Device and method for replacing gas in hollow-core optical fiber

Abstract

The invention provides a device and method for replacing gas in a hollow-core optical fiber, and the device comprises a high-pressure gas chamber which is provided with at least one hollow-core optical fiber interface and at least one gas inlet / outlet, the hollow-core optical fiber interface is used for being connected with a gas path at one end of the hollow-core optical fiber, and the other end of the hollow-core optical fiber is sealed; the gas path is connected with the gas inlet and outlet; the vacuum pump is connected with the gas inlet and outlet through a gas path and is used for extracting residual gas in the hollow-core optical fiber; and the high-pressure gas source is connected with the gas inlet and outlet through a gas path and is used for filling high-pressure gas into the hollow-core optical fiber. Gas in the hollow-core optical fiber can be exhausted and replaced, the air pressure state in the hollow-core optical fiber is improved, and the signal transmission performance and the long-term use stability of the optical fiber are enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of hollow-core optical fibers, and in particular relates to a device and method for replacing gas inside a hollow-core optical fiber. Background Art

[0002] Hollow-core optical fiber consists of a hollow capillary structure containing a gas. Some gas molecules have a significant absorption effect on electromagnetic waves in common communication bands, resulting in gas absorption losses. For example, water vapor molecules have strong absorption losses for electromagnetic waves between 1320nm and 1500nm, while carbon dioxide gas molecules have certain absorption losses for electromagnetic waves around 1580nm and 1600nm. These losses can cause distortion of communication signals, thereby reducing the transmission performance of hollow-core optical fiber.

[0003] Due to the presence of carbon impurities in the raw material of optical fiber quartz, a certain amount of carbon dioxide gas is generated and retained within the optical fiber after the high-temperature drawing process. Furthermore, during the drawing process, water vapor and carbon dioxide molecules from the air can enter the fiber from the bottom of the drawn fiber strands. These factors lead to absorption losses of water vapor and carbon dioxide in the hollow-core fiber after the drawing process.

[0004] Furthermore, due to the cooling process after high-temperature drawing, the relative pressure inside hollow-core fibers is typically negative. Therefore, during hollow-core fiber testing or when a hollow-core fiber breaks unexpectedly, the end face of the fiber is exposed to the outside air. Due to the negative pressure differential between the inside and outside of the fiber, outside air can easily be drawn into the hollow-core fiber, along with "pollutant" gas molecules such as water vapor and carbon dioxide, further degrading fiber performance.

[0005] Chinese patent application CN115390194A discloses a miniaturized hollow-core fiber gas chamber connection device with adjustable internal air pressure. By connecting the two ends of a hollow-core fiber to an air chamber, the gas pressure inside the hollow-core fiber can be easily adjusted. However, this solution does not address how to remove the "contaminated gas" already inside the hollow-core fiber. Summary of the Invention

[0006] In response to the above-mentioned defects or improvement needs of the prior art, the present invention proposes a hollow-core optical fiber internal gas replacement device and method, which can discharge and replace the gas inside the hollow-core optical fiber, improve the internal air pressure state of the hollow-core optical fiber, and enhance the optical fiber signal transmission performance and long-term use stability.

[0007] To achieve the above objectives, according to a first aspect of the present invention, a hollow-core optical fiber internal gas displacement device is provided, comprising: The high-pressure gas chamber is provided with at least one hollow-core optical fiber interface and at least one gas inlet and outlet, wherein the hollow-core optical fiber interface is used to communicate with one end of the hollow-core optical fiber, and the other end of the hollow-core optical fiber is sealed; Gas line, connected to the gas inlet and outlet; A vacuum pump connected to the gas inlet and outlet through a gas path, used to extract residual gas in the hollow-core optical fiber; The high-pressure gas source is connected to the gas inlet and outlet through the gas path and is used to fill the hollow-core optical fiber with high-pressure gas.

[0008] According to the above solution, an optical detection component is also included, which is connected to the other end of the hollow-core optical fiber and is used to monitor the gas state inside the hollow-core optical fiber in real time.

[0009] According to the above scheme, there is one optical detection component; The other end of the hollow-core optical fiber is provided with a connector for plugging and unplugging with the optical detection component.

[0010] According to the above solution, the connector is a jumper with an APC interface, and the jumper is fused with the hollow-core optical fiber.

