Low temperature resistant optical fiber and method for manufacturing the same

Abstract

The embodiment of the present application provides a low-temperature-resistant optical fiber and a preparation method thereof. The low-temperature-resistant optical fiber comprises a core body and a first coating layer, a second coating layer and a third coating layer which are sequentially coated on the surface of the core body from inside to outside; the glass transition temperature of the first coating layer is less than or equal to the glass transition temperature of the second coating layer; and the glass transition temperature of the second coating layer is less than the glass transition temperature of the third coating layer. The low-temperature-resistant optical fiber is used to realize the effects of low additional attenuation, high mechanical strength and long-term stability in the environment of-70 DEG C to-60 DEG C.

Description

Technical Field

[0001] This application relates to the field of optical fibers, and more particularly to a low-temperature resistant optical fiber and its fabrication method. Background Technology

[0002] Optical fiber is lightweight, resistant to electromagnetic interference, and has a large transmission capacity, making it suitable for both communication and fiber optic sensors. As the use of optical fiber becomes increasingly widespread, its environmental conditions become more complex, and harsh working environments require optical fibers to possess properties such as high-temperature and low-temperature resistance.

[0003] Optical fibers typically consist of bare fibers (stripped fibers) and coating materials, usually unmodified acrylic resins. Their glass transition temperatures (Tg) are generally above -30°C, and they are prone to embrittlement in low-temperature environments below -40°C. This leads to stress concentration at the interface between the coating and the fiber body (cladding), resulting in abnormal optical signal attenuation. Furthermore, at low temperatures, the coating's rigidity increases while its ductility decreases, making it difficult to buffer the mechanical stress caused by the fiber's contraction at low temperatures. This results in a significant increase in the additional attenuation of existing optical fibers in environments below -50°C (exceeding 0.01 dB / km at 1550 nm wavelength), and the attenuation fluctuation amplitude increases with decreasing temperature, leading to an increase in the bit error rate. In addition, existing coating materials have insufficient thermal stability, with thermal weight loss at 85°C / 8 weeks generally exceeding 8%, and large deviations in low-temperature curing degree (e.g., differences in curing degree between layers ≥10%), further exacerbating the instability of optical fiber performance.

[0004] Therefore, there is an urgent need to provide a low-temperature resistant optical fiber to solve the problems of increased additional attenuation, low mechanical strength, and insufficient long-term stability of existing optical fibers at low temperatures. Summary of the Invention

[0005] This application provides a low-temperature resistant optical fiber and its preparation method, which aims to improve the low-temperature resistance of the optical fiber.

[0006] In a first aspect, embodiments of this application provide a low-temperature resistant optical fiber, including a core and a first coating, a second coating, and a third coating sequentially coated on the surface of the core from the inside out.

[0007] The glass transition temperature of the first coating is less than or equal to the glass transition temperature of the second coating;

[0008] The glass transition temperature of the second coating is lower than that of the third coating.

[0009] In one possible implementation, the glass transition temperature of the first coating is less than or equal to -50°C;

[0010] And / or, the glass transition temperature of the second coating is -50°C to -40°C;

[0011] And / or, the glass transition temperature of the third coating is greater than or equal to 60°C.

[0012] In one possible implementation, the Young's modulus of the first coating is less than or equal to the Young's modulus of the second coating.

[0013] The Young's modulus of the second coating is less than that of the third coating;

[0014] And / or, the elongation at break of the first coating is greater than or equal to the elongation at break of the second coating;

[0015] The elongation at break of the second coating is greater than that of the third coating.

[0016] In one possible implementation, the Young's modulus of the first coating is 0.3 MPa-0.5 MPa;

[0017] And / or, the Young's modulus of the second coating is 0.5 MPa-0.7 MPa;

[0018] And / or, the Young's modulus of the third coating is greater than or equal to 800 MPa;

[0019] And / or, the elongation at break of the first coating is greater than or equal to 180%;

[0020] And / or, the elongation at break of the second coating is 150%-180%;

[0021] And / or, the elongation at break of the third coating is 15%-50%;

[0022] And / or, the refractive index of the first coating is 1.47-1.49;

[0023] And / or, the refractive index of the second coating is 1.47-1.49;

[0024] And / or, the refractive index of the third coating is 1.52-1.54.

[0025] In one possible implementation, the first coating comprises a first acrylic resin and a first modifier, wherein the first modifier has a mass fraction of 10%-15% in the first coating, and the first modifier comprises at least one of polyisobutylene glycol, polybutylene adipate, polybutylene succinate, polyethylene succinate, aliphatic diisocyanate, aromatic diisocyanate, polyethylene, styrene, methacrylic acid, hydroxyl acrylate, and polycaprolactone.

[0026] And / or, the second coating comprises a second acrylic resin and a second modifier, wherein the second modifier has a mass fraction of 8%-12% in the second coating, and the second modifier comprises at least one of polyisobutylene glycol, polybutylene adipate, polybutylene succinate, polyethylene succinate, aliphatic diisocyanate, aromatic diisocyanate, polyethylene, styrene, methacrylic acid, hydroxyl acrylate, and polycaprolactone;

[0027] And / or, the third coating comprises a third acrylic resin and a third modifier, wherein the third modifier has a mass fraction of 2%-6% in the third coating, and the third modifier comprises at least one of polyisobutylene glycol, polybutylene adipate, polybutylene succinate, polyethylene succinate, aliphatic diisocyanate, aromatic diisocyanate, polyethylene, styrene, methacrylic acid, hydroxy acrylate, and polycaprolactone.

[0028] In one possible implementation, the diameter of the core is 124μm-126μm;

[0029] And / or, the thickness of the first coating is 2μm-8μm;

[0030] And / or, the thickness of the second coating is 20μm-35μm;

[0031] And / or, the thickness of the third coating is 17.5μm-37.5μm.

[0032] Secondly, embodiments of this application provide a method for preparing the above-mentioned low-temperature resistant optical fiber, comprising: melting an optical fiber preform and drawing it in a first inert gas to obtain a bare optical fiber;

[0033] Under a second inert gas, the bare optical fiber is first coated and cured with a first slurry to obtain a first intermediate; the first intermediate is coated and cured with a second slurry to obtain a second intermediate; and the second intermediate is coated and cured with a third slurry to obtain a third intermediate.

