Gas replacement and detection system and method in hollow-core optical fiber

Abstract

The invention discloses a system and a method for replacing and detecting gas in a hollow-core optical fiber. The system comprises a positive pressure gas chamber, a negative pressure gas chamber, a positive pressure source, a negative pressure source and an optical detection device, the positive pressure air chamber and the negative pressure air chamber are two independent sealed cavities; a phosgene parallel coupling module is arranged in each of the positive pressure air chamber and the negative pressure air chamber; each phosgene parallel coupling module comprises a solid core optical fiber and an inner guide hollow core optical fiber; the inner guide hollow-core optical fiber is connected with a to-be-tested hollow-core optical fiber; the solid-core optical fiber is connected with an optical detection device; the positive pressure source and the negative pressure source are respectively connected to the positive pressure gas chamber and the negative pressure gas chamber and are used for forming gas replacement flow in the hollow-core optical fiber to be detected; and the optical detection device is used for evaluating the replacement state of gas in the to-be-detected hollow-core optical fiber. According to the invention, a miniaturized double-end active driving gas replacement system is constructed, and real-time optical monitoring is combined, so that rapid and controllable replacement of gas in the to-be-detected hollow-core optical fiber and real-time sensing and feedback of a process state are realized.

Description

Technical Field

[0001] This invention belongs to the field of hollow optical fiber application technology, and specifically relates to a system and method for gas replacement and detection in hollow optical fiber. Background Technology

[0002] Anti-resonant hollow-core fiber (AR-HCF), with its unique hollow microstructure, can confine light waves within an air core for transmission, providing an ideal platform for light-matter interactions. By filling the fiber core with specific functional gases (such as gases for Raman gain, calibration gases for trace detection, or inert gases for nonlinear processes), its application potential in fields such as gas lasers, high-sensitivity sensing, quantum optics, and advanced spectroscopy can be greatly expanded. Therefore, achieving controllable and efficient filling and replacement of the gas inside the hollow-core fiber, and real-time, in-situ monitoring of its internal gas state, is a key prerequisite for realizing these high-end applications.

[0003] Currently, technologies for treating the internal gas of hollow optical fibers mainly fall into two categories. One category is the "permeation method" for long optical fibers, such as the scheme disclosed in Chinese patent application CN120717706A. This method places the entire optical fiber coil in a large high-pressure cavity, relying on the slow permeation of gas through the cladding material to increase the internal pressure of the fiber core, thereby resisting the intrusion of external gases. This method is suitable for long-term stability treatment before the optical fiber leaves the factory, but the processing cycle is long (tens of hours), the equipment is bulky, and it cannot perform rapid and active gas composition management and dynamic monitoring of integrated devices.

[0004] Another type is the traditional "purge method," which involves injecting high-pressure gas into one end of the optical fiber and expelling the existing gas from the other end. While this method is direct, it has significant drawbacks: for longer sections (especially hundreds of meters or more) of hollow optical fiber, the replacement efficiency of the traditional purge method is significantly reduced, and the replacement time is often too long; the replacement process lacks effective process monitoring, making it impossible to determine in real time whether the internal gas has reached the target purity or pressure; furthermore, conventional purge devices are bulky and difficult to integrate into compact optical systems or experimental platforms, resulting in poor flexibility.

[0005] Therefore, there is an urgent need for a miniaturized, integrated processing system that is flexible in operation, can quickly and controllably complete the gas replacement inside hollow optical fibers, and can monitor the replacement process and results in real time and in situ. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a gas replacement and detection system and method within hollow-core optical fibers. This invention achieves rapid and controllable gas replacement within the hollow-core optical fiber under test, along with real-time sensing and feedback of the process status, by constructing a miniaturized, dual-end actively driven gas replacement system and combining it with real-time optical monitoring.