[0011] According to the above solution, the optical detection component is an optical time domain reflectometer.

[0012] According to the above scheme, the gas circuit is provided with a mixing branch, a charging branch, a pumping branch and a deflation branch; among which, One end of the mixing branch is connected to the gas inlet and outlet, and the other end of the mixing branch is connected to one end of the inflation branch, the exhaust branch and the deflation branch respectively; The other end of the inflation branch is connected to the high-pressure gas source, the other end of the exhaust branch is connected to the vacuum pump, and the other end of the deflation branch is connected to the outside world; The mixing branch, the charging branch, the exhaust branch and the deflation branch are respectively provided with switch valves.

[0013] According to the above scheme, pressure gauges are respectively connected to the inflation branch, the exhaust branch and the high-pressure gas chamber.

[0014] According to the above solution, at least one of a gas purifier, a booster pump and a pressure reducer is connected in series on the inflation branch line.

[0015] According to the above solution, the inner diameter of the hollow-core fiber interface is larger than the outer diameter of the hollow-core fiber, and is sealed and connected to the outside of the hollow-core fiber through sealant, so that the interior of the hollow-core fiber is connected to the high-pressure gas chamber gas path.

[0016] According to a second aspect of the present invention, a method for replacing gas inside a hollow-core optical fiber using the hollow-core optical fiber internal gas replacement device is provided, comprising the following steps: Use a vacuum pump to evacuate the gas path, high-pressure gas chamber and hollow-core optical fiber to reach a predetermined low pressure; High-pressure gas is filled into the gas path, high-pressure gas chamber and hollow-core optical fiber through a high-pressure gas source. After reaching a predetermined high pressure, the high-pressure gas chamber is kept sealed and maintained within a certain pressure range, so that the high-pressure gas can flow into the hollow-core optical fiber. When the high-pressure gas reaches the other end of the hollow-core optical fiber or the preset position, it stops.

[0017] According to the above method, before the high-pressure gas is charged, the gas introduced from the high-pressure gas source is purified and the purified gas is pressurized.

[0018] According to the above method, the process of high-pressure gas passing into the hollow-core optical fiber is monitored by an optical time domain reflectometer, thereby determining the position where the high-pressure gas reaches the hollow-core optical fiber.

[0019] According to the above method, when the high-pressure gas reaches the preset position of the hollow-core optical fiber, the gas replacement is stopped, the high-pressure gas in the gas chamber and the gas path is discharged, the hollow-core optical fiber is removed, the part between the other end of the hollow-core optical fiber and the preset position is cut off, and the two end faces of the hollow-core optical fiber are sealed and preserved.

[0020] According to the above method, the process of high-pressure gas introduction into the hollow-core optical fiber is monitored by optical time domain reflectometry, specifically including: After inflation, the light reflection intensity of the hollow-core fiber near one end of the hollow-core fiber increases significantly, i.e., a bulge appears, indicating that the high-pressure gas has successfully entered the fiber. The range covered by the bulge indicates the length of the high-pressure gas immersed in the fiber. As the inflation time increases, the bulge gradually moves backward, indicating that the high-pressure gas gradually moves from the inflation end of the high-pressure gas chamber to the other end of the hollow-core optical fiber; Until the bulge reaches the preset position of the hollow-core optical fiber.

[0021] According to a third aspect of the present invention, there is provided a hollow-core optical fiber obtained by the hollow-core optical fiber internal gas replacement method, comprising an internal gas having a certain pressure, wherein the pressure distribution of the internal gas is: Immediately after the treatment, the air pressure at one end of the hollow-core fiber is much higher than that at the other end, and both are higher than the outside atmospheric pressure; After the treatment is completed and the hollow fiber is sealed and placed for a certain period of time, the air pressure inside the hollow fiber is evenly distributed.

[0022] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art: 1. By adopting a combination of a high-pressure gas chamber, an air circuit, a vacuum pump, and a high-pressure gas source, after extracting the residual gas from one end of the hollow-core optical fiber, high-pressure gas is injected into the hollow-core optical fiber from the other end. The remaining gas is left at the other end of the hollow-core optical fiber and removed by interception, thereby completely replacing the original gas inside the hollow-core optical fiber, improving the additional attenuation problem caused by gas absorption, and on the other hand, increasing the gas pressure inside the hollow-core optical fiber and enhancing the long-term stability of the optical fiber. The high-pressure gas chamber can be connected to more than one hollow-core optical fiber and replace the gas for multiple hollow-core optical fibers at the same time, greatly improving the processing efficiency.