[0034] The third intermediate is subjected to heat treatment to obtain the low-temperature resistant optical fiber.

[0035] In one possible implementation, the melting temperature is 1700℃-2200℃;

[0036] The wire drawing speed is greater than or equal to 2000 m / min;

[0037] The flow rate of the first inert gas is 10 L / min - 50 L / min;

[0038] The first inert gas and / or the second inert gas includes at least one of argon and helium;

[0039] The oxygen content of the first inert gas and / or the second inert gas is less than or equal to 100 ppm.

[0040] In one possible implementation, the first slurry comprises a first acrylic resin and a first modifier;

[0041] The pressure of the first coating is 0.2 MPa-0.6 MPa, and the temperature of the first coating is 35℃-55℃;

[0042] The relative degree of curing of the first curing is greater than or equal to 90%;

[0043] And / or, the second slurry comprises a second acrylic resin and a modifier;

[0044] The pressure of the second coating is 0.2 MPa-0.6 MPa, and the temperature of the second coating is 35℃-55℃;

[0045] The relative degree of curing in the second curing stage is greater than or equal to 92%;

[0046] And / or, the third slurry comprises a third acrylic resin and a modifier;

[0047] The pressure of the third coating is 0.2 MPa-0.6 MPa, and the temperature of the third coating is 35℃-55℃;

[0048] The relative degree of curing of the third curing process is greater than or equal to 92%.

[0049] In one possible implementation, the deviation between the relative degree of cure of the first curing and the relative degree of cure of the second curing is less than or equal to 6%;

[0050] And / or, the deviation between the relative degree of cure of the second curing and the relative degree of cure of the third curing is less than or equal to 6%;

[0051] And / or, the deviation between the relative degree of cure of the first curing and the relative degree of cure of the third curing is less than or equal to 6%.

[0052] In one possible implementation, the heat treatment temperature is 40°C-60°C, and the heat treatment time is 24h-48h.

[0053] The low-temperature resistant optical fiber and its preparation method provided in this application achieve the effect of reducing the additional loss of the optical fiber at -70℃ to -60℃ and improving its mechanical strength by controlling the glass transition temperature of the first coating, the second coating and the third coating from the inside to the outside to change in a gradient increasing trend. Attached Figure Description

[0054] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0055] Figure 1 A schematic diagram of the structure of the low-temperature resistant optical fiber provided in this application.

[0056] Figure label:

[0057] 001: Core; 002: First coating; 003: Second coating; 004: Third coating.

[0058] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0059] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0060] In existing technologies, in environments below -50°C, the fiber core / cladding (quartz glass) and the external protective coating (polymer) of optical fibers have different coefficients of thermal expansion. When the temperature drops sharply, the different layers shrink to varying degrees, generating enormous internal stress. This stress causes microscale bending (microbending) in straight optical fibers, leading to optical signal leakage and a significant increase in additional fiber attenuation (exceeding 0.01 dB / km at 1550 nm wavelength). Furthermore, the attenuation fluctuation amplitude increases with decreasing temperature, resulting in a rise in the communication bit error rate. Moreover, if the Tg of a common coating is high or uniform, it will transform from a soft "rubber state" to a hard "glass state" at low temperatures. The hardened coating cannot effectively buffer and disperse stress; instead, it will transfer thermal stress more directly to the glass fiber, exacerbating microbending.

[0061] The low-temperature resistant optical fiber provided in this application solves the technical problems of low-temperature sensitivity and thermal stability of optical fibers by setting a three-layer coating with varying glass transition temperature on the surface of the preform.

[0062] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will be described below with reference to the accompanying drawings.

[0063] Figure 1 A schematic diagram of the structure of the low-temperature resistant optical fiber provided in this application is shown below. Figure 1 As shown, the low-temperature resistant optical fiber includes a core 001 and a first coating 002, a second coating 003, and a third coating 004 sequentially coated on the surface of the core from the inside out; the glass transition temperature of the first coating 002 is less than or equal to the glass transition temperature of the second coating 003; the glass transition temperature of the second coating 003 is less than the glass transition temperature of the third coating 004.

[0064] In this application, the first coating with a relatively lower glass transition temperature serves as the first layer in direct contact with the optical fiber preform. Even at extremely low temperatures, it can still maintain a high elastic modulus and flexibility, absorb and buffer most of the initial stress caused by thermal mismatch, reduce the shear force and lateral pressure transmitted to the brittle optical fiber preform, fundamentally suppress the generation of microbending, and maintain good adhesion and bonding with the surface of the optical fiber preform even when the temperature changes, preventing debonding and the generation of voids.

[0065] The second coating, serving as a transition layer between the first and third coatings, has a glass transition temperature greater than or equal to that of the first coating and less than or equal to that of the third coating. This allows the modulus of the outer material of the optical fiber preform to gradually change with variations in external temperature, preventing abrupt changes in mechanical properties from "extremely soft" to "extremely hard." Furthermore, through its viscoelastic behavior, it further dissipates and redistributes the stress transmitted from the outer layer.

[0066] The third coating, as the outermost protective shell, has a high glass transition temperature, which allows it to maintain high modulus and mechanical strength at low temperatures. It provides necessary mechanical protection (wear resistance, flattening resistance) and shape stability for the entire optical fiber structure, preventing macroscopic bending caused by external mechanical forces.

[0067] This "hard outside, soft inside, gradient transition" structure achieves effects similar to "graded vibration damping" or "impedance matching" when dealing with low temperatures. On the one hand, by gradually "hardening" the structure from the inside out, the enormous thermal stress generated at low temperatures is buffered, dissipated, and redistributed step by step, ensuring that the stress transmitted to the fiber core is minimized, thereby suppressing microbending that leads to light leakage to the greatest extent and significantly reducing microbending loss. On the other hand, the optical performance (attenuation) of the optical fiber becomes more stable over a wider temperature range (especially in the low-temperature range). Its attenuation-temperature curve becomes flatter, that is, its sensitivity to temperature changes is reduced, thus reducing the low-temperature sensitivity of the optical fiber. Furthermore, it also reduces the fatigue stress applied to the core during each temperature cycle, improving the long-term service life and reliability of the optical fiber under cyclic conditions such as diurnal temperature variation and seasonal changes. At the same time, the high Tg third coating also provides sufficient mechanical protection at room temperature or high temperature; while the flexibility of the inner layer is also beneficial for buffering daily bending and lateral pressure at room temperature.

