High temperature resistant carbon-sealed coated optical fiber and method of making same

Abstract

The application relates to the field of optical transmission cables, in particular to a high-temperature-resistant carbon sealing coated optical fiber and a manufacturing method thereof. The optical fiber structure is sequentially composed of an optical fiber body, an amorphous carbon sealing layer and a silicon-substituted polyimide coating layer from inside to outside. The amorphous carbon sealing layer is deposited on the surface of the optical fiber body through an in-situ high-temperature pyrolysis and carbon deposition method, and the silicon-substituted polyimide coating layer is formed on the surface of the optical fiber through a low-speed drawing and online infiltration heat curing coating process. The optical fiber not only has good adaptability to high-temperature environments, but also can solve the problems of increased optical fiber transmission loss, easily corroded coating layer and reduced service life caused by high pressure, high humidity and high salinity in the well, and meets the demand of the optical fiber hydrogen resistance in the high-pressure hydrogen-rich environment in the oil and gas field well.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical transmission cable, in particular to a high-temperature-resistant carbon-sealed coated optical fiber and a manufacturing method thereof. BACKGROUND

[0002] Optical fiber sensing technology has important applications in oil and gas exploration. Since the downhole environment of oil and gas fields belongs to a harsh environment with high temperature, high pressure and high hydrogen content, the optical fiber for detection and transmission usually needs to be armored into a cable with a steel pipe to realize high-pressure resistance of the optical cable, and an optical fiber that can resist high temperature and hydrogen damage is also needed to meet the long-term use requirements in the above environment.

[0003] At present, the domestic high-temperature-resistant optical fiber mainly has 150℃ temperature-resistant grade, 300℃ temperature-resistant grade and 600℃ or above temperature-resistant grade. Among them: (1) the 150℃ temperature-resistant grade optical fiber uses ultraviolet-curable high-temperature-resistant acrylic modified resin as the optical fiber coating layer, and the shelf product of this type of optical fiber includes 150℃ carbon-sealed coated optical fiber and 150℃ non-carbon-coated ordinary optical fiber; the coating and curing of the optical fiber coating layer can be realized by the optical fiber drawing online ultraviolet light curing process, which can adapt to different drawing speeds, but the high-temperature-resistant grade is low, and the typical long-term working temperature of the mainstream product is in the range of about 150℃; (2) the 300℃ temperature-resistant grade optical fiber currently mainly uses polyimide as the coating layer, which can realize long-term work at a temperature of about 300℃ and short-term work at 350℃-400℃. Due to the characteristics of low viscosity and weak adhesion of ordinary polyimide coating, it cannot be cured by ultraviolet light, and two or more layers of coating are needed to achieve the practical target coating layer thickness; (3) the optical fiber with a temperature-resistant grade of 600℃ or above generally uses metal material as the coating layer, but special metal liquid sputtering or chemical electroplating method is needed to realize metal coating, which is complex and high in manufacturing cost.

[0004] The downhole environment is generally above 300℃, and as described above, the 300℃ temperature-resistant grade optical fiber in the prior art only has good adaptability to high temperature environment, and cannot solve the problems of increased transmission loss of optical fiber, easy corrosion of coating layer and reduced service life caused by high pressure, high humidity and high salinity in downhole, and cannot meet the demand of hydrogen damage resistance of optical fiber in the high-pressure hydrogen-rich environment of oil and gas downhole.

[0005] Therefore, it is necessary to innovate the existing high-temperature-resistant optical fiber to meet the harsh environment of high temperature, high pressure and high hydrogen content in oil and gas downhole. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a high-temperature-resistant carbon-sealed coated optical fiber and a manufacturing method thereof to solve the problems of the prior art and adapt to the harsh environment of high temperature, high pressure and high hydrogen content in oil and gas downhole.

[0007] To achieve the above object, the technical scheme adopted by the present application is:

[0008] A high-temperature-resistant carbon-sealed coated optical fiber, characterized in that the optical fiber structure comprises, from inside to outside, an optical fiber body 1, an amorphous carbon sealing layer 2, and a silicon-substituted polyimide coating layer 3; the thickness of the amorphous carbon sealing layer 2 is 20-50 nm.

[0009] Further, the optical fiber body 1 is a bend-insensitive waveguide structure.

[0010] Further, the diameter of the silicon-substituted polyimide coating layer 3 is 90-155 μm.

