CN101726792B - High-temperature resistant optical fiber and method for manufacturing same - Google Patents

Abstract

The invention relates to a high-temperature-resistant optical fiber used in the technical fields of special optical fiber communication, high-power laser transmission and sensing and a manufacturing method thereof. Including the optical fiber and the coating on the outer surface of the optical fiber, the coating is polyimide coating, the thickness of one side of the coating is 5-25 μm, and the Young's modulus of the cured polyimide coating is equal to or greater than 2GPa, its glass transition temperature is equal to or higher than 300°C, and its refractive index ranges from 1.38 to 1.78; the polyimide coating is formed by dipping and curing a polyimide solution on the outer surface of the optical fiber, including Pre-coating, pre-curing and secondary coating. The invention can be used in high temperature and harsh working environment, the long-term use temperature can be as high as 300°C, and the use characteristics are stable and can maintain good durability. The high temperature resistant optical fiber product manufactured by the method of the invention has a screening strength of 100kpsi, and the length of the product segment can reach 4km or even 6km.

Description

A high temperature resistant optical fiber and its manufacturing method

technical field

The invention relates to a high-temperature-resistant optical fiber used in the technical fields of special optical fiber communication, high-power laser transmission and sensing and a manufacturing method thereof.

Background technique

With the development of optical fiber technology, the application range of optical fiber has been extended to various high temperature and harsh environment systems. These systems require optical fibers to maintain good characteristics in harsh environments, which puts forward high optical, mechanical, environmental stability and reliability requirements for optical fibers. The existing conventional UV-cured polyacrylate coated optical fiber will seriously age or even fail when the temperature exceeds 85°C. It is easy to cause natural breakage of optical fiber, which cannot meet the reliability requirements of optical fiber transmission in high temperature environment. Chinese patent CN200620128456.7 discloses a high temperature resistant optical fiber, but the patent does not specifically introduce the coating structure and performance of the optical fiber and the method of manufacturing the optical fiber.

Contents of the invention

The technical problem to be solved by the present invention is to provide a high-temperature-resistant optical fiber with excellent high-temperature resistance and stable characteristics and a manufacturing method thereof in view of the above-mentioned deficiencies in the prior art.

The technical solution of the high-temperature-resistant optical fiber provided by the present invention is: comprising an optical fiber and a coating coated on the outer surface of the optical fiber, the optical fiber is composed of a silica glass core layer and a silica glass cladding surrounding the core layer, the difference is that The coating coated on the quartz glass cladding is a polyimide coating, and the single side thickness of the polyimide coating is 5-25 μm, and the Young's modulus of the cured polyimide coating is It is equal to or greater than 2GPa, its glass transition temperature is equal to or higher than 300°C, and its refractive index ranges from 1.38 to 1.78; the polyimide is an aromatic heterocyclic polymer compound containing imide chain segments; the The polyimide coating is formed by dipping the outer surface of the optical fiber with a polyimide solution and curing it by heating.

According to the above scheme, for optical fibers with a silica glass outer cladding diameter less than or equal to 220 μm, the polyimide coating unilateral thickness is 8% to 11% of the outer cladding diameter; for optical fibers with a quartz glass outer cladding diameter greater than or equal to 330 μm, The thickness of one side of the polyimide coating is 4% to 6% of the diameter of the outer cladding.

According to the above scheme, the optical fiber is a high-temperature-resistant optical fiber for sensing, the diameter of the outer cladding of quartz glass is 125 μm, the thickness of the polyimide coating is 15 μm on one side, and the attenuation coefficient of the optical fiber is less than 3.5 dB/km in the 850 nm window. The attenuation coefficient in the 1300nm window is less than 1.5dB/km.

According to the above scheme, the optical fiber is a high-temperature-resistant optical fiber for transmission in the visible to infrared band, and its outer cladding diameter of quartz glass is 220 μm, 440 μm or 660 μm, etc., and the corresponding polyimide coating has a single side thickness of 15 μm, 15 μm or 25 μm etc., the attenuation coefficient of the optical fiber is less than or equal to 10dB/km in the 850nm window, and the attenuation coefficient in the 1064nm window is less than or equal to 10dB/km.