[0023] 2. By adopting an optical detection component to connect with the hollow-core optical fiber in a plug-in manner, during the entire gas replacement process, only one optical detection component is used to realize the high-pressure gas introduction process of multiple hollow-core optical fibers, saving costs.

[0024] 3. By rationally setting the gas path and setting various valves, sensors and functional components, the efficiency and quality of the replacement gas can be further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural diagram of an embodiment of the present invention.

[0026] Figure 2 Schematic diagram of a method flow according to an embodiment of the present invention.

[0027] Figure 3 The results of monitoring the inflation process of hollow-core optical fiber using optical time domain reflectometry.

[0028] Figure 4 The results of optical time domain reflectometry monitoring of a hollow-core optical fiber sealed after gas replacement.

[0029] In the picture: 1. Hollow-core optical fiber; 2. Optical time-domain reflectometer; 3. High-pressure gas chamber; 4. Gas circuit; 5. High-pressure gas source; 6. Gas purifier; 7. Booster pump; 8. Vacuum pump.

[0030] 11. First jumper; 21. Second jumper; 22. Flange; 31. Hollow-core optical fiber interface; 32. Pressure gauge; 33. High-pressure gas chamber safety valve; 41. Booster pump pressure gauge; 42. Vacuum pump pressure gauge; 43. Booster pump control valve; 44. Vacuum pump control valve; 45. Exhaust valve; 46. Pressure-maintaining stop valve; 47. Vent branch; 51. Pressure reducer. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0032] According to the first aspect of the present invention, this embodiment provides a hollow core optical fiber internal gas replacement device, such as Figure 1 As shown, it includes a high-pressure gas chamber 3, a gas circuit 4, a vacuum pump 8 and a high-pressure gas source 5.

[0033] High-pressure gas chamber 3 is a pressure vessel capable of withstanding pressures ranging from -0.1 MPa to 10 MPa. High-pressure gas chamber 3 is equipped with at least one hollow-core fiber interface 31 and at least one gas inlet and outlet. Hollow-core fiber interface 31 is connected to one end of hollow-core fiber 1, while the other end of hollow-core fiber 1 is sealed.

[0034] In certain embodiments, the inner diameter of the hollow-core fiber interface 31 is larger than the outer diameter of the hollow-core fiber 1 and is sealed to the exterior of the hollow-core fiber 1 via a sealant, thereby connecting the interior of the hollow-core fiber to the high-pressure gas chamber. The other end of the hollow-core fiber 1 is fused to a first jumper cable 11, which has an APC interface. The device also includes an optical time-domain reflectometer 2, which is connected to a second jumper cable 21, also having an APC interface (i.e., flange 22). The optical time-domain reflectometer 2 is pluggable and connected to the hollow-core fiber 1 via the APC interface. Because the entire replacement process is relatively lengthy, there is no need to constantly monitor the air pressure inside the hollow-core fiber 1. Therefore, a single optical time-domain reflectometer 2 can be used to monitor the internal air pressure of multiple hollow-core fibers 1. The optical time-domain reflectometer 2 can also be replaced with other optical detection components.

[0035] Also be provided with pressure gauge 32 above high pressure chamber 3, working range is 0-150Mpa. In addition, also be provided with safety valve above high pressure chamber 3, can automatically release pressure when air pressure exceeds air chamber scope, make air pressure be reduced to working pressure.

[0036] Gas circuit 4, connected to the gas inlet and outlet, is a high-pressure pipeline capable of withstanding at least 20 MPa. It includes a mixing branch, an inflation branch, an exhaust branch, and a deflation branch 47. One end of the mixing branch is connected to the gas inlet and outlet, while the other end is connected to one end of each of the inflation, exhaust, and deflation branches 47. A pressure-maintaining shutoff valve 46 is provided on the mixing branch.

