CN116879999A - Low-loss temperature-resistant optical fiber and preparation method thereof - Google Patents
Low-loss temperature-resistant optical fiber and preparation method thereof Download PDFInfo
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- CN116879999A CN116879999A CN202310767941.7A CN202310767941A CN116879999A CN 116879999 A CN116879999 A CN 116879999A CN 202310767941 A CN202310767941 A CN 202310767941A CN 116879999 A CN116879999 A CN 116879999A
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 157
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 239000011248 coating agent Substances 0.000 claims abstract description 183
- 238000000576 coating method Methods 0.000 claims abstract description 183
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 138
- 239000004642 Polyimide Substances 0.000 claims abstract description 100
- 229920001721 polyimide Polymers 0.000 claims abstract description 100
- 229920006259 thermoplastic polyimide Polymers 0.000 claims abstract description 93
- 229920001187 thermosetting polymer Polymers 0.000 claims abstract description 91
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 69
- 239000011159 matrix material Substances 0.000 claims abstract description 65
- 238000005253 cladding Methods 0.000 claims abstract description 57
- 239000002105 nanoparticle Substances 0.000 claims abstract description 46
- 239000000835 fiber Substances 0.000 claims abstract description 27
- 239000011247 coating layer Substances 0.000 claims description 21
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- 239000010410 layer Substances 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 18
- VXEGSRKPIUDPQT-UHFFFAOYSA-N 4-[4-(4-methoxyphenyl)piperazin-1-yl]aniline Chemical compound C1=CC(OC)=CC=C1N1CCN(C=2C=CC(N)=CC=2)CC1 VXEGSRKPIUDPQT-UHFFFAOYSA-N 0.000 claims description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 8
- 239000001301 oxygen Substances 0.000 claims description 8
- 229910052760 oxygen Inorganic materials 0.000 claims description 8
- 239000005049 silicon tetrachloride Substances 0.000 claims description 8
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 6
- 239000001257 hydrogen Substances 0.000 claims description 6
- 229910052739 hydrogen Inorganic materials 0.000 claims description 6
- 238000005245 sintering Methods 0.000 claims description 5
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- 230000000052 comparative effect Effects 0.000 description 13
- 229920005575 poly(amic acid) Polymers 0.000 description 11
- 239000000758 substrate Substances 0.000 description 11
- 238000010998 test method Methods 0.000 description 9
- ILAHWRKJUDSMFH-UHFFFAOYSA-N boron tribromide Chemical compound BrB(Br)Br ILAHWRKJUDSMFH-UHFFFAOYSA-N 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- 239000000203 mixture Substances 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
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- -1 tetracarboxylic dianhydride compound Chemical class 0.000 description 5
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- 229910004298 SiO 2 Inorganic materials 0.000 description 3
- GTDPSWPPOUPBNX-UHFFFAOYSA-N ac1mqpva Chemical compound CC12C(=O)OC(=O)C1(C)C1(C)C2(C)C(=O)OC1=O GTDPSWPPOUPBNX-UHFFFAOYSA-N 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 239000012159 carrier gas Substances 0.000 description 3
- 239000001307 helium Substances 0.000 description 3
- 229910052734 helium Inorganic materials 0.000 description 3
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 3
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- XHXFXVLFKHQFAL-UHFFFAOYSA-N phosphoryl trichloride Chemical compound ClP(Cl)(Cl)=O XHXFXVLFKHQFAL-UHFFFAOYSA-N 0.000 description 2
- 238000006068 polycondensation reaction Methods 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- WZCQRUWWHSTZEM-UHFFFAOYSA-N 1,3-phenylenediamine Chemical compound NC1=CC=CC(N)=C1 WZCQRUWWHSTZEM-UHFFFAOYSA-N 0.000 description 1
- CBCKQZAAMUWICA-UHFFFAOYSA-N 1,4-phenylenediamine Chemical compound NC1=CC=C(N)C=C1 CBCKQZAAMUWICA-UHFFFAOYSA-N 0.000 description 1
- VLDPXPPHXDGHEW-UHFFFAOYSA-N 1-chloro-2-dichlorophosphoryloxybenzene Chemical compound ClC1=CC=CC=C1OP(Cl)(Cl)=O VLDPXPPHXDGHEW-UHFFFAOYSA-N 0.000 description 1
- DKKYOQYISDAQER-UHFFFAOYSA-N 3-[3-(3-aminophenoxy)phenoxy]aniline Chemical compound NC1=CC=CC(OC=2C=C(OC=3C=C(N)C=CC=3)C=CC=2)=C1 DKKYOQYISDAQER-UHFFFAOYSA-N 0.000 description 1
- ZWQOXRDNGHWDBS-UHFFFAOYSA-N 4-(2-phenylphenoxy)aniline Chemical group C1=CC(N)=CC=C1OC1=CC=CC=C1C1=CC=CC=C1 ZWQOXRDNGHWDBS-UHFFFAOYSA-N 0.000 description 1
- LFBALUPVVFCEPA-UHFFFAOYSA-N 4-(3,4-dicarboxyphenyl)phthalic acid Chemical compound C1=C(C(O)=O)C(C(=O)O)=CC=C1C1=CC=C(C(O)=O)C(C(O)=O)=C1 LFBALUPVVFCEPA-UHFFFAOYSA-N 0.000 description 1
- NVKGJHAQGWCWDI-UHFFFAOYSA-N 4-[4-amino-2-(trifluoromethyl)phenyl]-3-(trifluoromethyl)aniline Chemical group FC(F)(F)C1=CC(N)=CC=C1C1=CC=C(N)C=C1C(F)(F)F NVKGJHAQGWCWDI-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
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- 238000002156 mixing Methods 0.000 description 1
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- 238000005491 wire drawing Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02033—Core or cladding made from organic material, e.g. polymeric material
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02395—Glass optical fibre with a protective coating, e.g. two layer polymer coating deposited directly on a silica cladding surface during fibre manufacture
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
Abstract
The application provides a low-loss temperature-resistant optical fiber and a preparation method thereof, wherein the low-loss temperature-resistant optical fiber comprises a fiber core (10), a cladding (20), a thermosetting polyimide coating (31) and a thermoplastic polyimide coating (32) which are sequentially arranged from inside to outside, the thermosetting polyimide coating doped with silica nanoparticles and the thermoplastic polyimide coating are combined to form the optical fiber coating, the thermoplastic polyimide coating is positioned on the outermost layer of the optical fiber coating, and the thermal shrinkage of the thermosetting polyimide and the thermoplastic polyimide is prevented from generating bubble to cause coating defects based on the interaction of the silica nanoparticles with the thermosetting polyimide matrix and the thermoplastic polyimide matrix, so that the bending performance of the optical fiber can be effectively improved, and the service life of the optical fiber can be further effectively prolonged.