According to the above scheme, the optical fiber is a high-temperature-resistant optical fiber for transmission from ultraviolet to visible bands, and its quartz glass cladding diameter is 220 μm, 440 μm or 660 μm, etc., and the corresponding polyimide coating thickness is 15 μm, 15 μm or 25 μm, etc., The attenuation coefficient of the optical fiber is less than 200dB/km in the 300nm window, and the attenuation coefficient in the 800nm window is less than 10dB/km.

The technical scheme of the high temperature resistant optical fiber manufacturing method of the present invention is:

Drawing the cleaned and dried optical fiber preform into fiber on a drawing device, including preform melting and spinning, surface coating treatment, and winding; the surface coating treatment is polyimide coating treatment, including preform Coating, pre-curing and secondary coating; the melting drawing is to send the preform into the high-temperature electric melting furnace for heating through the preform feeding mechanism, and the feeding speed range of the preform is controlled at 0.03~15mm/min; the high-temperature furnace The temperature control range of the work is 1700~2400℃. After one end of the preform is melted in the high temperature zone, a melting cone is formed under the action of gravity and surface tension. The tip of the cone is drawn and extended by the drawing mechanism to become an optical fiber; the range of drawing speed Controlled at 2m/min~20m/min, the typical value is 4m/min.

The pre-coating is that the optical fiber coming out of the high-temperature furnace passes through an outer diameter monitoring unit and then enters the pre-coating device. The device includes a storage bottle and a coating cup with a pointed mouth. The storage bottle is filled with high-pressure pure Gas, use air pressure to squeeze the coating solution in the storage bottle into the coating cup, so that the polyimide solution maintains an appropriate pressure in the coating cup. The viscosity range of polyimide solution is 1000cps to 10000cps, and the typical viscosity range is 5000cps to 10000cps, the optical fiber enters the coating cup and passes through the rubber nozzle at the bottom, so that the surface of the optical fiber is dipped with a layer of uniform coating solution.

The pre-curing is a pre-curing device in which the optical fiber coated with the solution passes through the pre-curing device. The pre-curing device is a cylindrical electric furnace placed vertically. The cylindrical high-temperature zone in the inner cavity of the electric furnace is the pre-curing channel. The diameter of the pre-curing channel is 20 to 28mm, the high temperature area is divided into two areas, one is the solvent volatilization area, the temperature range is 100 ℃ ~ 240 ℃, the other is the molecular synthesis area, the temperature is 240 ℃ ~ 460 ℃, the optical fiber is pulled by the winding mechanism at a uniform speed Slowly pass through the high temperature zone, the time for the optical fiber to pass through the high temperature zone of the electric furnace is 10 to 30 seconds.

The steps of pre-coating and pre-curing can be cycled (repeated) for 1 to 3 times.

The pre-coating and pre-curing process forms a uniform polyimide coating layer on the outer surface of the optical fiber, which is an undercoat layer. The thickness of the undercoat layer accounts for half or more of the final coating thickness, and the Young's modulus is equal to or greater than 2GPa. , the glass transition temperature is equal to or higher than 300°C.

The secondary coating is to perform secondary coating and curing on the pre-coated and pre-cured optical fiber. The pre-cured optical fiber enters the horizontal box-type resistance furnace through the guide wheel group for curing. The " A liner impregnated with polyimide solution is placed at the bottom of the V" groove. When the optical fiber passes through the guide wheel set, it will be coated with a very thin layer of paint, and then the optical fiber enters the box under the pull of the winding wheel. The high temperature zone of the box-type electric furnace is divided into two areas, one is the solvent volatilization area, the temperature range of this area is 120 ° C ~ 300 ° C, to complete the volatilization process of the solvent; the other is the molecular synthesis area, the temperature of this area is It is 300°C~500°C to complete the polymerization process of small solute molecules.

The second coating can be carried out 1 to 6 times to improve the curing quality of the coating and control the appropriate coating thickness to achieve the strengthening and toughening effect on the optical fiber.

For the secondary coating, two sets of guide wheels are set at both ends of the box-type electric furnace, so that the cured optical fiber is guided by the second guide wheel set and returned to the first guide wheel set for coating, and then enters the box-type electric furnace for curing. The bottom of the "V" groove of the guide wheel of the wheel set is lined with a liner impregnated with polyimide solution. The liner at the bottom of the V-shaped groove of the second guide wheel set is not impregnated with the paint solution, but only serves as a guide. The second guide wheel set passes through the periphery of the box-type electric furnace and returns to the first guide wheel set, and then repeats the above-mentioned process of guide wheel coating and box-type electric furnace curing, and this cycle repeats coating-curing for many times to form the final high-temperature-resistant optical fiber product. Up to 6 cycles are possible.