[0011] A method for manufacturing a high-temperature-resistant carbon-sealed coated optical fiber, characterized in that the method comprises the following steps:

[0012] Step 1: a preform rod for drawing the optical fiber body 1 is sent into a drawing furnace of a drawing machine, the preform rod is heated to above 2000℃ by the drawing furnace, and the preform rod is drawn into the optical fiber body 1 with a bend-insensitive waveguide structure through high-temperature melting traction;

[0013] Step 2: the optical fiber body 1 formed in Step 1 is passed through an in-situ high-temperature gas-phase carbon layer deposition device, a gas aerosol containing not less than one carbon-containing element compound is introduced into the deposition device in advance, the high-temperature cracking reaction of the carbon-containing element compound gas aerosol is carried out on the surface of the optical fiber body 1 through the in-situ high-temperature cracking carbon deposition method, and the amorphous carbon sealing layer 2 is deposited on the surface of the optical fiber body 1; the thickness of the amorphous carbon sealing layer 2 on the surface of the optical fiber body 1 can be adjusted to be 20-50 nm by adjusting the concentration of the carbon-containing element compound gas in the deposition device and the residence time of the optical fiber body 1 in the deposition device;

[0014] Step 3: the optical fiber with the amorphous carbon sealing layer 2 formed in Step 2 is immersed in the liquid silicon-substituted polyimide high-temperature-resistant composite material on the surface of the optical fiber through a low-speed drawing online immersion and hot curing coating process;

[0015] Step 4: the carbon-sealed coated optical fiber with the liquid silicon-substituted polyimide high-temperature-resistant composite material formed in Step 3 is subjected to gradient heating in a segmented hot curing furnace, so that the liquid silicon-substituted polyimide high-temperature-resistant composite material wrapped on the surface of the optical fiber is converted into a solid state to form the silicon-substituted polyimide coating layer 3.

[0016] The present application has the following beneficial effects compared with the prior art:

[0017] The high-temperature-resistant carbon sealing coated optical fiber prepared by the application has an amorphous carbon sealing layer with a thickness of 20-50 nm, so that the optical fiber has higher compactness and flexibility, the dynamic fatigue coefficient of the optical fiber is above 210, the service life and reliability of the optical fiber can be effectively improved, the hydrogen damage resistance effect is remarkable in a high-pressure hydrogen-rich environment, and the body absorption loss of the optical fiber does not increase obviously; the external coating layer is a silicon substituted polyimide coating layer, which combines the flexible elasticity of silane bond and the high-temperature resistance of traditional polyimide, so that the micro-bending of the optical fiber can be reduced, and the single-layer coating can take into account the lower attenuation coefficient and higher temperature resistance grade of the optical fiber. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a schematic diagram of the optical fiber structure of the application;

[0019] Figure 2 It is an energy dispersive spectrometer element distribution test diagram of the optical fiber body edge and amorphous carbon sealing layer of the application;

[0020] Figure 3 It is a scanning electron microscope test full view diagram of the optical fiber body of the application;

[0021] Figure 4 It is a scanning electron microscope test local enlarged view diagram of the amorphous carbon sealing layer of the application.

[0022] BRIEF DESCRIPTION OF DRAWINGS:

[0023] 1, optical fiber body; 2, amorphous carbon sealing layer; 3, silicon substituted polyimide coating layer. DETAILED DESCRIPTION

[0024] In order to make the technical scheme and advantages of the application more clearly understood, the application will be further described in detail in combination with the drawings and examples.

[0025] The carbon sealing coated optical fiber is formed by a special carbon sealing coating process to form a dense carbon layer on the surface of the optical fiber, slow down the growth of micro-cracks on the surface of the optical fiber, seal and isolate the surface of the optical fiber from the environment, prevent the influence of moisture and hydrogen on the mechanical strength and optical performance of the optical fiber, reduce the increase of transmission loss caused by hydrogen permeation of the optical fiber in a high-humidity and high-pressure environment, improve the fatigue resistance and stress corrosion sensitivity parameters of the optical fiber, and thus improve the service life and reliability of the optical fiber (as shown in the following formula).

[0026]

[0027] Wherein: ts is the optical fiber lifetime (unit s), tp is the screening time (unit s), m is the slope of the optical fiber strength distribution curve Weibull distribution curve, n is the fatigue coefficient, Np is the number of breaks during screening (times / km), L is the optical fiber length (km), F is the allowable break probability, σp is the minimum strength after screening, and σs is the static stress strength (use stress).