[0068] In some specific embodiments, the glass transition temperature of the first coating is less than or equal to -50°C.

[0069] For example, the glass transition temperature of the first coating can be -90°C, -80°C, -70°C, -60°C, -50°C, etc.

[0070] In some specific embodiments, the glass transition temperature of the second coating is -50°C to -40°C.

[0071] For example, the glass transition temperature of the second coating can be a range of -50°C, -49°C, -48°C, -47°C, -46°C, 45°C, 44°C, 43°C, 42°C, 41°C, 40°C, or any combination thereof.

[0072] In some specific embodiments, the glass transition temperature of the third coating is greater than or equal to 60°C.

[0073] For example, the glass transition temperature of the third coating can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, etc.

[0074] In some specific embodiments, the Young's modulus of the first coating is less than or equal to the Young's modulus of the second coating; the Young's modulus of the second coating is less than the Young's modulus of the third coating.

[0075] By making the Young's modulus of the three-layer coating increase from the inside to the outside, harmful stresses (especially lateral pressures that cause optical loss) can be "blocked" and "dissipated" in the coating system to protect the optical integrity of the fiber core. In addition, the Tg gradient of the coating can be coordinated to give the optical fiber superior environmental adaptability, especially maintaining low loss and stability under harsh conditions such as low temperature and temperature difference.

[0076] In some specific embodiments, the Young's modulus of the first coating is 0.3 MPa-0.5 MPa.

[0077] For example, the Young's modulus of the first coating is in the range of 0.3 MPa, 0.4 MPa, 0.5 MPa, or any combination thereof.

[0078] In some specific embodiments, the Young's modulus of the second coating is 0.5 MPa-0.7 MPa.

[0079] For example, the Young's modulus of the second coating is in the range of 0.5 MPa, 0.6 MPa, 0.7 MPa, or any combination thereof.

[0080] In some specific implementations, the Young's modulus of the third coating is greater than or equal to 800 MPa.

[0081] For example, the Young's modulus of the third coating can be 80MPa, 850MPa, 900MPa, 950MPa, 1000MPa, etc.

[0082] In some specific embodiments, the elongation at break of the first coating is greater than or equal to the elongation at break of the second coating; the elongation at break of the second coating is greater than the elongation at break of the third coating.

[0083] By controlling the elongation at break to decrease from the inside out, the first coating achieves the highest elongation at break, acting like an extremely strong rubber band. This ensures it always operates within its elastic or large deformation range without breaking, thus providing durable protection for the fiber core. Furthermore, during repeated bending of the optical fiber (such as during construction, cabling, and dynamic applications), the inner layer undergoes repeated stretching-compression cycles. Controlling the high elongation at break of the first and second coatings means they possess better toughness and fatigue resistance, capable of withstanding more deformation cycles without developing microcracks or breaking. This improves the mechanical reliability and lifespan of the optical fiber during installation and use.

[0084] In some specific embodiments, the elongation at break of the first coating is greater than or equal to 180%.

[0085] For example, the elongation at break of the first coating can be 180%, 190%, 200%, 210%, 220%, 230%, 240%, 250%, etc.

[0086] In some specific embodiments, the elongation at break of the second coating is 150%-180%.

[0087] For example, the elongation at break of the second coating may be a range of 150%, 155%, 160%, 165%, 170%, 175%, 180%, or any combination thereof.

[0088] In some specific implementations, the elongation at break of the third coating is 15%-50%.

[0089] For example, the elongation at break of the third coating can be a range of 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any combination thereof.

[0090] In some specific embodiments, the refractive index of the first coating is 1.47-1.49.

[0091] By controlling the refractive index of the first coating to be 1.47-1.49 (greater than the refractive index of the core), according to optical principles, light leaking into the cladding will no longer undergo total internal reflection when it encounters the coating interface, but will instead be refracted into the first coating. Once inside, the light will be rapidly absorbed by the coating and converted into negligible heat, thus being effectively "stripped away" and eliminated.

[0092] For example, the refractive index of the first coating may be in the range of 1.47, 1.48, 1.49, or any two of them.

[0093] In some specific embodiments, the refractive index of the second coating is 1.47-1.49.

[0094] By controlling the refractive index of the second coating to 1.47-1.49, it can be ensured that the very small portion of light that may be scattered or not fully absorbed from the first coating is suppressed when it reaches the second coating, preventing unwanted guidance or resonance of light between different coating interfaces.

[0095] For example, the refractive index of the second coating may be in the range of 1.47, 1.48, 1.49, or any two of them.

[0096] In some specific embodiments, the refractive index of the third coating is 1.52-1.54.

[0097] By controlling the refractive index of the third coating to 1.52-1.54, an optical waveguide structure is formed between it and the adjacent second coating. Light of specific wavelengths (especially light leaking from the core or light coupled through the evanescent field) can be effectively confined and guided to propagate within the third coating or near its interface, thereby achieving highly sensitive fiber optic sensing and special laser or gain functions.

[0098] For example, the refractive index of the third coating may be in the range of 1.52, 1.53, 1.54, or any combination thereof.

[0099] In some specific embodiments, the first coating includes a first acrylic resin and a first modifier, wherein the mass fraction of the first modifier in the first coating is 10%-15%, and the first modifier includes at least one of polyethylene, styrene, methacrylic acid, hydroxy acrylate, polyisobutylene glycol, polybutylene adipate, aliphatic diisocyanate, polycaprolactone, aromatic diisocyanate, polybutylene succinate, and polyethylene succinate.

[0100] In some specific embodiments, the second coating includes a second acrylic resin and a second modifier. The second modifier has a mass fraction of 8%-12% in the second coating. The second modifier includes at least one of polyethylene, styrene, methacrylic acid, hydroxy acrylate, polyisobutylene glycol, polybutylene adipate, aliphatic diisocyanate, polycaprolactone, aromatic diisocyanate, polybutylene succinate, and polyethylene succinate.

