passivating color center defects, and a stepped annealing operation on the single-mode optical fiber according to the customized processing strategy. A sealing module is used to coat and cure a sealing layer on the surface of the single-mode fiber after the stepped annealing operation is completed, so as to obtain an attenuation-suppressed radiation-resistant single-mode fiber.

[0015] This invention provides a method for suppressing attenuation of single-mode optical fiber under irradiation conditions, comprising: obtaining the core doping parameters of the single-mode optical fiber to be treated; calculating, based on the core doping parameters, a target hydrogen loading concentration of the single-mode optical fiber for suppressing radiation-induced attenuation; calculating, based on the target hydrogen loading concentration, two-stage hydrogen loading process parameters for hydrogen infiltration into the optical fiber and stepped annealing process parameters for removing free hydrogen from the optical fiber to eliminate hydrogen loss background attenuation, thereby obtaining a customized treatment strategy; and, based on the customized treatment strategy, sequentially performing two-stage hydrogen loading operations and pre-irradiation for exciting and passivating color center defects on the single-mode optical fiber. The process involves step annealing and a curing sealing layer applied to the surface of the single-mode fiber to obtain an attenuation-suppressed radiation-resistant single-mode fiber. This solves the technical problem of how to reasonably determine the appropriate processing conditions based on the material characteristics of the single-mode fiber to be processed, while taking into account both radiation defect suppression and background transmission loss control. It achieves quantitative matching between hydrogen-loaded processing conditions and the core material characteristics of the single-mode fiber, reduces the additional attenuation caused by radiation-induced color center defects, and reduces hydrogen loss background attenuation caused by excessive free hydrogen. This improves the transmission stability and long-term radiation resistance reliability of the single-mode fiber under irradiation. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the attenuation suppression method for single-mode optical fiber under irradiation environment in one embodiment of the present invention; Figure 2 This is a schematic diagram of an embodiment of the attenuation suppression system for single-mode optical fiber under irradiation environment in this invention.

[0018] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. The step numbers in the following embodiments are set only for ease of explanation, and there is no limitation on the order between the steps. The execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0020] The following describes in detail, with reference to the accompanying drawings, a method for attenuation suppression of single-mode optical fiber under irradiation environment according to an embodiment of the present invention.

[0021] Figure 1 This invention provides a method for attenuation suppression of single-mode optical fiber under irradiation conditions, comprising: Step S1: Obtain the core doping parameters of the single-mode fiber to be processed; calculate the target hydrogen concentration of the single-mode fiber used to suppress radiation-induced attenuation based on the core doping parameters.

[0022] Specifically, the core doping parameters are first obtained from the fabrication records or sampling test results of the single-mode fiber to be processed. These parameters include at least the content of components such as germanium, fluorine, phosphorus, and chlorine, which affect the formation of glass network defects and hydrogen diffusion behavior, and are uniformly converted to the same mass fraction or mole fraction. Then, using the empirical hydrogen-carrying range of a reference single-mode fiber as an initial reference, the contribution trend of each doping component to radiation-sensitive defect precursors is determined. Specifically, when the germanium and phosphorus content increases, the tendency for color center formation is enhanced, and the target hydrogen-carrying concentration increases accordingly. When the fluorine doping ratio increases, the glass network compactness and defect passivation requirements change, compensating for and correcting the target hydrogen-carrying concentration. When the chlorine residue is high, the correction magnitude is increased in the direction of increasing defect precursors. After superimposing these trends, a truncation verification is performed in conjunction with the allowable upper limit of hydrogen-related background attenuation in the fiber, resulting in a target hydrogen-carrying concentration that satisfies defect passivation requirements without introducing excessive hydrogen absorption. In this embodiment, the above scheme makes the hydrogen-carrying concentration correspond to the actual doping state of the fiber core, improving the consistency of radiation-induced attenuation suppression.

[0023] Step S2: Based on the target hydrogen loading concentration, calculate the two-stage hydrogen loading process parameters for hydrogen permeation into the optical fiber, and the stepped annealing process parameters for removing free hydrogen from the optical fiber to eliminate hydrogen loss background attenuation, thus obtaining a customized treatment strategy.

[0024] Specifically, using the target hydrogen loading concentration as the core constraint for process design, the two-stage hydrogen loading process parameters are determined by first considering the cladding diameter of the single-mode fiber to be processed, the pressure and temperature resistance of the coating layer, and the diffusion characteristics of hydrogen in quartz glass. The first stage employs a relatively low hydrogen pressure and a long holding time, allowing hydrogen molecules to slowly penetrate radially into the fiber, reducing abrupt changes in outer layer concentration. The second stage increases the hydrogen pressure and shortens the supplementary holding time based on the first stage penetration, bringing the hydrogen content in the fiber core region closer to the target hydrogen loading concentration. Subsequently, based on the target hydrogen loading concentration and the upper limit of allowable hydrogen loss background attenuation, the stepped annealing process parameters are determined in reverse. First, a lower annealing temperature is used to release free hydrogen in the cladding and near-surface layers. Then, a higher annealing temperature, without damaging the fiber structure, promotes the desorption of excess free hydrogen in the fiber core, while retaining effective hydrogen already involved in defect passivation. The aforementioned pressure, temperature, and time are recorded in the processing log, forming a customized processing strategy. In this embodiment, the above scheme matches the hydrogen penetration depth with the degree of annealing dehydrogenation, reducing background attenuation caused by excess hydrogen.

[0025] Step S3: According to the customized processing strategy, perform a two-stage hydrogen loading operation, a pre-irradiation operation to excite and passivate color center defects, and a stepped annealing operation on the single-mode fiber in sequence.

[0026] Specifically, single-mode optical fiber is wound onto a clean, pressure-resistant tray and placed into a temperature-controlled autoclave. Following a customized processing strategy, the first stage of hydrogen loading is performed. Under set low pressure and constant temperature conditions, the pressure is maintained to allow hydrogen molecules to diffuse uniformly from the outer cladding towards the fiber core. Once the outer layer concentration gradient becomes relatively flat, the process switches to the second stage of hydrogen loading, increasing the hydrogen pressure and maintaining pressure until the core region reaches the target hydrogen concentration. After hydrogen loading, the optical fiber is pre-irradiated. The irradiation dose and time are limited according to the processing strategy. This pre-irradiation is used to excite potential defect precursors into hydrogen-passivated color center defects and to promote the binding of already infiltrated hydrogen to the defect sites. Subsequently, a stepped annealing process is initiated. First, near-surface free hydrogen is released at a low temperature, and then excess free hydrogen in the core is removed at a higher temperature, preventing increased hydrogen loss background attenuation. In this embodiment, the above scheme continuously connects the hydrogen loading, defect excitation, and dehydrogenation processes, improving the stability of the radiation attenuation treatment.

[0027] Step S4: After the stepped annealing operation is completed, a curing sealing layer is coated on the surface of the single-mode fiber to obtain an attenuation-suppressed radiation-resistant single-mode fiber.

[0028] Specifically, after stepped annealing, the single-mode fiber undergoes slow cooling and surface cleaning to remove any adsorbed moisture, volatiles, and fine particles that may remain from the annealing process, preventing them from being trapped in the subsequent sealing layer. The fiber is then continuously passed through a coating mold to uniformly coat the outer surface of the cladding with a sealing coating. The coating thickness is controlled according to the fiber's bending radius and subsequent winding requirements to avoid excessive thickness that could reduce flexibility. After coating, UV pre-curing or thermal curing is used to form a continuous, dense film layer. The cured fiber is then retested for outer diameter, adhesion, and attenuation to confirm that the sealing layer does not introduce additional microbending loss. The sealing layer serves to block external moisture and oxygen from entering, while also slowing the outward escape of residual effective hydrogen, resulting in an attenuation-suppressed radiation-resistant single-mode fiber. In this embodiment, the above scheme improves the environmental stability and long-term radiation attenuation resistance of the treated fiber.

[0029] In a specific embodiment, calculating the target hydrogen concentration of the single-mode fiber for suppressing radiation-induced attenuation based on the fiber core doping parameters includes: The molar percentage of fluorine and the residual percentage of chlorine in the single-mode fiber to be processed are obtained as the core doping parameters. The molar percentage of fluorine and the residual percentage of chlorine are multiplied by the corresponding first defect conversion coefficient and second defect conversion coefficient, respectively, to calculate the fluorine-induced defect density base and the chlorine-induced defect density base. The product of the molar percentage of fluorine and the residual percentage of chlorine is calculated, and combined with the preset lattice distortion constant, the dihalogen synergistic additional defect density is calculated. The density of the non-bridging oxygen hole center precursor is obtained by summing the base values ​​of the fluorine-induced defect density, the base values ​​of the chlorine-induced defect density, and the dihalogen-synergistic additional defect density. The stoichiometric multiplier is calculated based on the theoretical molar ratio of the hydrogen molecule to the non-bridged oxygen hole center precursor during the bonding and passivation reaction, and the preset hydrogen molecule thermal diffusion escape compensation coefficient. The target hydrogen concentration of the single-mode fiber used to suppress radiation-induced attenuation is calculated by multiplying the density of the non-bridged oxygen hole center precursor by the stoichiometric multiplier.

[0030] Specifically, a process for obtaining core doping parameters for the single-mode fiber to be processed is first established. For fibers with complete production records, material formulation records formed during the preform deposition, sintering, and drawing stages can be directly retrieved to extract the molar percentage of fluorine and the residual percentage of chlorine in the core region. For fibers with incomplete batch sources or requiring verification, representative samples are taken from the same batch of fibers, and secondary ion mass spectrometry, electron probe microanalysis, or equivalent elemental analysis are used to detect the elemental distribution within the core cross-section, eliminating interference from cladding signals on the core detection results. To avoid inconsistencies in subsequent calculations, the molar percentage of fluorine and the residual percentage of chlorine are normalized according to the molar proportions of elements involved in the composition statistics in the core glass network. The molar percentage of fluorine represents the proportion of fluorine in the core relative to the total molar amount of related elements in the core, and the residual percentage of chlorine represents the proportion of residual chlorine in the core relative to the total molar amount of related elements in the core. Both are used as inputs for subsequent defect precursor estimation.

