CN113759459A - Preparation method of high-temperature-resistant fiber Bragg grating array - Google Patents

Preparation method of high-temperature-resistant fiber Bragg grating array Download PDF

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CN113759459A
CN113759459A CN202111071126.4A CN202111071126A CN113759459A CN 113759459 A CN113759459 A CN 113759459A CN 202111071126 A CN202111071126 A CN 202111071126A CN 113759459 A CN113759459 A CN 113759459A
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optical fiber
bragg grating
coating
grating array
fiber bragg
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CN113759459B (en
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郑羽
江昕
邹琪琳
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Beijing Perception Technology Co ltd
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Beijing Perception Technology Co ltd
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    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02Optical fibres with cladding with or without a coating
    • G02B6/02057Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02076Refractive index modulation gratings, e.g. Bragg gratings
    • G02B6/0208Refractive index modulation gratings, e.g. Bragg gratings characterised by their structure, wavelength response
    • G02B6/021Refractive index modulation gratings, e.g. Bragg gratings characterised by their structure, wavelength response characterised by the core or cladding or coating, e.g. materials, radial refractive index profiles, cladding shape
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02Optical fibres with cladding with or without a coating
    • G02B6/02057Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02076Refractive index modulation gratings, e.g. Bragg gratings
    • G02B6/02123Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating
    • G02B6/02133Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating using beam interference
    • G02B6/02138Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating using beam interference based on illuminating a phase mask

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)

Abstract

The invention provides a preparation method of a high-temperature-resistant fiber Bragg grating array, which relates to the technical field of fiber grating preparation and comprises the following steps: step S1, coating a single-mode optical fiber perform with a single-layer polyimide coating to obtain a single-layer polyimide coated optical fiber; step S2, performing fixed point grating writing on the single-layer polyimide coated optical fiber to form an optical fiber Bragg grating array; and step S3, carrying out secondary coating of the single-layer polyimide coating optical fiber on the single-layer polyimide coated optical fiber with the optical fiber Bragg grating array to prepare the high-temperature-resistant optical fiber Bragg grating array. The preparation method has the beneficial effects that the problem that the existing polyimide coating fiber Bragg grating array cannot tolerate high temperature is solved, the polyimide coating fiber Bragg grating array prepared by the technical scheme can tolerate the high temperature of 300-350 ℃, the use scene of the grating array is widened, and the preparation method can be widely applied to sensing monitoring of oil and gas exploitation transportation, power generation facilities and large-scale industrial equipment.