[0101] In some specific embodiments, the third coating comprises a third acrylic resin and a third modifier, wherein the mass fraction of the third modifier in the third coating is 2%-6%, and the third modifier comprises at least one of polyethylene, styrene, methacrylic acid, hydroxy acrylate, polyisobutylene glycol, polybutylene adipate, aliphatic diisocyanate, polycaprolactone, aromatic diisocyanate, polybutylene succinate, and polyethylene succinate.

[0102] In this embodiment, the modifiers used, such as polyisobutylene glycol, polycaprolactone, polybutylene succinate (PBS), and polyethylene succinate (PES), contain long aliphatic chains or ester bonds, exhibiting strong chain mobility and significantly reducing the glass transition temperature (Tg) of the coating. Furthermore, these chains maintain a certain degree of mobility at low temperatures. In addition, the hydroxyl acrylates or oligomers can penetrate into the polymer network, increasing the intermolecular distance and weakening intermolecular forces, thereby inhibiting brittle fracture at low temperatures and improving the low-temperature flexibility and resistance to embrittlement of the coating.

[0103] Aliphatic diisocyanates react with polyester / polyether polyols (such as polybutylene adipate, polybutylene succinate, and polyethylene succinate) to form polyurethane elastomers. This structure consists of hard segments (isocyanates) and soft segments (polyols). The soft segments provide low-temperature elasticity, while the hard segments maintain mechanical strength, allowing the coating to withstand bending or stretching at low temperatures. Polyethylene and styrene can form interpenetrating networks, dispersing stress through physical crosslinking points, optimizing the crosslinking network structure, reducing crack propagation at low temperatures, and balancing the strength and elasticity of the coating. Furthermore, polyethylene and polyesters can reduce crystallinity and avoid low-temperature catalysis by crosslinking with aromatic diisocyanates.

[0104] Monomers containing polar groups, such as methacrylic acid and hydroxy acrylate, can improve the chemical bonding between the coating and the core, prevent interface debonding at low temperatures, and enhance interface adhesion.

[0105] Structures such as polycaprolactone and aromatic diisocyanates can enhance the hydrolysis resistance of coatings in low-temperature and humid environments, prevent physical damage caused by ice crystal formation after water absorption, and improve the coating's hydrolysis and chemical resistance. Saturated carbon chain structures such as polyethylene and polyisobutylene glycol are not easily oxidized and can slow down aging and embrittlement under long-term low-temperature environments.

[0106] In some embodiments, by controlling the mass fraction of the first modifier in the first coating to be 10%-15%, the Young's modulus of the first coating is relatively low. When the optical fiber is subjected to external lateral pressure or when the temperature changes and the material shrinks, the first coating will deform first, absorbing and buffering most of the stress, thus preventing these stresses from acting directly on the glass optical fiber and causing micro-bending.

[0107] In some embodiments, by controlling the mass fraction of the second modifier in the second coating to be 8%-12%, it is made into a transition layer with a moderate modulus, allowing stress to be smoothly transmitted and dissipated within the material, thus avoiding the risk of severe shearing and delamination at the interface.

[0108] In some embodiments, by controlling the mass fraction of the third modifier in the third coating to be 2%-6%, the high modulus obtained makes it less prone to deformation and can effectively resist macroscopic deformation caused by external environment (such as cabling, laying, and extrusion), providing a stable "protective shell" for the inner soft layer and optical fiber.

[0109] In some specific implementations, the core diameter is 124μm-126μm.

[0110] The diameter of the control core is 124μm-126μm, which can ensure welding and connection efficiency, maintain optical mode stability, and guarantee mechanical strength.

[0111] For example, the diameter of the core can be a range of 124 μm, 125 μm, 126 μm, or any combination thereof.

[0112] In some specific embodiments, the thickness of the first coating is 2μm-8μm.

[0113] Under the aforementioned gradient distribution of glass transition temperature, Young's modulus, and elongation at break, the flexibility of the optical fiber and the bending radius can be improved by controlling the thickness of the first coating to be 2μm-8μm.

[0114] For example, the thickness of the first coating can be a range of 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, or any combination thereof.

[0115] In some specific embodiments, the thickness of the second coating is 20μm-35μm.

[0116] By controlling the thickness of the second coating to be 20μm-35μm, a smooth mechanical gradient can be achieved, and the first and third coatings can be firmly bonded together to prevent delamination.

[0117] For example, the thickness of the second coating can be a range of 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, 30 μm, 32 μm, 35 μm or any combination thereof.

[0118] In some specific embodiments, the thickness of the third coating is 17.5 μm-37.5 μm.

[0119] When the thickness of the third coating is 17.5μm-37.5μm, it can provide stronger resistance to wear, lateral pressure, micro-bending and external impact.

[0120] For example, the thickness of the third coating can be a range of 17.5 μm, 19.5 μm, 21.5 μm, 23.5 μm, 25.5 μm, 27.5 μm, 29.5 μm, 31.5 μm, 33.5 μm, 35.5 μm, 37.5 μm, or any combination thereof.

[0121] The low-temperature resistant optical fiber provided in this application embodiment controls the glass transition temperature of the first coating to be less than or equal to the glass transition temperature of the second coating, and the glass transition temperature of the second coating to be less than the glass transition temperature of the third coating. This allows the first coating to effectively absorb the mechanical stress generated by low-temperature shrinkage and avoid stress concentration at the interface between the cladding and the coating. The second coating further disperses the stress and reduces optical signal attenuation. The third coating provides mechanical protection and environmental stability, significantly improving the performance of the optical fiber in extremely cold environments. This enables the optical fiber to achieve low additional attenuation, high mechanical strength, and long-term service reliability in environments ranging from -60°C to -70°C.

[0122] This application also provides a method for preparing the above-mentioned low-temperature resistant optical fiber, the method comprising:

[0123] Bare optical fibers are obtained by melting the optical fiber preform and drawing it in a first inert gas.

[0124] Under a second inert gas, the bare optical fiber is first coated and cured with a first slurry to obtain a first intermediate; the first intermediate is coated and cured with a second slurry to obtain a second intermediate; and the second intermediate is coated and cured with a third slurry to obtain a third intermediate.

[0125] The third intermediate was heat-treated to obtain low-temperature resistant optical fiber.

[0126] This application employs an oxygen-free curing and heat treatment process on the slurry on the surface of bare optical fibers, which can ensure the uniformity of the cross-linked network of the coating and the release of residual stress, thereby improving the additional attenuation performance and long-term service reliability of the optical fiber in extremely cold environments.