The viscosity range of the coating solution used for secondary coating is 1000cps to 10000cps, and the typical viscosity range is 1000cps to 7000cps.

After the secondary coating is cured, the polyimide coating layer outside the optical fiber primer layer is formed as the outer coating layer. The Young's modulus of the outer coating material is equal to or greater than 2GPa, and the typical value is not less than 4GPa, that is, the modulus of the outer coating is higher than that of the inner coating, because the outer coating is used to withstand the external application environment, and the higher Young's modulus The amount helps to improve the mechanical reliability of the fiber. The glass transition temperature of the outer coating is equal to or higher than 300°C, and the typical transition temperature is higher than 350°C. The thickness of the outer coating is 1/3 to 1/2 of the total thickness of the polyimide coating, with HTG50/125 Taking /155 optical fiber as an example, the thickness of the outer coating is 5 μm to 7.5 μm. The key factors affecting the thickness are the viscosity of the solution, the drawing speed of the optical fiber, and the curing time.

An exhaust system is provided at the outlet of the lower end of the pre-cured electric furnace cavity and/or at the outlet of the box-type electric furnace for secondary coating and curing, and the exhaust air volume is 30~50L/min. The function of the ventilation is to remove the solvent molecules in the pre-curing channel in time to promote the curing reaction, and to avoid the pollution of the indoor environment by the waste gas generated by the curing process.

The above-mentioned winding is that the high-temperature-resistant optical fiber made by the secondary coating process passes through the second outer diameter monitoring unit, and finally enters the winding mechanism for winding, and the length of the winding can reach 4km or even 6km at a time. The take-up is to wind a relatively long optical fiber on a take-up barrel with a diameter of not less than 400mm. The speed of the take-up barrel is controlled by a computer-controlled precision servo motor. The speed is associated with the first outer diameter monitoring unit to Controls the diameter of the optical fiber silica glass cladding. The function of the second outer diameter monitoring unit is to monitor the coating geometry of the optical fiber product, but not to control it.

The technical scheme of the special equipment for manufacturing high temperature resistant optical fiber of the present invention is as follows:

It includes a melting wire drawing device and a winding mechanism, and a pre-coating device and a pre-curing device are installed on the melting wire drawing device and the winding mechanism. The pre-coating device and the pre-curing device are provided with 1 to 3 sets, which are connected in series alternately. After the coating device and the pre-curing device, a secondary coating and curing device is installed, and the output end of the secondary coating and curing device is connected with the winding mechanism.

According to the above scheme, the pre-coating device is composed of a storage bottle containing polyimide solution and a coating cup with a pointed mouth. The storage bottle is filled with high-pressure pure gas, and the storage bottle is filled with air pressure. The coating solution is squeezed into the coating cup.

According to the above scheme, the pre-curing device is a vertically placed cylindrical electric furnace, and the cylindrical high-temperature zone in the inner cavity of the electric furnace is the pre-curing channel. The high-temperature zone is divided into two zones, one is the solvent volatilization zone, and the temperature range is 100 ℃ ~ 240 ℃, the other is the molecular synthesis area, the temperature is 240 ℃ ~ 460 ℃.

According to the above scheme, the secondary coating and curing device includes a box-type electric furnace installed horizontally, two sets of guide wheels are correspondingly arranged at both ends of the box-type circuit, and the number of guide wheels of the two sets of guide wheels is the same, ranging from 1 to 6 pieces, among which the bottom of the "V" groove of the first guide wheel group is padded with a liner impregnated with polyimide solution, which is installed at the entry end of the box-type electric furnace, and the second guide wheel set is installed in the box At the outlet end of the electric furnace, the box-type electric furnace corresponds to the upper end of each guide wheel of the two-end guide wheel group and sets the curing channel tangentially, and the lower end of each guide wheel of the two-end guide wheel group tangentially corresponds to the outside of the box-type electric furnace.

According to the above scheme, an exhaust device is provided at the outlet of the lower end of the pre-cured electric furnace cavity and/or at the outlet of the box-type electric furnace for secondary coating and curing, and the exhaust air volume is 30~50L/min.