[0031] After obtaining the aforementioned core doping parameters, the contributions of fluorine and chlorine to the formation of non-bridging oxygen hole center precursors were evaluated. The molar percentage of fluorine corresponds to the first defect conversion coefficient, which reflects the ability of a unit molar percentage of fluorine to be converted into the fluorine-induced defect density base under preset irradiation conditions. The residual percentage of chlorine corresponds to the second defect conversion coefficient, which reflects the ability of a unit residual percentage of chlorine to be converted into the chlorine-induced defect density base. Here, the fluorine-induced defect density base refers to the basic contribution of non-bridging oxygen hole center precursors corresponding to fluorine-related glass network distortion, bond angle perturbation, or uneven local charge compensation; the chlorine-induced defect density base refers to the basic contribution corresponding to weak bond structures, impurity-induced defect sites, or insufficient local structural relaxation caused by residual chlorine. Both types of defect density bases use the same density expression caliber, which can be expressed as the number of precursors per unit volume of core glass or as the precursor equivalent per unit mole of core glass, but they must not be mixed in the same batch of calculations.

[0032] After obtaining the baseline values ​​for fluorine-induced and chlorine-induced defect densities, the synergistic effect of the coexistence of fluorine and chlorine on the core glass network must be considered. The effect of a single halogen on defect precursors is mainly manifested in changes to the local bonding environment. However, when both the molar percentage of fluorine and the residual percentage of chlorine increase simultaneously, the bond length distribution, bond angle constraints, and charge balance in the local core structure will experience superimposed perturbations. The number of defect precursors is not simply determined linearly by the two basic contributions. Therefore, the degree of coupling between the molar percentage of fluorine and the residual percentage of chlorine is used as the basis for judging the synergistic effect, and combined with a preset lattice distortion constant, the synergistic additional defect density of the two halogens is calculated. The lattice distortion constant is used to characterize the amplification effect of fluorine and chlorine on the local distortion intensity of the quartz glass network when they coexist; its value can be determined by irradiation attenuation tests, electron paramagnetic resonance defect characterization, or historical calibration data of similar optical fibers. To ensure consistency in physical meaning, the dihalogen synergistic defect density uses the same density unit as the base values ​​of fluorine-induced defect density and chlorine-induced defect density. When the molar percentage of fluorine or the residual percentage of chlorine is low, this synergistic term decreases as the coupling degree between the two decreases, and should not be artificially set as a fixed constant.

[0033] Subsequently, the baseline fluorine-induced defect density, baseline chlorine-induced defect density, and dihalogen-synergistic additional defect density are summed on the same scale to obtain the non-bridging oxygen hole center precursor density. This non-bridging oxygen hole center precursor density characterizes the number of potential sites that may form non-bridging oxygen hole center-like defects under subsequent irradiation, and is the direct basis for calculating the target hydrogen loading concentration. The above summation process follows a unidirectional derivation relationship from material composition to the number of defect precursors, without using the target hydrogen loading concentration to deduce the precursor density, nor substituting subsequent hydrogen loading results back into the precursor density calculation, thus avoiding circular reasoning. If the detected molar percentage of fluorine or the residual percentage of chlorine is lower than the instrument detection limit, it can be processed according to the conservative value corresponding to the detection limit or the verified zero contribution boundary. However, the processing rules should be consistent within the same batch of optical fibers to avoid data distortion within the batch.

[0034] After obtaining the density of the non-bridging oxygen hole center precursor, the stoichiometric multiplier required for hydrogen molecules to participate in bonding passivation is determined. This stoichiometric multiplier is determined by two parts: the theoretical molar ratio of hydrogen molecules to the non-bridging oxygen hole center precursor for bonding passivation, and the hydrogen molecule thermal diffusion escape compensation coefficient. The theoretical molar ratio describes the minimum hydrogen molecule supply required to complete defect passivation and is a fundamental constraint at the reaction equivalence level. The hydrogen molecule thermal diffusion escape compensation coefficient compensates for the loss of some free hydrogen that cannot participate in effective passivation due to radial diffusion, temperature rise desorption, or surface escape during subsequent hydrogen loading, pre-irradiation, and annealing processes. This compensation coefficient should be greater than or equal to the basic level required to meet the theoretical reaction equivalence and should be calibrated in conjunction with the fiber cladding diameter, the hydrogen retention capacity of the coating, the planned annealing temperature range, and the holding time. If the annealing temperature is high or the holding time is long in subsequent processes, the hydrogen molecule thermal diffusion escape compensation coefficient will increase accordingly; if the coating protection and low-temperature hydrogen retention conditions are good, the compensation range will decrease accordingly, but it must not be lower than the minimum supply requirement required to complete theoretical passivation.

[0035] Finally, the density of the non-bridged oxygen hole center precursor is matched with the stoichiometric multiplier to obtain the target hydrogen loading concentration for suppressing radiation-induced attenuation. This target hydrogen loading concentration represents the effective hydrogen content level that the core region of the single-mode fiber to be treated needs to achieve, rather than the hydrogen pressure itself in the autoclave. Subsequent two-stage hydrogen loading process parameters can be converted into pressure, temperature, and holding time based on this target hydrogen loading concentration. To prevent an increase in hydrogen-related background absorption due to an excessively high target hydrogen loading concentration, the calculation results can also be checked for consistency with the preset hydrogen loss background attenuation constraint. When the calculation results exceed the acceptable upper limit corresponding to this constraint, process correction should be prioritized by adjusting the subsequent annealing and dehydrogenation conditions or re-examining the source of the defect conversion coefficient, rather than simply increasing the hydrogen loading intensity. Through the above processing, the molar ratio of fluorine, the residual ratio of chlorine, the defect conversion coefficient, the lattice distortion constant, the theoretical molar ratio, and the thermal diffusion escape compensation coefficient all have clear physical meanings, and the parameters are passed step by step in the order of "core composition identification, defect precursor estimation, passivation equivalent determination, and target hydrogen loading concentration output". In this embodiment, the above scheme establishes a correspondence between the target hydrogen concentration and the halogen doping state and the number of potential color center defects in the single-mode fiber to be treated, thereby improving the targeting and repeatability of radiation-induced attenuation suppression treatment.

[0036] In a specific embodiment, based on the target hydrogen loading concentration, the two-stage hydrogen loading process parameters for hydrogen permeation into the optical fiber and the stepped annealing process parameters for removing free hydrogen from the optical fiber to eliminate hydrogen loss background attenuation are calculated, resulting in a customized processing strategy, including: Based on the target hydrogen loading concentration and the cladding diameter of the single-mode optical fiber, the first-order low-pressure permeation pressure and time for establishing the permeation channel, and the second-order high-pressure solid solution pressure and time for achieving concentration saturation are calculated and combined to generate the dual-order hydrogen loading process parameters. Based on the target hydrogen concentration, the first-order low-temperature desorption temperature and time for removing interstitial free hydrogen and the second-order high-temperature relaxation temperature and time for releasing lattice stress are calculated and combined to generate the stepped annealing process parameters for removing free hydrogen inside the optical fiber to eliminate hydrogen loss and background attenuation. The two-stage hydrogen loading process parameters and the stepped annealing process parameters are sequentially spliced ​​together to obtain a customized processing strategy.

[0037] Specifically, after obtaining the target hydrogen concentration, the structural dimensions of the single-mode fiber to be processed are first read. The cladding diameter serves as the primary geometric constraint for the radial diffusion of hydrogen molecules from the fiber's outer surface to the core. A larger cladding diameter results in a longer diffusion path for hydrogen molecules to reach the core, thus extending the first-order low-pressure permeation time. Conversely, a smaller cladding diameter reduces radial diffusion resistance, allowing for a shorter low-pressure permeation time, but it is still necessary to ensure a gentle concentration gradient between the near-surface cladding and the core. The first-order low-pressure permeation pressure is not aimed at rapidly reaching saturation, but rather at establishing a stable permeation channel. The pressure is set lower than the second-order high-pressure solution pressure and is verified by considering the fiber coating's pressure resistance, the autoclave's sealing level, and the upper limit of safe operation to prevent sudden changes in the outer hydrogen concentration from causing uneven subsequent processing.

[0038] After determining the parameters for the first-stage low-pressure permeation, the second-stage high-pressure solution treatment pressure and time are calculated based on the target hydrogen loading concentration. The purpose of the second-stage high-pressure solution treatment is to increase the dissolution driving force of hydrogen molecules in the quartz glass network, making the effective hydrogen content in the fiber core region close to the target hydrogen loading concentration. The higher the target hydrogen loading concentration, the higher the second-stage high-pressure solution treatment pressure or holding time should be; however, these are not increased indefinitely, but rather matched within the allowable range of the autoclave's rated pressure, the optical fiber's mechanical strength, and the risk of hydrogen-related background absorption. If the target hydrogen loading concentration is high and the cladding diameter is large, the second-stage solution treatment time should be extended first, and the solution treatment pressure should be increased while not exceeding the equipment's safety limit. If the target hydrogen loading concentration is low or the cladding diameter is small, the second-stage solution treatment intensity should be reduced to avoid excessive free hydrogen remaining in the fiber core and cladding gap. The first-stage low-pressure permeation pressure, the first-stage low-pressure permeation time, the second-stage high-pressure solution treatment pressure, and the second-stage high-pressure solution treatment time together constitute the two-stage hydrogen loading process parameters. The first stage focuses on diffusion uniformity, while the second stage focuses on concentration achievement. The two stages are executed in the order of low pressure first, then high pressure, and cannot be interchanged.

