Gas micro-concentration pretreatment device and method for hollow-core optical fiber preform

Abstract

The invention relates to a hollow-core optical fiber preform gas micro-concentration pretreatment device and method.The device comprises a detection device and a treatment device, and the detection device comprises an optical fiber beam splitter and a detection light source connected with the input end of the optical fiber beam splitter; one path of the output end of the optical fiber beam splitter is connected with the signal processing unit after being introduced into the optical fiber preform, the other path of the output end of the optical fiber beam splitter is connected with the signal processing unit after being introduced into the contrast unit, and the processing device comprises a high-pressure gas source and a vacuum pump which are communicated with an inner cavity of the optical fiber preform. According to the method, effective intervention measures are taken on the preform in the preorder link of optical fiber preparation, so that the gas atmosphere purity in the preform or an intermediate transition body can be improved, and the carbon dioxide gas concentration in the inner cavity of the hollow preform is reduced; therefore, the influence of the carbon dioxide absorption peak of the hollow-core microstructure optical fiber on the transmission performance of the optical fiber in a communication system is improved, and the preparation quality and efficiency of the hollow-core optical fiber are ensured.

Description

Technical Field

[0001] The present invention relates to a device and method for micro-concentration pretreatment of gas in a hollow fiber preform, belonging to the technical fields of optical communication and transmission. Background Art

[0002] Hollow microstructure optical fibers have the advantages of low delay, low dispersion coefficient, low nonlinearity, and wide bandwidth because optical signals are mainly transmitted in their air cores. As an important candidate for upgrading traditional solid-core optical fibers, they can provide new solutions for low-latency optical communication. However, current practical application verifications in communication transmission systems such as dense wavelength division multiplexing show that optical signals will experience extremely obvious attenuation increases at certain wavelengths when passing through hollow microstructure optical fibers, resulting in a significant deterioration of transmission performance and seriously affecting transmission efficiency. Based on a comprehensive analysis of experimental results and relevant theoretical research, this situation occurs because during the fiber preparation process, there are carbon dioxide molecules or impurity adsorption in the hollow microstructure optical fibers, and it is difficult to ensure a high-purity gas atmosphere in the air core region. Therefore, when optical signals are transmitted, these carbon dioxide molecules or impurities will absorb light energy at specific wavelengths or bands, generating carbon dioxide gas absorption peaks, which will inevitably affect the fiber performance and applications.

[0003] In the existing publicly available technologies, such as CN116124696A, CN115266638A, CN110470625A, CN113588624A, and CN115266640A, a gas concentration detection device or system based on a hollow fiber is disclosed in a similar form. The main principle is to use the hollow fiber as a gas chamber, introduce a certain amount of the gas to be measured into it, and then use the interaction between laser and the gas to be measured to process the output optical signal and conduct comparative analysis to obtain the concentration and composition information of the gas to be measured. Although the above patent documents all utilize the characteristics of the hollow microstructure optical fiber as a platform for the interaction between light and matter, these technologies mainly focus on applications such as fiber sensing or nonlinear optics, and do not mention the improvement of the transmission performance of the hollow microstructure optical fiber, such as the carbon dioxide gas absorption peak. Therefore, they cannot meet the urgent requirements of optical communication. How to improve the gas atmosphere of the hollow microstructure optical fiber and reduce the impact of the carbon dioxide gas absorption peak on the communication system is an urgent problem to be solved. Summary of the Invention

[0004] The problem to be solved by the present invention is to provide a device and method for micro-concentration pretreatment of gas in a hollow fiber preform in view of the deficiencies of the above-mentioned existing technologies, which can improve the purity of the internal gas atmosphere of the hollow fiber and reduce the impact of the carbon dioxide gas absorption peak on the transmission performance of the fiber in the communication system.

[0005] The technical solution of the pretreatment device adopted by the present invention to solve the above-mentioned problems is as follows: It includes a detection device and a processing device. The detection device includes an optical fiber beam splitter and a detection light source connected to the input end of the optical fiber beam splitter. One output end of the optical fiber beam splitter passes through an optical fiber preform and then is connected to a signal processing unit, and the other output end passes through a reference unit and is connected to the signal processing unit. The processing device includes a high-pressure gas source and a vacuum pump connected to the inner cavity of the optical fiber preform.