Description
Technical Field
The application relates to the technical field of optical fibers, in particular to a low-loss temperature-resistant optical fiber and a preparation method thereof.
Background
The optical fiber can be used as a distributed temperature sensor, and is suitable for temperature monitoring of long-distance large-range scenes. Due to the elasto-optic effect and the thermo-optic effect of the material, when the ambient temperature changes, the refractive index of the optical fiber material changes, the Phase difference of the optical pulses also changes, and the Phase change information is analyzed by a Phase-OTDR distributed optical fiber vibration demodulator to realize temperature sensing.
Optical fibers are generally composed of a core, a cladding and a coating material, wherein the coating material is used for ensuring that various performance indexes of the optical fiber can meet the use requirements. The general coating material is an acrylic resin material, and the optical fiber can be stably used at 60-85 ℃ after the acrylic resin coating is coated, but when the temperature is continuously increased, the molecular structure of the coating material is damaged, so that the optical fiber cannot be normally used. Polyimide has the advantage of high temperature resistance compared with acrylic resin and is often used as an optical fiber coating. However, on one hand, polyimide material has higher Young's modulus, and optical fiber adopting the material as a coating is hard, has insufficient flexibility, and is not easy to control the transmission loss of the optical fiber; on the other hand, polyimide solution as a coating layer is subjected to polycondensation reaction in the curing process, so that the surface of the bare optical fiber is easy to shrink and foam, and the formed optical fiber coating layer is uneven in thickness or defective, so that the service life of the optical fiber is shortened.
In view of this, it is highly desirable for those skilled in the art to develop a temperature resistant optical fiber having good toughness and uniform coating thickness.
Disclosure of Invention
The application mainly aims to provide a low-loss temperature-resistant optical fiber, which solves the problems that the optical fiber taking polyimide as a coating in the prior art is insufficient in flexibility and the thickness of the optical fiber coating is uneven or defects are generated due to polyimide thermal shrinkage.
In order to achieve the above object, according to one aspect of the present application, there is provided a low-loss temperature-resistant optical fiber including a core, a cladding, a thermosetting polyimide coating layer and a thermoplastic polyimide coating layer disposed in this order from the inside to the outside, the thermosetting polyimide coating layer including a thermosetting polyimide matrix and silica nanoparticles dispersed in the thermosetting polyimide matrix, the thermoplastic polyimide coating layer including a thermoplastic polyimide matrix and silica nanoparticles dispersed in the thermoplastic polyimide matrix.
Further, the thermosetting polyimide coating has Young's modulus of 3-8 GPa and thermal expansion coefficient of 2-4 x 10 -5 a/DEG C; the Young's modulus of the thermoplastic polyimide coating is 0.5-2 GPa, and the thermal expansion coefficient is 4.5-5.5X10 -5 /℃。
Further, the mass fraction of the silica nano particles in the thermosetting polyimide coating is 1-5%; and/or the mass fraction of the silica nano particles in the thermoplastic polyimide coating is 1-5%.
Further, the cladding comprises a silica matrix and an inorganic oxide doped in the silica matrix, the inorganic oxide having a thermal expansion coefficient of 1 to 5×10 -5 /℃。
Further, the thermal expansion coefficient of the inorganic oxide is 1.5 to 1.6X10 -5 /℃。
Further, the inorganic oxide includes B 2 O 3 Or P 2 O 5 At least one of them.
Further, the molar concentration of the inorganic oxide in the silica matrix of the cladding layer is 2 to 5mol%.
Further, the thickness of the thermosetting polyimide coating is 10-15 mu m; the thickness of the thermoplastic polyimide coating is 2.5-5 mu m; the diameter of the fiber core is 5-70 mu m; the thickness of the cladding layer is 30-220 μm.
In order to achieve the above object, according to one aspect of the present application, there is provided a method for manufacturing a low-loss temperature-resistant optical fiber comprising the steps of: step S1: providing a fiber core, depositing SiO on the fiber core 2 And forming a cladding layer coated on the surface of the fiber core by using an optional inorganic oxide, and sintering to obtain an optical fiber preform; step S2: drawing the preform rod to obtain a bare optical fiber; step S3: sequentially coating a thermosetting polyimide coating and a thermoplastic polyimide coating on the surface of the bare optical fiber to obtain a low-loss temperature-resistant optical fiber; wherein the core, cladding, inorganic oxide, thermoset polyimide coating and thermoplastic polyimide coating each have the same meaning as described above.
Further, in step S1, the method for preparing the cladding layer includes: silicon tetrachloride, oxygen, hydrogen and optionally inorganic compounds are mixed and reacted to form the cladding.
Further, in step S3, the preparation process of the thermosetting polyimide coating and the thermoplastic polyimide coating each independently includes coating and curing, and the coating temperature is 35 to 50 ℃ respectively.
Further, the curing light source comprises a long-wave infrared light source and a medium-short-wave infrared light source, the wavelength of the long-wave infrared light source is 3.0-5.0 mu m, and the wavelength of the medium-short-wave infrared light source is 0.8-2.5 mu m.