[0039] After determining the parameters for the two-stage hydrogen loading process, the stepped annealing process parameters are configured based on the target hydrogen loading concentration. Since both effective hydrogen participating in defect passivation and unbonded interstitial free hydrogen exist within the fiber after hydrogen loading, the annealing process requires first removing easily migratable free hydrogen, and then releasing the residual stress caused by hydrogen loading, pre-irradiation, and local rearrangement of the glass network. The first-stage low-temperature desorption temperature is constrained to avoid damaging the already formed passivated bonds and significantly altering the fiber glass structure; its temperature level is lower than the second-stage high-temperature relaxation temperature, primarily promoting the outward diffusion of free hydrogen near the cladding surface and in interstitial locations. The higher the target hydrogen loading concentration, the longer the low-temperature desorption time is required to reduce hydrogen loss background attenuation caused by excessive free hydrogen; when the target hydrogen loading concentration is low, the low-temperature desorption time can be appropriately shortened, but the background stability requirement before attenuation retesting must still be met.

[0040] The second-order high-temperature relaxation temperature and time are set around the lattice stress release. This stage temperature is higher than the first-order low-temperature desorption temperature, used to promote the relaxation of local stresses in the glass network caused by hydrogen entry, defect passivation, and preceding thermal processes, but must not reach the temperature range that would lead to softening of the fiber cladding structure, coating failure, or degradation of transmission performance. For fibers with a high target hydrogen concentration, the high-temperature relaxation time can be appropriately extended to reduce attenuation fluctuations caused by local stress concentration and residual free hydrogen; for fibers with a low target hydrogen concentration, milder relaxation conditions are used to achieve structural stabilization without introducing additional thermal damage. The first-order low-temperature desorption temperature, the first-order low-temperature desorption time, the second-order high-temperature relaxation temperature, and the second-order high-temperature relaxation time together constitute the stepped annealing process parameters. The low-temperature segment is responsible for free hydrogen removal, and the high-temperature segment is responsible for lattice stress release. The boundaries of the two temperature and time segments remain independent.

[0041] After calculating the above parameters, the two-stage hydrogen loading process parameters and the stepped annealing process parameters are spliced ​​together according to the process sequence to form a customized treatment strategy. This customized treatment strategy records at least the first-stage low-pressure permeation pressure and time, the second-stage high-pressure solution pressure and time, the first-stage low-temperature desorption temperature and time, and the second-stage high-temperature relaxation temperature and time, and writes the switching conditions between each stage into the process record. During the time sequence splicing, the low-pressure permeation stage precedes the high-pressure solution stage to establish the basis for radial hydrogen molecule permeation; after the high-pressure solution stage is completed, the stepped annealing stage begins, and the low-temperature desorption stage is executed before the high-temperature relaxation stage to remove easily migratable free hydrogen before stabilizing the fiber core glass network. If the process record shows changes in the target hydrogen loading concentration, cladding diameter, or equipment safety upper limit, the pressure, temperature, and holding time of the corresponding stage are updated synchronously to ensure that the parameters of each stage are driven by the same target hydrogen loading concentration, avoiding a disconnect between hydrogen loading intensity and the degree of dehydrogenation during annealing. In this embodiment, the above scheme continuously matches the two-stage hydrogen loading and stepped annealing around the target hydrogen loading concentration, taking into account the effective hydrogen permeation of the fiber core, removal of free hydrogen and release of lattice stress, thereby reducing the hydrogen loss background attenuation and improving the consistency of radiation resistance treatment.

[0042] In a specific embodiment, the step of sequentially performing a two-stage hydrogen loading operation, a pre-irradiation operation for exciting and passivating color center defects, and a stepped annealing operation on the single-mode fiber according to the customized processing strategy includes: According to the customized processing strategy, the single-mode optical fiber is subjected to the dual-stage hydrogen loading operation in a temperature-controlled autoclave with the first-stage low-pressure permeation pressure and the second-stage high-pressure solid solution pressure. After the two-stage hydrogen loading operation is completed, the single-mode fiber is subjected to the pre-irradiation operation for exciting and passivating color center defects using a pulsed gamma-ray source, wherein the pulse interval time of the pulsed gamma-ray source is controlled to be greater than the preset local heat dissipation threshold of the fiber to prevent the internal bound hydrogen from escaping due to heat. After the pre-irradiation operation is completed, the stepped annealing operation is performed in a dynamic vacuum furnace at the first low-temperature desorption temperature and the second high-temperature relaxation temperature.

[0043] Specifically, in the implementation process, the single-mode optical fiber to be treated is first wound around a pressure-resistant, temperature-resistant, and hydrogen-free tray according to a specified bending radius. Before entering the temperature-controlled autoclave, a visual inspection and end-face sealing are performed to prevent surface contaminants or micro-cracks at the ends from introducing additional damage during the high-pressure hydrogen loading process. The temperature-controlled autoclave is pre-evacuated and purged with inert gas to reduce interference from oxygen, water vapor, and other impurities. Subsequently, according to a customized treatment strategy, the temperature is raised to the required range for hydrogen loading, and hydrogen is first introduced to the first-order low-pressure permeation pressure and maintained for the corresponding first-order low-pressure permeation time. This allows hydrogen molecules to diffuse from the outer surface of the fiber to the cladding interior under a relatively gentle pressure gradient, gradually establishing radial permeation channels to the fiber core. This stage does not aim for rapid saturation of the fiber core hydrogen content, but rather focuses on reducing abrupt changes in outer hydrogen concentration and minimizing the radial concentration gradient, thereby providing a uniform diffusion basis for subsequent high-pressure solid solution treatment.

[0044] After the first-stage low-pressure permeation, without removing the single-mode fiber, the hydrogen pressure inside the temperature-controlled autoclave is increased to the second-stage high-pressure solution pressure according to the customized treatment strategy, and maintained for the second-stage high-pressure solution time. The second-stage high-pressure solution pressure is higher than the first-stage low-pressure permeation pressure, and its function is to increase the driving force for hydrogen molecules to enter the gaps in the quartz glass network, so that the effective hydrogen content in the fiber core area gradually approaches the target hydrogen concentration. During the pressure increase process, a segmented pressure increase or a slow pressure increase method is adopted to avoid local stress concentration in the coiled fiber caused by sudden pressure changes. During the pressure holding process, the pressure and temperature inside the autoclave are continuously monitored. When the pressure deviates from the range limited by the customized treatment strategy, a stable state is maintained by adding hydrogen or depressurizing. After the second-stage high-pressure solution is completed, the pressure is first reduced to a safe release range, and then the residual hydrogen is replaced with an inert gas to prevent safety risks caused by high-temperature and high-pressure hydrogen during the autoclave opening stage, and at the same time to avoid surface micro-damage to the fiber due to sudden depressurization.

[0045] After the two-stage hydrogen loading operation is completed, the single-mode fiber is transferred to the pre-irradiation station, maintaining its coiled state and ensuring the minimum bending radius is not lower than the process allowable value to prevent mechanical bending loss from being superimposed on subsequent attenuation evaluation. Pre-irradiation is performed using a pulsed gamma-ray source. The irradiation dose, single-pulse energy, and number of pulses are set according to a customized processing strategy. The purpose is to excite potential color center defect precursors in the fiber core glass network into active defect sites capable of passivating with hydrogen, and to promote the bonding and passivation of previously infiltrated hydrogen near these defect sites. Compared to continuous irradiation, the pulsed gamma-ray source can distribute irradiation energy at time intervals, facilitating control of local heat accumulation in the fiber. During execution, the pulse interval is set to be greater than a preset local heat dissipation threshold for the fiber; this threshold refers to the shortest time required for the irradiated area of ​​the fiber to dissipate absorbed energy without affecting the stability of bound hydrogen after a single pulse. When the pulse interval is less than or equal to the threshold, the local heat has not been fully released, and the bound hydrogen that has entered the vicinity of the defect site may be desorbed or diffused outward due to the temperature rise, so it is not allowed to enter the next pulse irradiation.

[0046] During pre-irradiation, the position of the fiber optic tray, the uniformity of the irradiation field, and the ambient temperature rise should be monitored to ensure that each fiber segment within the same winding layer receives relatively consistent irradiation. If the single-mode fiber is long, a rotating tray or a zoned step-irradiation method can be used to sequentially place fiber segments at different locations within the effective irradiation area, but each zone must still adhere to the same pulse interval control rules. After pre-irradiation, instead of allowing it to sit naturally for an extended period to replace subsequent annealing, it should be promptly transferred to a dynamic vacuum furnace according to a customized treatment strategy to prevent the disorderly escape of free hydrogen in an uncontrolled environment, which could lead to discrepancies between the actual degree of hydrogen removal and the process records.

[0047] When performing stepped annealing in a dynamic vacuum furnace, the furnace chamber is first evacuated to a preset vacuum state, and continuous or intermittent evacuation is maintained to ensure that free hydrogen released from the fiber is promptly discharged. Subsequently, the temperature is increased to the first-stage low-temperature desorption temperature and held for the first-stage low-temperature desorption time. This stage, with temperatures lower than the second-stage high-temperature relaxation temperature, primarily drives the outward diffusion of free hydrogen from the near-surface layer of the cladding, the fiber core gaps, and unbonded areas. Since the first-stage low-temperature desorption mainly removes interstitial free hydrogen, the heating rate should not be too rapid to avoid concentrated escape of free hydrogen causing local micropore pressure fluctuations or additional attenuation changes. After low-temperature desorption, the dynamic vacuum furnace continues to rise to the second-stage high-temperature relaxation temperature and holds for the second-stage high-temperature relaxation time. This releases local lattice stress in the pre-irradiated fiber core glass network after the two-stage hydrogen loading, stabilizing the structure near the passivated defects. The second-order high-temperature relaxation temperature is higher than the first-order low-temperature desorption temperature, but it is still limited by the stability of the optical fiber glass structure and the heat resistance of the coating structure. It cannot exceed the upper limit of the customized treatment strategy on the grounds of increasing the hydrogen desorption rate.

