A device and method for gas replacement inside hollow optical fiber

Abstract

This invention proposes a device and method for gas replacement inside hollow optical fibers. The device includes a high-pressure gas chamber, at least one hollow optical fiber interface, and at least one gas inlet and outlet. The hollow optical fiber interface is used to connect to a gas path at one end of the hollow optical fiber, while the other end of the hollow optical fiber is sealed. A gas path is connected to the gas inlet and outlet. A vacuum pump, connected to the gas inlet and outlet via the gas path, is used to extract residual gas from the hollow optical fiber. A high-pressure gas source, connected to the gas inlet and outlet via the gas path, is used to fill the hollow optical fiber with high-pressure gas. This invention can expel and replace the gas inside the hollow optical fiber, improving the internal gas pressure state, enhancing the optical fiber signal transmission performance, and improving long-term stability.

Description

Technical Field

[0001] This invention belongs to the field of hollow optical fiber technology, specifically relating to a device and method for gas replacement inside a hollow optical fiber. Background Technology

[0002] Hollow-core optical fibers consist of a hollow capillary structure containing gas. For electromagnetic waves in common communication bands, some gas molecules exhibit significant absorption, resulting in gas absorption loss. For example, water vapor molecules show strong absorption loss in the 1320nm-1500nm electromagnetic wave range, while carbon dioxide molecules show some absorption loss in the approximately 1580nm and 1600nm electromagnetic wave ranges. These losses can cause distortion in communication signals, thereby reducing the transmission performance of hollow-core optical fibers.

[0003] Because the quartz raw materials for optical fibers may contain carbon impurities, a certain amount of carbon dioxide gas is generated and retained inside the fiber after the high-temperature drawing process. Furthermore, during the drawing process, water vapor and carbon dioxide molecules from the air can also enter the fiber from the bottom of the fiber strand. These factors result in absorption losses related to water vapor and carbon dioxide gas in the finished hollow-core optical fiber.

[0004] Furthermore, due to the cooling process after the optical fiber is drawn at high temperatures, the relative air pressure inside the hollow fiber is usually negative. Therefore, during the testing of the hollow fiber or when the hollow fiber breaks accidentally, the end face of the hollow fiber will be exposed to the outside air. Under the influence of the negative pressure difference between the inside and outside of the fiber, outside air is easily drawn into the hollow fiber, and "polluting gas" molecules such as water vapor and carbon dioxide in the air also enter, further reducing the performance of the optical fiber.

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

[0006] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention proposes a gas replacement device and method for hollow optical fiber, which can discharge and replace the gas inside the hollow optical fiber, improve the internal gas pressure state of the hollow optical fiber, enhance the optical fiber signal transmission performance and long-term stability.

[0007] To achieve the above objectives, according to a first aspect of the present invention, a gas replacement device for hollow optical fiber is provided, comprising:

[0008] The high-pressure gas chamber is equipped with at least one hollow fiber interface and at least one gas inlet and outlet, wherein the hollow fiber interface is used to connect to one end of the hollow fiber, and the other end of the hollow fiber is sealed.

[0009] Gas passage, connected to the gas inlet and outlet;

[0010] A vacuum pump, connected to the gas inlet and outlet via a gas passage, is used to extract residual gas from hollow optical fibers.

[0011] The high-pressure gas source is connected to the gas inlet and outlet via a gas path and is used to fill the hollow optical fiber with high-pressure gas.

[0012] According to the above scheme, it also includes an optical detection component, which is connected to the other end of the hollow fiber to monitor the gas state inside the hollow fiber in real time.

[0013] According to the above scheme, there is one optical detection component;

[0014] The other end of the hollow fiber is equipped with a connector for plugging and unplugging into the optical detection component.

[0015] According to the above scheme, the connector is a patch cord with an APC interface, and the patch cord is fused to the hollow fiber.

[0016] According to the above scheme, the optical detection component is an optical time domain reflectometer.

[0017] According to the above scheme, the gas circuit includes a mixing branch, a filling branch, a suction branch, and a venting branch; among which...