By applying the technical scheme provided by the application, the low-loss temperature-resistant optical fiber is used as the optical fiber coating in a mode of combining the thermosetting polyimide coating doped with the silica nanoparticles and the thermoplastic polyimide coating, and the thermoplastic polyimide coating is positioned on the outermost layer of the optical fiber coating, so that the coating defect caused by bubbles generated by thermal contraction of the thermosetting polyimide and the thermoplastic polyimide can be prevented, the bending performance of the optical fiber can be effectively improved, and the service life of the optical fiber can be further effectively prolonged based on the interaction of the silica nanoparticles with the thermosetting polyimide matrix and the thermoplastic polyimide matrix and the good toughness of the thermoplastic polyimide.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:
FIG. 1 is a schematic diagram showing a cross-sectional structure of a low-loss temperature-resistant optical fiber according to an embodiment of the present application;
FIG. 2 is a schematic flow chart of the low-loss temperature-resistant optical fiber manufacturing in one embodiment of the application.
Wherein the above figures include the following reference numerals:
10. a fiber core; 20. a cladding layer; 31. a thermosetting polyimide coating; 32. a thermoplastic polyimide coating; 100. a wire drawing furnace; 210. bare optical fiber; 220. a low-loss temperature-resistant optical fiber; 301. a first applicator; 302. a second applicator; 401. a first long wavelength infrared light source; 403. a second long wavelength infrared light source; 402. a first mid-to-short wavelength infrared light source; 404. a second mid-to-short wavelength infrared light source; 501. a first optical fiber outer diameter monitor; 502. a second optical fiber outer diameter monitor; 503. a third optical fiber outer diameter monitor; 504. a fourth optical fiber outer diameter monitor; 600. an optical fiber preform; 700. a positioning wheel; 800. traction wheels.
Detailed Description
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.
As analyzed by the background technology of the application, because the polyimide material is adopted in the optical fiber coating in the prior art, the polyimide material has higher Young modulus, so that the optical fiber adopting the polyimide material as the coating is harder, has insufficient flexibility, is not easy to control the transmission loss of the optical fiber, and in addition, the polyimide material has higher solution content, and is used as the coating to generate polycondensation reaction in the curing process to cause shrinkage bubbles of the coating, so that the formed optical fiber coating has uneven thickness or defects. In order to solve the problem, the application provides a low-loss temperature-resistant optical fiber and a preparation method thereof.
In one exemplary embodiment of the present application, there is provided a low-loss, temperature-resistant optical fiber, as shown in fig. 1, comprising a core 10, a cladding 20, a thermosetting polyimide coating 31 and a thermoplastic polyimide coating 32, which are sequentially disposed from inside to outside, wherein the thermosetting polyimide coating 31 comprises a thermosetting polyimide matrix and silica nanoparticles dispersed in the thermosetting polyimide matrix, and the thermoplastic polyimide coating 32 comprises a thermoplastic polyimide matrix and silica nanoparticles dispersed in the thermoplastic polyimide matrix.
By applying the technical scheme of the application, the low-loss temperature-resistant optical fiber provided by the application adopts the mode of combining the thermosetting polyimide coating 31 doped with the silica nanoparticles and the thermoplastic polyimide coating 32 as the optical fiber coating, and the thermoplastic polyimide coating 32 is positioned at the outermost layer of the optical fiber coating, so that the coating defect caused by bubbles generated by thermal contraction of the thermosetting polyimide and the thermoplastic polyimide can be prevented, the bending performance of the optical fiber can be effectively improved, and the service life of the optical fiber can be further effectively prolonged based on the interaction of the silica nanoparticles with the thermosetting polyimide matrix and the thermoplastic polyimide matrix and the good toughness of the thermoplastic polyimide.
In the application, the silica nanoparticles are respectively dispersed in the thermosetting polyimide matrix and the thermoplastic polyimide matrix, and as the silica nanoparticles can be closely piled and overlapped on the surfaces of the thermosetting polyimide matrix and the thermoplastic polyimide matrix to form a rigid supporting effect, the thermal shrinkage of the thermosetting polyimide matrix and the thermoplastic polyimide matrix is prevented, in addition, the silica nanoparticles are dispersed in the matrix, and the silica nanoparticles have higher bond energy based on the silica bonds in the silica nanoparticles, so that the adhesion of the interface of the thermosetting polyimide matrix and the thermoplastic polyimide matrix can be enhanced, and the thermal stability is improved.
In the present application, the above-mentioned raw material for forming the thermosetting polyimide matrix is a first polyamic acid selected from the group consisting of tetracarboxylic dianhydrides and diamines, wherein the tetracarboxylic dianhydride compound includes one or more of pyromellitic dianhydride, 3',4' -benzophenone tetracarboxylic dianhydride, 4'- (hexafluoroisopropylidene) phthalic anhydride, and the diamine compound includes one or more of p-phenylenediamine, m-phenylenediamine, 4' -diaminodiphenyl ether, 1, 3-bis (3-aminophenoxy) benzene, preferably has a number average molecular weight of 3000 to 5000 and a viscosity of 8000 to 15000mpa.s. The raw material for forming the thermoplastic polyimide matrix is second polyamic acid, wherein the second polyamic acid is selected from compounds consisting of tetracarboxylic dianhydrides and diamines, and the tetracarboxylic dianhydride compounds are one or more of 3,3',4' -diphenyl ether tetracarboxylic dianhydride, 2, 3',4' -biphenyl tetracarboxylic dianhydride and 3,4,3',4' -biphenyl tetracarboxylic dianhydride; the diamine compound is one or more of 2,2' -bis (trifluoromethyl) -4,4' -diaminobiphenyl, 4' -bis (4-aminophenoxy) biphenyl and amino modified polysiloxane, and preferably has a number average molecular weight of 1000-2600 and a viscosity of 5000-8000Pa.s. The second polyamic acid forming the thermoplastic polyimide substrate is different from the first polyamic acid forming the thermosetting polyimide substrate, and is a linear polymer, and the thermoplastic polyimide substrate is different from the thermosetting polyimide substrate in the processing process, so that the thermoplastic polyimide substrate has good toughness, and can be used as a coating of an optical fiber, and the bending performance and the optical performance of the optical fiber can be effectively improved.