Description

Preparation method of high-temperature-resistant fiber Bragg grating array
Technical Field
The invention relates to the technical field of fiber bragg grating preparation, in particular to a preparation method of a high-temperature-resistant fiber bragg grating array.
Background
Bragg fiber arrays, or what are known as "clean-up" fiber optics, are favored by various engineering applications due to their excellent quasi-distributed sensing capabilities. However, there are more applications in harsh environments that place new demands on the bragg fiber array. For example, in the environment of higher temperature and higher pressure, the performance of the bragg grating array is reduced in various aspects, which mainly include the following aspects: (1) the fiber grating array is prepared based on single pulse exposure, and fading can occur under the condition of high temperature; (2) the fiber grating array preparation system is coated by polyacrylic resin, wherein common polyacrylic resin generally resists the temperature of 80 ℃, high-temperature resistant polyacrylic resin resists the temperature of 150 ℃, and the high-temperature environment cannot be met; (3) due to the problem of high-temperature fading of the grating, the fiber grating array cannot be coated by thermosetting during preparation, and the temperature of the thermosetting process is as high as 300-500 ℃.
The existing high-temperature resistant fiber Bragg grating array adopts a preparation method that a polyimide coated fiber is used, femtosecond ultraviolet light penetrates through the polyimide coating, and a standing point scanning writing mode is used for preparing the Bragg grating. The femtosecond laser standing point writing mode enables the grating to have high temperature resistance. However, the technology has high equipment cost, poor stability in the grating writing process and poor spectrum type consistency of each grating in the grating array, and influences subsequent use. On the other hand, the technical threshold is high, only one company in Germany can provide products based on the process all over the world, and the products are sold in limited quantity in China.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a preparation method of a high-temperature-resistant fiber Bragg grating array, which comprises the following steps:
step S1, coating a single-mode optical fiber perform with a single-layer polyimide coating to obtain a single-layer polyimide coated optical fiber;
step S2, performing fixed point grating writing on the single-layer polyimide coated optical fiber to form an optical fiber Bragg grating array;
and step S3, carrying out secondary coating of the single-layer polyimide coating optical fiber on the single-layer polyimide coated optical fiber with the optical fiber Bragg grating array to prepare the high-temperature-resistant optical fiber Bragg grating array.
Preferably, in the step S1, the thickness of the single polyimide coating is 2 to 5 micrometers.
Preferably, in the step S2, a fiber bragg grating with a reflectivity is written in the single-layer polyimide coated optical fiber in multiple pulses at every other interval without stripping the single-layer polyimide coating, so as to form the fiber bragg grating array.
Preferably, the distance is 0-100 m.
Preferably, the reflectance is 0.1% to 99%.
Preferably, the number of pulses for the multi-pulse writing is 1 to 109Next, the pulse frequency is not higher than 200 HZ.
Preferably, in step S2, the writing process of the multi-pulse writing is a two-beam interference method or a phase mask method.
Preferably, before performing step S2, the method further includes performing hydrogen-loaded pretreatment on the single-layer polyimide-coated optical fiber.
Preferably, in the step S3, the thickness of the single polyimide coating layer coated twice is 5 to 25 micrometers.
Preferably, the step S1 and the step S3 are performed by using a thermosetting optical fiber drawing system.
The technical scheme has the following advantages or beneficial effects: the preparation method of the high-temperature-resistant fiber Bragg grating array has the characteristics of low cost and high efficiency, and solves the problem that the existing polyimide coating fiber Bragg grating array cannot resist high temperature, the polyimide coating fiber Bragg grating array prepared by the technical scheme can resist the high temperature of 300-350 ℃, the limitation that the common grating array can only resist 80 ℃ is greatly broken through, the use scene of the grating array is widened, and the preparation method can be widely applied to sensing monitoring of oil and gas exploitation transportation, power generation facilities and large-scale industrial equipment.
Drawings
Fig. 1 is a schematic flow chart of a method for manufacturing a high temperature resistant fiber bragg grating array according to a preferred embodiment of the present invention;
FIG. 2 is a graph illustrating the degradation of the reflectivity of the grating in accordance with the preferred embodiment of the present invention;
FIG. 3 is a graph showing the relationship between grating reflectivity degradation and process speed in a preferred embodiment of the present invention;
FIG. 4 is a scanning electron microscope micrograph of a single polyimide coated fiber in accordance with a preferred embodiment of the present invention.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments. The present invention is not limited to the embodiment, and other embodiments may be included in the scope of the present invention as long as the gist of the present invention is satisfied.
In a preferred embodiment of the present invention, based on the above problems in the prior art, a method for manufacturing a high temperature resistant fiber bragg grating array is provided, as shown in fig. 1, including:
step S1, coating a single-mode optical fiber perform with a single-layer polyimide coating to obtain a single-layer polyimide coated optical fiber;
step S2, performing fixed point grating writing on the single-layer polyimide coated optical fiber to form an optical fiber Bragg grating array;
and step S3, carrying out secondary coating of the single-layer polyimide coating on the single-layer polyimide coated optical fiber with the optical fiber Bragg grating array to prepare the high-temperature-resistant optical fiber Bragg grating array.
Specifically, in this embodiment, the single-mode optical fiber preform is a high-photosensitivity single-mode optical fiber preform, and a thermosetting optical fiber drawing system is preferably used to coat a single-layer polyimide coating on the high-photosensitivity single-mode optical fiber preform so as to collect a single-layer polyimide coated optical fiber with a required length. In a preferred embodiment of the present invention, in step S1, the thickness of the single polyimide coating is 2 to 5 μm to ensure the basic fiber-drawing strength of the optical fiber. The single-layer polyimide coating has the characteristics of smooth surface and high ultraviolet transparency, and preferably can be fluorine-containing polyimide, and the light transmittance at 248nm needs to be more than 80%. It is to be understood that the fluorine-containing polyimide is merely an example of the present invention, and the present invention is not limited thereto.
More specifically, the thermosetting fiber drawing system may be a fiber drawing tower with thermosetting capability, which may have a multi-stage thermosetting coating function, in this embodiment, only one stage of thermosetting coating is used to attach a thinner polyimide coating on the optical fiber. Preferably, during preparation, the coated single-layer polyimide coating is required to be completely cured, no solvent is left, and multi-temperature-zone thermal curing can be adopted, wherein the temperature zone length is not less than 800 mm. Further, in step S1, the production speed of the single-layer polyimide coated optical fiber is 4 to 30m/min, and the actual production speed depends on the heat curing efficiency. It should be understood that the above-mentioned manner of thermal curing in multiple temperature zones is only an example of the present disclosure, and the present disclosure is not limited thereto.