[0048] After stepped annealing, the fiber is cooled to a safe removal temperature in a dynamic vacuum furnace using a controlled cooling method, then restored to ambient pressure and removed from the single-mode fiber. Throughout the process, the two-stage hydrogen loading operation, pre-irradiation operation, and stepped annealing operation are sequentially linked according to a customized processing strategy: first, the fiber core achieves the target hydrogen content through low-pressure infiltration and high-pressure solution treatment; then, color center defects are excited and passivated using pulsed gamma rays; finally, excess free hydrogen is removed and the glass network is stabilized through low-temperature desorption and high-temperature relaxation. The pressure, time, pulse interval, temperature, and holding time for each stage all originate from the same processing strategy and cannot be adjusted independently in subsequent stages, detached from the target hydrogen loading concentration of the preceding stages, to ensure causal consistency between hydrogen entry, defect passivation, and free hydrogen removal. In this embodiment, the above scheme forms a continuous and controlled process for hydrogen loading, pre-irradiation, and stepped annealing, suppressing radiation-induced color center decay while reducing background decay caused by thermally escaped bound hydrogen and residual free hydrogen.

[0049] In a specific embodiment, the step of performing the dual-stage hydrogen loading operation on the single-mode optical fiber in a temperature-controlled autoclave according to the customized processing strategy, using the first-stage low-pressure permeation pressure and the second-stage high-pressure solid solution pressure sequentially, includes: The customized processing strategy is analyzed to obtain the first-order low-pressure permeation pressure and the second-order high-pressure solid solution pressure; Hydrogen gas is introduced into the temperature-controlled high-pressure autoclave to the first-stage low-pressure permeation pressure to perform the first-stage hydrogen permeation on the single-mode optical fiber. After the first stage of hydrogen permeation is completed, an inert buffer gas is injected into the temperature-controlled high-pressure vessel to absorb the adiabatic heat generated by gas compression. After injecting the inert buffer gas, hydrogen is continuously introduced into the temperature-controlled autoclave to the second-stage high-pressure solid solution pressure to perform the second-stage hydrogen permeation on the single-mode optical fiber, thus completing the two-stage hydrogen loading operation.

[0050] Specifically, in implementation, the hydrogen loading process record in the customized treatment strategy is first read and analyzed to confirm the first-stage low-pressure permeation pressure, first-stage low-pressure permeation time, second-stage high-pressure solution treatment pressure, and second-stage high-pressure solution treatment time. These parameters are then checked for consistency with the rated pressure, temperature control range, and hydrogen pipeline pressure rating of the temperature-controlled autoclave. The single-mode optical fiber to be treated is wound onto a clean tray with a bending radius not less than the allowable radius. The tray material is selected to be non-hydrogen-absorbing, non-volatile, and dimensionally stable under high pressure. The tray, along with the optical fiber, is then fed into the temperature-controlled autoclave. After the autoclave is sealed, the air inside is first evacuated, and then residual oxygen and water vapor are replaced with an inert gas. After confirming that the atmosphere inside the autoclave meets the hydrogen introduction conditions, the temperature is raised to the hydrogen loading temperature range specified in the customized treatment strategy.

[0051] During the first stage of hydrogen permeation, hydrogen gas is slowly introduced into the temperature-controlled autoclave until the pressure inside the autoclave reaches the first-stage low-pressure permeation pressure, and this pressure is maintained for the first-stage low-pressure permeation time. The pressure in this stage is lower than the second-stage high-pressure solution treatment pressure. Its function is not to immediately bring the fiber core to the target hydrogen concentration, but rather to encourage hydrogen molecules to first enter the near-surface layer of the fiber cladding under a relatively gentle pressure gradient, and then gradually diffuse radially towards the fiber core. During the pressure holding process, the pressure and temperature inside the autoclave are continuously monitored. When the pressure drops slightly, a small flow rate of hydrogen is used to restore it to the first-stage low-pressure permeation pressure, avoiding temperature disturbances caused by rapid one-time gas replenishment. When the temperature deviates from the hydrogen-carrying temperature range, it is corrected by the temperature-controlled jacket or the autoclave heating system to ensure that the first stage of hydrogen permeation remains in a stable thermal state. After the first stage, a continuous hydrogen diffusion base has been formed between the outer and inner layers of the fiber, reducing abrupt concentration gradients for subsequent high-pressure solution treatment.

[0052] After the first stage of hydrogen permeation is completed, the hydrogen pressure is not directly and rapidly increased to the second-stage high-pressure solution pressure. Instead, an inert buffer gas is first injected into the temperature-controlled autoclave. The inert buffer gas can be nitrogen, argon, or other gases that do not react with hydrogen or quartz glass. Its function is to absorb the adiabatic heat generated during subsequent hydrogen filling and gas compression, and to dilute the concentrated temperature rise caused by localized high-speed gas intake. When injecting the inert buffer gas, the total pressure inside the autoclave should be kept within the allowable range of the temperature-controlled autoclave, and the inert buffer gas and hydrogen inside the autoclave should form a uniform mixed atmosphere under circulating fan or diffusion-controlled static conditions. This buffering step does not change the calculation basis of the target hydrogen concentration, nor does it replace the second stage of hydrogen permeation. It merely establishes thermal buffer conditions between the first and second stages to prevent the instantaneous temperature rise during the pressurization process from causing abnormal diffusion or premature escape of hydrogen already inside the optical fiber.

[0053] After the inert buffer gas injection is completed, hydrogen is continuously introduced into the temperature-controlled autoclave, and the partial pressure of hydrogen in the autoclave is increased to the level corresponding to the second-stage high-pressure solution pressure through segmented pressurization or continuous slow pressurization. The second-stage high-pressure solution pressure here is based on a customized treatment strategy. In actual control, the total pressure in the autoclave and the effective partial pressure of hydrogen should be distinguished; the total pressure after the addition of the inert buffer gas cannot be used to replace the hydrogen solution driving force. After reaching the second-stage high-pressure solution pressure, the second-stage high-pressure solution time is maintained, allowing hydrogen molecules to further enter the gaps in the fiber core glass network under the action of a higher solution driving force, and making the effective hydrogen content in the fiber core region close to the target hydrogen loading concentration. During the pressure holding period, pressure, temperature, and holding time are continuously recorded. If the hydrogen partial pressure falls below the allowable fluctuation range due to hydrogen absorption or minor leakage, it is corrected by adding hydrogen at a small flow rate. If the temperature rises due to compression heat or external heat sources, it is restored to the set range by cooling the autoclave or pausing pressurization before continuing pressure holding.

[0054] After the second stage of hydrogen permeation, the hydrogen supply is stopped, and controlled pressure reduction is carried out while maintaining temperature control. Once the pressure inside the reactor drops to a safe range for opening, the residual hydrogen is replaced with inert gas, and the single-mode optical fiber is removed. In the entire two-stage hydrogen loading operation, the first-stage low-pressure permeation pressure is used to establish a stable permeation channel, the second-stage high-pressure solution treatment pressure is used to drive the fiber core to the target hydrogen-loaded state, and the inert buffer gas is only used to absorb the adiabatic heat during the pressure increase process and suppress local temperature rise. The functional boundaries of the three are clear, and the execution order must not be reversed. In this embodiment, the above scheme improves the uniformity of hydrogen loading in the optical fiber and reduces the impact of pressure increase thermal disturbance on the stability of internal hydrogen distribution through the continuous coordination of low-pressure pre-permeation, inert gas thermal buffering, and high-pressure solution treatment.

[0055] In a specific embodiment, after the two-stage hydrogen loading operation is completed, the pre-irradiation operation for exciting and passivating color center defects is performed on the single-mode optical fiber using a pulsed gamma-ray source, including: After the two-stage hydrogen loading operation is completed, the single-mode optical fiber is fixed in a grounded conductive clamp. The single-mode optical fiber is pulsed with the pulsed gamma ray source, and the Compton transient charge excited in the silica matrix of the optical fiber by the pulsed irradiation is simultaneously extracted through the grounded conductive clamp. In an electrostatic-free environment that derives the Compton transient charge, hydrogen molecules inside the optical fiber are induced to combine with the excited defects, thus completing the pre-irradiation operation used to excite and passivate color center defects.

[0056] Specifically, in practice, after the two-stage hydrogen loading operation is completed and safe depressurization and inert gas replacement are achieved, the single-mode optical fiber is removed from the temperature-controlled autoclave and transferred to the pre-irradiation station in a low-humidity, clean environment. During the transfer, the original coiling radius of the optical fiber is maintained, and it is not pulled or repeatedly bent to avoid micro-bending loss under local mechanical stress after hydrogen loading. Subsequently, the single-mode optical fiber is fixed in a grounded conductive clamp. The conductive clamp can be made of aluminum alloy, stainless steel, or nickel-plated copper, and a flexible conductive pad is provided on the clamping surface to ensure stable contact with the outer surface of the optical fiber without being damaged. The conductive clamp is connected to the grounding terminal of the irradiation chamber through a low-resistance grounding wire. After clamping, the continuity between the clamp and the grounding terminal is checked to confirm that the grounding path is continuous and reliable. Then, the clamp and the optical fiber are placed in the effective irradiation area of ​​the pulsed gamma-ray source.

[0057] Before pre-irradiation begins, the single-pulse dose, number of pulses, irradiation distance, and pulse interval of the pulsed gamma-ray source are set according to a customized processing strategy, ensuring that the pulse interval exceeds a preset local heat dissipation threshold for the optical fiber. This local heat dissipation threshold refers to the shortest interval required for the transient temperature rise caused by radiation energy deposition in the irradiated area of ​​the optical fiber to decrease to a level that does not affect the stability of internally bound hydrogen after a single pulse irradiation. This threshold can be pre-calibrated based on the fiber cladding diameter, the number of winding layers, the thermal conductivity of the clamps, and the environmental heat dissipation conditions. If the pulse interval is too short, local heat will accumulate between adjacent pulses, causing hydrogen molecules that have diffused to the vicinity of defects to undergo thermal activation and migration, and even escape from near passivation sites. Therefore, the control logic should prioritize extending the pulse interval as a safe approach, rather than increasing the processing speed by shortening the interval.