For improving the bending property of the optical fiber, it is preferable that the thermosetting polyimide coating 31 has a Young's modulus of, for example, 3GPa, 4GPa, 5GPa, 6GPa, 7GPa, 8GPa or a range of any two values of composition, and a coefficient of thermal expansion of, for example, 2X 10 -5 /℃、2.5×10 -5 /℃、3×10 -5 /℃、3.5×10 -5 /℃、4×10 -5 A range value consisting of/DEG C or any two values; the thermoplastic polyimide coating 32 has a Young's modulus of, for example, 0.5GPa, 1GPa, 1.5GPa, 2GPa or any two values ranging in composition and a coefficient of thermal expansion of 4.5X10 -5 /℃、5×10 -5 /℃、5.5×10 -5 A range of values consisting of/DEG C or any two values.
The young's modulus value of the coating has an important influence on the performance of the optical fiber, the young's modulus value of the coating is too small to play a role in protecting the bare optical fiber 210, the young's modulus value of the coating is too large, the obtained optical fiber is hard, the flexibility is insufficient, the transmission loss of the optical fiber is not easy to control, and when the thermosetting polyimide coating 31 and the thermoplastic polyimide coating 32 with young's modulus values in the above range are adopted, the obtained optical fiber has better bending performance. In addition, the thermal expansion coefficient represents the relative elongation or volume change of the material caused by unit temperature change, and the thermal expansion coefficient is in the range, so that the deformation performance of the optical fiber along with the temperature can be effectively improved.
In order to further improve the performance of the optical fiber, it is preferable that the mass fraction of the silica nanoparticles in the thermosetting polyimide coating 31 is 1 to 5% (e.g., 1%, 2%, 3%, 4%, 5%), the mass fraction of the silica nanoparticles in the thermoplastic polyimide coating 32 is 1 to 5% (e.g., 1%, 2%, 3%, 4%, 5%), the silica nanoparticles are too small to be doped in the thermosetting polyimide coating 31 and the thermoplastic polyimide coating 32, and do not play a role in preventing the coating from heat shrinkage to avoid the formation of bubbles, and the too large mass fraction of the doping adversely affects the properties possessed by the coating itself, thereby affecting the performance of the resulting optical fiber, and in the above range, the silica nanoparticles can play a favorable role in preventing the heat shrinkage of the coating and improving the thermal stability of the coating, thereby further improving the performance of the optical fiber.
In some embodiments, to increase the strain capacity of the cladding 20, it is preferable that the cladding 20 includes a silica matrix and an inorganic oxide doped in the silica matrix, preferably the inorganic oxide has a coefficient of thermal expansion of 1 to 5×10 -5 Preferably 1.5 to 1.6X10 g/DEG C -5 At a temperature of about/DEG C, the inorganic oxide includes, but is not limited to, B 2 O 3 Or P 2 O 5 At least one of them. By doping B in the silica matrix of the cladding 20 2 O 3 And/or P 2 O 5 SiO can be increased 2 The coefficient of thermal expansion of the material causes the fiber to increase the strain capacity of the cladding 20 under temperature changes and further acts on the fiberOn the core 10, to further increase the strain capacity of the cladding 20 by changing the relative magnitude of the refractive index of the core 10, it is preferable to dope B in the silica matrix of the cladding 20 2 O 3 And P 2 O 5 And B is 2 O 3 And P 2 O 5 The molar mass ratio of (2) is 1.5:1-3:1.
The molar concentration of the inorganic oxide in the silica matrix in the cladding 20 is 1 to 8mol% (1 mol%, 3mol%, 5mol%, 7mol%, 8 mol%), and more preferably 2 to 5mol%, and the molar concentration of the inorganic oxide in the silica matrix in the cladding 20 is too low to improve SiO 2 The thermal expansion coefficient of the material has the advantages of small strain quantity of the cladding 20, insensitivity to temperature and excessively high doping quantity of inorganic oxide, thus being not only beneficial to SiO 2 The material itself has excellent properties such as high light transmittance and refractive index, and the thermal expansion coefficient is too high, resulting in SiO 2 The thermal stability of the material is poor. Accordingly, the molar concentration of the inorganic oxide in the silica matrix in the cladding 20 is within the above range, and the strain capacity of the cladding 20 can be improved, thereby improving the sensitivity of the fiber to temperature sensing.
In the present application, the core 10 is made of silica glass as a main material, and the core 10 is a double concentric cylinder having a diameter of 5 to 70 μm, wherein the diameter of a single mode fiber core is 5 to 10 μm (e.g., 5 μm, 9 μm, 10 μm), and the diameter of a multimode fiber core is 30 to 62.5 μm (e.g., 50 μm, 62.5 μm). The cladding 20 is provided on the outer layer of the core 10, and the cladding 20 has a thickness of 30 to 220 μm, which has a lower refractive index than the core 10, to avoid loss of light during propagation.
In some embodiments, to enhance the performance of the optical fiber, it is preferable that the thickness of the thermosetting polyimide coating layer 31 is 5 to 20 μm, more preferably 10 to 15 μm, and it is preferable that the thickness of the thermoplastic polyimide coating layer 32 is 1 to 8 μm, more preferably 2.5 to 5 μm, and to ensure that the thicknesses of the thermosetting polyimide coating layer 31 and the thermoplastic polyimide coating layer 32 are within the above-mentioned ranges, the thermosetting polyimide coating layer 31 and the thermoplastic polyimide coating layer 32 each include at least 1 layer. In the thickness range of the coating, the obtained optical fiber can realize continuous screening of 100KPsi strain intensity, the tensile strength of the optical fiber is more than 4.5GPa, the requirement of high temperature resistance of the optical fiber is met, the optical fiber can resist the temperature of 300 ℃, and the change of the tensile strength after 100 hours is not more than 10 percent at the temperature of 300 ℃.
