Preparation method of all-fiber type hollow-core anti-resonance optical fiber low-pressure gas cavity
By combining a fiber taper machine and a metal gas chamber with a turbomolecular pump, the gas absorption spectrum is monitored in real time, which solves the pollution and miniaturization problems of the hollow-core optical fiber low-pressure gas cavity and achieves efficient and stable gas cavity preparation.
Patent Information
- Application Number
- CN202511094793.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-06
- Publication Date
- 2025-10-14
AI Technical Summary
When preparing a low-pressure gas cavity in a hollow-core optical fiber, the intrusion of outside air causes contamination and a decrease in the purity of the gas cavity. Existing sealing methods are cumbersome, inefficient, and not suitable for miniaturization.
A fiber taper machine is used to prepare thermally expanded and reversely tapered optical fibers. A metal gas chamber and a turbomolecular pump are used for gas exchange. A tunable laser and a photodetector are used to monitor the gas absorption spectrum in real time. A pollution-free miniaturized gas cavity is achieved through fusion splicing and UV adhesive sealing.
The preparation of a pollution-free, miniaturized, low-loss hollow-core antiresonant fiber low-pressure gas cavity has been achieved, ensuring gas purity and stability, which is suitable for gas interaction research.
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Figure CN120779529A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of optical fiber devices, and in particular relates to a method for preparing an all-fiber hollow-core anti-resonant optical fiber low-pressure gas cavity. Background Art
[0002] Hollow-core fiber, a revolutionary optical transmission medium, boasts a unique structural design that elevates optical performance to new heights. Unlike traditional solid-core fiber, hollow-core fiber uses air as its core medium, surrounded by a quartz glass cladding. This innovative structural design offers three key advantages: First, the interaction between the light field and the quartz material is significantly reduced, resulting in lower dispersion characteristics for hollow-core fiber; second, nonlinear optical effects are significantly suppressed, with the nonlinear coefficient reduced by three orders of magnitude compared to conventional fiber; and third, it exhibits an extremely high power damage threshold.
[0003] Hollow-core antiresonant fibers utilize a unique transverse cladding structure that strictly confines the optical field within the longitudinal air core, enabling efficient transmission of optical signals in the low-refractive-index medium of air. This unique design enables hollow-core antiresonant fibers to exhibit numerous exceptional properties in applications, including low dispersion, low nonlinearity, a high power damage threshold, low-temperature sensitivity, low transmission latency, and a wide operating bandwidth, making them ideal for applications such as high-power laser transmission, ultrafast optics, and low-latency communications.
[0004] Hollow-core antiresonant fibers, with their broadband, low-loss, large mode area, and simplified structure, have found important applications in numerous high-tech fields. In gas lasers, they have significantly improved power and beam quality; in fiber-optic sensing systems, they have greatly enhanced detection sensitivity and response speed; and in scenarios such as precision machining and broadband transmission, they have demonstrated performance advantages unmatched by traditional optical fibers. These successful applications not only validate the technological maturity of hollow-core fibers but also herald their promising future in the optoelectronics field. With continuous advancements in fabrication processes and growing demand for applications, hollow-core fibers are moving from the laboratory to industrialization, poised to play a key role in emerging fields such as quantum communications, ultrafast lasers, and biomedicine, driving technological innovation across the optoelectronics industry.
[0005] By injecting a specific gas into the hollow core fiber, the hollow core fiber connects the single mode fiber to achieve airtightness, successfully constructs a gas cavity structure, and can significantly enhance the interaction between light and gas molecules. This innovative design provides a new method for the study of gas nonlinear properties and spectral properties. Compared with traditional gas absorption cells, photonic crystal fiber gas absorption cavities have shown significant advantages due to their excellent stability, small size, and all-fiber design. For high-pressure conditions, previous studies have shown that low pump power is a very important indicator in Raman fiber lasers, as it means that the laser can operate with lower energy consumption, thereby reducing costs and energy consumption. The hollow core fiber high pressure gas can help researchers study nonlinear optical phenomena such as stimulated Raman scattering more deeply. In addition, the gas-filled hollow core fiber gas cavity also shows significant value in the study of weak molecular transitions and high-resolution spectroscopy, especially at low pressures, which can reveal the saturated absorption spectrum of molecules, showing narrower linewidths and higher resolution. On the other hand, the hollow core fiber low pressure gas cavity has broad application prospects in laser frequency stabilization and gas detection.