[0007] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution: The present invention provides a gas replacement and detection system in hollow optical fiber, including a positive pressure chamber, a negative pressure chamber, a positive pressure source, a negative pressure source, and an optical detection device; The positive pressure chamber and the negative pressure chamber are two independent sealed cavities, and are respectively equipped with a positive pressure interface and a negative pressure interface; Both the positive pressure chamber and the negative pressure chamber are equipped with a built-in optical-gas parallel coupling module. The optical-gas parallel coupling module includes a solid optical fiber and an inner-guided hollow optical fiber. The two are optically coupled in the sealed cavity, and the central channel of the inner-guided hollow optical fiber is connected to the sealed cavity. The inner hollow fiber passes through the sealed cavity and is used to connect the hollow fiber to be tested. The solid optical fiber passes through the sealed cavity and is used to connect to the optical detection device; The positive pressure source and the negative pressure source are respectively connected to the positive pressure interface and the negative pressure interface, and are used to actively establish and control the pressure difference between the positive pressure chamber and the negative pressure chamber, so as to form a double-ended actively driven gas displacement flow inside the hollow optical fiber under test. The optical detection device is used to monitor the changes in optical transmission characteristics in real time through the detection optical path formed by the solid optical fiber and the hollow optical fiber under test during the gas replacement process, so as to evaluate the gas replacement state inside the hollow optical fiber under test.

[0008] The positive pressure source described in this invention refers to any gas supply device or system capable of providing a pressure higher than ambient air pressure with controllable pressure; the negative pressure source refers to any pumping device or system capable of providing a vacuum lower than ambient air pressure with controllable vacuum. Specific implementations include, but are not limited to: for positive pressure sources, combinations of high-pressure gas cylinders and pressure reducing valves, miniature air compressors, integrated positive pressure control devices, etc., can be used; for negative pressure sources, vacuum pumps (such as rotary vane pumps, diaphragm pumps, and vortex pumps), Venturi vacuum generators, integrated negative pressure (vacuum) control devices, etc. Their core function is to provide controlled positive or negative pressure to the corresponding gas chamber.

[0009] Furthermore, the built-in optical-gas parallel coupling module also includes an adapter element for fixing the solid fiber and the inner-guided hollow fiber.

[0010] As a preferred embodiment of the present invention, the adapter element is a base with a V-groove, and the solid optical fiber and the inner hollow optical fiber are aligned and fixed in the V-groove.

[0011] As another preferred technical solution of the present invention, the adapter element is a sleeve, the solid optical fiber and the inner hollow optical fiber are connected by fusion splicing, and the side wall of the inner hollow optical fiber is provided with microholes or microgrooves to connect its central channel with the positive pressure chamber or negative pressure chamber.

[0012] Furthermore, both the positive pressure chamber and the negative pressure chamber include a chamber body and an openable cover plate, and the cover plate and the chamber body are sealed by a chamber sealing element.

[0013] Furthermore, the internal pressure of the positive pressure chamber and the negative pressure chamber is detected by a pressure sensing unit; the pressure sensing unit is constructed in any of the following ways: (a) Pressure sensors independently installed on the positive pressure chamber and the negative pressure chamber, respectively; or (b) The pressure sensing modules integrated inside each of the positive and negative pressure sources.

[0014] Furthermore, the hollow-core optical fiber and the solid-core optical fiber each pass through the sealed cavity via independent optical fiber sealing structures.

[0015] Furthermore, the end of the solid optical fiber that exits the sealed cavity is connected to the optical detection device via an optical fiber jumper.

[0016] Furthermore, the optical detection device is a transmission-type optical power monitoring system or an optical time-domain reflectometer.

[0017] Another aspect of the present invention provides a method for gas replacement and detection within hollow optical fibers using the system described above, comprising the following steps: Connect the two ends of the hollow fiber under test to the gas paths of the positive pressure chamber and the negative pressure chamber respectively, and establish a detection optical path through the hollow fiber under test; Through the positive and negative pressure sources, a pressure difference is actively established and controlled between the positive and negative pressure chambers, thereby forming a gas displacement flow driven from the positive pressure chamber to the negative pressure chamber in the hollow fiber under test. During the gas replacement process, the optical detection device acquires the optical signal flowing through the hollow fiber under test and its changes in real time. The progress or completion status of gas replacement is determined based on the changes in the optical signal.