After the single-layer polyimide coating optical fiber is obtained by coating the single-layer polyimide coating, in a preferred embodiment of the present invention, in step S2, a fiber bragg grating with a reflectivity is written into the single-layer polyimide coated optical fiber in multiple pulses at intervals without stripping the single-layer polyimide coating, so as to form a fiber bragg grating array.
Specifically, in the embodiment, in the grating writing process, the single polyimide coating layer outside the single polyimide coated optical fiber does not need to be stripped, gratings can be written by using a method including, but not limited to, a double-beam interference method and a phase mask method, a laser light source adopted in grating writing includes, but not limited to, a high-coherence ultraviolet laser generated by a deep ultraviolet excimer laser, the wavelength of the high-coherence ultraviolet laser can be 193nm, 248nm and the like, and the laser energy range is 2-50 mJ.
As a preferred embodiment, a single layer polyimide coated fiber may be subjected to a hydrogen-loaded pre-treatment prior to grating writing to improve grating writing efficiency. After hydrogen-carrying pretreatment, on the premise of not stripping a single-layer polyimide coating, writing the grating with a certain reflectivity by multiple pulses, and ensuring that the fiber Bragg grating cannot be completely faded out in a high-temperature environment, wherein the pulse frequency is preferably 1-109Next, the pulse frequency is not higher than 200 Hz. More preferably, due to the lower pulse frequency, the fiber writing system platform is required to be completely isolated from vibration during grating writing.
In this embodiment, the reflectivity of a single fiber bragg grating obtained by grating writing is 0.1% to 99%. In the grating writing process, in order to form a fiber Bragg grating array, the optical fiber cannot be cut off, and a fiber Bragg grating with determined reflectivity is written at regular intervals. In the process of writing the fiber grating, one side is used for placing the fiber, and the other side is used for collecting the fiber written with the grating. The interval range of the fiber Bragg grating is 0-100 m, and the central wavelength of the fiber Bragg grating can be adjusted at will. In some applications, exactly the same center wavelength is required.
After the grating writing is finished, the secondary coating of the single-layer polyimide coating is preferably performed by using a thermosetting optical fiber drawing system, an optical fiber pay-off disc can be added on the top of the thermosetting optical fiber drawing system, the single-layer polyimide coated optical fiber with the optical fiber Bragg grating array formed and prepared after the grating writing is arranged in the pay-off disc, and the optical fiber passes through the thermosetting system in the drawing system to form the single-layer polyimide coating which is secondarily coated. The thermosetting optical fiber drawing system can be an optical fiber drawing tower with thermosetting capability, the optical fiber drawing tower can have a multi-stage thermosetting coating function, preferably, the thickness of a single-layer polyimide coating for secondary coating is 5-25 micrometers, and the outer diameter of an optical fiber is increased by 10-50 micrometers through final secondary coating. Wherein, the process speed of the secondary coating is 3-30m/min, and the actual process speed depends on the heat curing efficiency of the system.
In this embodiment, after the second coating, the reflectivity of the written fiber bragg grating is decreased, as shown in fig. 2, based on the original reflectivity R0 (%), the reflectivity is decreased by Δ R (%), the final reflectivity R1 is (1- Δ R) × R0, and the Δ R generally has a value range of 1% to 60%, and the specific value depends on the stroke length of the thermal curing system, the temperature of the thermal curing system, and the process speed. As shown in fig. 3, the filled circles are used to represent the original grating reflectivity, and the empty circles are used to represent the degraded grating reflectivity, and the relationship between the grating reflectivity and the process speed can be seen. Preferably, the outer diameter of the optical fiber after final coating is 130-180 micrometers, and the screening strength of the optical fiber can reach 50-200 kpsi.
In summary, it can be seen that, in the technical scheme, the fiber bragg grating array is prepared in three steps, after the optical fiber is drawn from the preform into the optical fiber, the prepared single-layer polyimide coated optical fiber is collected, the optical fiber is written into the grating in an off-line manner, and then secondary coating reinforcement is performed, so that the adjustment of the grating reflectivity, the grating spatial position and the grating wavelength distribution is more free compared with the existing online continuous preparation of the fiber bragg grating array by adopting a drawing tower.
In a preferred embodiment of the present invention, the preparation method of the technical scheme is adopted to prepare the high temperature resistant fiber bragg grating array, and specifically comprises the following steps:
based on a thermocuring optical fiber drawing system, coating a single-layer polyimide coating by using a high-photosensitivity single-mode optical fiber preform and an ultraviolet high-transmittance polyimide coating, and collecting a single-layer polyimide coated optical fiber with the length of 1 km; the thickness of the single-layer polyimide coating is 4-6 microns through microscope test, and is shown in figure 4.
A single layer of polyimide coated fiber was then written with a fixed-point grating. During grating writing, the single polyimide coating layer outside the optical fiber is not required to be stripped. Wherein, a phase mask plate method is selected to write in the grating; the laser light source is high-coherence ultraviolet laser (with the wavelength of 248nm and the like) generated by a deep ultraviolet excimer laser, and the laser energy is as follows: 20 mJ. On the premise of not stripping the polyimide coating, the reflectivity grating is written in by multiple pulses, and the optical fiber Bragg grating is ensured not to be completely faded out in a high-temperature environment. Wherein the pulse frequency is 50Hz, and the total exposure time is 360 s. Every 20m of fiber was written in a 1km fiber for a total of 49 gratings, and the average grating reflectivity was tested to be 56%.
And finally, a thermosetting optical fiber drawing system is used, and an optical fiber releasing disc is additionally arranged at the top of the drawing system. And arranging the grating array obtained in the last step in a fiber placing disc, and passing the optical fiber through a thermal curing system in a wire drawing system to perform secondary coating on the optical fiber. The draw tower may have a multi-stage thermal cure coating function with a final secondary coating increasing the outer diameter of the fiber by 25 microns and a final coated outer diameter of the fiber of 155 microns. Wherein the optical fiber recoating process speed is 10 m/min. The reflectivity of the written fiber Bragg grating is reduced, and the average reflectivity of the final test is 23%.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims (10)