In another exemplary embodiment of the present application, there is also provided a method for preparing a low-loss temperature-resistant optical fiber, including the steps of: step S1: providing a core 10, depositing SiO on the core 10 2 And optionally an inorganic oxide to form a cladding 20 coating the surface of the core 10, and sintering to obtain an optical fiber preform 600; step S2: drawing the preform 600 to obtain a bare optical fiber 210; step S3: the surface of the bare optical fiber 210 is coated with a thermosetting polyimide coating 31 and a thermoplastic polyimide coating 32 in order, thereby obtaining a low-loss temperature-resistant optical fiber.
In some embodiments, the low-loss temperature-resistant optical fiber preparation process sequentially comprises the following steps according to the flow shown in fig. 2: providing an optical fiber preform 600, drawing the optical fiber preform 600 by a drawing furnace 100 to obtain a bare optical fiber 210, testing the diameter of the bare optical fiber 210 by a bare fiber diameter meter 510, coating the bare optical fiber 210 with a mixture of a first polyamic acid capable of forming a matrix of thermosetting polyimide and silica nanoparticles by a first coater 301 to form a first coating to be cured, which is coated outside a cladding 20, and then sequentially carrying out long-wave infrared radiation curing and medium-wave infrared radiation curing on the first coating to be cured by a first long-wave infrared light source 401, a first optical fiber outer diameter monitor 501, a first medium-short-wave infrared light source 402 and a second optical fiber outer diameter monitor 502 to enable the first coating to be cured to form a thermosetting polyimide coating 31, monitoring the diameter of the optical fiber after each curing in the curing process, and obtaining the optical fiber coated with the thermosetting polyimide coating 31 after the curing is finished. Then, the optical fiber coated with the thermosetting polyimide coating 31 is coated with a mixture of a second polyamic acid capable of forming a thermoplastic polyimide matrix and silica nanoparticles by a second coater 302 to form a second coating to be cured, which is coated outside the thermosetting polyimide coating 31, and then the second coating to be cured is sequentially cured by long-wave infrared radiation and medium-wave infrared radiation by a second long-wave infrared light source 403, a third optical fiber outer diameter monitor 503, a second medium-short-wave infrared light source 404 and a fourth optical fiber outer diameter monitor 504, and the diameter of the optical fiber after each curing is monitored, so that the low-loss temperature-resistant optical fiber 220 is obtained after the curing is completed, and the optical fiber is wound into a disc by a positioning wheel 700 and a traction wheel 800.
In some embodiments, in the step S1, the method for preparing the cladding 20 includes: the cladding 20 is formed by mixing silicon tetrachloride, oxygen, hydrogen and optionally inorganic compound, preferably boron tribromide and/or phosphorus oxychloride, so that the optional inorganic compound is fully reacted with silicon tetrachloride, oxygen and hydrogen mixed gas. The cladding 20 and the core 10 are sintered together to form the optical fiber preform 600, and the bulk material of the preform 600 is silica.
In some embodiments, in the step S2, the optical fiber preform 600 is placed in the optical fiber drawing furnace 100, the optical fiber drawing furnace 100 is one of an induction drawing furnace and a graphite drawing furnace, the temperature of the optical fiber drawing furnace 100 is raised to 1800-2200 ℃, the optical fiber preform 600 is placed in the drawing furnace 100 to be melted, the melted environment is filled with a protective gas, preferably an inert gas, and the gas is one or two of argon gas and helium gas, the flow rate of the gas mixture is 10-50L/min, the oxygen content is less than or equal to 100ppm in the protective gas environment, the optical fiber drawing speed is greater than or equal to 50m/min, the optical fiber preform 600 is passed through the optical fiber drawing furnace 100 to obtain a bare optical fiber 210 with a smaller diameter, and then the prepared bare optical fiber 210 is monitored by the bare fiber diameter meter 510, and the diameter deviation of the cladding 20 is controlled within ±1μm.
In the present application, in order to further improve the accuracy of the diameter of the cladding 20, the deviation of the diameter of the cladding 20 is controlled by adjusting the furnace temperature, and the temperature adjustment range per minute is Δt=tx|r 0 -R 1 | a Wherein R is 0 For the target cladding 20 diameter, R 1 Is the actual cladding 20 diameter. Tx is an adjustment reference value, and is generally 1-10 ℃. Adjusting coefficient alpha and speed deviationThe difference is related, the value is generally 1-5, and when the deviation DeltaV of the actual speed and the target speed is within plus or minus 0.5m/min, the Tx value is 3-5; tx takes a value of 1-3 when the deviation DeltaV between the actual speed and the target speed is positive and negative 0.5-1 m/min. The actual cladding 20 diameter is greater than the target cladding 20 diameter value, the temperature is adjusted to decrease, and the temperature is adjusted to increase when the actual cladding 20 diameter is less than the target cladding 20 diameter.
In the present application, in the above step S3, the preparation process of the thermosetting polyimide coating 31 and the thermoplastic polyimide coating 32 each independently includes coating and curing, wherein the above preparation process of the thermosetting polyimide coating 31 includes: the bare optical fiber 210 is coated with a mixture of first polyamic acid and silica nanoparticles capable of forming a thermosetting polyimide matrix material through a first coater 301 to form a first coating to be cured, and then sequentially passes through a first long-wavelength infrared light source 401, a first optical fiber outer diameter monitor 501, a first medium-short wavelength infrared light source 402 and a second optical fiber outer diameter monitor 502, and the first coating to be cured sequentially undergoes long-wave infrared radiation curing and medium-short wave infrared radiation curing to obtain an optical fiber coated with the thermosetting polyimide coating 31; the thermoplastic polyimide coating 32 described above is prepared by the process comprising: the optical fiber wrapped with the thermosetting polyimide coating 31 is coated with a mixture of second polyamic acid and silica nanoparticles capable of forming a thermoplastic polyimide matrix by a second coater 302 to form a second coating to be cured, and then the second coating to be cured is sequentially cured by long-wave infrared radiation and medium-wave infrared radiation by a second long-wavelength infrared light source 403, a third optical fiber outer diameter monitor 503, a second medium-short-wavelength infrared light source 404 and a fourth optical fiber outer diameter monitor 504, so as to obtain the low-loss temperature-resistant optical fiber 220.