The beneficial effect that the present invention obtains is:

1. The high-temperature-resistant optical fiber composed of polyimide with a specific thickness as the coating layer of the present invention includes high-temperature-resistant communication optical fiber, energy transmission optical fiber, sensing optical fiber, etc., which can be used in high temperature and harsh working environments, and the long-term use temperature can be as high as 300°C, which overcomes the disadvantage that polyacrylate-coated optical fibers produced by conventional UV curing processes cannot withstand harsh working environments. And the use characteristics are stable, and it still maintains good durability in harsh environments.

2. The high-temperature-resistant optical fiber manufacturing method of the present invention can accurately control the diameter of the optical fiber silica glass cladding and the coating diameter of the optical fiber to ensure that the deviation of the cladding diameter does not exceed ±2%, and the deviation of the coating diameter does not exceed ±3%. The high-temperature-resistant optical fiber product produced by the method of the invention has a screening strength of 100kpsi, and the length of the product segment can reach 4km or even 6km.

Description of drawings

Figure 1 is a cross-sectional view of a precoated cup in one embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view of a pre-curing furnace in an embodiment of the present invention.

Fig. 3 is a schematic diagram of a box-type circuit curing channel in secondary curing.

Fig. 4 is a schematic diagram of the special equipment for high temperature resistant optical fiber of the present invention.

Detailed ways

The present invention will be described in further detail below through the embodiments and the accompanying drawings.

Various high temperature resistant optical fibers in the present invention are prepared by pre-coating plus secondary coating process. The key to the process lies in the temperature setting of the pre-curing furnace and box-type electric furnace and the temperature setting of the preform electric melting furnace. Embodiments of the present invention are further described below.

The first embodiment: the fiber type is HT50/55/65, which is a kind of ultraviolet transmission fiber. The preform rod with a diameter of 21mm is melted and shrunk in a high-temperature heat field of 2180°C and stretched to form an optical fiber. At a pulling speed of 12m/min, it is coated with a polyimide coating to form a finished optical fiber. The cladding diameter of the optical fiber silica glass is 55 μm, the diameter of the polyimide coating is 65 μm, and the thickness of one side of the coating is 5 μm. The viscosity of the paint solution of the primer layer is 5500cps, the curing time is 5 seconds, and the temperature in the high temperature zone of the pre-curing electric furnace is set to 230°C in the solvent volatilization zone and 375°C in the molecular synthesis zone. The Young's modulus of the cured primer layer is 2.2 GPa, the glass transition temperature is 330° C., the refractive index is 1.5, and the thickness on one side is 2.5 μm. The viscosity of the outer coating solution is 1500cps, and the temperature in the high temperature zone of the secondary curing electric furnace is set to 270°C in the solvent volatilization zone and 400°C in the molecular synthesis zone. The cured outer coating has a Young's modulus of 4.5 GPa, a glass transition temperature of 350° C., and a single side thickness of 2.5 μm. The optical fiber has an attenuation coefficient of 1.2dB/m in the 200nm window and 180dB/km in the 300nm window.

The second embodiment: the fiber type is HT9/125/155, which is a high-temperature-resistant single-mode fiber for communication. The preform rod with a diameter of 44mm is melted and drawn in a high-temperature heat field at 2100°C to form an optical fiber. At a drawing speed of 10m/min, it is coated with a polyimide coating to form a finished optical fiber. The cladding diameter of the optical fiber silica glass is 125 μm, the diameter of the polyimide coating is 155 μm, and the thickness of one side of the coating is 15 μm. The viscosity of the primer coating solution is 5100cps, and the curing time is 6 seconds. The temperature settings in the high temperature zone of the pre-curing electric furnace are 235°C in the solvent volatilization zone and 380°C in the molecular synthesis zone. The Young's modulus of the cured primer layer is 2.5 GPa, the glass transition temperature is 315° C., the refractive index is 1.54, and the thickness on one side is 7.5 μm. The viscosity of the outer coating solution is 2000cps, and the temperature in the high temperature zone of the secondary curing electric furnace is set to 230°C in the solvent volatilization zone and 390°C in the molecular synthesis zone. The cured outer coating has a Young's modulus of 7.5 GPa, a glass transition temperature of 370° C., and a single side thickness of 7.5 μm. The optical fiber has an attenuation coefficient of 0.6dB/km in the 1310nm window and 0.5dB/km in the 1550nm window.