[0028] Therefore, the working principle of the present application is:

[0029] First, the in-situ high-temperature pyrolysis carbon deposition method is used to deposit a thick amorphous carbon sealing layer 2 on the surface of the optical fiber body 1, and the optical fiber structure formed is shown in Figure 1 In Figure 1 , the optical fiber structure from inside to outside is the optical fiber body 1 prepared by the quartz waveguide, the amorphous carbon sealing layer 2, and the polysilicon polyimide coating layer 3. As shown in Figure 2 The optical fiber body edge and the amorphous carbon sealing layer energy spectrometer element distribution test diagram show that when scanning from the optical fiber body to the outside of the edge, the signal intensity of the chemical elements silicon (Si) and oxygen (O) of quartz, which is the main material of the optical fiber body 1, decreases, and the signal intensity of carbon (C) increases, indicating that the optical fiber body 1 surface contains the amorphous carbon sealing layer 2, and the thickness reaches 20nm-50nm, as shown in Figure 3 and Figure 4 According to GB / T 15972.33-2008 "Optical fiber test method specification Part 33: Measurement method and test procedure of mechanical properties-Stress corrosion sensitivity parameter", the dynamic fatigue parameter (i.e. dynamic n value) of the optical fiber reaches more than 200.

[0030] On the basis of the above technical solution, when the diameter of the optical fiber body 1 is 78μm-82μm, the diameter of the polysilicon polyimide coating layer 3 is 90μm-110μm, when the diameter of the optical fiber body 1 is 123μm-127μm, the diameter of the polysilicon polyimide coating layer 3 is 135μm-155μm.

[0031] The polysilicon polyimide coating layer 3 is coated on the surface of the amorphous carbon sealing layer 2 by the optical fiber drawing online single-layer thin-wall coating method, and is solidified from liquid to solid by using a segmented heat curing furnace. The polysilicon polyimide coating layer 3 is a high-temperature resistant composite material with a glass transition temperature (Tg) of 200℃-300℃ and a Young's modulus of 2GPa. The polysilicon polyimide combines the flexible elasticity of silane bonds and the high-temperature resistance of traditional polyimide. When the optical fiber coated with the polysilicon polyimide works in a high-temperature environment of 300℃, the environment temperature is higher than the glass transition temperature (Tg) of the polysilicon polyimide, and it is in a high-elastic state, which is more flexible than ordinary polyimide materials, reduces the optical fiber micro-bending, and can balance the lower attenuation coefficient and higher temperature resistance grade of the optical fiber through single-layer coating.

[0032] The method for manufacturing the optical fiber in the present application comprises the following steps:

[0033] Step 1: install a segmented thermal curing furnace in advance at a suitable position of a tower where the fiber drawing machine is located;

[0034] Step 2: install a pre-designed and processed primary coating cup and primary coating die below the bare fiber diameter gauge of the fiber drawing machine and close to the position above the segmented thermal curing furnace;

[0035] Step 3: install a pre-designed and processed in-situ high-temperature vapor carbon layer deposition device at a suitable position of the tower where the fiber drawing machine is located;

[0036] Step 4: clamp the optical fiber preform for drawing the optical fiber body to the rod feeding device of the fiber drawing machine;

[0037] Step 5: feed the preform into the fiber drawing furnace of the fiber drawing machine, heat and melt, and draw into a fiber under the action of gravity;

[0038] Step 6: pass the optical fiber body 1 formed in the above step 5 through the in-situ high-temperature vapor carbon layer deposition device described in step 3, and prepare an amorphous carbon sealing layer 2 on the outside of the optical fiber body 1 by in-situ high-temperature pyrolytic carbon deposition;

[0039] Step 7: pass the optical fiber with the amorphous carbon sealing layer 2 formed in the above step 6 through the primary coating die described in step 2, and add a liquid silicon-containing polyimide high-temperature resistant composite material into the primary coating cup, and wrap the liquid silicon-containing polyimide high-temperature resistant composite material on the surface of the optical fiber by extrusion under a certain pressure;

[0040] Step 8: use the segmented thermal curing furnace described in step 1 to perform gradient heating on the carbon sealing coated optical fiber with the liquid silicon-containing polyimide high-temperature resistant composite material wrapped on the surface of the optical fiber formed in the above step 7, so that the liquid silicon-containing polyimide high-temperature resistant composite material wrapped on the surface of the optical fiber is converted into a solid state.

[0041] Example 1: a high-temperature resistant carbon sealing coated optical fiber with a nominal diameter of 80 μm for the optical fiber body 1 and a nominal diameter of 105 μm for the coating layer.