[0127] In some specific implementations, the melting temperature is 1700℃-2200℃.

[0128] By controlling the melting temperature of the optical fiber preform to 1700℃-2200℃, its glass structure can be made more uniform, density fluctuations can be reduced, the lower limit of scattering loss determined by the material itself can be lowered, and low-attenuation, high-bandwidth optical performance can be achieved to meet the requirements of high-speed communication.

[0129] For example, the melting temperature can be a range of 1700°C, 1800°C, 1900°C, 2000°C, 2100°C, 2200°C, or any combination thereof.

[0130] In some specific implementations, the wire drawing speed is greater than or equal to 2000 m / min.

[0131] For example, the wire drawing speed can be 2000m / min, 2100m / min, 2200m / min, 2300m / min, 2400m / min, 2500m / min, etc.

[0132] In some specific implementations, the flow rate of the first inert gas is 10 L / min to 50 L / min.

[0133] In some specific implementations, the flow rate of the second inert gas is 10 L / min to 50 L / min.

[0134] In some specific embodiments, the first inert gas includes at least one of argon and helium.

[0135] In some specific embodiments, the second inert gas includes at least one of argon and helium.

[0136] In some specific implementations, the oxygen content of the first inert gas is less than or equal to 100 ppm.

[0137] In some specific embodiments, the oxygen content of the second inert gas is less than or equal to 100 ppm.

[0138] In some specific embodiments, the first slurry includes a first acrylic resin and a first modifier; the pressure of the first coating is 0.2 MPa-0.6 MPa, the temperature of the first coating is 35°C-55°C, and the relative degree of curing of the first curing is greater than or equal to 90%.

[0139] Specifically, a first slurry containing a first acrylic resin and a first modifier is coated onto the surface of a bare optical fiber formed by drawing at a pressure of 0.2 MPa to 0.6 MPa, while maintaining the coating temperature at 35°C to 55°C. Then, a first curing process is performed using ultraviolet light to obtain a first intermediate. The relative degree of curing of the obtained first curing is greater than or equal to 90%.

[0140] In some embodiments, the first slurry further includes a first organic solvent, which includes at least one of toluene, ethyl acetate, and butanone.

[0141] For example, the pressure of the first coating is in the range of 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa or any combination thereof; the temperature of the first coating is in the range of 35°C, 40°C, 45°C, 50°C, 55°C or any combination thereof; and the relative degree of curing of the first curing is 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc.

[0142] In some specific embodiments, the second slurry includes a second acrylic resin and a second modifier; the pressure of the second coating is 0.2 MPa-0.6 MPa, the temperature of the second coating is 35°C-55°C, and the relative degree of curing of the second curing is greater than or equal to 92%.

[0143] Specifically, a second slurry containing a second acrylic resin and a second modifier is coated onto the surface of the first intermediate under a pressure of 0.2 MPa to 0.6 MPa, maintaining the coating temperature at 35°C to 55°C. Then, a second curing process is performed using ultraviolet light to obtain the second intermediate. The relative degree of curing in the second curing is greater than or equal to 92%.

[0144] In some embodiments, the second slurry further includes a second organic solvent, which includes at least one of toluene, ethyl acetate, and butanone.

[0145] For example, the pressure of the second coating is in the range of 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa or any combination thereof; the temperature of the second coating is in the range of 35°C, 40°C, 45°C, 50°C, 55°C or any combination thereof; and the relative degree of curing of the second curing is 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc.

[0146] In some specific embodiments, the third slurry includes a third acrylic resin and a third modifier; the pressure of the third coating is 0.2 MPa-0.6 MPa, the temperature of the third coating is 35°C-55°C, and the relative degree of curing of the third curing is greater than or equal to 92%.

[0147] Specifically, a third slurry containing a third acrylic resin and a third modifier is coated onto the surface of the second intermediate under a pressure of 0.2 MPa-0.6 MPa, maintaining the coating temperature at 35℃-55℃. Then, a third curing process is performed using ultraviolet light to obtain the third intermediate. The relative degree of curing in the third curing is greater than or equal to 92%.

[0148] In some embodiments, the third slurry further includes a third organic solvent, which includes at least one of toluene, ethyl acetate, and butanone.

[0149] For example, the pressure of the third coating is in the range of 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa or any combination thereof; the temperature of the third coating is in the range of 35°C, 40°C, 45°C, 50°C, 55°C or any combination thereof; and the relative degree of curing of the third curing is 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc.

[0150] In some embodiments, the first modifier includes at least one selected from polyisobutylene glycol, polybutylene adipate, polybutylene succinate, polyethylene succinate, aliphatic diisocyanate, aromatic diisocyanate, polyethylene, styrene, methacrylic acid, hydroxy acrylate, and polycaprolactone; the second modifier includes at least one selected from polyisobutylene glycol, polybutylene adipate, polybutylene succinate, polyethylene succinate, aliphatic diisocyanate, aromatic diisocyanate, polyethylene, styrene, methacrylic acid, hydroxy acrylate, and polycaprolactone; and the third modifier includes at least one selected from polyisobutylene glycol, polybutylene adipate, polybutylene succinate, polyethylene succinate, aliphatic diisocyanate, aromatic diisocyanate, polyethylene, styrene, methacrylic acid, hydroxy acrylate, and polycaprolactone.

[0151] During ultraviolet curing, more than 90% of the light emitted by the light source has a wavelength between 370nm and 400nm.

[0152] In this embodiment, a relative curing degree of 90% or higher means that the three-layer coating forms a fully cross-linked three-dimensional network structure, which gives it high modulus and high elasticity, enabling it to effectively buffer the lateral pressure, bending or twisting of the optical fiber during cabling, laying and use, like a "spring pad".

[0153] In some specific implementations, the deviation between the relative degree of curing of the first curing and the relative degree of curing of the second curing is less than or equal to 6%.

[0154] In some specific implementations, the deviation between the relative degree of curing of the second curing and the relative degree of curing of the third curing is less than or equal to 6%.

[0155] In some specific implementations, the deviation between the relative degree of curing of the first curing and the relative degree of curing of the third curing is less than or equal to 6%.