[0018] The beneficial effects of this invention are as follows: 1. Dual-end active drive effectively improves replacement efficiency and uniformity: This invention utilizes two independent sealed cavities (positive and negative pressure chambers) and their respective connected positive and negative pressure sources to form a dual-end active driving architecture at both ends of the hollow fiber under test. This architecture can actively establish and precisely control the pressure difference, forming a strong axial pressure gradient from the positive pressure end to the negative pressure end, thereby driving the gas to form a high-speed, directional displacement flow inside the hollow fiber under test. Based on the displacement mechanism driven by the coordinated action of pressure boundaries on both sides, it is fundamentally superior to unidirectional, passive purging that only applies pressure from one end. The system and method of this invention can significantly shorten the gas displacement time of long-span hollow fibers, and significantly improve displacement efficiency and uniformity, providing key technical support for applications such as gas lasers and high-sensitivity sensing that require a fast, clean, and uniform gas environment.

[0019] 2. Integrated in-situ optical monitoring enables visualization and closed-loop control of the replacement process: This invention integrates an optical detection device into a displacement system. Simultaneously with gas displacement, an optical signal continuously passes through an in-situ sensing optical path formed by the hollow-core optical fiber under test. By acquiring and analyzing optical response signals (such as changes in transmission spectrum, backscattering, or loss at specific wavelengths), it is possible to obtain real-time, non-destructive state information reflecting the gas composition, pressure, or uniformity within the fiber. This achieves "visualized" perception and quantitative evaluation of the gas displacement process, enabling operators to accurately determine the displacement endpoint (such as when gas purity or pressure reaches a set value). This lays the foundation for intelligent control based on real-time feedback and meets the high requirements for precise gas state monitoring in applications such as quantum optics and advanced spectroscopy.

[0020] 3. Highly miniaturized and modular design enhances operational flexibility: This invention, through ingenious design, keeps the volume of the core photo-gas parallel coupling module inside the gas chamber within a relatively small range (e.g., 0.75 cm²). 3 The volume of both the positive and negative pressure chambers can be miniaturized (e.g., not exceeding 10 cm³). 3 This makes the entire system compact and highly integrated, allowing it to be easily placed on standard optical platforms, mobile carts, or integrated into complex experimental setups and mobile testing equipment. The modular design also simplifies system assembly, maintenance, and adaptation to different specifications of hollow optical fibers, completely overcoming the shortcomings of traditional large penetration chambers or bulky purging devices in terms of flexibility.

[0021] 4. The core interface (photo-gas parallel coupling module) has a flexible structure, adapting to diverse application scenarios: The photoelectric parallel coupling module can be reliably coupled in various ways, such as mechanical alignment bonding (exposed end face) or fusion splicing followed by side openings / grooving. The side opening design, in particular, ensures low-loss optical coupling while avoiding direct airflow impact on the fiber end face, reducing the risk of contamination and damage, and increasing the gas exchange area, which can further improve response speed. This design flexibility allows the invention to better adapt to the varying requirements of reliability, response speed, or cleanliness in different application scenarios, from high-power laser gas filling to trace gas detection.

[0022] 5. Possesses deep cleaning and extremely high homogenization capabilities, meeting the needs of cutting-edge experiments: The positive and negative pressure gas chambers in this invention can be used simultaneously, and their operating states can be alternately switched to cause periodic changes in the pressure states of the positive and negative pressure chambers, thereby actively generating intense pressure fluctuations and transient flow within the hollow-core optical fiber under test. This unique "perturbation mode" effectively overcomes the limitations of stable laminar flow, forcefully stripping gas molecules adsorbed on the inner wall of the optical fiber and promoting radial mixing of the gas across the fiber cross-section. Therefore, the system not only enables rapid replacement but also achieves deep cleaning and extreme homogenization that are difficult to achieve with traditional methods, providing a solution for hollow-core optical fibers in fields such as quantum optics and precision spectroscopy where gas purity and homogenization have stringent requirements. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the gas replacement and detection system inside the hollow optical fiber according to Embodiment 1 of the present invention.

[0024] Figure 2 This is a schematic diagram of the positive pressure chamber and the negative pressure chamber in Embodiment 1 of the present invention, wherein (a) is the positive pressure chamber and (b) is the negative pressure chamber.

[0025] Figure 3 This is a schematic diagram of the gas replacement and detection system inside the hollow optical fiber according to Embodiment 3 of the present invention.