[0042] The optical fiber preparation steps in this example are as follows:

[0043] Step 1: install a 6-segment segmented thermal curing furnace in advance at a suitable position of a tower where the fiber drawing machine is located;

[0044] Step 2: install a pre-designed and processed primary coating cup and primary coating die below the bare fiber diameter gauge of the fiber drawing machine and close to the position above the segmented thermal curing furnace, and the die hole diameter is 208 μm;

[0045] Step 3: Install the in-situ high-temperature vapor carbon deposition device, which is designed and processed in advance, at a suitable position of the tower of the drawing machine;

[0046] Step 4: Clamping the thin-diameter bend-insensitive optical fiber preform for drawing the optical fiber body 1 to the rod feeding device of the drawing machine;

[0047] Step 5: Feeding the preform into the drawing furnace of the drawing machine, heating and melting at a high temperature of 2150℃, and drawing into a fiber under the action of gravity;

[0048] Step 6: Passing the optical fiber body 1 formed in the above step 5 through the in-situ high-temperature vapor carbon deposition device described in step 3, and preparing the amorphous carbon sealing layer 2 on the outside of the optical fiber body 1 by the in-situ high-temperature pyrolytic carbon deposition method; by adjusting the concentration of the carbon-containing compound gas in the deposition device to 75% (v%) and the residence time of the optical fiber body 1 in the deposition device to 6s, the amorphous carbon sealing layer 2 on the surface of the optical fiber body 1 is prepared;

[0049] Step 7: Passing the optical fiber with the amorphous carbon sealing layer 2 formed in the above step 6 through the primary coating die described in step 2, and adding the liquid of the silicon-containing polyimide high-temperature resistant composite material in the primary coating cup, and using the low-speed drawing online immersion heat curing coating process to immerse and wrap the liquid silicon-containing polyimide high-temperature resistant composite material on the surface of the optical fiber by 0.03MPa pressure extrusion;

[0050] Step 8: Using the 6-section segmented heat curing furnace described in step 1 to linearly heat the carbon sealing coated optical fiber with the liquid silicon-containing polyimide high-temperature resistant composite material wrapped in the above step 7 from 150℃ to 450℃, so that the liquid silicon-containing polyimide high-temperature resistant composite material wrapped on the surface of the optical fiber is converted into a solid state to form the silicon-containing polyimide coating layer 3.

[0051] The prepared optical fiber is tested, the diameter of the optical fiber body 1 is 79.8μm, the thickness of the amorphous carbon sealing layer 2 is 20.27nm, the diameter of the silicon-containing polyimide coating layer 3 is 103.8μm, the dynamic fatigue coefficient of the optical fiber is 216, the attenuation coefficient of the optical fiber at room temperature is 0.306dB / km@1550nm, and the attenuation coefficient of the optical fiber after 250 hours of environmental high-temperature aging at 300℃ is 0.309dB / km@1550nm. The absorption loss of the φ79.8μm optical fiber coated with carbon at 300℃ before and after 144 hours of continuous hydrogen loading test at 1.2MPa is compared with that of the same type of 300℃ non-coated carbon optical fiber as shown in Table 1.

[0052] Table 1 Comparison of absorption loss before and after hydrogen loading

[0053]

[0054]

[0055] Example 2: High-temperature resistant carbon-sealed coated optical fiber with a fiber body 1 having a nominal diameter of 125 μm and a coating layer having a nominal diameter of 145 μm.

[0056] The fiber preparation steps in this example are as follows:

[0057] Step 1: A 6-section segmented thermal curing furnace is installed in advance at a suitable position on the tower of the fiber drawing machine;

[0058] Step 2: A one-time coating cup and a one-time coating die, which are designed and processed in advance, are installed below the bare fiber diameter gauge of the fiber drawing machine and near the position above the segmented thermal curing furnace, and the die aperture is 220 μm;

[0059] Step 3: A high-temperature in-situ gas-phase carbon layer deposition device, which is designed and processed in advance, is installed at a suitable position on the tower of the fiber drawing machine;

[0060] Step 4: A fine-diameter bend-insensitive optical fiber preform for drawing the fiber body 1 is clamped to the preform feeding device of the fiber drawing machine;

[0061] Step 5: The preform is fed into the fiber drawing furnace of the fiber drawing machine, heated and melted at a high temperature of 2160 °C, and drawn into a fiber under the action of gravity;

[0062] Step 6: The fiber body 1 formed in the above step 5 is passed through the high-temperature in-situ gas-phase carbon layer deposition device described in step 3, and an amorphous carbon sealing layer 2 is prepared on the outside of the fiber body 1 by the high-temperature in-situ pyrolytic carbon deposition method. By adjusting the concentration of the carbon-containing compound gas in the deposition device to 83% (v%) and the residence time of the fiber body 1 in the deposition device to 9 s, the amorphous carbon sealing layer 2 is prepared on the surface of the fiber body 1;