[0037] The other end of the inflation branch is connected to a high-pressure gas source 5. High-pressure gas source 5 is typically rated at 15 MPa and contains inert gases that have no significant impact on hollow-core fiber communication capabilities. These gases include, but are not limited to, nitrogen, argon, and helium. The gas source can be changed based on actual usage. A pressure reducer 51 is installed at the outlet of high-pressure gas source 5 to reduce the gas pressure to the inlet pressure of gas purifier 6. Starting from high-pressure gas source 5, the inflation branch is connected in series with gas purifier 6, booster pump 7, booster pump pressure gauge 41, and booster pump control valve 43. Gas purifier 6 removes impurities such as water vapor from the outlet gas of high-pressure gas source 5 and then passes the gas to booster pump 7. After purification by the gas purifier, the impurity content is less than 1 ppb. Booster pump 7 regulates the pressure of the gas entering the high-pressure chamber, which should be between 1 MPa and 10 MPa. A pressure gauge 41 for monitoring the outlet pressure and a valve 43 for controlling the opening and closing of the booster pump 7 are installed in the outlet pipeline of booster pump 7.

[0038] The other end of the exhaust branch is connected to a vacuum pump 8, which is also equipped with a vacuum pump pressure gauge 42 and a vacuum pump control valve 44. The vacuum pump 8 is primarily used to extract impurity gases from the high-pressure gas chamber 3 and gas path 4 before the experiment begins. The vacuum pump control valve 4 is controlled according to the reading of the vacuum pressure gauge 42 to roughly adjust the vacuum level in the high-pressure gas chamber.

[0039] The other end of the deflation branch 47 is connected to the outside world. An exhaust valve 45 is provided on the deflation branch 47 to exhaust excess gas in the gas path 4. For example, after the gas replenishment process is completed, the exhaust valve 45 can be opened to exhaust the high-pressure gas in the gas path 4.

[0040] The device described in the present invention can monitor the current working pressure in real time through the pressure gauge on the high-pressure gas chamber; during the gas replenishment process, the gas replenishment pressure can be adjusted by the pressure pump; in the present invention, the replenishment gas is purified by a gas purifier, thereby avoiding the increase in absorption loss of the optical fiber caused by impurities that may exist in the replenishment gas; at the same time, after closing the pressure-maintaining stop valve on the gas path, the gas chamber pressure can be kept constant, thereby replenishing the gas at a stable constant pressure; in addition, the safety valve on the high-pressure gas chamber will automatically release the pressure when the pressure exceeds the rated value, further ensuring the safety of the gas replenishment process; the present invention also monitors the current gas replenishment progress in real time through an optical time domain reflectometer, and can adjust the working pressure according to actual needs.

[0041] According to the second aspect of the present invention, this embodiment further provides a method for replacing gas inside a hollow-core optical fiber using the hollow-core optical fiber internal gas replacement device, comprising the following steps: After the hollow-core optical fiber is drawn, it is connected to the gas replacement device inside the hollow-core optical fiber, and the air path, high-pressure air chamber and hollow-core optical fiber are evacuated by a vacuum pump to reach a predetermined low pressure; High-pressure gas is filled into the gas path, high-pressure gas chamber and hollow-core optical fiber through a high-pressure gas source. After reaching a predetermined high pressure, the high-pressure gas chamber is kept sealed and maintained within a certain pressure range, so that the high-pressure gas can flow into the hollow-core optical fiber. When the high-pressure gas reaches the other end of the hollow-core optical fiber or the preset position, it stops.

[0042] Preferably, before the high-pressure gas is charged, the gas introduced from the high-pressure gas source is purified and the purified gas is pressurized.

[0043] Furthermore, the process of high-pressure gas passing into the hollow-core optical fiber is monitored by an optical time domain reflectometer, thereby determining the position where the high-pressure gas reaches the hollow-core optical fiber.

[0044] Because the vacuum pump cannot completely remove the residual gas in the hollow-core fiber, a small amount of gas may remain inside the hollow-core fiber. Therefore, the high-pressure gas cannot reach the other end of the hollow-core fiber. When the high-pressure gas reaches the preset position of the hollow-core fiber, a small section of the hollow-core fiber may still remain. Stop gas replacement, exhaust the high-pressure gas in the air chamber and gas path, remove the hollow-core fiber, cut the section between the other end of the hollow-core fiber and the preset position, and seal both ends of the hollow-core fiber for storage.

[0045] This embodiment provides a complete gas replacement such as Figure 2 As shown, specifically including: S1. After the hollow core optical fiber 1 is drawn, one end thereof is connected to the high-pressure gas chamber 3, and the other end is connected to the jumper 11 and connected to the jumper 21 of the optical time domain reflectometer 2 through the flange 22.