[0026] Figure 4 This is a schematic diagram of the positive pressure chamber and the negative pressure chamber in Embodiment 3 of the present invention, wherein (c) is the positive pressure chamber and (d) is the negative pressure chamber.

[0027] Figure 5 This is a schematic diagram of the gas replacement and detection system inside the hollow optical fiber according to Embodiment 4 of the present invention.

[0028] In the diagram, 1: Positive pressure chamber, 101: Positive pressure interface; 2: Negative pressure chamber, 201: Negative pressure interface; 3: Positive pressure source; 4: Negative pressure source; 5: Pressure sensor; 6: Optical-gas parallel coupling module, 601: Solid fiber; 602: Hollow fiber with inner guide; 603: Adapter element; 7: Hollow fiber under test; 8: Solid fiber inlet / outlet sealing block; 9: Hollow fiber inlet / outlet sealing block; 10: Light source; 11: Photodetector; 12: Optical time domain reflectometer. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] like Figure 1 and Figure 2 As shown, Embodiment 1 of the present invention provides a gas replacement and detection system for a basic structure in a hollow optical fiber.

[0032] The main body of the system includes: a positive pressure chamber 1, a negative pressure chamber 2, a positive pressure source 3, a negative pressure source 4, and an optical detection device consisting of a light source 10 and a photodetector 11.

[0033] The positive pressure chamber 1 and negative pressure chamber 2 are two independent miniature sealed cavities. Positive pressure chamber 1 is equipped with a positive pressure interface 101, and negative pressure chamber 2 is equipped with a negative pressure interface 201. Positive pressure source 3 and negative pressure source 4 are respectively connected to their corresponding interfaces via pipelines, providing controllable positive and negative pressures to the interior of the chambers. In this embodiment 1, the positive pressure source 3 is preferably a high-pressure gas cylinder + electronic pressure reducing valve. The high-pressure gas cylinder provides a high-pressure gas source, and the electronic pressure reducing valve is responsible for accurately outputting and regulating the required pressure. The negative pressure source 4 is preferably a small vacuum pump used to evacuate air from the negative pressure chamber 2. Positive pressure chamber 1 and negative pressure chamber 2 are each equipped with a pressure sensor 5 for real-time monitoring of the internal pressure. Each chamber includes a chamber body and an openable cover plate, which is sealed to the chamber body via a chamber seal (sealing ring) and fastening screws.

[0034] Both the positive pressure chamber 1 and the negative pressure chamber 2 are equipped with a built-in photo-gas parallel coupling module 6. This module 6 includes a quartz base serving as an adapter element 603, with a V-groove on the base. A solid optical fiber 601 and an inner-guided hollow optical fiber 602 are precisely aligned and bonded within the V-groove using UV-curable adhesive, achieving an optimized coupling loss ≤0.5dB. After bonding, the end face of the inner-guided hollow optical fiber 602 is exposed to the chamber environment, allowing its central channel to directly communicate with the sealed cavity. The overall volume of the photo-gas parallel coupling module 6 is controlled to be no more than 0.75cm². 3 .

[0035] The hollow-core fiber 602 and the solid-core fiber 601 each exit the sealed cavity through independent fiber sealing structures. Specifically, the solid-core fiber 601 passes through a dedicated solid-core fiber inlet / outlet sealing block 8 (fiber sealing structure) on the wall of the air chamber and exits the sealed cavity of the air chamber, where it is connected to one end of a solid-core fiber jumper via fusion splicing outside the air chamber. The other ends of the two solid-core fiber jumpers are connected to the light source 10 and the photodetector 11, respectively. The hollow-core fiber 602 passes through another independent hollow-core fiber inlet / outlet sealing block 9 on the wall of the air chamber and exits the sealed cavity of the air chamber, with its end used to connect to the hollow-core fiber 7 under test via fusion splicing.

[0036] The total volume of the positive pressure chamber 1 and the negative pressure chamber 2 is designed to not exceed 10 cm³. 3 This ensures the miniaturization of the system.

[0037] Example 2

[0038] The main difference between Embodiment 2 and Embodiment 1 is the specific structure of the phos-gas parallel coupling module 6, which aims to achieve faster gas exchange and thus improve the system response speed.