[0058] During pulsed irradiation, gamma photons, upon entering the silica matrix of the optical fiber, excite transient electrons and holes through Compton scattering and other processes, forming Compton transient charges. Simultaneously, this excites potential color center defect precursors in the fiber core glass network to a state more readily reacting with hydrogen. If these transient charges accumulate locally on the fiber surface or in the clamping region, they can easily form a weak electrostatic field. This field can interfere with the hydrogen migration path near charged defect sites and may create an electrostatic repulsion environment between adjacent defect sites. To avoid this effect, pulsed irradiation and grounding are performed simultaneously. That is, while each pulse generates transient charges, the Compton transient charges are discharged to the grounding end through a discharge path formed by the outer surface of the fiber, the flexible conductive pad, the conductive clamp, and the grounding wire. This discharge process does not participate in hydrogen pressure control or change the pre-irradiation dose setting; its function is limited to reducing electrostatic disturbances caused by the accumulation of transient charges during irradiation.

[0059] Under the electrostatic repulsion-free environment maintained by the grounded conductive clamp, hydrogen molecules introduced into the optical fiber by the bi-stage hydrogen loading can maintain relatively stable migration and reaction conditions near the irradiation-excited defects. As the pulsed gamma-ray source irradiates according to the set number of times, some non-bridged oxygen hole center precursors or other radiation-sensitive defects are excited into active defect sites. The hydrogen molecules surrounding these sites bond and passivate, transforming defects that might otherwise form absorption centers in actual radiation service environments into a more stable passivated state ahead of time. During the process, the continuity of clamp grounding, the temperature rise of the optical fiber surface, and the stability of the irradiation field can be monitored simultaneously. If the grounding path is abnormal or the temperature rise of the irradiated area exceeds the allowable range of the process, the next pulse irradiation should be suspended until the grounding state is restored or the heat is fully dissipated before continuing the process, to ensure that the pre-irradiation is always under controlled conditions.

[0060] For longer single-mode optical fibers, the fiber optic tray can be moved or slowly rotated in sections along with the conductive clamp, allowing different coiled areas to sequentially enter the effective irradiation field of the pulsed gamma source. During section processing, each section adopts the same pulse interval control rule and the same grounding requirement to avoid insufficient defect excitation in a certain section due to insufficient irradiation dose, or reduced passivation efficiency due to untimely discharge of transient charges. After pre-irradiation, the ground connection is maintained for a short period of stability to allow residual transient charges to be fully discharged before the single-mode fiber is transferred to the subsequent dynamic vacuum furnace stepped annealing process to remove unbonded interstitial hydrogen and release local lattice stress. In this embodiment, the above scheme synchronously discharges Compton transient charges through the grounded conductive clamp, enabling pulsed gamma pre-irradiation to complete defect excitation and hydrogen passivation under low electrostatic disturbance conditions, improving the stability of color center defect passivation.

[0061] In a specific embodiment, the step of coating and curing a sealing layer onto the surface of the single-mode fiber after the stepped annealing operation to obtain an attenuation-suppressed radiation-resistant single-mode fiber includes: After the stepped annealing operation is completed, a silicon carbide-carbon transition film with a gradient carbon-silicon ratio is deposited on the bare surface of the single-mode optical fiber by chemical vapor deposition as the first anti-seepage layer of the curing and sealing layer. A fluorinated polyimide resin is coated on the outside of the first impermeable layer and thermally cured at a preset curing temperature to form the second radiation-resistant layer of the cured sealing layer, thereby obtaining an attenuation-suppressed radiation-resistant single-mode optical fiber.

[0062] Specifically, in practice, after the stepped annealing operation, the single-mode fiber is first slowly cooled in a controlled clean environment to lower the fiber temperature to a safe range that does not cause rapid condensation of surface-adsorbed water. Then, any volatiles, fine particles, and weakly adhering contaminants that may remain from the annealing process are removed. For bare fiber segments with the original coating removed, surface treatment can be performed using dry inert airflow purging, mild plasma activation, or rapid cleaning with anhydrous solvents to improve the bonding stability between the subsequent thin film and the silica surface. The surface treatment intensity should be limited to not etching the cladding, not changing the fiber outer diameter, and not introducing microcracks, avoiding turning the sealing process into a new source of transmission loss.

[0063] After surface pretreatment, the single-mode optical fiber is fed into the chemical vapor deposition (CVD) reaction chamber, and the bare fiber continuously passes through the deposition area along the axial direction. Air and water vapor are first removed from the reaction chamber, then a carrier gas and silicon- and carbon-containing reaction precursors are introduced. At a preset deposition temperature, the reactants are deposited on the surface of the bare fiber to form a silicon carbide-carbon transition film. The gradient carbon-silicon ratio refers to a relatively higher silicon content on the side of the film closest to the silicon dioxide bare fiber surface to facilitate a better interface transition with the fiber surface; as the deposition thickness increases, the carbon content gradually increases, resulting in higher density and barrier properties on the outer side of the film. This gradient is not achieved by changing the material type all at once, but by continuously adjusting the gas inlet ratio of the silicon-containing and carbon-containing precursors, the deposition time, and the stability of the flow field in the reaction chamber. This allows the carbon-silicon ratio to change gradually along the film thickness direction, thereby reducing the interfacial stress between the single hard coating and the quartz optical fiber caused by the difference in thermal expansion.

[0064] After the silicon carbide-carbon transition film is deposited, its thickness continuity, appearance integrity, and adhesion are inspected. The film thickness should be sufficient to form a continuous impermeable barrier without significantly reducing the flexibility of the optical fiber. If the thickness is insufficient, water vapor and oxygen may still enter along micropores or weak interfaces; if the thickness is too large, additional bending stress may be induced during coiling or thermal cycling. This first impermeable layer mainly functions to block the entry of external water vapor and oxygen and slow down the outward diffusion of residual effective hydrogen. At the same time, the gradient carbon-silicon ratio structure mitigates the difference in interfacial modulus between the bare fiber and the outer organic resin, providing a stable substrate for the second radiation-resistant layer.

[0065] Subsequently, a fluorinated polyimide resin is coated on the outside of the first impermeable layer. Before coating, the fluorinated polyimide resin should be filtered, degassed, and its viscosity adjusted to ensure that it forms a uniform coating layer when the optical fiber is drawn through the coating mold. During the coating process, the drawing speed, mold gap, and resin supply pressure are controlled to ensure that the resin layer is continuously distributed along the circumference of the optical fiber, avoiding eccentricity, bubbles, pinholes, or local accumulation. The fluorinated structure in the fluorinated polyimide resin helps improve the material's low moisture absorption and radiation resistance, while the polyimide skeleton provides good heat resistance and mechanical protection, making it suitable as a second radiation-resistant layer on the outside of the curing and sealing layer. This second radiation-resistant layer does not replace the inorganic barrier function of the first impermeable layer, but rather provides flexible protection, resistance to radiation aging, and environmental isolation on its outside, with a clear functional boundary between the two layers.

[0066] After coating, the single-mode optical fiber coated with fluorinated polyimide resin is fed into the thermosetting channel, and staged heating and holding curing are performed at the preset curing temperature. During the heating phase, a sudden temperature rise should be avoided to prevent the resin surface from forming a film too quickly, thus hindering the escape of the internal solvent. During the holding phase, the resin undergoes sufficient imidization or cross-linking curing to form a continuous and dense second radiation-resistant layer. During the cooling phase, controlled cooling is used to gradually release the thermal stress between the first anti-permeability layer, the second radiation-resistant layer, and the fiber cladding. The preset curing temperature is based on the curing requirements of the fluorinated polyimide resin and must not exceed the upper temperature limit allowed by the previous hydrogen passivation state and the stability of the optical fiber structure, to prevent the effective hydrogen from escaping again or introducing additional thermal damage due to overheating.

[0067] After thermal curing, the resulting single-mode fiber is retested for outer diameter consistency, coating adhesion, bend passability, and transmission attenuation. If local coating peeling, pinholes, or abnormal attenuation spikes are detected, the fiber segment should be discarded or re-sealed. If all indicators meet the process requirements, the first anti-permeability layer and the second anti-radiation layer are confirmed to constitute a cured sealing layer, resulting in an attenuation-suppressed radiation-resistant single-mode fiber. The entire sealing process follows the sequence of "bare fiber surface cleaning, inorganic gradient anti-permeability, fluorinated polyimide coating, and thermal curing stabilization," without replacing the gradient silicon carbide-carbon transition film with a single thick organic coating, and without directly coating the second anti-radiation layer before completing the first anti-permeability layer inspection. In this embodiment, the above scheme reduces the impact of water vapor, oxygen, and hydrogen escaping on the fiber attenuation stability through the synergistic sealing of the gradient inorganic anti-permeability layer and the fluorinated polyimide anti-radiation layer.

[0068] In a specific embodiment, after the stepped annealing operation is completed, a silicon carbide-carbon transition film with a gradient carbon-silicon ratio is deposited on the bare surface of the single-mode optical fiber using chemical vapor deposition as the first impermeable layer of the cured sealing layer, comprising: After the stepped annealing operation is completed, the single-mode optical fiber is placed in a chemical vapor deposition reaction chamber, and a mixed precursor gas containing silane and methane is introduced into the reaction chamber. During the chemical vapor deposition process, the flow rate ratio of silane in the mixed precursor gas is continuously reduced and the flow rate ratio of methane is simultaneously increased according to a preset time function. By continuously adjusting the flow ratio, a silicon carbide-carbon transition film with a gradient carbon-silicon ratio, rich in silicon on the inner side and rich in carbon on the outer side, is deposited on the bare surface of the single-mode optical fiber, and serves as the first anti-seepage layer of the curing and sealing layer.