[0018] 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 charging branch, the evacuation branch and the venting branch respectively.

[0019] The other end of the inflation branch is connected to a high-pressure air source, the other end of the evacuation branch is connected to a vacuum pump, and the other end of the deflation branch is connected to the outside.

[0020] Each of the mixing branch, inflation branch, extraction branch, and deflation branch is equipped with a switch valve.

[0021] According to the above scheme, pressure gauges are connected to the inflation branch, the extraction branch, and the high-pressure chamber, respectively.

[0022] According to the above scheme, at least one of the following is connected in series on the inflation branch: a gas purifier, a booster pump, and a pressure reducer.

[0023] According to the above scheme, the inner diameter of the hollow fiber interface is larger than the outer diameter of the hollow fiber, and it is sealed to the outside of the hollow fiber with sealant, so that the inside of the hollow fiber is connected to the air passage of the high-pressure air chamber.

[0024] According to a second aspect of the present invention, a method for gas replacement inside a hollow optical fiber using the aforementioned hollow optical fiber internal gas replacement device is provided, comprising the following steps:

[0025] The gas path, high-pressure gas chamber and hollow optical fiber are evacuated by a vacuum pump to achieve the predetermined low gas pressure.

[0026] High-pressure gas is introduced into the gas path, high-pressure chamber and hollow optical fiber by a high-pressure gas source. After reaching the predetermined high pressure, the high-pressure chamber is kept sealed and maintained within a certain pressure range, so that the high-pressure gas can be introduced into the hollow optical fiber.

[0027] The high-pressure gas stops when it reaches the other end of the hollow fiber or a preset position.

[0028] Following the above method, the gas introduced from the high-pressure gas source is purified before being filled with high-pressure gas, and then the purified gas is pressurized.

[0029] Using the above method, the process of high-pressure gas being introduced into the hollow optical fiber is monitored by an optical time domain reflectometer, thereby determining the location where the high-pressure gas reaches the hollow optical fiber.

[0030] Following the above method, once the high-pressure gas reaches the preset position of the hollow fiber, gas replacement is stopped, the high-pressure gas in the gas chamber and gas path is discharged, the hollow fiber is removed, the portion between the other end of the hollow fiber and the preset position is cut off, and both ends of the hollow fiber are sealed and stored.

[0031] Using the above method, the process of introducing high-pressure gas into a hollow optical fiber is monitored by an optical time-domain reflectometer, specifically including:

[0032] After inflation, the light reflection intensity of a portion of the hollow fiber near one end increases significantly, i.e., a bulge appears, indicating that the high-pressure gas has been successfully introduced into the fiber; the range covered by the bulge indicates the length of the high-pressure gas that has penetrated into the fiber.

[0033] 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 chamber to the other end of the hollow optical fiber.

[0034] Until the bulge reaches the preset position of the hollow fiber.

[0035] According to a third aspect of the present invention, a hollow optical fiber obtained by the aforementioned hollow optical fiber internal gas replacement method is provided, comprising an internal gas with a certain pressure, wherein the pressure distribution of the internal gas is as follows:

[0036] Immediately after processing, the air pressure at one end of the hollow optical fiber is much higher than that at the other end, and both are higher than the external atmospheric pressure.

[0037] After processing and sealing for a certain period of time, the air pressure inside the hollow optical fiber is evenly distributed.

[0038] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0039] 1. By employing a combination of a high-pressure gas chamber, gas path, vacuum pump, and high-pressure gas source, residual gas is extracted from one end of the hollow fiber, and high-pressure gas is then introduced into the other end. The remaining original gas is left at the other end of the hollow fiber and removed by cutting, thereby completely replacing the original gas inside the hollow fiber. This improves the additional attenuation problem caused by gas absorption and increases the gas pressure inside the hollow fiber, enhancing the long-term stability of the fiber. The high-pressure gas chamber can connect to more than one hollow fiber, simultaneously replacing gas in multiple hollow fibers, greatly improving processing efficiency.