[0006] Since fiber fusion is usually carried out in an open environment, when preparing a hollow core fiber low pressure cavity, external air inevitably enters the hollow core fiber, which not only increases the pressure of the gas cavity, but also reduces the purity of the gas, which has a certain impact on the purity of the gas inside the hollow core fiber. To solve the above problems, some researchers have proposed an innovative sealing scheme: a V-shaped groove is used at the output end to couple the hollow core fiber with the single mode fiber, and the connection part is placed in a sealed vacuum chamber with controllable air pressure. This design effectively prevents the entry of external air, ensuring the purity and stability of the gas cavity. However, these methods are accompanied by complex spatial light coupling, low coupling efficiency, and bulky vacuum chambers, which limit the miniaturization of the system. Another method is to temporarily fill a high-pressure buffer gas into the hollow core fiber low pressure gas cavity. After filling the buffer gas, the hollow core fiber is cut and fused. The buffer gas reduces the pollution of the atmosphere to the low pressure gas cavity. However, this method is limited by the length of the fusion time, and once the fusion time is too long, it will cause irreversible pollution to the gas cavity. Since the fusion process is not airtight, the buffer gas can only reduce the impact of air to a certain extent, and cannot guarantee the purity of the gas cavity. SUMMARY
[0007] The technical problems solved by the present application are the monitoring of the gas exchange process during the preparation of the low pressure gas cavity, and the sealing and fusion of the all-fiber type hollow core anti-resonant fiber low pressure gas cavity. The present application provides a preparation method for an all-fiber type hollow core anti-resonant fiber low pressure gas cavity, to realize the preparation of an all-fiber type hollow core anti-resonant fiber low pressure gas cavity with no pollution, miniaturization, low loss, and high performance.
[0008] The present invention provides a method for preparing an all-fiber hollow-core antiresonant fiber low-pressure gas cavity, which involves a fiber taper machine, a fiber fusion splicer, a tunable laser 1, a hollow-core antiresonant fiber 4, a metal gas chamber 5, a ceramic ferrule 6, a thermally expanded single-mode fiber 7, a turbomolecular pump 8, a high-pressure gas cylinder 9, and a photodetector 10. The specific steps are: (1) Thermally expand and reversely taper an ordinary single-mode optical fiber using an optical fiber taper machine to obtain a reverse-tapered optical fiber 2, wherein the core size of the reverse-tapered optical fiber 2 can match the core size of the hollow-core anti-resonant optical fiber 4, and the length of the hollow-core anti-resonant optical fiber 4 is about 10 meters; the reverse-tapered optical fiber 2 and one end of the hollow-core anti-resonant optical fiber 4 are fused together using an optical fiber fusion splicer to obtain a fusion point 3, and the fusion point 3 is encapsulated with a heat shrink tube and a metal sleeve; (2) Align and couple the other end of the hollow-core antiresonant fiber 4 with the thermally expanded single-mode fiber 7 through the ceramic ferrule 6; place the ceramic ferrule 6 into the metal gas chamber 5, and lead the optical fiber out of the metal gas chamber 5 through the Wilson seal structure; connect the gas pipe to the metal gas chamber 5 through the turbomolecular pump 8 and the high-pressure gas cylinder 9; connect the tuned laser 1 and the reverse tapered fiber 2, the single-mode fiber 7 and the photodetector 10 through the fiber jumper to complete the system construction; (3) After the system is built, the metal gas chamber 5 is evacuated by the turbomolecular pump 8 to discharge the impurity gas in the hollow-core anti-resonance fiber 4; then, the hollow-core anti-resonance fiber 4 is filled with high-pressure gas of 2 to 3 atmospheres through the high-pressure gas cylinder 9; the hollow-core anti-resonance fiber 4 is depressurized by the turbomolecular pump (8) to below 0.1 atmospheres; during the gas exchange process, the absorption spectrum of the gas in the gas cavity is monitored in real time by the tunable laser 1 and the photodetector (10), and the time of pumping, filling and depressurization is controlled by real-time monitoring; (4) After the pressure reduction is completed, the hollow-core anti-resonance optical fiber 4 near the side of the metal gas chamber 5 is partially discharged using a fusion splicer, so that the hollow-core anti-resonance optical fiber 4 is completely collapsed to achieve sealing, and then the collapsed area is cut; (5) The cut hollow-core anti-resonant fiber 4 is fused with a prepared graded-index multimode fiber to precisely cut the graded-index multimode fiber to a certain length; the graded-index fiber with the precisely cut length is fused with an ordinary single-mode fiber to obtain a full-fiber hollow-core anti-resonant fiber low-pressure gas cavity.