In some embodiments, in order to further improve the coating effect, it is preferable that the coating pressure is 0.05-0.2 MPa, and the coating temperature is 35-50 ℃ respectively, wherein, the coating temperature is too high, which can cause the thermosetting polyimide matrix material and the thermoplastic polyimide matrix material to generate gel, causing abnormal coating, and the coating temperature is too low, which can not effectively reduce the viscosity of the thermosetting polyimide matrix material and the thermoplastic polyimide matrix material, causing uneven coating, so that the coating temperature is controlled within the above range, and the obtained coating meets the requirements.
The cured light source comprises a first long wavelength infrared light source 401, a second long wavelength infrared light source 403, a first middle and short wavelength infrared light source 402 and a second middle and short wavelength infrared light source 404, wherein the wavelengths of the first long wavelength infrared light source 401 and the second long wavelength infrared light source 403 are 3.0-5.0 mu m, the wavelengths of the first middle and short wavelength infrared light source 402 and the second middle and short wavelength infrared light source 404 are 0.8-2.5 mu m, the temperature of the first long wavelength infrared light source 401 is controlled to be 80-150 ℃, the temperature of the first middle and short wavelength infrared light source 402 is controlled to be 150-350 ℃, the temperature of the second middle and short wavelength infrared light source 403 is controlled to be 80-120 ℃, and the temperature of the second middle and short wavelength infrared light source 404 is controlled to be 120-300 ℃.
In order to improve the performance of the coating and avoid coating defects, the application adopts the long-wave infrared radiation curing firstly and then the medium-short-wave infrared radiation curing, compared with the traditional resistance heating curing mode, the heat is transferred from the outer layer to the inner layer, the inner layer solvent can not volatilize in time, after the outer layer is cured to form a film, bubbles can be generated by volatilizing the inner solvent again to cause the film to crack, and the strength weak point is formed.
In some embodiments, the first coating to be cured, after being cured by the first long wavelength infrared light source 401, has a coating thickness that does not drop more than 60% from the initial coating thickness, after being cured by the first medium and short wavelength infrared light source 402, has a coating thickness that does not drop more than 75% from the initial coating thickness, the second coating to be cured, after being cured by the second long wavelength infrared light source 403, has a coating thickness that does not drop more than 60% from the initial coating thickness, and after being cured by the second medium and short wavelength infrared light source 404, has a coating thickness that does not drop more than 75% from the initial coating thickness, thereby reducing defects caused by shrinkage of the coating during thermal curing.
In the application, the optical fiber is prepared by adopting the positioning wheel 700 and the traction wheel 800 according to a certain traction speed under the control of a traction speed reducer, the speed reducer speed reduction ratio is not less than 100, the speed adjustment precision is not more than 0.05m/min, and the traction speed is 5-30 m/min. The drawing speed is too slow, so that the efficiency of optical fiber preparation is reduced due to overlong curing time, the drawing speed is too fast, the curing is not finished, the performance of the coating is poor, the quality of the optical fiber is affected, and the curing effect of the coating can be effectively improved in the range.
In addition, the diameter of the optical fiber cladding 20 is related to the drawing speed, the rod feeding speed, and the preform 600 diameter, and the relationship between the rod feeding speed and the drawing speed is that in order to control the diameter deviation of the cladding 20 within + -1 μm while keeping the drawing speed fluctuation within a small rangeWherein, the diameter of the preform 600 is Dp, the diameter of the target cladding 20 is Dc, the pulling speed is Vc, and the reference speed of rod feeding is Vp.
The beneficial effects of the present application will be further described below with reference to examples and comparative examples:
example 1
The embodiment provides a low-loss temperature-resistant optical fiber, which comprises a fiber core 10, a cladding 20, a thermosetting polyimide coating 31 and a thermoplastic polyimide coating 32, wherein the fiber core 10 is a single-mode fiber core with the diameter of 9 mu m, the thickness of the cladding 20 is 58 mu m, and B is dispersed in a silicon dioxide matrix of the cladding 20 2 O 3 (B 2 O 3 The thickness of the thermosetting polyimide coating 31 was 10. Mu.m, and the thickness of the thermosetting polyimide coating 31 (Young's modulus was 3.2GPa, thermal expansion coefficient was 3.5X10) -5 Per c) comprises a thermoset polyimide matrix and silica nanoparticles dispersed in the thermoset polyimide matrix (silica nanoparticles are 2% by mass in the thermoset polyimide coating) and a thermoplastic polyimide coating 32The thermoplastic polyimide coating 32 (Young's modulus of 1.5GPa, thermal expansion coefficient of 5X 10) -5 Per c) comprises a thermoplastic polyimide matrix and silica nanoparticles dispersed in the thermoplastic polyimide matrix (the mass fraction of silica nanoparticles in the thermoplastic polyimide coating is 2%).
The low-loss temperature-resistant optical fiber is prepared by the following steps:
(1) Providing a fiber core 10, placing the fiber core 10 in an OVD device, adding a mixed gas of silicon tetrachloride, oxygen and hydrogen in the OVD device to deposit silicon dioxide on the fiber core, loading boron tribromide into the OVD device through carrier gas to form a cladding 20 on the surface of the fiber core 10, and sintering to obtain the optical fiber preform 600.
The carrier gas is inert gas, the gas is one of argon and helium, the molar mass of silicon tetrachloride is 169.9g/mol, the molar ratio of boron tribromide to silicon tetrachloride is 2.1%, the flow of the mixed gas of silicon tetrachloride and boron tribromide is 60g/min, the flow of oxygen is 30L/min, the flow of hydrogen is 60L/min, the inlet amount of the carrier gas is 20L/min, the deposition time is 1200min, and the sintering temperature is 1450 ℃. B in the cladding layer 20 2 O 3 The molar concentration in the silica matrix was 3.5mol%.
(2) The optical fiber preform 600 is placed in a drawing furnace 100, the drawing speed is 20m/min, the temperature of the drawing furnace 100 is increased to 1800-2200 ℃, the preform 600 is placed in the drawing furnace 100 for melting, the melting environment is filled with a protective gas, the protective gas is preferably inert gas, the gas is one or two of argon and helium, the flow of the mixed gas is 10-50L/min, and the oxygen content is less than or equal to 100ppm in the protective gas environment, so that the bare optical fiber 210 is prepared.