[0063] Step 7: The fiber with the amorphous carbon sealing layer 2 formed in the above step 6 is passed through the one-time coating die described in step 2, and a liquid silicon-containing polyimide high-temperature resistant composite material is added to the one-time coating cup, and the material is extruded by a pressure of 0.04 MPa, and the liquid silicon-containing polyimide high-temperature resistant composite material is coated on the surface of the fiber by the low-speed fiber drawing online immersion and thermal curing coating process;

[0064] Step 8: The carbon-sealed coated fiber with the liquid silicon-containing polyimide high-temperature resistant composite material coated thereon formed in the above step 7 is heated by the 6-section segmented thermal curing furnace described in step 1 from 150 °C to 450 °C in a linear gradient, so that the liquid silicon-containing polyimide high-temperature resistant composite material coated on the surface of the fiber is converted into a solid state to form a silicon-containing polyimide coating layer 3.

[0065] The prepared optical fiber was tested, the diameter of the optical fiber body 1 was 125.1 μm, the thickness of the amorphous carbon sealing layer 2 was 29.62 nm, the diameter of the silicon substituted polyimide coating layer 3 was 145.3 μm, the dynamic fatigue coefficient of the optical fiber was 253, the attenuation coefficient of the optical fiber at room temperature was 0.282 dB / km@1550 nm, and the attenuation coefficient of the optical fiber after 250 hours of high-temperature environmental aging at 300℃ was 0.286 dB / km@1550 nm. The absorption loss of the 300℃ carbon sealing coated φ125.1 μm optical fiber before and after 144 hours of continuous hydrogen loading test at 1.2 MPa was compared with that of the same type of 300℃ non-coated carbon optical fiber as shown in Table 2.

[0066] Table 2 Comparison of absorption loss before and after hydrogen loading

[0067]

[0068] The above-mentioned embodiments are only used to illustrate the present application, and are not intended to limit the present application. Any skilled person in the art can make various modifications, changes or replacements without departing from the technical scope disclosed in the present application. Therefore, all equivalent and similar technical methods should be covered within the patent protection scope of the present application.

Claims

1. A method for making a high temperature resistant carbon-sealed coated optical fiber, characterized by: It comprises the following steps: Step 1: the preform for drawing the optical fiber body (1) is sent into the drawing furnace of the drawing machine, and the preform is heated to above 2000 DEG C by the drawing furnace, and is drawn into the optical fiber with the bending insensitive waveguide structure by high temperature melting traction; Step 2: the optical fiber body (1) formed in the above step 1 is passed through the in-situ high temperature gas phase carbon layer deposition device, the carbon element containing compound aerosol containing not less than 1 is introduced into the deposition device in advance, the high temperature cracking reaction of the above carbon element containing compound aerosol is carried out by the in-situ high temperature cracking carbon deposition method, the amorphous carbon sealing layer (2) is deposited on the surface of the optical fiber body (1), and the amorphous carbon sealing layer (2) with different thickness of 20nm-50nm on the surface of the optical fiber body (1) can be prepared by adjusting the carbon element containing compound gas concentration in the deposition device and the residence time of the optical fiber body (1) in the deposition device; Step 3: the optical fiber with amorphous carbon sealing layer (2) formed in the above step 2 is immersed in the liquid state of the silicon polyimide high temperature resistant composite material on the surface of the optical fiber by using the low speed drawing on-line immersion heat curing coating process; Step 4: the carbon sealing coated optical fiber wrapped with liquid silicon polyimide high temperature resistant composite material formed in the above step 3 is heated from 150 DEG C to 450 DEG C by using the 6-stage sectional heat curing furnace, so that the liquid silicon polyimide high temperature resistant composite material wrapped on the surface of the optical fiber is converted into solid state, and the silicon polyimide coating layer (3) is formed.

2. The manufacturing method of the high temperature resistant carbon sealing coated optical fiber according to claim 1, wherein: the optical fiber structure comprises the optical fiber body (1), the amorphous carbon sealing layer (2) and the silicon polyimide coating layer (3) from inside to outside; the thickness of the amorphous carbon sealing layer (2) is 20nm-50nm.

3. The manufacturing method of the high temperature resistant carbon sealing coated optical fiber according to claim 1, wherein: the optical fiber body (1) is the bending insensitive waveguide structure.

4. The manufacturing method of the high temperature resistant carbon sealing coated optical fiber according to claim 1, wherein: the diameter of the silicon polyimide coating layer (3) is 90μm-155μm. ​ ​ ​

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