1. A preparation method of a high-temperature-resistant fiber Bragg grating array is characterized by comprising the following steps:
step S1, coating a single-mode optical fiber perform with a single-layer polyimide coating to obtain a single-layer polyimide coated optical fiber;
step S2, performing fixed point grating writing on the single-layer polyimide coated optical fiber to form an optical fiber Bragg grating array;
and step S3, carrying out secondary coating of the single-layer polyimide coating optical fiber on the single-layer polyimide coated optical fiber with the optical fiber Bragg grating array to prepare the high-temperature-resistant optical fiber Bragg grating array.
2. The method according to claim 1, wherein in the step S1, the thickness of the single-layer polyimide coating is 2 to 5 μm.
3. The method as claimed in claim 1, wherein in step S2, a fiber bragg grating with a reflectivity is written in the single-layer polyimide coated optical fiber in multiple pulses at every other interval without stripping the single-layer polyimide coating to form the fiber bragg grating array.
4. The method of claim 3, wherein the pitch is 0 to 100 m.
5. The method according to claim 3, wherein the reflectance is 0.1 to 99%.
6. The method according to claim 3, wherein the number of pulses for the multi-pulse writing is 1 to 109Next, the pulse frequency is not higher than 200 HZ.
7. The manufacturing method according to claim 3, wherein in the step S2, the writing process of the multi-pulse writing is a two-beam interference method or a phase mask method.
8. The method of claim 1, wherein before performing step S2, the method further comprises performing a hydrogen-loading pretreatment on the single-layer polyimide-coated optical fiber.
9. The method according to claim 1, wherein in the step S3, the thickness of the single polyimide coating layer coated twice is 5 to 25 μm.
10. The method as claimed in claim 1, wherein the step S1 and the step S3 are performed by applying the single polyimide coating layer using a thermosetting optical fiber drawing system.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114660704A (en) * 2022-03-23 2022-06-24 武汉理工大学 Temperature-resistant hydrogenated wire drawing tower grating array and preparation method thereof
CN115236797A (en) * 2022-08-12 2022-10-25 武汉理工大学 High-temperature-resistant weak-fiber grating array and preparation method thereof