[0069] Specifically, in practice, after the stepped annealing operation, the single-mode fiber is cooled to a suitable temperature for deposition in a dry, inert atmosphere, and the surface of the bare fiber is cleaned to remove residual volatiles, adsorbed water, and fine particles. The single-mode fiber is then fed into the chemical vapor deposition (CVD) chamber, allowing the bare fiber to stably pass through the deposition zone along the chamber axis, or exposed to a uniform reaction atmosphere while coiled and clamped. After the chamber is sealed, air and moisture are first evacuated, then a carrier gas is introduced for replacement. Once the oxygen and moisture content are reduced to within the allowable range, a mixed precursor gas containing silane and methane is introduced into the chamber, and the temperature, pressure, and total gas flow rate are adjusted to a stable state suitable for silicon carbide-carbon thin film deposition.

[0070] In the initial stage of deposition, the flow rate proportion of silane in the mixed precursor gas is relatively high, while the flow rate proportion of methane is relatively low, resulting in the deposition of a silicon-rich interface layer on the side closest to the bare silica fiber surface. This silicon-rich interface layer can form a smoother chemical and structural transition with the surface of the single-mode fiber, reducing the interfacial stress between the subsequent outer film and the quartz substrate caused by differences in composition and thermal expansion. As the chemical vapor deposition process continues, the flow rate proportion of silane is continuously reduced according to a preset time function, while the flow rate proportion of methane is increased simultaneously, causing the carbon-silicon ratio in the deposited film to gradually change along the thickness direction. The time function can adopt a linear gradient, a piecewise smooth gradient, or an exponentially approaching gradient, but a continuous adjustment rule should be maintained within the same deposition batch to avoid abrupt changes in the silane or methane flow rate that could cause obvious layering interfaces within the film.

[0071] When the deposition enters the outer layer formation stage, the methane flow rate is higher than in the initial stage, and the outer side of the film gradually transforms into a carbon-rich structure to improve the compactness, radiation resistance, and barrier capability against the escape of water vapor, oxygen, and residual effective hydrogen of the first impermeable layer. During the deposition process, the pressure, temperature, silane flow rate, methane flow rate, and carrier gas flow rate in the reaction chamber are continuously monitored to ensure that the total supply of mixed precursor gases remains stable, while the carbon-silicon composition changes only in a controlled manner with a preset time function. After deposition, the supply of silane and methane is stopped, and the reaction chamber is purged with inert gas. After the reaction byproducts are discharged, the single-mode optical fiber is removed. Thus, a silicon carbide-carbon transition film with a silicon-rich inner side, a carbon-rich outer side, and a continuously transitioning carbon-silicon ratio is formed on the surface of the bare fiber, which serves as the first impermeable layer of the curing and sealing layer. In this embodiment, the above scheme forms a gradient impermeable structure by continuously adjusting the precursor flow rate ratio, taking into account both interfacial adhesion stability and outer barrier capability.

[0072] In a specific embodiment, the step of coating the outside of the first impermeable layer with fluorinated polyimide resin and thermally curing it at a preset curing temperature to form the second radiation-resistant layer of the cured sealing layer, thereby obtaining an attenuation-suppressed radiation-resistant single-mode optical fiber, includes: The liquid fluorinated polyimide resin is uniformly coated on the outside of the first impermeable layer; The coated resin surface is pre-crosslinked using an ultraviolet light source to form a microporous closed membrane on the outer surface of the resin. After the microporous sealing membrane is formed, the thermal curing is carried out at the preset curing temperature with a gradient increase, so that the solvent inside the resin can be slowly diffused out through the gaps between molecules, forming a dense, pinhole-free second radiation-resistant layer of the cured sealing layer, thus obtaining an attenuation-suppressed radiation-resistant single-mode optical fiber.

[0073] Specifically, after the first impermeable layer is formed and its surface inspection is completed, the single-mode optical fiber is sent to the resin coating station. Before coating, the outer surface of the first impermeable layer is purged with a dry, inert airflow to remove any fine particles and weakly adsorbed gases that may remain after the deposition reaction, and to confirm that there are no pinholes, peeling, or local cracks on the surface of the silicon carbide-carbon transition film. Subsequently, the liquid fluorinated polyimide resin is filtered and vacuum degassed to ensure that the resin does not contain solid impurities or large air bubbles; if necessary, the resin viscosity is controlled by adjusting the solvent ratio to ensure that it can be stably spread on the outside of the first impermeable layer during continuous fiber traction without sagging, edge shrinkage, or uneven circumferential thickness.

[0074] During coating, a single-mode optical fiber with a pre-formed first impermeable layer is passed through a coating mold at a stable pulling speed. Liquid fluorinated polyimide resin is uniformly coated onto the outside of the first impermeable layer under the constraint of the mold gap, forming a continuous wet film. The thickness of this wet film is determined by meeting the requirements of radiation protection and bending flexibility. If it is too thin, it is difficult to form a complete environmental isolation layer; if it is too thick, it may introduce additional stress during subsequent thermosetting shrinkage. After coating, high-temperature thermosetting is not performed immediately. Instead, a UV light source is used to pre-crosslink the resin surface. The UV light irradiation direction is uniformly arranged along the circumference of the optical fiber, so that the resin surface receives relatively consistent light energy. The irradiation intensity and irradiation time are limited to inducing only a limited depth of crosslinking on the surface layer, avoiding excessive UV energy penetrating into the resin interior and causing premature overall hardening.

[0075] During the UV pre-crosslinking process, localized segmental crosslinking and an increase in surface viscosity occur on the outer surface of the fluorinated polyimide resin, gradually forming a microporous closed membrane. This microporous closed membrane is not a dense, hard shell that completely blocks the escape of small molecules from the resin interior; rather, it forms a continuous, flexible surface structure with limited pore size on the outer surface. This structure seals open bubble channels and surface pores while preserving the path for solvent molecules to slowly diffuse out through the intermolecular gaps. This treatment avoids rapid skinning of the resin surface and the formation of pinholes due to trapped solvent expansion during direct high-temperature curing. It also reduces thickness shifts in the wet film caused by excessive fluidity in the initial heating stage. After UV pre-crosslinking, the resin outer surface should be checked for continuous shine, absence of obvious bubble breaks, and localized exposure of the substrate. Only after confirming the formation of the microporous closed membrane should the thermosetting stage begin.

[0076] During thermosetting, the pre-crosslinked single-mode optical fiber is fed into a zoned thermosetting oven, and the temperature is gradually increased according to the preset curing temperature. The initial heating stage uses a relatively gentle heating rate, allowing residual solvent inside the resin to diffuse outward through the intermolecular gaps under mild thermal drive and slowly drain through the microporous sealing membrane. The intermediate heat preservation stage promotes further imidization and chain rearrangement within the fluorinated polyimide resin, gradually transforming the wet film into a stable solid layer from the inside out. The final curing stage raises the temperature to the preset curing temperature range, ensuring the second radiation-resistant layer achieves the required degree of crosslinking, heat resistance, and radiation resistance stability. Throughout the gradient heating process, the outer surface microporous sealing membrane maintains morphology and inhibits pores, while the internal solvent is slowly diffused out; both work together to prevent pinholes, blistering, and localized collapse.

[0077] After curing, the single-mode fiber is subjected to controlled cooling to gradually release the thermal stress between the second radiation-resistant layer, the first anti-seepage layer, and the bare fiber. Subsequently, the coating outer diameter consistency, surface continuity, adhesion, bendability, and transmission attenuation changes before and after treatment are tested. If pinholes, cracks, localized desorption, or abnormal attenuation increases are found in the second radiation-resistant layer, the corresponding section should be deemed a seal failure and discarded or reworked. If the test results meet the process requirements, it is confirmed that the fluorinated polyimide resin has formed a dense, pinhole-free second radiation-resistant layer outside the first anti-seepage layer. The cured sealing layer, composed of the first anti-seepage layer and the second radiation-resistant layer, can slow down the outward escape of residual effective hydrogen and reduce the impact of water vapor, oxygen, and radiation aging on the fiber transmission performance, thereby obtaining an attenuation-suppressed radiation-resistant single-mode fiber. In this embodiment, the above scheme controls the resin film formation process through ultraviolet pre-crosslinking and gradient temperature thermal curing, improving the density and long-term sealing stability of the second radiation-resistant layer.

[0078] In a specific embodiment, the step of using an ultraviolet light source to pre-crosslink the coated resin surface to form a microporous closed membrane on the outer surface of the resin includes: The ultraviolet absorption spectrum of the fluorinated polyimide resin is obtained, and a target ultraviolet band with absorbance greater than a preset cutoff value is extracted from the ultraviolet absorption spectrum to ensure that the penetration depth of photon energy is less than a preset surface thickness threshold. Based on the target ultraviolet band, the ultraviolet light source is configured as a ring array light source with an emission wavelength in the target ultraviolet band; The coated resin surface is isotropically irradiated using the ring array light source to strictly limit the photopolymerization reaction within the surface thickness threshold, thereby completing the pre-crosslinking treatment and forming a uniformly thick microporous closed membrane on the outer surface of the resin.

[0079] Specifically, after uniformly coating the outer side of the first impermeable layer with fluorinated polyimide resin, samples from the same batch of resin are first taken for ultraviolet absorption spectroscopy testing to obtain the absorbance distribution of the resin at different ultraviolet wavelengths. The ultraviolet absorption spectrum is used to characterize the resin's ability to absorb ultraviolet photons. The higher the absorbance, the more fully the light energy is absorbed on the resin surface, and the shallower the penetration depth into the resin interior. Subsequently, wavelengths with absorbance greater than a preset cutoff value are selected from the ultraviolet absorption spectrum as target ultraviolet bands. The preset cutoff value is determined in advance based on the resin wet film thickness, the desired pre-crosslinking depth, and the subsequent thermal curing solvent removal requirements. Its function is to ensure that the photon energy of the selected wavelength mainly acts near the resin outer surface, making the effective penetration depth of the photopolymerization reaction less than the preset surface thickness threshold, and preventing premature overall crosslinking of the resin interior.