[0039] In this embodiment 2, the adapter element 603 of the optical-gas parallel coupling module 6 is a miniature sleeve (a small cylindrical metal sleeve). First, the solid fiber 601 and the inner hollow fiber 602 are directly arc-fused on a fiber optic fusion splicer to obtain a low-loss (e.g., ≤0.3dB) fusion point. Subsequently, using femtosecond laser micromachining technology, one or more micrometer-scale radially perforated micropores or axially perforated microgrooves are precisely machined on the sidewall of the inner hollow fiber 602 near the fusion point. After machining, this fiber segment containing the fusion point and micropores / microgrooves is fixed inside the sleeve with adhesive. The sleeve has precision capillary holes at both ends for the fiber to pass through, and its sidewalls have through holes to ensure that when it is installed in the gas chamber, the micropores / microgrooves on the sidewalls of the inner hollow fiber 602 can communicate with the sealed cavity (gas chamber environment) of the gas chamber through the through holes in the sidewalls of the sleeve.

[0040] Therefore, in this embodiment, the gas does not need to be exchanged solely through the fiber endface, but can directly and rapidly enter and exit the central channel of the inner hollow fiber 602 through micro-holes or micro-grooves in the fiber sidewalls. This design significantly increases the effective gas exchange area and shortens the gas diffusion path, resulting in higher efficiency and faster dynamic response during gas replacement. This structure is particularly suitable for applications requiring the study of transient dynamics of gas-light interaction or those with stringent requirements for replacement time.

[0041] Example 3

[0042] like Figure 3 and Figure 4 As shown, this embodiment 3 provides an integrated implementation scheme for a gas pressure supply and control system. Unlike embodiment 1, which uses separate pressure sources and external pressure sensors 5, the core improvement of this embodiment 3 lies in the use of a highly integrated and intelligent integrated pressure control device as the positive pressure source 3 and negative pressure source 4 of the system, respectively.

[0043] Specifically, the positive pressure source 3 is an integrated high-pressure pneumatic control device. This device is a multi-functional integrated module that integrates a miniature positive pressure generating unit (such as a precision pneumatic pump or a miniature compressor), a high-precision proportional valve for accurately adjusting the outlet pressure, a pneumatic sensing module for real-time monitoring of the output pressure, and an embedded microprocessor responsible for signal processing and closed-loop control. All these components are compactly packaged in a single housing. Similarly, the negative pressure source 4 is an integrated negative pressure pneumatic control device that integrates a miniature vacuum pump, a vacuum control valve, a pneumatic sensing module (vacuum sensing module), and control circuitry on a similar principle. These two integrated devices are connected to the positive pressure interface 101 and negative pressure interface 201 of the positive pressure chamber 1 and negative pressure chamber 2, respectively, via pneumatic pipelines. In this configuration, the detection of the internal pressure of the chambers is directly performed by the pneumatic sensing modules within these two integrated devices, thus eliminating the need to install an additional independent pneumatic sensor 5 on the chamber body as in Embodiment 1, simplifying the chamber structure and reducing potential leakage points.

[0044] Example 4

[0045] Embodiment 4 of the present invention provides a preferred embodiment of an optical detection system. For example... Figure 5 As shown, unlike Embodiment 1 which uses a discrete light source 10 and photodetector 11 to form a transmission monitoring system, the core improvement of Embodiment 4 is that it uses an optical time domain reflectometer 12 as an integrated optical detection device.

[0046] Specifically, the optical detection device is an optical time-domain reflectometer (OTDR) 12. This instrument is a highly integrated functional module, internally containing a pulsed laser emitter as the signal source and a high-sensitivity backscattered light detection and processing system as the signal receiving and analysis unit. In use, the OTD 12 injects a series of nanosecond or picosecond-level optical pulses into the hollow fiber 7 under test via a solid fiber jumper and an optical-gas parallel coupling module 6. As these optical pulses propagate in the hollow fiber 7, Rayleigh scattering produces weak, continuously returning backscattered light. The OTD 12 accurately detects and records the change in the intensity of these backscattered lights over time (precisely corresponding to the transmission distance of the light in the fiber), forming a backscattering curve. By analyzing the backscattering curve, the average loss change of the hollow fiber 7 under test during the gas replacement process can be obtained, thereby assessing the overall progress and uniformity of the gas replacement, and spatially locating and quantifying local loss changes caused by gas replacement. This system is particularly suitable for testing longer sections of hollow-core optical fiber, enabling simultaneous assessment of gas replacement uniformity and diagnosis of fiber optic link health in a single measurement. The use of an optical time-domain reflectometer (OTDR) significantly simplifies optical path connection procedures, enhances system integration and ease of operation in the field or on-site, and provides an effective means for intelligent, distributed monitoring of the gas filling process in hollow-core optical fibers.