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JP2001013334A (en) * 1999-06-29 2001-01-19 Showa Electric Wire & Cable Co Ltd Fiber type detecting element, its production and apparatus for production and sensor using the same
JP2003295009A (en) * 2002-04-02 2003-10-15 Hitachi Cable Ltd Method of recoating optical fiber bragg grating and optical fiber
CN102645176A (en) * 2012-05-18 2012-08-22 哈尔滨工业大学 High-temperature resistant FBG (fiber bragg grating) sheet type strain sensor and manufacturing method thereof
CN106019467A (en) * 2016-07-08 2016-10-12 深圳市畅格光电有限公司 Manufacture method of high temperature resistant fiber grating
CN108827916A (en) * 2018-04-20 2018-11-16 武汉理工大学 Light fibre humidity transducer and preparation method thereof based on lithium chloride doped polyimide
CN111830626A (en) * 2020-07-29 2020-10-27 武汉理工大学 Method for preparing wavelength division and time division multiplexing low-reflectivity high-temperature fiber grating array

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001013334A (en) * 1999-06-29 2001-01-19 Showa Electric Wire & Cable Co Ltd Fiber type detecting element, its production and apparatus for production and sensor using the same
JP2003295009A (en) * 2002-04-02 2003-10-15 Hitachi Cable Ltd Method of recoating optical fiber bragg grating and optical fiber
CN102645176A (en) * 2012-05-18 2012-08-22 哈尔滨工业大学 High-temperature resistant FBG (fiber bragg grating) sheet type strain sensor and manufacturing method thereof
CN106019467A (en) * 2016-07-08 2016-10-12 深圳市畅格光电有限公司 Manufacture method of high temperature resistant fiber grating
CN108827916A (en) * 2018-04-20 2018-11-16 武汉理工大学 Light fibre humidity transducer and preparation method thereof based on lithium chloride doped polyimide
CN111830626A (en) * 2020-07-29 2020-10-27 武汉理工大学 Method for preparing wavelength division and time division multiplexing low-reflectivity high-temperature fiber grating array

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114660704A (en) * 2022-03-23 2022-06-24 武汉理工大学 Temperature-resistant hydrogenated wire drawing tower grating array and preparation method thereof
CN115236797A (en) * 2022-08-12 2022-10-25 武汉理工大学 High-temperature-resistant weak-fiber grating array and preparation method thereof
CN115236797B (en) * 2022-08-12 2024-04-16 武汉理工大学 High-temperature-resistant weak fiber grating array and preparation method thereof

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