[0009] In the present invention, the metal gas chamber 5 has good gas tightness, and the hollow core antiresonant optical fiber (4) and the thermally expanded single-mode optical fiber 7 are sealed by a plug, and gas exchange is carried out using an air pipe, a turbomolecular pump 8, and a high-pressure gas cylinder 9.
[0010] In the present invention, the tunable laser (1) and the photodetector (10) monitor the absorption spectrum of the gas in the gas cavity in real time, and the time of gas extraction, gas filling and pressure reduction is controlled by real-time monitoring.
[0011] In the present invention, one end of the hollow-core anti-resonant fiber 4 is discharged and collapsed by a fusion splicer, and the hollow-core anti-resonant fiber 4 is sealed by the collapse. After cutting, the hollow-core anti-resonant fiber 4 is fusion-spliced with a graded-index fiber, and then the graded-index fiber is fusion-spliced with a single-mode fiber to seal it.
[0012] The present invention also provides an all-fiber hollow-core anti-resonance fiber low-pressure gas cavity prepared by the method of the present invention.
[0013] The present invention successfully fabricates a miniaturized, high-performance hollow-core antiresonant fiber low-pressure cavity, and enables real-time monitoring of the gas absorption spectrum during the fabrication process. The hollow-core antiresonant fiber low-pressure cavity fabricated in this invention exhibits strong sealing properties, a simple structure, and easily repeatable experiments, making it suitable for most studies of hollow-core fiber-gas interactions. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 This is a schematic structural diagram of the device for preparing the all-fiber hollow-core anti-resonant fiber low-pressure gas cavity of the present invention.
[0015] Figure 2 This is a cross-sectional view of the hollow-core antiresonant optical fiber of the present invention.
[0016] Figure 3 This is a side view of the fusion point of the hollow-core antiresonant optical fiber and the reverse-tapered optical fiber of the present invention.
[0017] Figure 4 This is a side view of the fusion point of the hollow-core antiresonant fiber and the reverse graded-index fiber of the present invention.
[0018] Figure 5 This is the absorption spectrum of the carbon dioxide sample in the low-pressure gas cavity of the hollow-core antiresonant optical fiber of the present invention.
[0019] The numbers in the figure are: 1 is a tunable laser, 2 is a thermally expanded reverse tapered fiber, 3 is a fusion point, 4 is a hollow-core antiresonant fiber, 5 is a metal gas chamber, 6 is a ceramic ferrule, 7 is a thermally expanded single-mode fiber, 8 is a turbomolecular pump, 9 is a high-pressure gas cylinder, and 10 is a photodetector. DETAILED DESCRIPTION
[0020] The present application realizes the preparation of a low-pressure gas cavity by replacing and purifying the gas in the hollow-core anti-resonant fiber cavity. First, one side of the hollow-core anti-resonant fiber (4) is fused with a single-mode optical fiber to ensure efficient optical signal transmission. Second, the other side of the hollow-core anti-resonant fiber (4) is coupled with a single-mode optical fiber using a ceramic insert, further ensuring the stability and accuracy of signal transmission. Finally, the low-pressure cavity is sealed using UV glue, effectively preventing gas contamination and external environmental interference. The metal gas chamber (5) has good airtightness, which can ensure the purity of the gas in the gas cavity during gas exchange, thereby improving the accuracy of the experiment.
[0021] Figure 2 The hollow-core anti-resonant fiber (4) used to prepare the all-fiber low-pressure cavity has a 6-ring nested capillary structure and is a typical negative curvature nodeless design. It significantly improves the light field binding ability and reduces transmission loss through multi-stage anti-resonance mechanism.