[0047] Installation method of hollow fiber internal gas replacement and detection system Step 1: Core module installation and gas chamber sealing Module preparation: Check and confirm that the two optical-gas parallel coupling modules 6 are intact. If a mechanical alignment type (such as a base with a V-groove) is used, ensure that the solid fiber 601 and the inner hollow fiber 602 are aligned and bonded in place; if a fusion splicing side hole type is used, confirm that the fusion splice is firm and the micro-holes / micro-grooves on the side wall are unobstructed.

[0048] Insertion Module: Open the covers of the positive pressure chamber 1 and the negative pressure chamber 2. Place the two photo-gas parallel coupling modules 6 into the designated slots or positioning structures in the positive pressure chamber 1 and the negative pressure chamber 2, respectively, ensuring that the photo-gas parallel coupling modules 6 are placed stably and that the end face or side wall micro-holes / micro-grooves of the inner hollow fiber 602 are fully exposed to the environment of the chamber.

[0049] Fiber optic cable lead-out and sealing: The solid fiber 601 and the hollow fiber 602 of each optical-gas parallel coupling module 6 are carefully threaded through the corresponding independent fiber sealing structures (solid fiber entry / exit sealing block 8 and hollow fiber entry / exit sealing block 9) on the gas chamber wall of their respective gas chambers. Excessive bending or lateral forces on the fibers should be avoided during threading.

[0050] Sealing the air chambers: Clean the sealing surfaces of the positive pressure air chamber 1, negative pressure air chamber 2, and cover plate, and place the air chamber seals (such as O-rings). Close the cover plate and use the provided fastening screws (such as hex screws) to tighten them evenly in sequence to ensure uniform pressure between the cover plate and the air chamber body, forming a reliable sealed cavity.

[0051] Step 2: Connecting the gas, power, and signal systems Connect the pressure source: Using a suitable gas pipeline (such as a polytetrafluoroethylene tube), connect and secure the output port of the positive pressure source 3 to the positive pressure port 101 of the positive pressure chamber 1; similarly, connect and secure the output port of the negative pressure source 4 to the negative pressure port 201 of the negative pressure chamber 2.

[0052] Connecting the pressure sensor 5: If the system is equipped with a separate pressure sensor 5, install it on the sensor interface reserved in the air chamber and connect its signal line (such as an electrical connector or communication cable) to the display instrument or control system.

[0053] Connecting the optical inspection device: Reliably connect the end of the solid fiber 601 exiting the air chamber to the input / output port of the optical inspection device via fiber optic fusion splice or flange-type fiber optic connector. If using solid fiber patch cords as a relay, ensure that the loss at all fiber optic connection points is within acceptable limits.

[0054] Connect the hollow fiber 7 to be tested: The two ends of the hollow fiber 7 to be tested are fused to the ends of the inner-conducting hollow fiber 602 that emerges from the two air chambers by arc fusion. After fusion, the fusion joint can be protected as necessary (e.g., by heating the shrink tubing).

[0055] Electrical connection: Connect the positive pressure source 3, the negative pressure source 4, the optical detection device, and possible control systems to the power supply.

[0056] Step 3: System Initialization and Function Verification 1. Air tightness check (pressure holding test): Turn on the positive pressure source 3 and slowly fill the complete closed air circuit system, consisting of the positive pressure chamber 1, the hollow fiber under test 7, and the negative pressure chamber 2, with a certain test pressure. Close the valve of the positive pressure source 3 and observe the reading of the air pressure sensing unit (independent air pressure sensor 5 or integrated air pressure sensing module) connected to the air chamber. The pressure should not drop significantly within several minutes. This step verifies the airtightness of all connection points from the interface of the positive pressure source 3 through the entire air circuit to the interface of the negative pressure source 4.