[0156] By controlling the relative curing degree deviation between each layer to be less than or equal to 6%, external stress can be smoothly transmitted and dispersed, avoiding stress concentration in any layer, thereby maximizing the protection of the bare optical fiber and suppressing microbending loss. Simultaneously, each coating layer also serves to block moisture and chemical substances. Controlling the relative curing degree deviation to be less than or equal to 6% is beneficial for optimizing the mechanical integrity and interface stability of the optical fiber.

[0157] In some specific embodiments, the first coating has a thermal weight loss rate of less than or equal to 6% over 8 weeks at 85°C and less than or equal to 8% over 8 weeks at 125°C.

[0158] In some specific embodiments, the second coating has a thermal weight loss rate of less than or equal to 6% over 8 weeks at 85°C and less than or equal to 8% over 8 weeks at 125°C.

[0159] In some specific embodiments, the third coating has a thermal weight loss rate of less than or equal to 6% over 8 weeks at 85°C and less than or equal to 8% over 8 weeks at 125°C.

[0160] In some specific implementations, the heat treatment temperature is 40℃-60℃ and the heat treatment time is 24h-48h.

[0161] Specifically, the heat treatment includes: heat-treating the third intermediate in an oxygen-free environment at 40℃-60℃ for 24h-48h, and then cooling the third intermediate to room temperature in an oxygen-free environment to obtain low-temperature resistant optical fiber.

[0162] In some embodiments, the third intermediate may be pretreated by standing for 2 hours at 23°C and relative humidity less than or equal to 35%RH, and then heat-treated by raising the ambient temperature to 40°C-60°C at a heating rate of less than or equal to 1°C / min.

[0163] Since the coating material undergoes a slow reaction process after the optical fiber is taken out, this step helps the optical fiber to react further. Controlling the oxygen content can reduce the generation of oxygen-containing free radicals in the coating material. Oxygen-containing free radicals can damage the molecular carbon chain, affecting the reaction of the coating material and the strength of the optical fiber. After this step, the optical fiber provided by this application has the ability to use at -70℃ to -60℃ with an additional loss of less than or equal to 0.01dB / km.

[0164] The preparation method provided in this application reduces the additional loss of the optical fiber at ultra-low temperatures by sequentially coating the surface of the bare optical fiber with three layers and controlling the relative curing degree of the three layers.

[0165] The technical solution of this application will be further described below using specific embodiments.

[0166] Example 1

[0167] A low-temperature resistant optical fiber includes a core and a first coating, a second coating, and a third coating sequentially coated on the surface of the core from the inside out.

[0168] Its preparation methods include:

[0169] The optical fiber preform is melted at 2000℃ in an argon atmosphere with an oxygen content of less than or equal to 100 pm, and then drawn into fibers at a drawing speed of 2000 m / min to obtain bare optical fibers.

[0170] According to the mass fraction, 85 parts of acrylic resin, 10 parts of the first modifier polyisobutylene glycol, and 5 parts of the first organic solvent (toluene and ethyl acetate in a volume ratio of 1:2) were mixed evenly to prepare the first slurry. The temperature of the first slurry was controlled at 35°C. Then, the first slurry was coated onto the surface of the bare optical fiber at a coating pressure of 0.6 MPa under an argon atmosphere with an oxygen content of less than or equal to 100 pm. It was then cured by ultraviolet light, and the relative degree of curing was 90%, resulting in the first intermediate. At this point, the mass fraction of the first modifier in the first coating was 10.53%.

[0171] According to the mass ratio, 88 parts of acrylic resin, 9 parts of the second modifier polybutylene adipate, and 3 parts of the second organic solvent (toluene and ethyl acetate in a volume ratio of 1:1) were mixed evenly to prepare a second slurry. The temperature of the second slurry was controlled at 45°C. Then, the second slurry was coated onto the surface of the first intermediate at a coating pressure of 0.4 MPa under an argon atmosphere with an oxygen content of less than or equal to 100 pm. It was then cured by ultraviolet light, and the relative degree of curing was 92%, thus obtaining the second intermediate. At this point, the mass fraction of the second modifier in the formed second coating was 9.27%.

[0172] According to the mass ratio, 94 parts of acrylic resin, 3 parts of the third modifier polybutylene succinate, and 3 parts of the third organic solvent (toluene and ethyl acetate in a volume ratio of 1:2) were mixed evenly to prepare the third slurry. The temperature of the third slurry was controlled at 65°C. Then, the third slurry was coated onto the surface of the second intermediate at a coating pressure of 0.2 MPa under an argon atmosphere with an oxygen content of less than or equal to 100 pm. It was then cured by ultraviolet light, and the relative degree of curing was 92%, thus obtaining the third intermediate. At this point, the mass fraction of the third modifier in the formed third coating was 3.09%.

[0173] The third intermediate was first placed in an environment of 23℃ and 35%RH for 2 hours, and then the ambient temperature was raised to 40℃ at a heating rate of 1℃ / min for 48 hours to obtain low-temperature resistant optical fiber.

[0174] Example 2

[0175] A low-temperature resistant optical fiber has a structure that is basically the same as that of Example 1; its preparation method is basically the same as that of Example 1, except that in the first slurry, the mass fraction of acrylic resin is 79.9 parts and the mass fraction of the modifier polyisobutylene glycol is 14.1 parts. At this time, the mass fraction of the first modifier polyisobutylene glycol in the first coating is 15%.

[0176] Example 3

[0177] A low-temperature resistant optical fiber has a structure that is basically the same as that of Example 1; its preparation method is basically the same as that of Example 1, except that in the first slurry, the mass fraction of acrylic resin is 78.96 parts and the mass fraction of the first modifier polyisobutylene glycol is 15.04 parts. At this time, the mass fraction of the first modifier polyisobutylene glycol in the first coating is 16%.

[0178] Example 4

[0179] A low-temperature resistant optical fiber has a structure that is basically the same as that of Example 1; its preparation method is basically the same as that of Example 1, except that in the first slurry, the mass fraction of acrylic resin is 85.54 parts and the mass fraction of the first modifier polyisobutylene glycol is 8.46 parts. At this time, the mass fraction of the first modifier polyisobutylene glycol in the first coating is 9.00%.