[0006] According to the above solution, the signal processing unit includes a carbon dioxide detector and a data analysis and processing module. The carbon dioxide detector converts the received optical signal into an electrical signal and transmits it to the data analysis and processing module.

[0007] According to the above solution, one output end of the optical fiber beam splitter is connected to the front capillary at the tapered end or the tail end of the optical fiber preform, and the receiving end of the carbon dioxide detector is connected to the rear capillary at the tail end or the tapered end of the optical fiber preform.

[0008] According to the above solution, the reference unit is a carbon dioxide gas chamber.

[0009] According to the above solution, the input end of the optical fiber beam splitter is connected to the detection light source through an optical fiber. The output ends of the optical fiber beam splitter are respectively connected to the front capillary at the tapered end or the tail end of the optical fiber preform and the carbon dioxide gas chamber of the reference unit through optical fibers. The carbon dioxide detector is connected to the rear capillary at the tail end or the tapered end of the optical fiber preform through an optical fiber. The carbon dioxide gas chamber is connected to the carbon dioxide detector of the reference unit through an optical fiber.

[0010] According to the above solution, the detection light source is a tunable broadband light source.

[0011] According to the above solution, the optical fiber is a single-mode optical fiber.

[0012] According to the above solution, the optical fiber beam splitter is an optical fiber beam splitter with adjustable splitting ratio.

[0013] According to the above solution, the high-pressure gas source and the vacuum pump are respectively connected in series with gas path control components and are connected to the inner cavity of the optical fiber preform.

[0014] According to the above solution, the gas path control components include a gas valve with a check function and a pressure reducing valve.

[0015] According to the above solution, the carbon dioxide concentration in the high-pressure gas source is less than 0.1 ppm.

[0016] According to the above solution, the high-pressure gas source and the vacuum pump are connected to the inner cavity of the optical fiber preform through a sealing end cover configured with the tail end of the optical fiber preform.

[0017] According to the above solution, the high-pressure gas source and the vacuum pump are connected to the inner cavity of the optical fiber preform through a sealed tank.

[0018] According to the above solution, the sealed tank includes a sealed housing, in which a bottom support seat and an upper support frame are installed. Sealed through holes configured with the rear capillary and the front capillary are respectively provided at the upper and lower ends of the sealed housing, and the sealed housing is connected to the high-pressure gas source and the vacuum pump.

[0019] The technical solution of the pretreatment device of the present invention is as follows:

[0020] Install and connect the hollow optical fiber preform in place by using the above device.

[0021] Detect the carbon dioxide concentration of the gas in the cavity of the optical fiber preform: adjust the output wavelength of the detection light source to the characteristic wavelength of the carbon dioxide absorption peak, use an optical fiber splitter to make the optical signal pass through the optical fiber preform and the reference unit respectively, and then be received by a carbon dioxide detector, and transmit the converted signal to the data analysis and processing module. The data analysis and processing module uses the carbon dioxide concentration obtained after processing the optical signal of the reference unit as a calibration, and then compares and analyzes the converted signal of the optical fiber preform with it to obtain the initial carbon dioxide concentration V in the preform. 0 ,

[0022] Pretreat the gas in the cavity of the hollow optical fiber preform: open the vacuum pump and the gas path control valve, evacuate the cavity until the vacuum degree is less than 10 Pa, then close the vacuum pump and the gas path control valve, and then open the high-pressure gas source and the gas path control valve to fill the cavity until the pressure in the cavity reaches 0.2 Mpa, and then close the high-pressure gas source and the gas path control valve.

[0023] According to the above solution, the above-mentioned pretreatment evacuation and inflation are repeated multiple times so that the carbon dioxide concentration V of the gas in the preform cavity after pretreatment 1 is lower than 0.1 ppm; preferably, the carbon dioxide concentration is lower than 0.01 ppm or 0.001 ppm.

[0024] According to the above solution, the splitting ratio of the optical fiber splitter is 1:1.

[0025] According to the above solution, coupling ports for single-mode fiber connection are provided at both ends of the carbon dioxide gas cavity of the reference unit to realize the effective transmission of the optical signal in the reference unit.

[0026] According to the above solution, the pressure in the carbon dioxide gas cavity is 0.2 Mpa; the carbon dioxide concentration in the high-pressure gas source is less than 0.1 ppm.