[0080] After obtaining the target ultraviolet band, the ultraviolet light source is configured as a ring array light source with an emission wavelength within the target ultraviolet band. The ring array light source is arranged circumferentially around the single-mode fiber, with the optical axis of each emitting unit pointing towards the center region of the fiber. The illumination intensity at different circumferential positions is kept consistent through independent constant current driving or uniform power calibration. If the target ultraviolet band is a narrow band, a narrow-spectrum ultraviolet emitting unit with a center wavelength falling within that band is selected; if the target ultraviolet band covers a certain range, the output spectrum is limited by filters or light source combinations to prevent low-absorption ultraviolet light from penetrating too deeply into the resin. After the light source configuration is completed, the circumferential illuminance of the ring irradiation area is detected to confirm that the irradiation differences in the upper, lower, left, and right directions of the fiber are within the allowable range of the process, preventing deviations in the thickness of the microporous sealing film caused by unilateral irradiation.

[0081] During the pre-crosslinking treatment, the coated single-mode optical fiber is passed through the irradiation area of ​​the ring array light source at a stable speed, or is irradiated in a stationary coiled state. The ring array light source simultaneously outputs ultraviolet light in the target ultraviolet band from the circumference of the fiber, resulting in an isotropic light energy distribution on the outer surface of the resin. Due to the high absorbance of this band in the fluorinated polyimide resin, the light energy is mainly absorbed by the surface resin, causing limited crosslinking of the surface chain segments and a rapid increase in viscosity, while the internal resin remains in a state where solvent can migrate slowly. The irradiation time and traction speed are matched according to a preset surface thickness threshold. Insufficient irradiation results in discontinuous surface crosslinking, making it difficult to seal open micropores; excessive irradiation extends the photopolymerization reaction into the inner layer, hindering the diffusion and discharge of solvent through the intermolecular gaps during the subsequent thermosetting stage.

[0082] As the annular irradiation continues, a microporous sealed film of uniform thickness gradually forms on the outer surface of the resin. This microporous sealed film seals open pores and bubble breaks on the resin surface, making it less prone to pinholes and shrinkage cavities during subsequent gradient temperature thermosetting. Simultaneously, its crosslinking degree is limited within the surface thickness threshold, still allowing the solvent inside the resin to slowly diffuse out through the intermolecular gaps. After pre-crosslinking, the continuity of the circumferential surface of the optical fiber, the uniformity of the film layer, and any abnormalities such as localized whitening, cracking, or exposure of the substrate are inspected. Only after confirming that the microporous sealed film has not formed a hard shell defect due to unilateral irradiation or excessive crosslinking is the subsequent thermosetting process initiated. In this embodiment, the above scheme, through selective ultraviolet absorption spectroscopy and isotropic irradiation with an annular array, confines the pre-crosslinking to the resin surface area, improving the thickness uniformity of the microporous sealed film and the quality of the second radiation-resistant layer.

[0083] In a specific embodiment, the method of isotropically irradiating the coated resin surface with the ring array light source to strictly limit the photopolymerization reaction within the surface thickness threshold, thereby completing the pre-crosslinking treatment and forming a uniformly thick microporous closed membrane on the outer surface of the resin, includes: Within the irradiation area of ​​the annular array light source, a swirling inert protective gas is coaxially injected along the direction of fiber travel to form a dynamic cyclone barrier around the coated resin surface. The dynamic cyclone barrier is used to displace oxygen from the outer surface of the resin to eliminate the surface oxygen inhibition effect during photopolymerization, and the centripetal shear force generated by the dynamic cyclone barrier is used simultaneously to perform hydrodynamic centering of the liquid resin. Under the oxygen-free encapsulation and centering constraint of the dynamic cyclone barrier, the coated resin surface after centering is subjected to isotropic annular irradiation using the annular array light source, so as to strictly limit the photopolymerization reaction within the surface thickness threshold and complete the pre-crosslinking treatment, thereby forming the microporous closed membrane with uniform thickness in a geometrically coaxial and fully crosslinked state.

[0084] Specifically, in practice, after the fluorinated polyimide resin is coated, the single-mode optical fiber is continuously drawn into the irradiation area of ​​the annular array light source. To ensure that the outer surface of the resin is in a low-oxygen, coaxial, and thickness-stable state before pre-crosslinking, a coaxial gas guiding structure is set at the entrance of the irradiation area, allowing the inert protective gas to enter along the fiber's travel direction and forming a swirling airflow through nozzles with tangential guide grooves or spiral guide surfaces. The inert protective gas can be nitrogen or argon, whose chemical properties do not participate in the resin crosslinking reaction or react with the first impermeable layer. After the swirling airflow enters the annular irradiation area, it forms a continuously enveloping dynamic cyclone barrier around the coated resin outer surface. This barrier moves forward with the fiber traction direction, ensuring that the resin outer surface is always covered by an inert atmosphere.

[0085] The dynamic cyclone barrier is primarily used to remove oxygen from the resin's outer surface. During the UV pre-crosslinking process of fluorinated polyimide resin, if oxygen is present on the surface, oxygen molecules will capture photo-initiated active free radicals, slowing down the crosslinking rate of the resin surface and forming sticky, incompletely crosslinked, or locally unclosed micropore regions with oxygen-inhibited polymerization. By continuously sweeping the resin's outer surface with a coaxially swirling inert protective gas, the oxygen concentration can be reduced to a level that does not affect the continuous photopolymerization reaction, allowing the resin surface to undergo uniform pre-crosslinking when irradiated by the ring array light source. This oxygen removal function only serves the surface photopolymerization process, does not change the selection criteria for the target UV band, and does not replace subsequent gradient temperature thermosetting.

[0086] Simultaneously, the dynamic cyclone barrier also exerts a hydrodynamic centering effect on the liquid resin. Since the resin still possesses a certain degree of fluidity immediately after coating, fiber traction, mold exit disturbances, or gravity can cause circumferential eccentricity of the resin layer. The swirling inert airflow forms an approximately symmetrical circumferential flow field around the outer surface of the resin, generating a balanced shear constraint pointing towards the fiber axis. This causes locally thicker resin areas to undergo more significant surface shear leveling, while locally thinner areas are prevented from being further thinned by unilateral airflow. Thus, before entering UV irradiation, the liquid resin tends to be coaxial with the geometric center of the fiber, resulting in a more rounded outer contour of the wet film, providing a geometric basis for forming a uniformly thick microporous sealed film. The airflow velocity and swirling intensity should be limited to the extent that they can remove oxygen and center the resin without breaking the wet film or causing surface ripples, preventing excessive airflow from causing resin splashing, exposure of the substrate, or circumferential thickness oscillations.

[0087] After the dynamic cyclone barrier stabilizes, the annular array light source is activated to provide isotropic annular irradiation to the centered resin surface. The emission wavelength of each emitting unit is within the aforementioned target ultraviolet band, and the light energy is primarily absorbed by the resin surface, limiting the photopolymerization reaction to a preset surface thickness threshold. Because the resin surface is encapsulated by an inert, oxygen-free gas, the surface active groups are not deactivated by oxygen inhibition. Furthermore, since the resin wet film is centered and constrained by the cyclone flow field, the path length of ultraviolet light received at all circumferential locations is essentially the same as the resin thickness, maintaining a uniform surface cross-linking depth. As the optical fiber continuously passes through the irradiation area, a geometrically coaxial, fully cross-linked, and uniformly thick microporous closed membrane gradually forms on the resin surface. This membrane seals open pores and microbubble ruptures on the surface while retaining channels for the internal solvent to slowly diffuse out through intermolecular gaps.

[0088] After pre-crosslinking, a short-term purging with inert protective gas is maintained to keep residual oxygen and volatile small molecules away from the film surface. Then, the annular array light source is turned off, and the optical fiber is fed into the subsequent gradient temperature thermal curing process. If online monitoring reveals film eccentricity, localized stickiness, surface ripples, or exposed substrate, the inert protective gas flow rate, swirl angle, optical fiber pulling speed, or UV irradiation time should be adjusted accordingly. Surface defects should not be compensated for by increasing the UV penetration depth, as this would disrupt the process logic of "surface pre-crosslinking and slow internal solvent removal." In this embodiment, the above scheme simultaneously achieves oxygen removal and fluid centering through a dynamic cyclone barrier, enabling the annular UV pre-crosslinking to be completed under oxygen-free and coaxial conditions, improving the crosslinking integrity and thickness uniformity of the microporous closed membrane.

[0089] The attenuation suppression method for single-mode optical fiber under irradiation in the embodiments of the present invention has been described above. The attenuation suppression system for single-mode optical fiber under irradiation in the embodiments of the present invention is described below. Please refer to [link to relevant documentation]. Figure 2 One embodiment of the attenuation suppression system for single-mode optical fiber under irradiation conditions in this invention includes: Acquisition module 1 is used to acquire the core doping parameters of the single-mode fiber to be processed; and to calculate the target hydrogen concentration of the single-mode fiber used to suppress radiation-induced attenuation based on the core doping parameters. Calculation module 2 is used to calculate, based on the target hydrogen loading concentration, the two-stage hydrogen loading process parameters for hydrogen permeation into the optical fiber, and the stepped annealing process parameters for removing free hydrogen from the optical fiber to eliminate hydrogen loss background attenuation, so as to obtain a customized processing strategy. Operation module 3 is used to sequentially perform a two-stage hydrogen loading operation, a pre-irradiation operation to excite and passivate color center defects, and a stepped annealing operation on the single-mode optical fiber according to the customized processing strategy. The sealing module 4 is used to coat and cure the sealing layer on the surface of the single-mode fiber after the stepped annealing operation is completed, so as to obtain an attenuation-suppressed radiation-resistant single-mode fiber.