(3) The thermosetting polyimide substrate doped with silica nanoparticles is polyamic acid (with the number average molecular weight of 4000 and the viscosity of 10000 mpa.s), and is coated by a first coater 301 at the temperature of 40 ℃, the traction speed is 20m/min, the coating pressure is 0.08MPa, after the coating is finished, the thermosetting polyimide substrate is coated by a first long-wavelength infrared light source 401 with the wavelength of 3.0-5.0 mu m, the light source temperature is 80-150 ℃ and the curing time is 0.05min, and then by a first middle-short-wavelength infrared light source 402 with the wavelength of 0.8-2.5 mu m, the light source temperature is 150-350 ℃ and the curing time is 0.05min. A thermosetting polyimide coating 31 was formed on the surface of the bare fiber 210, and the thermosetting polyimide coating 31 had a thickness of 10 μm.
(4) The thermoplastic polyimide substrate doped with silica nanoparticles is polyamic acid (number average molecular weight 2000, viscosity 6000 mpa.s), which is coated by a second coater 302 at a temperature of 40 ℃, the traction speed is 20m/min, the coating pressure is 0.06MPa, after the coating is finished, the thermoplastic polyimide substrate is passed through a second long-wavelength infrared light source 403, the wavelength of which is 0.8-2.5 μm, the light source temperature is 80-120 ℃, the curing time is 0.05min, and then is passed through a second medium-short-wavelength infrared light source 404, the wavelength of which is 0.8-2.5 μm, the light source temperature is 120-300 ℃, and the curing time is 0.05min. A thermoplastic polyimide coating 32 was formed on the surface of the thermosetting polyimide coating 31 formed on the surface of the bare optical fiber 210, and the thickness of the thermoplastic polyimide coating 32 was 5 μm, to obtain a low-loss temperature-resistant optical fiber 220.
Example 2
This embodiment differs from embodiment 1 in that the core 10 is a multimode core having a diameter of 50 μm and a thickness of 37.5 μm of the cladding 20, and P is dispersed in the silica matrix of the cladding 20 2 O 5 (P 2 O 5 The molar concentration of the silica matrix was 3.6 mol%), the thickness of the thermosetting polyimide coating 31 was 12. Mu.m, and the thickness of the thermosetting polyimide coating 31 (Young's modulus was 3.0GPa, and the coefficient of thermal expansion was 3.5X10) -5 Each of which was/deg.c) comprising a thermosetting polyimide substrate and silica nanoparticles dispersed in the thermosetting polyimide substrate (the mass fraction of the silica nanoparticles in the thermosetting polyimide coating layer was 2.3%), the thickness of the thermoplastic polyimide coating layer 32 was 2.5 μm, and the thickness of the thermoplastic polyimide coating layer 32 (Young's modulus was 1.2GPa, thermal expansion coefficient was 5×10) -5 Per c) comprises a thermoplastic polyimide matrix and silica nanoparticles dispersed in the thermoplastic polyimide matrix (the mass fraction of silica nanoparticles in the thermoplastic polyimide coating is 2.3%).
Example 3
The present embodiment is different from embodiment 1 in that the thermosetting polyimide coating 31 has a young's modulus of 8GPa.
Example 4
This example differs from example 1 in that the Young's modulus of the thermoplastic polyimide coating 32 is 0.5GPa.
Example 5
This example differs from example 1 in that the Young's modulus of the thermoplastic polyimide coating 32 is 2GPa.
Example 6
This example is different from example 1 in that the mass fraction of silica nanoparticles in the thermosetting polyimide coating 31 and the thermoplastic polyimide coating 32, respectively, is 1%.
Example 7
This example is different from example 1 in that the mass fraction of silica nanoparticles in the thermosetting polyimide coating 31 and the thermoplastic polyimide coating 32, respectively, is 5%.
Example 8
This embodiment differs from embodiment 1 in that B 2 O 3 The molar concentration in the silica matrix was 2mol%.
Example 9
This embodiment differs from embodiment 1 in that B 2 O 3 The molar concentration in the silica matrix was 5mol%.
Example 10
The present embodiment is different from the embodiments in that B 2 O 3 The molar concentration in the silica matrix was 10mol%.
Example 11
This embodiment differs from embodiment 1 in that the cladding layer 20 is not doped with an inorganic oxide.
Example 12
This example is different from example 1 in that the sum of the thickness of the thermosetting polyimide coating 31 and the thickness of the thermoplastic polyimide coating 32 is 15 μm, wherein the thickness of the thermosetting polyimide coating 31 is 5 μm and the thickness of the thermoplastic polyimide coating 32 is 10 μm.
Example 13
This example is different from example 1 in that the sum of the thickness of the thermosetting polyimide coating 31 and the thickness of the thermoplastic polyimide coating 32 is 15 μm, wherein the thickness of the thermosetting polyimide coating 31 is 14 μm and the thickness of the thermoplastic polyimide coating 32 is 1 μm.
Comparative example 1
This comparative example is different from example 1 in that the thermosetting polyimide coating 31 is not doped with silica nanoparticles.
Comparative example 2
This comparative example differs from example 1 in that the thermoplastic polyimide coating 32 is not doped with silica nanoparticles.
Comparative example 3
This comparative example is different from example 1 in that neither the thermosetting polyimide coating 31 nor the thermoplastic polyimide coating 32 is doped with silica nanoparticles.
Comparative example 4
This comparative example is different from the production method of example 1 in that only the thermosetting polyimide coating layer 31 is provided, and the thickness of the thermosetting polyimide coating layer 31 is 15 μm.
Comparative example 5
This comparative example is different from the production method of example 1 in that only the thermoplastic polyimide coating layer 32 is provided, and the thickness of the thermoplastic polyimide coating layer 32 is 15 μm.
The low-loss temperature-resistant optical fiber meeting the requirements can be obtained by adjusting the dosage of the corresponding raw materials in the above examples and comparative examples.