The third embodiment: the fiber type is HTG50/125/155, which is a high temperature resistant multimode fiber for sensing. The preform rod with a diameter of 40mm is melted and shrunk in a high-temperature heat field of 2150°C and stretched to form an optical fiber. At a pulling speed of 8m/min, it is coated with a polyimide coating to form a finished optical fiber. The cladding diameter of the optical fiber silica glass is 125 μm, the diameter of the polyimide coating is 155 μm, and the thickness of one side of the coating is 15 μm. The viscosity of the primer coating solution is 7000cps, and the curing time is 8 seconds. The temperature settings in the high temperature zone of the pre-curing electric furnace are 240°C in the solvent volatilization zone and 410°C in the molecular synthesis zone. The Young's modulus of the cured primer layer is 2.3 GPa, the glass transition temperature is 355° C., the refractive index is 1.6, and the thickness on one side is 10 μm. The viscosity of the coating solution for the outer coating is 1200cps, and the temperature settings in the high temperature zone of the secondary curing electric furnace are 260°C in the solvent volatilization zone and 410°C in the molecular synthesis zone. The cured outer coating has a Young's modulus of 4.5 GPa, a glass transition temperature of 370° C., and a single side thickness of 5 μm. The optical fiber has an attenuation coefficient of 2.6dB/km in the 850nm window and 0.8dB/km in the 1300nm window.

Fourth embodiment: the fiber type is HT400/440/470, which is a kind of laser transmission fiber. The preform rod with a diameter of 21mm is melted and shrunk in a high-temperature heat field of 2200°C and stretched to form an optical fiber. At a pulling speed of 5m/min, it is coated with a polyimide coating to form a finished optical fiber. The cladding diameter of the optical fiber silica glass is 440 μm, the diameter of the polyimide coating is 470 μm, and the thickness of one side of the coating is 15 μm. The viscosity of the primer coating solution is 6300cps, and the curing time is 12 seconds. The temperature settings in the high temperature zone of the pre-curing electric furnace are 227°C in the solvent volatilization zone and 445°C in the molecular synthesis zone. The Young's modulus of the cured primer layer is 3.4GPa, the glass transition temperature is 405° C., the refractive index is 1.45, and the thickness on one side is 10 μm. The viscosity of the outer coating solution is 3400cps, and the temperature settings in the high temperature zone of the secondary curing electric furnace are 290°C in the solvent volatilization zone and 435°C in the molecular synthesis zone. The cured outer coating has a Young's modulus of 6.0 GPa, a glass transition temperature of 410° C., and a single side thickness of 5 μm. The optical fiber has an attenuation coefficient of 180dB/km in the 300nm window and 8dB/km in the 800nm window.

In the fifth embodiment, the fiber type is HT600/660/710, which is a high damage threshold laser transmission fiber. The preform rod with a diameter of 22mm is melted and drawn in a high temperature heat field at 2200°C to form an optical fiber. At a drawing speed of 4m/min, it is coated with a polyimide coating to form a finished optical fiber. The cladding diameter of the optical fiber silica glass is 660 μm, the diameter of the polyimide coating is 710 μm, and the thickness of one side of the coating is 25 μm. The viscosity of the primer coating solution is 5700cps, the curing time is 15 seconds, and the temperature in the high temperature zone of the pre-curing electric furnace is set to 210°C in the solvent volatilization zone and 425°C in the molecular synthesis zone. The Young's modulus of the cured primer layer is 3.3 GPa, the glass transition temperature is 335° C., the refractive index is 1.42, and the thickness is 15 μm. The viscosity of the outer coating solution is 5300cps, and the temperature settings in the high temperature zone of the secondary curing electric furnace are 270°C in the solvent volatilization zone and 490°C in the molecular synthesis zone. The cured outer coating has a Young's modulus of 11 GPa, a glass transition temperature of 400° C., and a single side thickness of 10 μm. The optical fiber has an attenuation coefficient of 10dB/km in the 850nm window and 9.8dB/km in the 1064nm window.