[0046] S2. Open the vacuum pump control valve 44 and the pressure-maintaining stop valve 46, close the booster pump control valve 43 and the exhaust valve 45, and turn on the vacuum pump 8 to evacuate the gas path 4 and the high-pressure gas chamber 3 to discharge any contaminated gas that may be present.

[0047] S3. Close the vacuum pump control valve 44, open and adjust the pressure reducer 51 of the high-pressure gas source 5, so that the gas meets the working pressure of the gas purifier 6 and is introduced into it.

[0048] S4. Set the pressure of the booster pump 7. After the purified gas is introduced into the booster pump 7, the pressure increases to the set value. After the booster pump control valve 43 is opened, the high-pressure gas flows through the gas path and is introduced into the high-pressure gas chamber 3.

[0049] S5. Observe the pressure gauge 32 on the high-pressure gas chamber. When the indicated value reaches the value set by the booster pump 7, close the pressure-maintaining stop valve 46. At this time, the high-pressure gas in the high-pressure gas chamber 3 enters the interior of the hollow-core optical fiber 1. Then close the pressure reducer 51 and the booster pump 7, and open the exhaust valve 45 to discharge the gas in the gas path 4 from the exhaust port 47. Then close the booster pump valve 43.

[0050] S6. After the high-pressure gas enters the hollow-core optical fiber 1, it pushes the gas originally in the hollow-core optical fiber 1 to flow toward one end of the jumper 11. The air pressure in the hollow-core optical fiber 1 gradually increases near the end of the high-pressure gas chamber 3, and the high-pressure section gradually expands over time. The pressure change inside the hollow-core optical fiber 1 can be fed back through the indication results of the optical time domain reflectometer 2. Because the internal space of the hollow-core optical fiber 1 is very small, the pressure in the high-pressure gas chamber 3 will slowly decrease. According to the real-time results of the optical time domain reflectometer 2, when the high-pressure gas in the hollow-core optical fiber 1 approaches or reaches one end of the jumper 11, the pressure-maintaining shut-off valve 46 is opened to discharge the gas in the gas chamber 3 from the exhaust port 47, and the hollow-core optical fiber 1 is removed.

[0051] S7. According to the final result of the optical time domain reflectometer 2, the part of the hollow-core optical fiber close to the jumper 11 where the high-pressure gas does not reach or the part with lower pressure contains the original gas in the optical fiber. This part is cut off to complete the gas replacement in the hollow-core optical fiber 1. After cutting, the two end faces of the hollow-core optical fiber 1 are sealed and preserved.

[0052] Figure 3 This is the real-time monitoring result of a typical gas replacement process by optical time domain reflectometer 2. Figure 3 It can be seen that after inflation, the light reflection intensity of the part of the optical fiber length near the inflation end increases significantly, that is, a "bulge" appears, which indicates that the high-pressure gas has successfully entered the interior of the optical fiber, and the range covered by the "bulge" indicates the length of the high-pressure gas immersed in the optical fiber. As the inflation time increases, the "bulge" gradually advances backward, which indicates that the high-pressure gas gradually advances from the optical fiber interface end 31 on the high-pressure gas chamber to the fusion end with the jumper 11. By the sixth day, only about 80m of optical fiber remains without a "bulge". At this time, the hollow-core optical fiber can be removed, and the jumper 11 and the approximately 80m of optical fiber near it can be cut and discarded. At this time, the "contaminated gas" originally contained in the hollow-core optical fiber 1 has been replaced by the inactive gas that has been introduced.

[0053] The longer the optical fiber or the lower the pressure of the high-pressure gas used, the longer the gas replacement process takes. Table 1 shows the gas replacement time required for several typical embodiments. Generally speaking, the time required for gas replacement will not exceed 60 days.

[0054] In the wavelength range of 1600nm to 1601nm, carbon dioxide gas has three relatively high absorption peaks. The average amount of additional attenuation of these three absorption peaks is used as a typical value to measure the degree of gas contamination of the optical fiber.