[0040] 2. By using an optical detection component to connect to the hollow fiber, only one optical detection component is used to realize the high-pressure gas introduction process of multiple hollow fibers during the entire gas replacement process, thus saving costs.

[0041] 3. By rationally setting up the gas path and installing various valves, sensors, and functional components, the efficiency and quality of the replacement gas can be further improved. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of a structure according to an embodiment of the present invention.

[0043] Figure 2 This is a schematic diagram of a method flow according to an embodiment of the present invention.

[0044] Figure 3 The results are from the optical time domain reflectometer's monitoring of the air filling process of hollow optical fibers.

[0045] Figure 4 This is the monitoring result of an optical time domain reflectometer on a hollow optical fiber that has been sealed after gas replacement.

[0046] In the picture:

[0047] 1. Hollow-core optical fiber; 2. Optical time domain reflectometer; 3. High-pressure gas chamber; 4. Gas path; 5. High-pressure gas source; 6. Gas purifier; 7. Booster pump; 8. Vacuum pump.

[0048] 11. First jumper; 21. Second jumper; 22. Flange; 31. Hollow fiber optic 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 holding shut-off valve; 47. Venting branch; 51. Pressure reducer. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be 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 illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0050] According to a first aspect of the present invention, this embodiment provides a gas replacement device for hollow optical fibers, such as... Figure 1 As shown, it includes a high-pressure gas chamber 3, a gas path 4, a vacuum pump 8, and a high-pressure gas source 5.

[0051] The high-pressure chamber 3 is a pressure vessel capable of withstanding a pressure range of -0.1 MPa to 10 MPa. The high-pressure chamber 3 is provided with at least one hollow fiber optic interface 31 and at least one gas inlet and outlet. The hollow fiber optic interface 31 is used to connect to one end of the hollow fiber optic cable 1, and the other end of the hollow fiber optic cable 1 is sealed.

[0052] In some embodiments, the inner diameter of the hollow fiber interface 31 is larger than the outer diameter of the hollow fiber 1, and it is sealed to the outside of the hollow fiber 1 with sealant, allowing the interior of the hollow fiber to communicate with the high-pressure gas chamber. The other end of the hollow fiber 1 is fused to a first jumper 11, which has an APC interface. The device also includes an optical time-domain reflectometer 2, which is connected to a second jumper 21, which also has an APC interface (i.e., flange 22). The optical time-domain reflectometer 2 is plugged into the hollow fiber 1 via the APC interface. Since the entire replacement process is relatively long, it is not necessary to constantly monitor the internal air pressure of the hollow fiber 1. Therefore, one optical time-domain reflectometer 2 can be used to monitor the internal air pressure of multiple hollow fibers 1. The optical time-domain reflectometer 2 can also be replaced with other optical detection components.

[0053] A pressure gauge 32 is installed above the high-pressure chamber 3, with a working range of 0-150 MPa. In addition, a safety valve is installed above the high-pressure chamber 3, which can automatically release pressure when the air pressure exceeds the chamber's range, reducing the air pressure to the working pressure.

[0054] Gas line 4 is connected to the gas inlet and outlet and is a high-pressure pipeline capable of withstanding at least 20 MPa. Gas line 4 is equipped with a mixing branch, a charging branch, a evacuation branch, and a venting branch 47. 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 each of the charging, evacuation, and venting branches 47. A pressure-holding shut-off valve 46 is installed on the mixing branch.