In the sixth embodiment, the fiber type is HT1000/1100/1180, which is a visible to infrared transmission fiber. The preform rod with a diameter of 26mm is melted and shrunk in a high-temperature heat field of 2250°C and stretched to form an optical fiber. At a pulling speed of 2m/min, it is coated with a polyimide coating to form a finished optical fiber. The cladding diameter of the optical fiber silica glass is 1100 μm, the diameter of the polyimide coating is 1180 μm, and the thickness of one side of the coating is 40 μm. The viscosity of the primer coating solution is 8900cps, and the curing time is 30 seconds. The temperature settings in the high temperature zone of the pre-curing electric furnace are 225°C in the solvent volatilization zone and 410°C in the molecular synthesis zone. The Young's modulus of the cured primer layer is 2.1 GPa, the glass transition temperature is 380° C., the refractive index is 1.7, and the thickness on one side is 20 μm. The viscosity of the outer coating solution is 5300cps, and the temperature settings in the high temperature zone of the secondary curing electric furnace are 295°C in the solvent volatilization zone and 460°C in the molecular synthesis zone. The cured outer coating has a Young's modulus of 4.1 GPa, a glass transition temperature of 400° C., and a single side thickness of 20 μm. The optical fiber has an attenuation coefficient of 25dB/km in the 470nm window and 10dB/km in the 630nm window.

The embodiment of the equipment of the present invention is shown in the accompanying drawings. After the pre-coating cup 3, the quartz glass optical fiber 1 enters the pre-curing device 6 for pre-curing. Such pre-coating and pre-curing devices can be installed in 3 groups. In the simplified schematic diagram Only 1 group is listed. The pre-coating device consists of a storage bottle filled with polyimide solution and a coating cup 3 with a rubber tip 4. The storage bottle is filled with high-pressure pure gas, and the coating solution 2 in the storage bottle is squeezed by air pressure. Into the coating cup, the optical fiber passes through the pre-coating cup from the rubber tip at the bottom of the pre-coating cup and enters the pre-curing device 6. The pre-curing device is a cylindrical electric furnace placed vertically, and the high-temperature zone of the inner cavity of the electric furnace is cylindrical. That is the pre-curing channel, the high temperature zone is divided into two areas, one is the solvent volatilization area 7, the temperature range is 100°C-240°C, and the other is the molecular synthesis area 5, the temperature is 240°C-460°C. After pre-coating and pre-curing, the optical fiber is guided into the secondary coating and curing through the guide wheel 12. The secondary coating and curing device includes a box-type electric furnace 9 installed horizontally, and two sets of guide wheels are set at both ends of the box-type electric furnace. The number of guide wheels in the two sets of guide wheels is the same, ranging from 1 to 6. Among them, the bottom of the "V" groove of the first guide wheel set 13 guide wheels is padded with a liner impregnated with polyimide solution, which is installed on the The entry end of the box-type electric furnace, the second guide wheel group 11 is installed at the outlet end of the box-type electric furnace, and the upper end of each guide wheel of the box-type electric furnace corresponds to the two guide wheel groups. The lower end of the guide wheel is tangentially corresponding to the outside of the box-type electric furnace. After the first guide wheel set 13 is dip-coated with a thin layer of paint, it enters the box-type curing furnace 9 for secondary curing, and then is guided by the second guide wheel set 11 to return to the first guide wheel set to repeat the secondary coating and secondary curing process . Because the guide wheel set is composed of 6 concentric guide wheels with independent rotation, the process of guiding and curing the optical fiber through the guide wheel set can be up to 6 times. After 6 times of curing, the finished optical fiber is wound on the optical fiber supporting drum by the winding mechanism 10 . An exhaust device is provided at the outlet of the lower end of the pre-cured electric furnace cavity and/or at the outlet of the box-type electric furnace for secondary coating and curing, and the exhaust air volume is 30-50 L/min.

Claims (3)