[0027] According to the above solution, one end of the hollow fiber preform is a tapered end, and its central through hole is inserted with a front capillary and melted and connected. The front capillary is connected to the beam splitter through a single-mode fiber. The other end of the hollow fiber preform is a tail end, and the end face of the tail end is provided with a sealing end cover. An air inlet and outlet joint is arranged on the sealing end cover and is respectively connected to a high-pressure gas source and a vacuum pump. A central through hole is opened on the sealing end cover to insert a rear capillary and melted and connected. The rear capillary is connected to the carbon dioxide detector through a single-mode fiber.

[0028] According to the above solution, through holes identical to the inner cavity are opened on the circumferential side surface of the hollow fiber preform, a pressure gauge and a vacuum gauge are respectively installed, and a porous capillary connected to the air inlet and outlet joint is installed in the inner cavity of the preform.

[0029] According to the above solution, the outer diameters of the front and rear capillaries are 1 - 2 mm, the inner diameters are 0.3 - 0.5 mm, and the lengths are 100 - 150 mm; the outer diameter of the porous capillary is 3 - 5 mm, the inner diameter is 1.0 - 2.0 mm, the length is 600 - 800 mm, and equidistant round holes are opened on the porous capillary, the hole pitch is 40 - 60 mm, and the hole diameter is 0.7 - 1.2 mm.

[0030] According to the above solution, the materials of the front and rear capillaries, the porous capillary and the hollow fiber preform are all pure silica glass, and its refractive index is 1.455.

[0031] The beneficial effects of the present invention are as follows: 1. The pretreatment device and method of the hollow microstructured preform based on gas micro-concentration detection and replacement provided by the present invention can improve the purity of the gas atmosphere inside the preform or the intermediate transition body by taking effective intervention measures in the previous stage of optical fiber preparation, reduce the carbon dioxide gas concentration in the inner cavity of the hollow preform, thereby improving the influence of the carbon dioxide absorption peak of the hollow microstructured optical fiber on the transmission performance of the optical fiber in the communication system, and ensuring the quality and efficiency of the hollow fiber preparation. 2. The structure of the present invention is set simply and reasonably, and is convenient to use. By performing air extraction and inflation treatment and arranging a porous capillary connected to an external gas path control component in the cavity of the hollow fiber preform, the switching speed of the gas state of the preform is accelerated, and the replacement efficiency of the internal gas atmosphere is improved. Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of the pretreatment device and method in the first embodiment of the present invention.

[0033] Figure 2 It is a three-dimensional structure diagram of the porous capillary in the first embodiment of the present invention.

[0034] Figure 3 It is a schematic structural diagram of the pretreatment device and method in the second embodiment of the present invention.

[0035] Figure 4 Comparison chart of the results of the absorption peak of the fiber based on the pretreatment of the hollow fiber preform by gas micro-concentration detection and displacement in the L band. Specific implementation mode

[0036] The present invention will be further described in detail below in conjunction with the embodiments of the present invention and the accompanying drawings.