[0055] The other end of the inflation branch is connected to the high-pressure gas source 5. The rated pressure of the high-pressure gas source 5 is generally 15MPa. It is filled with a non-reactive gas that has no significant impact on the communication capability of hollow optical fibers. This gas includes, but is not limited to, nitrogen, argon, and helium. The gas source can be changed according to the actual usage effect. A pressure reducer 51 is installed at the outlet of the high-pressure gas source 5 to reduce the gas pressure to reach the inlet pressure of the gas purifier 6. Starting from the high-pressure gas source 5, the gas purifier 6, the booster pump 7, the booster pump pressure gauge 41, and the booster pump control valve 43 are connected in series on the inflation branch. The gas purifier 6 is used to remove impurities such as water vapor from the gas outlet of the high-pressure gas source 5 and then introduces the gas into the booster pump 7. After purification by the gas purifier, the impurity content of the gas is less than 1ppb. The booster pump 7 is used to regulate the pressure of the gas entering the high-pressure chamber. This pressure value should be between 1MPa and 10MPa. A pressure gauge 41 for monitoring the outlet pressure and a valve 43 for controlling the opening and closing of the pipeline are installed on the outlet pipeline of the booster pump 7.

[0056] The other end of the evacuation branch is connected to the vacuum pump 8. The evacuation branch is also equipped with a vacuum pump pressure gauge 42 and a vacuum pump control valve 44. The vacuum pump 8 is mainly 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 can be controlled according to the reading of the vacuum pressure gauge 42 to roughly adjust the vacuum level in the high-pressure gas chamber.

[0057] The other end of the venting branch 47 is connected to the outside. The venting branch 47 is equipped with an exhaust valve 45 to discharge excess gas in the gas path 4. For example, after the gas replenishment process is completed, the exhaust valve 45 can be opened to discharge the high-pressure gas in the gas path 4.

[0058] The device described in this invention can monitor the current working pressure in real time via a pressure gauge on the high-pressure gas chamber. During gas replenishment, the gas replenishment pressure can be adjusted via a booster pump. In this invention, the replenishing gas is purified by a gas purifier, avoiding the possibility of impurities in the replenishing gas causing increased absorption loss in the optical fiber. Simultaneously, closing the pressure-holding shut-off valve on the gas line can keep the gas chamber pressure constant, thereby replenishing the gas at a stable constant pressure. In addition, the safety valve on the high-pressure gas chamber will automatically release pressure when the pressure exceeds the rated value, further ensuring the safety of the gas replenishment process. This invention also uses an optical time domain reflectometer to monitor the current gas replenishment progress in real time and can adjust the working pressure according to actual needs.

[0059] According to a second aspect of the present invention, this embodiment also provides a method for gas replacement inside a hollow optical fiber using the aforementioned hollow optical fiber internal gas replacement device, comprising the following steps:

[0060] After the hollow fiber is drawn, it is connected to the gas replacement device inside the hollow fiber. A vacuum pump is used to evacuate the gas path, high-pressure gas chamber and hollow fiber to achieve a predetermined low pressure.

[0061] High-pressure gas is introduced into the gas path, high-pressure chamber and hollow optical fiber by a high-pressure gas source. After reaching the predetermined high pressure, the high-pressure chamber is kept sealed and maintained within a certain pressure range, so that the high-pressure gas can be introduced into the hollow optical fiber.

[0062] The high-pressure gas stops when it reaches the other end of the hollow fiber or a preset position.

[0063] Preferably, the gas introduced from the high-pressure gas source is purified before being filled with high-pressure gas, and the purified gas is pressurized.

[0064] Furthermore, the process of introducing high-pressure gas into the hollow optical fiber is monitored by an optical time-domain reflectometer, thereby determining the location where the high-pressure gas reaches the hollow optical fiber.

[0065] Because the vacuum pump cannot completely remove the residual gas from the hollow fiber, a small amount of residual gas may remain inside. Therefore, the high-pressure gas cannot reach the other end of the hollow fiber. Even after the high-pressure gas reaches the preset position, a small section of the hollow fiber may still remain. Stop the gas replacement, expel the high-pressure gas from the gas chamber and gas path, remove the hollow fiber, cut off the portion between the other end of the hollow fiber and the preset position, and seal both ends of the hollow fiber for preservation.

[0066] The complete gas replacement provided in this embodiment is as follows: Figure 2 As shown, it specifically includes:

[0067] S1. After the hollow fiber 1 is drawn, one end 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.