Claims

1. A method for suppressing attenuation of single-mode optical fiber under irradiation, characterized in that, include: Obtain the core doping parameters of the single-mode fiber to be processed; calculate the target hydrogen concentration of the single-mode fiber to suppress radiation-induced attenuation based on the core doping parameters. Based on the target hydrogen loading concentration, the two-stage hydrogen loading process parameters for hydrogen permeation into the optical fiber and the stepped annealing process parameters for removing free hydrogen from the optical fiber to eliminate hydrogen loss and background attenuation are calculated, resulting in a customized treatment strategy. According to the customized processing strategy, the single-mode fiber is subjected to a two-stage hydrogen loading operation, a pre-irradiation operation to excite and passivate color center defects, and a stepped annealing operation in sequence. After the stepped annealing operation is completed, a curing sealing layer is coated on the surface of the single-mode fiber to obtain an attenuation-suppressed radiation-resistant single-mode fiber.

2. The attenuation suppression method for single-mode optical fiber under irradiation environment according to claim 1, characterized in that, The step of calculating the target hydrogen concentration of the single-mode fiber for suppressing radiation-induced attenuation based on the fiber core doping parameters includes: The molar percentage of fluorine and the residual percentage of chlorine in the single-mode fiber to be processed are obtained as the core doping parameters. The molar percentage of fluorine and the residual percentage of chlorine are multiplied by the corresponding first defect conversion coefficient and second defect conversion coefficient, respectively, to calculate the fluorine-induced defect density base and the chlorine-induced defect density base. The product of the molar percentage of fluorine and the residual percentage of chlorine is calculated, and combined with the preset lattice distortion constant, the dihalogen synergistic additional defect density is calculated. The density of the non-bridging oxygen hole center precursor is obtained by summing the base values ​​of the fluorine-induced defect density, the base values ​​of the chlorine-induced defect density, and the dihalogen-synergistic additional defect density. The stoichiometric multiplier is calculated based on the theoretical molar ratio of the hydrogen molecule to the non-bridged oxygen hole center precursor during the bonding and passivation reaction, and the preset hydrogen molecule thermal diffusion escape compensation coefficient. The target hydrogen concentration of the single-mode fiber used to suppress radiation-induced attenuation is calculated by multiplying the density of the non-bridged oxygen hole center precursor by the stoichiometric multiplier.

3. The attenuation suppression method for single-mode optical fiber under irradiation environment according to claim 1, characterized in that, Based on the target hydrogen loading concentration, the two-stage hydrogen loading process parameters for hydrogen infiltration into the optical fiber and the stepped annealing process parameters for removing free hydrogen from the optical fiber to eliminate hydrogen loss background attenuation are calculated, resulting in a customized processing strategy, including: Based on the target hydrogen loading concentration and the cladding diameter of the single-mode optical fiber, the first-order low-pressure permeation pressure and time for establishing the permeation channel, and the second-order high-pressure solid solution pressure and time for achieving concentration saturation are calculated and combined to generate the dual-order hydrogen loading process parameters. Based on the target hydrogen concentration, the first-order low-temperature desorption temperature and time for removing interstitial free hydrogen and the second-order high-temperature relaxation temperature and time for releasing lattice stress are calculated and combined to generate the stepped annealing process parameters for removing free hydrogen inside the optical fiber to eliminate hydrogen loss and background attenuation. The two-stage hydrogen loading process parameters and the stepped annealing process parameters are sequentially spliced ​​together to obtain a customized processing strategy.

4. The attenuation suppression method for single-mode optical fiber under irradiation environment according to claim 3, characterized in that, The process, according to the customized processing strategy, sequentially performs a two-stage hydrogen loading operation, a pre-irradiation operation to excite and passivate color center defects, and a stepped annealing operation on the single-mode fiber, including: According to the customized processing strategy, the single-mode optical fiber is subjected to the dual-stage hydrogen loading operation in a temperature-controlled autoclave with the first-stage low-pressure permeation pressure and the second-stage high-pressure solid solution pressure. After the two-stage hydrogen loading operation is completed, the single-mode fiber is subjected to the pre-irradiation operation for exciting and passivating color center defects using a pulsed gamma-ray source, wherein the pulse interval time of the pulsed gamma-ray source is controlled to be greater than the preset local heat dissipation threshold of the fiber to prevent the internal bound hydrogen from escaping due to heat. After the pre-irradiation operation is completed, the stepped annealing operation is performed in a dynamic vacuum furnace at the first low-temperature desorption temperature and the second high-temperature relaxation temperature.

5. The attenuation suppression method for single-mode optical fiber under irradiation environment according to claim 4, characterized in that, The process of performing the dual-stage hydrogen loading operation on the single-mode optical fiber in a temperature-controlled autoclave according to the customized processing strategy, using the first-stage low-pressure permeation pressure and the second-stage high-pressure solid solution pressure, includes: The customized processing strategy is analyzed to obtain the first-order low-pressure permeation pressure and the second-order high-pressure solid solution pressure; Hydrogen gas is introduced into the temperature-controlled high-pressure autoclave to the first-stage low-pressure permeation pressure to perform the first-stage hydrogen permeation on the single-mode optical fiber. After the first stage of hydrogen permeation is completed, an inert buffer gas is injected into the temperature-controlled high-pressure vessel to absorb the adiabatic heat generated by gas compression. After injecting the inert buffer gas, hydrogen is continuously introduced into the temperature-controlled autoclave to the second-stage high-pressure solid solution pressure to perform the second-stage hydrogen permeation on the single-mode optical fiber, thus completing the two-stage hydrogen loading operation.

6. The attenuation suppression method for single-mode optical fiber under irradiation environment according to claim 4, characterized in that, After the two-stage hydrogen loading operation is completed, the single-mode fiber is subjected to a pre-irradiation operation using a pulsed gamma-ray source to excite and passivate color center defects, including: After the two-stage hydrogen loading operation is completed, the single-mode optical fiber is fixed in a grounded conductive clamp. The single-mode optical fiber is pulsed with the pulsed gamma ray source, and the Compton transient charge excited in the silica matrix of the optical fiber by the pulsed irradiation is simultaneously extracted through the grounded conductive clamp. In an electrostatic-free environment that derives the Compton transient charge, hydrogen molecules inside the optical fiber are induced to combine with the excited defects, thus completing the pre-irradiation operation used to excite and passivate color center defects.

7. The attenuation suppression method for single-mode optical fiber under irradiation environment according to claim 1, characterized in that, After the stepped annealing operation is completed, a curing sealing layer is coated on the surface of the single-mode fiber to obtain an attenuation-suppressed radiation-resistant single-mode fiber, comprising: After the stepped annealing operation is completed, a silicon carbide-carbon transition film with a gradient carbon-silicon ratio is deposited on the bare surface of the single-mode optical fiber by chemical vapor deposition as the first anti-seepage layer of the curing and sealing layer. A fluorinated polyimide resin is coated on the outside of the first impermeable layer and thermally cured at a preset curing temperature to form the second radiation-resistant layer of the cured sealing layer, thereby obtaining an attenuation-suppressed radiation-resistant single-mode optical fiber.

8. The attenuation suppression method for single-mode optical fiber under irradiation environment according to claim 7, characterized in that, After the stepped annealing operation is completed, a silicon carbide-carbon transition film with a gradient carbon-silicon ratio is deposited on the bare surface of the single-mode optical fiber using chemical vapor deposition as the first impermeable layer of the cured sealing layer, comprising: After the stepped annealing operation is completed, the single-mode optical fiber is placed in a chemical vapor deposition reaction chamber, and a mixed precursor gas containing silane and methane is introduced into the reaction chamber. During the chemical vapor deposition process, the flow rate ratio of silane in the mixed precursor gas is continuously reduced and the flow rate ratio of methane is simultaneously increased according to a preset time function. By continuously adjusting the flow ratio, a silicon carbide-carbon transition film with a gradient carbon-silicon ratio, rich in silicon on the inner side and rich in carbon on the outer side, is deposited on the bare surface of the single-mode optical fiber, and serves as the first anti-seepage layer of the curing and sealing layer.

9. The attenuation suppression method for single-mode optical fiber under irradiation environment according to claim 7, characterized in that, The process of coating the outer side of the first impermeable layer with fluorinated polyimide resin and thermally curing it at a preset curing temperature to form the second radiation-resistant layer of the cured sealing layer, thereby obtaining an attenuation-suppressed radiation-resistant single-mode optical fiber, includes: The liquid fluorinated polyimide resin is uniformly coated on the outside of the first impermeable layer; The coated resin surface is pre-crosslinked using an ultraviolet light source to form a microporous closed membrane on the outer surface of the resin. After the microporous sealing membrane is formed, the thermal curing is carried out at the preset curing temperature with a gradient increase, so that the solvent inside the resin can be slowly diffused out through the gaps between molecules, forming a dense, pinhole-free second radiation-resistant layer of the cured sealing layer, thus obtaining an attenuation-suppressed radiation-resistant single-mode optical fiber.

10. A system for suppressing attenuation of single-mode optical fiber under irradiation, characterized in that, include: The acquisition module is used to acquire the core doping parameters of the single-mode fiber to be processed; and to calculate the target hydrogen concentration of the single-mode fiber for suppressing radiation-induced attenuation based on the core doping parameters. The calculation module is used to calculate, based on the target hydrogen loading concentration, the two-stage hydrogen loading process parameters for hydrogen permeation into the optical fiber, and the stepped annealing process parameters for removing free hydrogen from the optical fiber to eliminate hydrogen loss background attenuation, so as to obtain a customized processing strategy. The operation module is used to sequentially perform a two-stage hydrogen loading operation, a pre-irradiation operation for exciting and passivating color center defects, and a stepped annealing operation on the single-mode optical fiber according to the customized processing strategy. A sealing module is used to coat and cure a sealing layer on the surface of the single-mode fiber after the stepped annealing operation is completed, so as to obtain an attenuation-suppressed radiation-resistant single-mode fiber.

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