[0055] Table 1

[0056] As shown in Table 1, after gas replacement, the hollow-core fiber 1 is filled with the inert gas, and the fiber's gas-added attenuation is significantly less than before gas replacement. Furthermore, because the fiber's interior is at a higher pressure than the external environment, it is more effectively protected against the ingress of external contaminants, minimizing the increase in gas-added attenuation over extended periods. Table 1 also indicates that the longer the fiber or the higher the gas pressure used, the greater its resistance to external gas ingress after gas replacement. Generally speaking, after gas replacement, the fiber's gas-added attenuation will not exceed 10% for at least 30 days, and up to 89 days.

[0057] After the gas replacement is completed, both ends of the optical fiber are sealed and placed. Figure 4 The optical time domain reflectometer readings for different placement times are shown in the figure. As can be seen from the figure, as the placement time increases, the reading at the air-filled end of the optical fiber slowly decreases, while the reading at the non-air-filled end rises rapidly. By the sixth day, the curve is close to a straight line, indicating that the air pressure inside the optical fiber is nearly evenly distributed.

[0058] Table 2

[0059] Table 2 shows the time required for the optical fiber to achieve uniform internal pressure distribution after gas replacement under several typical embodiments. It can be seen from the table that the longer the optical fiber or the greater the high-pressure gas pressure, the longer the time required to achieve uniform internal pressure distribution. Generally speaking, after the optical fiber gas replacement is completed, the internal pressure can be close to uniform distribution within 30 days at the latest.

[0060] Hollow-core optical fibers can be between 500m and 10km in length. Maintaining the high-pressure gas chamber for up to 60 days allows the high-pressure gas to fully flow through the entire fiber. The shorter the fiber or the higher the gas pressure, the shorter the time required. After treatment, the gas pressure at the gas-filled end of the hollow-core fiber is significantly higher than that at the monitoring end, but both are higher than the ambient atmospheric pressure. The gas absorption attenuation of the treated hollow-core fiber is reduced by over 70% compared to pre-treatment. Sealing the treated hollow-core fiber for up to 30 days will achieve a near-uniform internal pressure distribution. The shorter the fiber or the higher the gas pressure, the shorter the time required. If the treated hollow-core fiber is exposed to the ambient atmosphere with both ends open for at least 30 days, the gas absorption attenuation in the 1460nm to 1625nm band will not increase by more than 10%. The longer the fiber or the higher the gas pressure used, the longer the open period, up to a maximum of 90 days.

[0061] As a third aspect of the present invention, this embodiment further provides a hollow-core optical fiber obtained using the aforementioned hollow-core optical fiber internal gas replacement method, comprising an internal gas having a predetermined pressure, wherein the pressure distribution of the internal gas is such that immediately after treatment, the pressure at one end of the hollow-core optical fiber is significantly higher than the pressure at the other end, and both pressures are higher than the ambient atmospheric pressure; and after treatment and sealing for a predetermined period of time, the pressure within the hollow-core optical fiber is uniformly distributed. The predetermined period of time is 6-30 days, depending on the length of the hollow-core optical fiber and the gas pressure; the shorter the optical fiber and / or the higher the gas pressure, the shorter the required time.

[0062] It should be pointed out that, according to the needs of implementation, the various steps / components described in this application can be split into more steps / components, or two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0063] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A hollow-core optical fiber internal gas replacement device, characterized by: include: The high-pressure gas chamber is provided with at least one hollow-core optical fiber interface and at least one gas inlet and outlet, wherein the hollow-core optical fiber interface is used to communicate with one end of the hollow-core optical fiber, and the other end of the hollow-core optical fiber is sealed; Gas line, connected to the gas inlet and outlet; A vacuum pump connected to the gas inlet and outlet through a gas path, used to extract residual gas in the hollow-core optical fiber; The high-pressure gas source is connected to the gas inlet and outlet through the gas path and is used to fill the hollow-core optical fiber with high-pressure gas.

2. The hollow-core optical fiber internal gas replacement device according to claim 1, characterized in that: It also includes an optical detection component connected to the other end of the hollow-core optical fiber for real-time monitoring of the gas state inside the hollow-core optical fiber.

3. The hollow-core optical fiber internal gas replacement device according to claim 2, characterized in that: There is one optical detection component; The other end of the hollow-core optical fiber is provided with a connector for plugging and unplugging with the optical detection component.

4. The hollow-core optical fiber internal gas replacement device according to claim 3, characterized in that: The connector is a jumper with an APC interface, which is fused with the hollow-core optical fiber.