1. A method for manufacturing a high-temperature-resistant optical fiber, drawing the cleaned and dried optical fiber preform into a fiber on a wire drawing device, including melting and spinning the preform, surface coating treatment, and winding; it is characterized in that the described resistance High-temperature optical fiber includes an optical fiber and a coating on the outer surface of the optical fiber. The optical fiber is composed of a silica glass core and a silica glass cladding surrounding the core. The coating on the outer surface of the silica glass cladding is polyimide Amine coating, the thickness of one side of the polyimide coating is 5-25 μm, the Young’s modulus of the cured polyimide coating is equal to or greater than 2 GPa, and its glass transition temperature is equal to or higher than 300 °C, the refractive index ranges from 1.38 to 1.78; the polyimide is an aromatic heterocyclic polymer compound containing imide chain segments; the polyimide coating is dip-coated on the outer surface of the optical fiber The imide solution is cured by heating; the surface coating treatment is polyimide coating treatment, including pre-coating, pre-curing and secondary coating; the molten wire drawing is fed through a preform The mechanism sends the preform into the high-temperature electric melting furnace for heating, and the feeding speed range of the preform is controlled at 0.03-15mm/min; the temperature control range of the high-temperature furnace is 1700-2400°C, and one end of the preform is melted in the high-temperature zone after gravity Under the action of surface tension and surface tension, a melting cone is formed, and the tip of the cone is pulled and extended by the drawing mechanism to become an optical fiber; the range of drawing speed is controlled at 2m/min～20m/min; the pre-coating comes out of a high-temperature furnace The optical fiber passes through an outer diameter monitoring unit and then enters the pre-coating device, which includes a storage bottle and a coating cup with a pointed mouth. The storage bottle is filled with high-pressure pure gas, and the coating solution in the storage bottle is squeezed out by air pressure. Into the coating cup, so that the polyimide solution maintains an appropriate pressure in the coating cup. The viscosity of the polyimide solution ranges from 1000cps to 10000cps. After the optical fiber enters the coating cup, it passes through the rubber tip at the bottom, so that the surface of the fiber Dip coating with a layer of uniform coating solution; the pre-curing is a device in which the optical fiber coated with the solution is pre-cured. The pre-curing device is a cylindrical electric furnace placed vertically, and the cylindrical high-temperature zone of the inner cavity of the electric furnace is Pre-curing channel, the high temperature zone is divided into two areas, one is the solvent volatilization area, the temperature range is 100 ℃ ~ 240 ℃, the other is the molecular synthesis area, the temperature is 240 ℃ ~ 460 ℃, the optical fiber is pulled by the winding mechanism at a uniform speed Slowly pass through the high-temperature zone, and the time for the optical fiber to pass through the high-temperature zone of the electric furnace is 10 to 30 seconds; the pre-coating and pre-curing process is cycled 1 to 3 times; and the pre-coating and pre-curing process forms a uniform surface on the outer surface of the optical fiber. The polyimide coating layer is an undercoat layer, the thickness of the undercoat layer accounts for half or more of the thickness of the final coating layer, the Young's modulus is equal to or greater than 2GPa, and the glass transition temperature is equal to or higher than 300°C; the said The second coating is to coat and cure the pre-coated and pre-cured optical fiber again. The pre-cured optical fiber enters the horizontal box-type resistance furnace through the guide wheel group for curing. The "V" of the guide wheel The bottom of the groove is lined with a liner impregnated with polyimide solution. When the optical fiber passes through the guide wheel set, it will be dip-coated with a layer of pole Thin coating layer, and then the optical fiber enters the box-type electric furnace for curing under the traction of the winding wheel. The high-temperature zone of the box-type electric furnace is divided into two areas, one is the solvent volatilization area, and the temperature range of this area is 120 ° C ~ 300 ° C, The volatilization process of the solvent is completed; the other is the molecular synthesis area, the temperature of this area is 300 ℃ ~ 500 ℃, and the polymerization process of the solute small molecules is completed; the second coating is carried out 1 to 6 times. 2. The manufacturing method of high temperature resistant optical fiber according to claim 1, characterized in that the viscosity range of the used coating solution for the secondary coating is 1000cps to 10000cps, and the polyimide outside the optical fiber primer layer is formed after the secondary coating is cured Coating layer, called the outer coating, the modulus of the outer coating is higher than that of the inner coating, the glass transition temperature of the outer coating is equal to or higher than 300°C, and the thickness of the outer coating is 1% of the total thickness of the polyimide coating /3 to 1/2. 3. The manufacturing method of high-temperature-resistant optical fiber according to claim 1, characterized in that for optical fibers with a silica glass outer cladding diameter less than or equal to 220 μm, the thickness of the polyimide coating on one side is 8% to 11 μm of the outer cladding diameter. %; For optical fibers with a quartz glass outer cladding diameter greater than or equal to 330 μm, the thickness of the polyimide coating on one side is 4% to 6% of the outer cladding diameter.

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