[0068] S2. Open the vacuum pump control valve 44 and the pressure holding shut-off valve 46, close the booster pump control valve 43 and the exhaust valve 45, and turn on the vacuum pump 8 to perform vacuuming on the gas path 4 and the high-pressure gas chamber 3 to remove any polluting gases that may have been present.

[0069] S3. Close the vacuum pump control valve 44, open and adjust the pressure reducer 51 of the high-pressure gas source 5 to make the gas meet the working pressure of the gas purifier 6 and introduce it into it.

[0070] S4. Set the pressure of booster pump 7. After the purified gas is introduced into booster pump 7, the gas pressure increases to the set value. After opening booster pump control valve 43, the high-pressure gas flows through the gas path and is introduced into high-pressure gas chamber 3.

[0071] S5. Observe the pressure gauge 32 on the high-pressure chamber. When its reading reaches the set value of the booster pump 7, close the pressure holding shut-off valve 46. At this time, the high-pressure gas enters the interior of the hollow optical fiber 1 in the high-pressure chamber 3. Then close the pressure reducer 51 and the booster pump 7, and open the exhaust valve 45 to allow the gas in the gas path 4 to be discharged from the exhaust port 47. Then close the booster pump valve 43.

[0072] S6. After the high-pressure gas enters the hollow fiber 1, it pushes the original gas in the hollow fiber 1 towards one end of the jumper 11. The gas pressure in the hollow fiber 1 gradually increases at the end near the high-pressure chamber 3, and the high-pressure section gradually expands over time. The pressure change inside the hollow fiber 1 can be fed back by the reading of the optical time domain reflectometer 2. Because the internal space of the hollow fiber 1 is very small, the pressure in the high-pressure 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 fiber 1 approaches or reaches one end of the jumper 11, the pressure-holding shut-off valve 46 is opened, allowing the gas in the chamber 3 to be discharged from the exhaust port 47, and the hollow fiber 1 is removed.

[0073] S7. According to the final result of the optical time domain reflectometer 2, the part of the hollow fiber that is not reached by the high pressure gas near the jumper 11 or the part with lower pressure contains the original gas in the fiber. Cut off this part to complete the gas replacement in the hollow fiber 1. After cutting, seal and preserve both ends of the hollow fiber 1.

[0074] Figure 3 This is the real-time monitoring result of an optical time-domain reflectometer 2 (OTDR) for a typical gas displacement process. (Source: [Insert source here]) Figure 3 It can be seen that after inflation, the light reflection intensity of the fiber optic section near the inflation end increases significantly, resulting in a "bulge." This indicates that the high-pressure gas has successfully entered the fiber optic cable, and the area covered by the "bulge" indicates the length of the high-pressure gas that has penetrated into the fiber. As the inflation time increases, the "bulge" gradually moves backward, indicating that the high-pressure gas gradually advances from the fiber optic interface end 31 on the high-pressure chamber to the splice end with patch cord 11. By the sixth day, only about 80m of fiber optic cable remains without a "bulge." At this point, the hollow fiber optic cable can be removed, and patch cord 11, along with the approximately 80m of fiber optic cable nearby, can be cut and discarded. At this time, the "contaminating gas" originally contained in the hollow fiber optic cable 1 has been replaced by the introduced inert gas.

[0075] The longer the optical fiber or the lower the pressure of the high-pressure gas used, the longer the gas replacement process will take. Table 1 shows the gas replacement time required for several typical embodiments. Generally speaking, the gas replacement time will not exceed 60 days.

[0076] In the 1600nm to 1601nm band, carbon dioxide gas has three relatively high absorption peaks. The average amount of additional attenuation from these three absorption peaks is used as a typical value to measure the degree of gas contamination of optical fibers.