5. The hollow-core optical fiber internal gas replacement device according to any one of claims 2 to 4, characterized in that: The optical detection component is an optical time domain reflectometer.

6. The hollow-core optical fiber internal gas replacement device according to claim 1, characterized in that: The gas circuit is equipped with a mixing branch, a charging branch, a pumping branch and a deflation branch; among them, One end of the mixing branch is connected to the gas inlet and outlet, and the other end of the mixing branch is connected to one end of the inflation branch, the exhaust branch and the deflation branch respectively; The other end of the inflation branch is connected to the high-pressure gas source, the other end of the exhaust branch is connected to the vacuum pump, and the other end of the deflation branch is connected to the outside world; The mixing branch, the charging branch, the exhaust branch and the deflation branch are respectively provided with switch valves.

7. The hollow-core optical fiber internal gas replacement device according to claim 6, characterized in that: The inflation branch, the exhaust branch and the high-pressure gas chamber are respectively connected with pressure gauges.

8. The hollow-core optical fiber internal gas replacement device according to claim 6 or 7, characterized in that: At least one of a gas purifier, a booster pump and a pressure reducer is connected in series on the inflation branch line.

9. The hollow-core optical fiber internal gas replacement device according to claim 1, characterized in that: The inner diameter of the hollow-core fiber interface is larger than the outer diameter of the hollow-core fiber, and is sealed and connected to the outside of the hollow-core fiber through sealant, so that the interior of the hollow-core fiber is connected to the high-pressure gas chamber gas path.

10. A method for replacing gas inside a hollow-core optical fiber using the hollow-core optical fiber internal gas replacement device according to any one of claims 1 to 9, characterized in that: The following steps are involved: Use a vacuum pump to evacuate the gas path, high-pressure gas chamber and hollow-core optical fiber to reach a predetermined low pressure; High-pressure gas is filled into the gas path, high-pressure gas chamber and hollow-core optical fiber through a high-pressure gas source. After reaching a predetermined high pressure, the high-pressure gas chamber is kept sealed and maintained within a certain pressure range, so that the high-pressure gas can flow into the hollow-core optical fiber. When the high-pressure gas reaches the other end of the hollow-core optical fiber or the preset position, it stops.

11. The method for replacing gas inside a hollow-core optical fiber according to claim 10, wherein: Before the high-pressure gas is charged, the gas introduced from the high-pressure gas source is purified and the purified gas is pressurized.

12. The method for replacing gas inside a hollow-core optical fiber according to claim 10, wherein: The process of high-pressure gas passing into the hollow-core optical fiber is monitored by an optical time domain reflectometer, so as to determine the position where the high-pressure gas reaches the hollow-core optical fiber.

13. The method for replacing gas inside a hollow-core optical fiber according to claim 10, wherein: When the high-pressure gas reaches the preset position of the hollow-core optical fiber, stop gas replacement, exhaust the high-pressure gas in the air chamber and the air path, remove the hollow-core optical fiber, cut the part between the other end of the hollow-core optical fiber and the preset position, and seal the two end faces of the hollow-core optical fiber for storage.

14. The method for replacing gas inside a hollow-core optical fiber according to claim 12, wherein: The process of high-pressure gas injection into the hollow-core optical fiber is monitored by optical time domain reflectometry, including: After inflation, the light reflection intensity of the hollow-core fiber near one end of the hollow-core fiber increases significantly, i.e., a bulge appears, indicating that the high-pressure gas has successfully entered the fiber. The range covered by the bulge indicates the length of the high-pressure gas immersed in the fiber. As the inflation time increases, the bulge gradually moves backward, indicating that the high-pressure gas gradually moves from the inflation end of the high-pressure gas chamber to the other end of the hollow-core optical fiber; Until the bulge reaches the preset position of the hollow-core optical fiber.

15. A hollow-core optical fiber obtained by the method for replacing gas inside a hollow-core optical fiber according to any one of claims 10 to 14, characterized in that: Including internal gas with a certain pressure, the pressure distribution of the internal gas is: Immediately after the treatment, the air pressure at one end of the hollow-core fiber is much higher than that at the other end, and both are higher than the outside atmospheric pressure; After the treatment is completed and the hollow fiber is sealed and placed for a certain period of time, the air pressure inside the hollow fiber is evenly distributed.

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