[0180] Example 5

[0181] A low-temperature resistant optical fiber has a structure that is basically the same as that of Example 1; its preparation method is basically the same as that of Example 1, except that in the first slurry, the mass fraction of acrylic resin is 86.50 parts and the mass fraction of the first modifier polyisobutylene glycol is 7.50 parts. At this time, the mass fraction of the first modifier polyisobutylene glycol in the first coating is 7.98%.

[0182] Example 6

[0183] A low-temperature resistant optical fiber has a structure that is basically the same as that of Example 1; its preparation method is basically the same as that of Example 1, except that in the second slurry, the mass fraction of acrylic resin is 85.36 parts, the mass fraction of the second modifier poly(ethylene succinate) is 11.64 parts, and the mass fraction of the second modifier polyisobutylene glycol in the formed second coating is 12%.

[0184] Example 7

[0185] A low-temperature resistant optical fiber has a structure that is basically the same as that of Example 6; its preparation method is basically the same as that of Example 6, except that in the second slurry, the mass fraction of acrylic resin is 84.40 parts, the mass fraction of the second modifier poly(ethylene succinate) is 12.60 parts, and the mass fraction of the second modifier polyisobutylene glycol in the formed second coating is 12.99%.

[0186] Example 8

[0187] A low-temperature resistant optical fiber has a structure that is basically the same as that of Example 6; its preparation method is basically the same as that of Example 6, except that in the second slurry, the mass fraction of acrylic resin is 89.24 parts and the mass fraction of the second modifier poly(ethylene succinate) is 7.76 parts. At this time, the mass fraction of the second modifier poly(ethylene succinate) in the formed second coating is 8.00%.

[0188] Example 9

[0189] A low-temperature resistant optical fiber has a structure that is basically the same as that of Example 6; its preparation method is basically the same as that of Example 6, except that in the second slurry, the mass fraction of acrylic resin is 90.01 parts and the mass fraction of the second modifier poly(ethylene succinate) is 6.99 parts. At this time, the mass fraction of the second modifier poly(ethylene succinate) in the formed second coating is 7.21%.

[0190] Example 10

[0191] A low-temperature resistant optical fiber has a structure that is basically the same as that of Example 1; its preparation method is basically the same as that of Example 1, except that in the third slurry, the mass fraction of acrylic resin is 91.18 parts, the mass fraction of polyethylene as the third modifier is 5.82 parts, and the mass fraction of polybutylene succinate as the third modifier in the formed third coating is 6%.

[0192] Example 11

[0193] A low-temperature resistant optical fiber has a structure that is basically the same as that of Example 10; its preparation method is basically the same as that of Example 10, except that in the third slurry, the mass fraction of acrylic resin is 90.24 parts, the mass fraction of polyethylene as the third modifier is 6.76 parts, and at this time, the mass fraction of polybutylene succinate as the third modifier in the formed third coating is 6.97%.

[0194] Example 12

[0195] A low-temperature resistant optical fiber has a structure that is basically the same as that of Example 10; its preparation method is basically the same as that of Example 10, except that in the third slurry, the mass fraction of acrylic resin is 95.06 parts, the mass fraction of polyethylene as the third modifier is 1.94 parts, and the mass fraction of polybutylene succinate as the third modifier in the formed third coating is 2.00%.

[0196] Example 13

[0197] A low-temperature resistant optical fiber has a structure that is basically the same as that of Example 10; its preparation method is basically the same as that of Example 10, except that in the third slurry, the mass fraction of acrylic resin is 95.83 parts, the mass fraction of polyethylene as the third modifier is 1.17 parts, and the mass fraction of polybutylene succinate as the third modifier in the formed third coating is 1.21%.

[0198] Comparative Example 1

[0199] A low-temperature resistant optical fiber has a structure that is basically the same as that of Example 4; its preparation method is basically the same as that of Example 1, except that the mass fraction of acrylic resin in the first slurry is 94 parts, and the first modifier polyisobutylene glycol is not added.

[0200] Comparative Example 2

[0201] A low-temperature resistant optical fiber has a structure that is basically the same as that of Example 6; its preparation method is basically the same as that of Example 1, except that the mass fraction of acrylic resin in the second slurry is 97 parts, and no second modifier, polyethylene succinate, is added.

[0202] The physical properties of the low-temperature resistant optical fibers prepared in the examples and comparative examples are detailed in Tables 1-1, 1-2, and 1-3:

[0203] Table 1-1

[0204]

[0205] Table 1-2

[0206]

[0207] Table 1-3

[0208]

[0209] As shown in Tables 1-1, 1-2, and 1-3, the glass transition temperature, Young's modulus, elongation at break, and weight loss of the first, second, and third coatings in the optical fiber provided in this application exhibit a gradient change. However, in Comparative Example 1-2, when the first or second coating does not contain the first or second modifier, the glass transition temperature, Young's modulus, and weight loss of the first or second coating all decrease, while the elongation at break increases, resulting in a non-gradient change in the properties among the three coatings.

[0210] The following performance tests were performed on the low-temperature resistant optical fibers prepared in the examples and comparative examples:

[0211] (1) Additional loss at 1550nm: Performed according to GB / T15972.52 "Fiber Optic Test Methods Specification Part 52: Measurement Methods and Test Procedures for Environmental Performance - Temperature Cycling"; take a sample with a length of not less than 500m, and measure the initial attenuation value of 1550nm wavelength at the reference temperature (20℃±2℃). Place the fiber in a low temperature test chamber and keep it at -70℃±2℃ for 168h (7 days). During the test, the temperature deviation and stability meet the standard requirements. Immediately after the heat preservation stage, measure the attenuation value of 1550nm wavelength again at the test temperature. The difference between the attenuation value after the test and the value before the test is taken as the additional loss at 1550nm, in dB / km. Each sample is measured 3 times, and the arithmetic mean is taken. The uncertainty introduced by the measurement system is better than 0.02dB / km.

[0212] (2) Screening strength: Performed in accordance with GB / T15972.30 "Fiber Optic Test Methods Specification Part 30: Measurement Methods and Test Procedures for Mechanical Properties - Fiber Optic Screening Test". Take the finished fiber and apply a tensile stress of 150 kpsi to the screening device. The fiber should continuously withstand constant tension and not break when passing through the screening device.