[0057] Complete optical path connectivity and baseline testing: Turn on the optical detection device. Acquire and record the initial optical signal, depending on the type of optical detection device used, as the baseline for comparison in subsequent replacement processes: If it is a transmission-type optical power monitoring system (such as light source 10 and photodetector 11), record the baseline transmission spectrum when the hollow fiber 7 under test is filled with the initial gas. If it is an optical time-domain reflectometer 12, record the baseline backscattering curve of the current system.

[0058] By confirming whether a stable and reasonable baseline signal can be obtained, it is verified whether the complete optical path from the optical detection device, through the internal optical path of the system, and through the entire hollow fiber 7 under test is unobstructed.

[0059] 3. Pressure control and drive function verification: A low and safe initial test pressure difference is applied to the positive pressure source 3 and the negative pressure source 4 via the control system or manual operation to drive the gas flow within the system. The readings of the pressure sensing unit (such as a standalone pressure sensor 5 or an integrated pressure sensing module) are observed to accurately and stably reflect changes in this pressure difference. Simultaneously, the optical signals (such as optical power or backscattering curves) displayed by the optical detection device (such as a photodetector 11 or an optical time-domain reflectometer 12) are observed to produce corresponding, repeatable, minute fluctuations due to changes in gas pressure / density. This step verifies that the positive pressure source 3 and the negative pressure source 4 can establish and control the pressure difference as expected, and that this pressure change can be monitored by the system and elicit a detectable optical response, thus confirming the basic functionality of the system.

[0060] A method for gas replacement and detection within a hollow optical fiber, based on the system described in any of the above embodiments of the present invention, includes the following steps: Step S1: System Connection and Optical Path Establishment The two ends of the hollow fiber 7 under test are connected to the inner hollow fiber 602 of the positive pressure air chamber 1 and the negative pressure air chamber 2, respectively, thereby connecting the central channel of the hollow fiber 7 under test with the air path of the two air chambers. At the same time, the optical detection device is connected to the solid fiber 601 that passes through the air chamber, thereby establishing a detection optical path that runs through the positive pressure air chamber 1, the hollow fiber 7 under test, and the negative pressure air chamber 2. The target gas to be introduced (e.g., high-purity nitrogen, acetylene, or carbon dioxide) is determined. Before the replacement begins, the optical baseline signal (e.g., initial transmission spectrum or backscattering curve) of the original gas state inside the hollow fiber 7 under test is recorded by the optical detection device.

[0061] Step S2: Drive gas replacement The target gas supply is connected to the positive pressure source 3. By controlling the positive pressure source 3 and the negative pressure source 4, a pressure difference is actively established and controlled between the positive pressure chamber 1 and the negative pressure chamber 2, thereby driving the target gas to form a double-ended active gas displacement flow from the positive pressure chamber 1 to the negative pressure chamber 2, and displacing the gas inside the hollow fiber 7 under test.

[0062] Step S3: Real-time optical monitoring During the gas replacement process, the optical signal flowing through the detection optical path is acquired in real time by the optical detection device, and the replacement process is reflected in real time by analyzing the change of the signal relative to the baseline.

[0063] Step S4: State determination Based on the changing characteristics of the optical signal, the replacement process or completion status of the gas inside the hollow optical fiber 7 under test is determined. When the optical signal (such as the intensity of the characteristic absorption peak) reaches a preset stable threshold or standard spectrum, it is determined that the target gas replacement is complete, and then the positive pressure source 3 and the negative pressure source 4 can be controlled to stop working or switch to a maintenance state.

[0064] Optional step S5: Alternating perturbation mode For applications requiring deep cleaning or extremely high uniformity, the pressure states of the positive pressure source 3 and the negative pressure source 4 are alternately controlled to cause periodic changes in the pressure states of the positive pressure chamber 1 and the negative pressure chamber 2, thereby generating pressure disturbances within the hollow optical fiber 7 under test to enhance the gas replacement effect.

[0065] This invention achieves rapid and controllable gas replacement and real-time sensing and feedback of the process status by constructing a miniaturized, dual-end actively driven gas replacement system and combining it with real-time optical monitoring.