[0037] The first embodiment of the present invention is as Figure 1 、 2As shown in the figure, it includes a detection device and a processing device. The detection device includes an optical fiber beam splitter 2 and a detection light source 1 connected to the input end of the optical fiber beam splitter. The detection light source 1 is adjusted to the characteristic wavelength band of carbon dioxide absorption. One output end of the optical fiber beam splitter passes through an optical fiber preform 4 and then is connected to a signal processing unit, and the other output end passes through a reference unit and is connected to the signal processing unit. The optical fiber beam splitter is an optical fiber beam splitter with adjustable splitting ratio, and the splitting ratio is 1:1. The signal processing unit includes a carbon dioxide detector 15 and a data analysis and processing module 17. The carbon dioxide detector converts the received optical signal into an electrical signal and transmits it to the data analysis and processing module. There are 2 carbon dioxide detectors separately provided, and 1 data analysis and processing module can be shared. One output end of the optical fiber beam splitter is connected to the front capillary 3 at the tapered end of the optical fiber preform 4, and the receiving end of the carbon dioxide detector is connected to the rear capillary 5 at the tail end of the optical fiber preform. The reference unit is a carbon dioxide gas chamber 8, and the internal pressure of the carbon dioxide gas chamber is 0.2 Mpa; the input end of the optical fiber beam splitter is connected to the detection light source through an optical fiber 16, the output end of the optical fiber beam splitter is connected to the front capillary at the tapered end or the tail end of the optical fiber preform and the carbon dioxide gas chamber of the reference unit through optical fibers respectively, the carbon dioxide detector is connected to the rear capillary at the tail end or the tapered end of the optical fiber preform through an optical fiber, the carbon dioxide gas chamber is connected to the carbon dioxide detector of the reference unit through an optical fiber, and the optical fiber is a single-mode optical fiber. The processing device includes a high-pressure gas source 10 and a vacuum pump 11 connected to the inner cavity of the optical fiber preform. The high-pressure gas source and the vacuum pump are respectively connected in series with gas path control valves 12 and are connected to the inner cavity of the optical fiber preform through an air pipe 9. The gas path control valves include a gas valve with a check function and a pressure reducing valve. One end of the hollow optical fiber preform 4 is a tapered end, and its central through hole is placed in the front capillary 3 and is fused together. The front capillary is connected to the beam splitter through a single-mode optical fiber. The other end of the hollow optical fiber preform is a tail end, and a sealing end cover 6 is arranged on the end face of the tail end. An air inlet and outlet joint is arranged on the sealing cover and is respectively connected to the high-pressure gas source and the vacuum pump. A central through hole is opened on the sealing cover and the rear capillary 5 is placed in it and is fused together. The rear capillary is connected to the carbon dioxide detector 15 through a single-mode optical fiber. Through holes identical to the inner cavity are opened on the circumferential side surface of the hollow optical fiber preform, and a pressure gauge 13 and a vacuum gauge 14 are respectively installed. A porous capillary 7 connected to the air inlet and outlet joint is installed in the inner cavity of the preform. The outer diameter of the porous capillary is 4 mm, the inner diameter is 1.5 mm, and the length is 600 mm. Equally spaced round holes are opened on the porous capillary, the hole spacing is 50 mm, and the hole diameter is 1 mm. The outer diameters of the front and rear capillaries are 1.5 mm, the inner diameters are 0.4 mm, and the lengths are 120 mm.

[0038] Using the above device, the hollow fiber preform is installed and connected in place, and the carbon dioxide concentration of the gas in the cavity of the fiber preform is detected: the output wavelength of the detection light source is adjusted to the characteristic wavelength of the carbon dioxide absorption peak, and the optical fiber splitter is used to make the optical signal pass through the fiber preform and the reference unit respectively, and then received by the carbon dioxide detector, and the converted signal is transmitted to the data analysis and processing module. The data analysis and processing module uses the carbon dioxide concentration obtained after processing the optical signal of the reference unit as the calibration, and then compares and analyzes the converted signal of the fiber preform with it to obtain the initial carbon dioxide concentration V in the preform. 0 ; Then, the gas in the cavity of the hollow fiber preform is pretreated: the vacuum pump and the gas path control valve are opened, and the cavity is evacuated until the vacuum degree is less than 10 Pa, then the vacuum pump and the gas path control valve are closed, and then the high-pressure gas source and the gas path control valve are opened. The carbon dioxide concentration in the high-pressure gas source is less than 0.1 ppm, and the cavity is inflated until the pressure in the cavity reaches 0.2 Mpa, and then the high-pressure gas source and the gas path control valve are closed. Then, the carbon dioxide concentration of the gas in the cavity of the fiber preform is detected. The above-mentioned pretreatment evacuation, inflation and detection can be repeated multiple times, so that the carbon dioxide concentration V of the gas in the cavity of the pretreated preform 1 is lower than 0.1 ppm; preferably, the carbon dioxide concentration is lower than 0.01 ppm or 0.001 ppm.

[0039] The pretreated hollow fiber preform can be stretched into an intermediate transition body and then subjected to end face sealing treatment, and then the intermediate transition body is inserted into the wire drawing outer sleeve to complete the assembly of the wire drawing preform. During the wire drawing process, a gas with an appropriate pressure is filled into each part of the microstructural region to complete the fiber preparation.