[0213] The test results are detailed in Table 2:

[0214] Table 2

[0215]

[0216] As can be seen from the data in Table 2, the optical fiber provided in this application has an additional loss of less than 0.04 dB / km at 1550 nm.

[0217] When the glass transition temperature, Young's modulus, elongation at break, and weight loss of the first, second, or third coating do not exhibit a gradient change due to excessive or insufficient addition of various modifiers, the additional loss at 1550 nm of the resulting optical fiber will increase.

[0218] As can be seen from Comparative Examples 1-2, when the corresponding first modifier or second modifier is not added to the first coating or the second coating, the additional loss at 1550nm of the optical fiber further increases.

[0219] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A low-temperature resistant optical fiber, characterized in that, It includes a core and a first coating, a second coating, and a third coating that are sequentially coated on the surface of the core from the inside out; The glass transition temperature of the first coating is less than or equal to the glass transition temperature of the second coating; The glass transition temperature of the second coating is lower than that of the third coating.

2. The low-temperature resistant optical fiber according to claim 1, characterized in that, The glass transition temperature of the first coating is less than or equal to -50°C; And / or, the glass transition temperature of the second coating is -50°C to -40°C; And / or, the glass transition temperature of the third coating is greater than or equal to 60°C.

3. The low-temperature resistant optical fiber according to claim 1 or 2, characterized in that, The Young's modulus of the first coating is less than or equal to the Young's modulus of the second coating; The Young's modulus of the second coating is less than that of the third coating; And / or, the elongation at break of the first coating is greater than or equal to the elongation at break of the second coating; The elongation at break of the second coating is greater than that of the third coating.

4. The low-temperature resistant optical fiber according to claim 3, characterized in that, The Young's modulus of the first coating is 0.3 MPa-0.5 MPa; And / or, the Young's modulus of the second coating is 0.5 MPa-0.7 MPa; And / or, the Young's modulus of the third coating is greater than or equal to 800 MPa; And / or, the elongation at break of the first coating is greater than or equal to 180%; And / or, the elongation at break of the second coating is 150%-180%; And / or, the elongation at break of the third coating is 15%-50%; And / or, the refractive index of the first coating is 1.47-1.49; And / or, the refractive index of the second coating is 1.47-1.49; And / or, the refractive index of the third coating is 1.52-1.

54.

5. The low-temperature resistant optical fiber according to any one of claims 1-4, characterized in that, The first coating comprises a first acrylic resin and a first modifier, wherein the first modifier has a mass fraction of 10%-15% in the first coating, and the first modifier comprises at least one of polyisobutylene glycol, polybutylene adipate, polybutylene succinate, polyethylene succinate, aliphatic diisocyanate, aromatic diisocyanate, polyethylene, styrene, methacrylic acid, hydroxyl acrylate, and polycaprolactone. And / or, the second coating comprises a second acrylic resin and a second modifier, wherein the second modifier has a mass fraction of 8%-12% in the second coating, and the second modifier comprises at least one of polyisobutylene glycol, polybutylene adipate, polybutylene succinate, polyethylene succinate, aliphatic diisocyanate, aromatic diisocyanate, polyethylene, styrene, methacrylic acid, hydroxyl acrylate, and polycaprolactone; And / or, the third coating comprises a third acrylic resin and a third modifier, wherein the third modifier has a mass fraction of 2%-6% in the third coating, and the third modifier comprises at least one of polyisobutylene glycol, polybutylene adipate, polybutylene succinate, polyethylene succinate, aliphatic diisocyanate, aromatic diisocyanate, polyethylene, styrene, methacrylic acid, hydroxy acrylate, and polycaprolactone.

6. The low-temperature resistant optical fiber according to any one of claims 1-5, characterized in that, The diameter of the core is 124μm-126μm; And / or, the thickness of the first coating is 2μm-8μm; And / or, the thickness of the second coating is 20μm-35μm; And / or, the thickness of the third coating is 17.5μm-37.5μm.

7. A method for preparing a low-temperature resistant optical fiber according to any one of claims 1-6, characterized in that, include: Bare optical fibers are obtained by melting the optical fiber preform and drawing it in a first inert gas. Under a second inert gas, the bare optical fiber is first coated and cured with a first slurry to obtain a first intermediate. The first intermediate is subjected to a second coating and a second curing with a second slurry to obtain a second intermediate. The second intermediate is coated and cured with a third slurry to obtain a third intermediate; The third intermediate is subjected to heat treatment to obtain the low-temperature resistant optical fiber.

8. The preparation method according to claim 7, characterized in that, The melting temperature is 1700℃-2200℃; The wire drawing speed is greater than or equal to 2000 m / min; The flow rate of the first inert gas and / or the second inert gas is 10 L / min to 50 L / min; The first inert gas and / or the second inert gas includes at least one of argon and helium; The oxygen content of the first inert gas and / or the second inert gas is less than or equal to 100 ppm.

9. The preparation method according to claim 7, characterized in that, The first slurry comprises a first acrylic resin and a first modifier; The pressure of the first coating is 0.2 MPa-0.6 MPa, and the temperature of the first coating is 35℃-55℃; The relative degree of curing of the first curing is greater than or equal to 90%; And / or, the second slurry includes a second acrylic resin and a second modifier; The pressure of the second coating is 0.2 MPa-0.6 MPa, and the temperature of the second coating is 35℃-55℃; The relative degree of curing in the second curing stage is greater than or equal to 92%; And / or, the third slurry comprises a third acrylic resin and a third modifier; The pressure of the third coating is 0.2 MPa-0.6 MPa, and the temperature of the third coating is 35℃-55℃; The relative degree of curing of the third curing process is greater than or equal to 92%.

10. The method for preparing low-temperature resistant optical fiber according to claim 9, characterized in that, The deviation between the relative degree of cure of the first curing and the relative degree of cure of the second curing is less than or equal to 6%; And / or, the deviation between the relative degree of cure of the second curing and the relative degree of cure of the third curing is less than or equal to 6%; And / or, the deviation between the relative degree of cure of the first curing and the relative degree of cure of the third curing is less than or equal to 6%.

11. The method for preparing low-temperature resistant optical fiber according to claim 10, characterized in that, The heat treatment temperature is 40℃-60℃, and the heat treatment time is 24h-48h.

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