[0066] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0067] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A system for gas replacement and detection within a hollow optical fiber, characterized in that, It includes a positive pressure chamber, a negative pressure chamber, a positive pressure source, a negative pressure source, and an optical detection device; The positive pressure chamber and the negative pressure chamber are two independent sealed cavities, and are respectively equipped with a positive pressure interface and a negative pressure interface; Both the positive pressure chamber and the negative pressure chamber are equipped with a built-in optical-gas parallel coupling module. The optical-gas parallel coupling module includes a solid optical fiber and an inner-guided hollow optical fiber. The two are optically coupled in the sealed cavity, and the central channel of the inner-guided hollow optical fiber is connected to the sealed cavity. The inner hollow fiber passes through the sealed cavity and is used to connect the hollow fiber to be tested. The solid optical fiber passes through the sealed cavity and is used to connect to the optical detection device; The positive pressure source and the negative pressure source are respectively connected to the positive pressure interface and the negative pressure interface, and are used to actively establish and regulate the pressure difference between the positive pressure chamber and the negative pressure chamber, so as to form a double-ended actively driven gas displacement flow inside the hollow optical fiber under test. The optical detection device is used to monitor the changes in optical transmission characteristics in real time through the detection optical path formed by the solid optical fiber and the hollow optical fiber under test during the gas replacement process, so as to evaluate the gas replacement state inside the hollow optical fiber under test.

2. The gas replacement and detection system within a hollow optical fiber according to claim 1, characterized in that, The built-in photo-gas parallel coupling module also includes an adapter element for fixing the solid fiber and the inner-guided hollow fiber.

3. The gas replacement and detection system within a hollow optical fiber according to claim 2, characterized in that, The adapter element is a base with a V-groove, and the solid optical fiber and the inner hollow optical fiber are aligned and fixed in the V-groove.

4. The gas replacement and detection system within a hollow optical fiber according to claim 2, characterized in that, The adapter element is a sleeve, and the solid optical fiber and the inner hollow optical fiber are connected by fusion splicing. The sidewall of the inner hollow optical fiber is provided with microholes or microgrooves that allow its central channel to communicate with the positive or negative pressure air chamber.

5. The gas replacement and detection system within a hollow optical fiber according to claim 1, characterized in that, Both the positive pressure chamber and the negative pressure chamber include a chamber body and an openable cover plate, and the cover plate and the chamber body are sealed by a chamber sealing element.

6. The gas replacement and detection system within a hollow optical fiber according to claim 1, characterized in that, The internal pressure of the positive pressure chamber and the negative pressure chamber is detected by a pressure sensing unit; the pressure sensing unit is constructed in any of the following ways: (a) Pressure sensors independently installed on the positive pressure chamber and the negative pressure chamber, respectively; or (b) The pressure sensing modules integrated inside each of the positive and negative pressure sources.

7. The gas replacement and detection system within a hollow optical fiber according to claim 1, characterized in that, The hollow-core optical fiber and the solid-core optical fiber each pass through the sealed cavity through an independent optical fiber sealing structure.

8. The gas replacement and detection system in hollow optical fiber according to claim 1, characterized in that, The end of the solid optical fiber that exits the sealed cavity is connected to the optical detection device via an optical fiber jumper.

9. The gas replacement and detection system in hollow optical fiber according to claim 1, characterized in that, The optical detection device is a transmission-type optical power monitoring system or an optical time-domain reflectometer.

10. A method for gas replacement and detection within a hollow optical fiber using the system described in any one of claims 1 to 9, characterized in that, Includes the following steps: Connect the two ends of the hollow fiber under test to the gas paths of the positive pressure chamber and the negative pressure chamber respectively, and establish a detection optical path through the hollow fiber under test; Through the positive and negative pressure sources, a pressure difference is actively established and controlled between the positive and negative pressure chambers, thereby forming a gas displacement flow driven from the positive pressure chamber to the negative pressure chamber in the hollow fiber under test. During the gas replacement process, the optical detection device acquires the optical signal flowing through the hollow fiber under test and its changes in real time. The progress or completion status of gas replacement is determined based on the changes in the optical signal.

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