[0077] Table 1

[0078]

[0079] As shown in Table 1, after gas replacement, the hollow fiber 1 is filled with the inert gas, and the gas-induced attenuation of the fiber is much smaller than before gas replacement. Furthermore, because the internal pressure of the fiber is higher than the external environment, it is better able to prevent the ingress of external contaminating gases, ensuring that the fiber does not experience an increase in gas-induced attenuation over a long period. Table 1 also shows that the longer the fiber or the higher the gas pressure used, the stronger the fiber's resistance to the ingress of external gases after gas replacement. Generally speaking, after gas replacement, the gas-induced attenuation of the fiber will not exceed 10% for at least 30 days, and can last up to 89 days.

[0080] After the gas replacement is completed, both ends of the optical fiber are sealed and placed. Figure 4 The optical time domain reflectometer readings 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 decreases slowly, while the reading at the non-air-filled end increases rapidly. By the sixth day, the curve is close to a straight line, indicating that the internal air pressure of the optical fiber is nearly uniformly distributed.

[0081] Table 2

[0082]

[0083] Table 2 shows the time required for the optical fiber to achieve a uniform internal gas pressure distribution after gas replacement in several typical embodiments. As can be seen from the table, the longer the optical fiber or the greater the pressure of the high-pressure gas, the longer it takes to achieve a uniform internal gas pressure distribution. Generally speaking, after the optical fiber is gas replaced, it takes at least 30 days for the internal gas pressure to be nearly uniform.

[0084] The hollow-core optical fiber ranges in length from 500m to 10km. Maintaining high pressure in the high-pressure chamber for up to 60 days allows high-pressure gas to fully permeate the entire fiber; the shorter the fiber length or the higher the gas pressure, the shorter the required time. After treatment, the gas pressure at the gas-filled end of the hollow-core optical fiber is significantly higher than that at the monitoring end, but both are at higher atmospheric pressure. The gas absorption attenuation of the treated hollow-core optical fiber is reduced by more than 70% compared to before treatment. Sealing the treated hollow-core optical fiber for up to 30 days allows the internal gas pressure to become nearly uniform; the shorter the fiber length or the higher the gas pressure, the shorter the required time. If the treated hollow-core optical fiber is left open at both ends in the external atmosphere for at least 30 days, the increase in gas absorption attenuation in the 1460nm to 1625nm wavelength band will not exceed 10%. The longer the fiber or the higher the gas pressure used for replenishment, the longer the open-end placement time, but it cannot exceed 90 days.

[0085] As a third aspect of the present invention, this embodiment also provides a hollow optical fiber obtained by the above-described hollow optical fiber internal gas replacement method, comprising an internal gas with a certain pressure. The pressure distribution of the internal gas is as follows: immediately after treatment, the pressure at one end of the hollow optical fiber is much higher than that at the other end, and both are higher than the external atmospheric pressure; after being sealed and placed for a certain period of time after treatment, the pressure inside the hollow optical fiber is uniformly distributed. The certain period of time is 6-30 days, specifically related to the length of the hollow optical fiber and the gas pressure; the shorter the fiber length and / or the higher the gas pressure, the shorter the required time.

[0086] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0087] Those skilled in the art will readily understand 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 within the scope of protection of the present invention.

Claims

1. A device for gas replacement inside a hollow optical fiber, characterized in that: include: The high-pressure gas chamber is equipped with at least one hollow fiber interface and at least one gas inlet and outlet, wherein the hollow fiber interface is used to connect to one end of the hollow fiber, and the other end of the hollow fiber is sealed. Gas passage, connected to the gas inlet and outlet; A vacuum pump, connected to the gas inlet and outlet via a gas passage, is used to extract residual gas from hollow optical fibers. A high-pressure gas source, connected to the gas inlet and outlet via a gas path, is used to fill hollow optical fibers with high-pressure gas. It also includes an optical time-domain reflectometer, connected to the other end of the hollow fiber, for real-time monitoring of the gas state inside the hollow fiber, specifically including: After inflation, the light reflection intensity of a portion of the hollow fiber near one end increases significantly, i.e., a bulge appears, indicating that the high-pressure gas has been successfully introduced into the fiber; the range covered by the bulge indicates the length of the high-pressure gas that has penetrated into 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 chamber to the other end of the hollow optical fiber. Until the bulge reaches the preset position of the hollow fiber.