[0022] A single-mode optical fiber (7) with thermal expansion core and reverse taper is prepared by a fiber tapering machine. The specific steps are as follows: (1) use wire strippers to remove the coating layer of the single-mode optical fiber, use ethanol and acetone to clean the exposed part of the bare fiber several times to ensure the cleanliness of the fiber surface and the quality of the reverse tapering of the fiber, then install the clean single-mode optical fiber in the tapering machine and wait for use. (2) Set the parameters of the tapering machine, light up, and after a certain time of thermal expansion core, increase the mode field of the optical fiber. The expansion time will affect the effect of thermal expansion core. (3) After the expansion time is reached, anneal, keep the position of the optical fiber unchanged, set the flow of oxygen and hydrogen of the tapering machine, increase the flame of the flame, set the pushing speed and pushing distance, light up and move back, and complete the preparation of the reverse tapering fiber with thermal expansion core.
[0023] The present application uses a fiber fusion splicer to fuse the hollow-core anti-resonant fiber (4). Specifically, two optical fibers to be fused are cut, and the end surface of the optical fiber after cutting is clean and flat. Then the two cut optical fibers are aligned and positioned by a special clamp, and the axes of the two optical fibers are as coincident as possible to minimize the butt joint loss of the two optical fibers. The fusion splicer generates high temperature on the end surface of the two optical fibers, causing them to melt and fuse together quickly. Figure 3 The side view of the fusion point between the hollow-core anti-resonant fiber and the reverse tapering fiber after fusion.
[0024] The present application is to realize the real-time monitoring of the gas exchange process of the hollow-core anti-resonant fiber gas cavity. In the coupling process, another single-mode optical fiber is taken to expand the core by heat, and then the optical fiber is cut and put into the ceramic plug. The two ceramic plugs are put into the sleeve, and the collimation butt joint is carried out under the microscope. The position of the ceramic plug is adjusted so that there is a certain gap between the end face of the optical fiber to ensure the smoothness of the subsequent gas exchange. The coupling loss of the hollow-core anti-resonant fiber and the single-mode optical fiber is minimized by continuous rotation. In addition, after the alignment is completed, AB glue is used to fix the tail of the ceramic plug. A certain time is waited for the AB glue to completely solidify to ensure that the coupling point loss of the hollow-core anti-resonant fiber and the single-mode optical fiber is relatively stable in the subsequent installation process. The coupling point loss does not affect the absorption spectrum in the subsequent monitoring process.
[0025] In the present application, the turbo molecular pump (8) is connected with the vacuum chamber (5) to ensure the gas purity in the hollow-core anti-resonant fiber gas cavity. First, the impurity gas in the gas cavity is replaced by using a high-pressure gas flushing device. The metal gas chamber (5) is evacuated to maintain a high vacuum degree. The hollow-core anti-resonant fiber (4) is heated during this period. The purpose is to accelerate the gas exchange speed in the hollow-core anti-resonant fiber. After the vacuum is exhausted, high-pressure gas is injected into the metal gas chamber (5), and the high-pressure gas flows into the hollow-core anti-resonant fiber (4) through the micro tube flow effect. The absorption spectrum of the gas cavity is monitored. When the absorption spectrum is stable, it means that the gas replacement is completed. Then the gas cavity is depressurized by the turbo molecular pump (8). The change of the absorption spectrum can be observed during the depressurization process. With the increase of the pumping time, the absorption spectrum of the gas becomes more and more sharp. When the bandwidth of the absorption spectrum reaches a certain value, it means that the pressure of the hollow-core anti-resonant fiber gas cavity corresponds to how much.
[0026] After the depressurization is completed, the coupling point of the hollow-core anti-resonant fiber (4) is discharged and collapsed by the fusion machine, and the hollow-core anti-resonant fiber gas cavity is sealed. Then the collapsed point is cut under the microscope. After cutting, the flat end face of the hollow-core anti-resonant fiber (4) is fused with one end of the prepared graded-index fiber, and the other end of the graded-index fiber is cut and fused with the single-mode optical fiber. Figure 4 The side view of the fusion point of the hollow-core anti-resonant fiber and the reverse graded-index fiber.
[0027] After the fusion is completed, the preparation of the hollow-core anti-resonant fiber gas cavity is basically completed. In order to maintain the long-term stability of the hollow-core anti-resonant fiber low-pressure gas cavity, the two ends of the hollow-core anti-resonant fiber low-pressure gas cavity are sealed and reinforced by metal sleeve and glue. Figure 5 The absorption spectrum of the hollow-core anti-resonant fiber low-pressure gas cavity sample filled with carbon dioxide.