Test example 1
The low-loss temperature-resistant optical fibers provided in the above examples and comparative examples were subjected to the 1550nm attenuation coefficient of the optical fiber, the 1300nm attenuation coefficient of the optical fiber, the tensile strength of the optical fiber, and the temperature resistance level test, respectively, and the results are shown in table 1 below.
The optical fiber 1550nm attenuation coefficient test method adopts the national standard GBT 15972.40-2008 optical fiber test method specification 40: methods and test procedures for measuring transmission and optical properties-attenuation.
(2) The method for testing the 1300nm attenuation coefficient of the optical fiber adopts the national standard GBT 15972.40-2008 optical fiber test method specification part 40: methods and test procedures for measuring transmission and optical properties-attenuation.
(3) The optical fiber tensile strength test method adopts the national standard GBT 15972.31-2021 optical fiber test method Specification part 31: method for measuring mechanical properties and test procedure-tensile strength.
(4) The temperature resistance level test method comprises the following steps: the fiber was kept in a relaxed state (loop diameter no less than 150 mm) and placed in a 300 ℃ high temperature oven using standard GBT 15972.31-2021 fiber test method specification part 31: the mechanical property measuring method and test procedure-tensile strength are used for respectively testing the tensile strength before and after 100 hours of baking, and the tensile strength after baking is reduced by not more than 10%, so that the temperature resistance is good.
TABLE 1
Remarks: "/" indicates that no correlation test was performed.
From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects: according to the low-loss temperature-resistant optical fiber provided by the application, the thermosetting polyimide coating 31 doped with the silica nanoparticles and the thermoplastic polyimide coating 32 are combined to be used as the optical fiber coating, and the thermoplastic polyimide coating 32 is positioned at the outermost layer of the optical fiber coating, so that the optical fiber can simultaneously meet the requirement that the 1550nm attenuation coefficient of the optical fiber is not more than 0.65dB/km, the tensile strength of the optical fiber is not less than 4.8GPa, the temperature resistance grade is 300 ℃, and the bending performance of the optical fiber and the service life of the optical fiber at high temperature can be effectively improved based on the interaction of the silica nanoparticles with the thermosetting polyimide matrix and the thermoplastic polyimide matrix and the good toughness of the thermoplastic polyimide.
The above description is only of the preferred embodiments of the present application and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (10)
1. A low-loss temperature-resistant optical fiber, characterized in that the low-loss temperature-resistant optical fiber comprises a fiber core (10), a cladding (20), a thermosetting polyimide coating (31) and a thermoplastic polyimide coating (32) which are sequentially arranged from inside to outside, wherein the thermosetting polyimide coating (31) comprises a thermosetting polyimide matrix and silica nanoparticles dispersed in the thermosetting polyimide matrix, and the thermoplastic polyimide coating (32) comprises a thermoplastic polyimide matrix and silica nanoparticles dispersed in the thermoplastic polyimide matrix.
2. The low-loss, temperature-resistant optical fiber according to claim 1, characterized in that the thermosetting polyimide coating (31) has a young's modulus of 3-8 GPa and a coefficient of thermal expansion of 2-4 x 10 -5 a/DEG C; the thermoplastic polyimide coating (32) has a Young's modulus of 0.5-2 GPa and a coefficient of thermal expansion of 4.5-5.5X10 -5 /℃。
3. The low-loss, temperature-resistant optical fiber according to claim 1, characterized in that the mass fraction of silica nanoparticles in the thermosetting polyimide coating (31) is 1-5%;
and/or the mass fraction of the silica nanoparticles in the thermoplastic polyimide coating (32) is 1-5%.
4. A low-loss, temperature-resistant optical fiber according to any of claims 1 to 3, characterized in that the cladding (20) comprises a silica matrix and an inorganic oxide doped in the silica matrix, the inorganic oxideThe thermal expansion coefficient of the oxide is 1-5 multiplied by 10 -5 Preferably 1.5 to 1.6X10 at a temperature of each DEG C -5 /℃；
Preferably, the inorganic oxide comprises B 2 O 3 Or P 2 O 5 At least one of them.
5. The low-loss, temperature-resistant optical fiber according to claim 1, characterized in that the molar concentration of the inorganic oxide in the silica matrix of the cladding (20) is between 2 and 5mol%.
6. The low-loss, temperature-resistant optical fiber according to claim 1, characterized in that the thermosetting polyimide coating (31) has a thickness of 10-15 μm; the thickness of the thermoplastic polyimide coating (32) is 2.5-5 mu m; the diameter of the fiber core (10) is 5-70 mu m; the thickness of the cladding layer (20) is 30-220 mu m.
7. The preparation method of the low-loss temperature-resistant optical fiber is characterized by comprising the following steps of:
step S1: providing a fiber core, depositing SiO on the fiber core 2 And optionally forming a cladding (20) of inorganic oxide coating the surface of the fiber core, and sintering to obtain an optical fiber preform;
step S2: drawing the preform rod to obtain a bare optical fiber;
step S3: coating a thermosetting polyimide coating (31) and a thermoplastic polyimide coating (32) on the surface of the bare optical fiber in sequence to obtain the low-loss temperature-resistant optical fiber;
wherein the core (10), cladding (20), inorganic oxide, thermosetting polyimide coating (31) and thermoplastic polyimide coating (32) each have the same meaning as in any of claims 1 to 6.
8. The method according to claim 7, wherein the step S1, the method for preparing the clad layer (20) comprises: silicon tetrachloride, oxygen, hydrogen and optionally inorganic compounds are mixed and reacted to form the cladding (20).
9. The method of producing as claimed in claim 7, wherein the step S3, the preparation of the thermosetting polyimide coating layer (31) and the thermoplastic polyimide coating layer (32) each independently includes coating and curing, and the coating temperature is 35 to 50 ℃.
10. The method of claim 9, wherein the cured light source comprises a long-wave infrared light source having a wavelength of 3.0 to 5.0 μm and a medium-wave infrared light source having a wavelength of 0.8 to 2.5 μm.
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