2. The gas replacement device inside a hollow optical fiber according to claim 1, characterized in that: One optical time domain reflectometer; The other end of the hollow fiber is equipped with a connector for plugging and unplugging into the optical detection component.

3. The gas replacement device inside a hollow optical fiber according to claim 2, characterized in that: The connector is a patch cord with an APC interface, which is fused to a hollow fiber.

4. The gas replacement device inside a hollow optical fiber according to claim 1, characterized in that: The gas circuit includes a mixing branch, an inflation branch, an extraction 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 charging branch, the evacuation branch and the venting branch respectively. The other end of the inflation branch is connected to a high-pressure air source, the other end of the evacuation branch is connected to a vacuum pump, and the other end of the deflation branch is connected to the outside. Each of the mixing branch, inflation branch, extraction branch, and deflation branch is equipped with a switch valve.

5. The gas replacement device inside a hollow optical fiber according to claim 4, characterized in that: Pressure gauges are connected to the inflation branch, the extraction branch, and the high-pressure chamber.

6. The gas replacement device inside a hollow optical fiber according to claim 4 or 5, characterized in that: At least one of the following is connected in series on the inflation branch: a gas purifier, a booster pump, and a pressure reducer.

7. The gas replacement device inside a hollow optical fiber according to claim 1, characterized in that: The inner diameter of the hollow fiber optic interface is larger than the outer diameter of the hollow fiber optic cable, and it is sealed to the outside of the hollow fiber optic cable with sealant, so that the inside of the hollow fiber optic cable is connected to the high-pressure gas chamber.

8. A method for gas replacement inside a hollow optical fiber using the gas replacement device inside the hollow optical fiber according to any one of claims 1-7, characterized in that: Includes the following steps: The gas path, high-pressure gas chamber and hollow optical fiber are evacuated by a vacuum pump to achieve the predetermined low gas pressure. High-pressure gas is introduced into the gas path, high-pressure chamber and hollow optical fiber by a high-pressure gas source. After reaching the predetermined high pressure, the high-pressure chamber is kept sealed and maintained within a certain pressure range, so that the high-pressure gas can be introduced into the hollow optical fiber. The process of introducing high-pressure gas into hollow optical fiber is monitored by an optical time domain reflectometer, thereby determining the location where the high-pressure gas reaches the hollow optical fiber. The high-pressure gas stops when it reaches the other end of the hollow fiber or a preset position. Monitoring the high-pressure gas introduction process in hollow optical fibers using an optical time-domain reflectometer (OTDR) specifically includes: After inflation, the light reflection intensity of a portion of the hollow fiber near one end increases significantly, i.e., a bulge appears, indicating that the high-pressure gas has been successfully introduced into the fiber; the range covered by the bulge indicates the length of the high-pressure gas that has penetrated into 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 chamber to the other end of the hollow optical fiber. Until the bulge reaches the preset position of the hollow fiber.

9. The method for gas replacement inside hollow optical fiber according to claim 8, characterized in that: Before introducing high-pressure gas, the gas introduced from the high-pressure gas source is purified, and the purified gas is pressurized.

10. The method for gas replacement inside hollow optical fiber according to claim 8, characterized in that: Once the high-pressure gas reaches the preset position of the hollow fiber, gas replacement is stopped, the high-pressure gas in the gas chamber and gas path is discharged, the hollow fiber is removed, the portion between the other end of the hollow fiber and the preset position is cut off, and both ends of the hollow fiber are sealed and stored.

11. A hollow optical fiber obtained by the internal gas replacement method of hollow optical fiber according to any one of claims 8-10, characterized in that: Includes internal gas with a certain pressure, and the pressure distribution of the internal gas is as follows: Immediately after processing, the air pressure at one end of the hollow optical fiber is much higher than that at the other end, and both are higher than the external atmospheric pressure. After processing and sealing for a certain period of time, the air pressure inside the hollow optical fiber is evenly distributed.

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