[0028] The preferred embodiments of the present invention are as described above, but the scope of protection thereof is not limited thereto. Any equivalent modification, replacement, combination or simplification based on the core design concept of the present invention shall be deemed to fall within the scope of protection of the present invention.
Claims
1. A method for preparing an all-fiber hollow-core antiresonant fiber low-pressure gas cavity, characterized in that: It involves an optical fiber taper machine, an optical fiber fusion splicer, single-mode optical fiber, an air tube, a tunable laser, a hollow-core antiresonant optical fiber, a metal gas chamber, a ceramic ferrule, a thermally expanded single-mode optical fiber, a turbomolecular pump, a high-pressure gas cylinder, and a photoelectric detector. The specific steps are: (1) Thermally expanding and reverse tapering an ordinary single-mode optical fiber is performed by a fiber taper machine to obtain a reverse taper optical fiber (2), wherein the core size of the reverse taper optical fiber (2) can match the core size of the hollow core anti-resonant optical fiber (4), and the length of the hollow core anti-resonant optical fiber (4) is about 10 meters; the reverse taper optical fiber (2) and one end of the hollow core anti-resonant optical fiber (4) are fused by a fiber fusion splicer to obtain a fusion point (3), and the fusion point (3) is encapsulated with a heat shrink tube and a metal sleeve; (2) Align and couple the other end of the hollow-core antiresonant fiber (4) with the thermally expanded single-mode fiber (7) through a ceramic ferrule (6); place the ceramic ferrule (6) into a metal gas chamber (5), and lead the optical fiber out of the metal gas chamber (5) through a Wilson seal structure; connect the gas pipe to the metal gas chamber (5) through a turbomolecular pump (8) and a high-pressure gas cylinder (9); connect the tunable laser (1) and the reverse tapered fiber (2), the single-mode fiber (7) and the photodetector (10) through optical fiber jumpers to complete the system construction; (3) After the system is built, the metal gas chamber (5) is evacuated by a turbomolecular pump (8) to discharge the impurity gas in the hollow-core anti-resonance optical fiber (4); then, a high-pressure gas of 2 to 3 atmospheres is filled into the hollow-core anti-resonance optical fiber (4) through a high-pressure gas cylinder (9); the turbomolecular pump (8) is then used to reduce the pressure of the hollow-core anti-resonance optical fiber (4) to below 0.1 atmospheres; during the gas exchange process, the absorption spectrum of the gas in the gas chamber is monitored in real time by a tunable laser (1) and a photodetector (10), and the time of pumping, filling and reducing the pressure is controlled by real-time monitoring; (4) After the pressure reduction is completed, the hollow core anti-resonance optical fiber (4) near the side of the metal gas chamber (5) is subjected to partial discharge using a fusion splicer, so that the hollow core anti-resonance optical fiber (4) is completely collapsed to achieve sealing, and then the collapsed area is cut; (5) The cut hollow-core anti-resonant fiber (4) is fused with a graded-index multimode fiber to precisely cut the graded-index multimode fiber to a certain length; the graded-index fiber with the precisely cut length is fused with an ordinary single-mode fiber to obtain a full-fiber hollow-core anti-resonant fiber low-pressure gas cavity.
2. The preparation method according to claim 1, characterized in that The metal gas chamber (5) has good gas tightness, and the hollow-core antiresonant optical fiber (4) and the thermally expanded single-mode optical fiber (7) are sealed by a plug, and gas exchange is carried out using an air pipe, a turbomolecular pump (8) and a high-pressure gas cylinder (9).
3. The preparation method according to claim 1, characterized in that The tunable laser (1) and the photoelectric detector (10) monitor the absorption spectrum of the gas in the gas cavity in real time, and control the time of gas extraction, gas filling and pressure reduction through real-time monitoring.
4. The preparation method according to claim 1, characterized in that One end of the hollow-core anti-resonance optical fiber (4) is collapsed by discharge using a fusion splicer, and the hollow-core anti-resonance optical fiber (4) is sealed by utilizing the collapse; after cutting, the hollow-core anti-resonance optical fiber (4) is fusion-spliced with a graded-refractive-index optical fiber, and then the graded-refractive-index optical fiber is fusion-spliced with a single-mode optical fiber to seal.
5. An all-fiber hollow-core antiresonant fiber low-pressure gas cavity obtained by the preparation method according to any one of claims 1 to 4.