[0040] The second embodiment of the present invention is as follows Figure 3As shown, the difference from the previous embodiment is that the high-pressure gas source and the vacuum pump are connected to the inner cavity of the optical fiber preform through a sealed tank. The sealed tank includes a sealed housing 18, in which a bottom support seat 19 and an upper support frame 20 are arranged. The bottom support seat and the upper support frame are adjustable bottom support seat and adjustable upper support frame. Sealed through holes configured with the rear capillary and the front capillary are respectively arranged at the upper and lower ends of the sealed housing, and the sealed housing is connected to the high-pressure gas source and the vacuum pump. The hollow optical fiber preform 4 is placed in the sealed housing with the tapered end facing downwards, and the preform is vertically fixed by the combined action of the adjustable bottom support seat and the adjustable upper support frame. A hydrogen-oxygen torch 21 is also arranged at the bottom of the chamber for sealing the bottom of the preform after the pretreatment is completed. Front and rear capillaries are respectively arranged at the tapered end and the tail end of the preform, and single-mode optical fibers are respectively inserted into the front and rear capillaries to transmit the optical signals after beam splitting and passing through the microstructured preform to the carbon dioxide detector, so as to detect the carbon dioxide concentration in the cavity of the optical fiber preform. When the high-pressure gas cylinder and the vacuum pump are in the open state, the optical fiber preform is pretreated by pumping and inflating. When the carbon dioxide concentration displayed in the data analysis and processing module is lower than 0.1 ppm, the pretreatment of the hollow microstructured preform is achieved. Preferably, the carbon dioxide concentration is lower than 0.01 ppm or 0.001 ppm.

Claims

1. A gas micro-concentration pretreatment device for hollow core optical fiber preform, characterized in that The invention comprises a detection device and a processing device. The detection device comprises an optical fiber beam splitter and a detection light source connected to the input end of the optical fiber beam splitter. One path of the output end of the optical fiber beam splitter leads to the optical fiber preform rod and then connects to the signal processing unit, and the other path leads to the control unit and connects to the signal processing unit. The processing device comprises a high-pressure gas source and a vacuum pump connected to the inner cavity of the optical fiber preform rod.

2. The hollow core optical fiber preform gas micro-concentration pretreatment device according to claim 1, characterized in that The signal processing unit includes a carbon dioxide detector and a data analysis and processing module. The carbon dioxide detector converts the received optical signal into an electrical signal and transmits it to the data analysis and processing module.

3. The hollow core optical fiber preform gas micro-concentration pretreatment device according to claim 2, characterized in that The output end of the optical fiber beam splitter is connected to the front capillary of the tapered end or tail end of the optical fiber preform, and the receiving end of the carbon dioxide detector is connected to the rear capillary of the tail end or tapered end of the optical fiber preform.

4. The hollow core optical fiber preform gas micro-concentration pretreatment device according to claim 2 or 3, characterized in that The control unit is a carbon dioxide gas chamber.

5. The hollow core optical fiber preform gas micro-concentration pretreatment device according to claim 4, characterized in that The input end of the optical fiber beam splitter is connected to the detection light source through the optical fiber, the output end of the optical fiber beam splitter is respectively connected to the front capillary at the tapered end or the tail end of the optical fiber preform and the carbon dioxide gas cavity of the control unit through the optical fiber, the carbon dioxide detector is connected to the rear capillary at the tail end or the tapered end of the optical fiber preform through the optical fiber, and the carbon dioxide gas cavity is connected to the carbon dioxide detector of the control unit through the optical fiber.

6. The hollow core optical fiber preform gas micro-concentration pretreatment device according to claim 1 or 2, characterized in that The high-pressure gas source and the vacuum pump are respectively connected in series with the gas path control valve components and communicated with the inner cavity of the optical fiber preform rod; the gas path control valve components include a gas valve with a check function and a pressure reducing valve.

7. The hollow core optical fiber preform gas micro-concentration pretreatment device according to claim 6, characterized in that The high-pressure gas source and the vacuum pump are connected to the inner cavity of the optical fiber preform rod through a sealing cover configured at the rear end of the optical fiber preform rod.

8. The hollow core optical fiber preform gas micro-concentration pretreatment device according to claim 6, characterized in that The high-pressure gas source and the vacuum pump are connected to the inner cavity of the optical fiber preform rod through the sealing tank.

9. The hollow core optical fiber preform gas micro-concentration pretreatment device according to claim 8, characterized in that The sealed tank comprises a sealed shell, in which a bottom support seat and an upper support frame are arranged, and the upper and lower ends of the sealed shell are respectively provided with sealed through holes configured with the rear capillary and the front capillary, and the sealed shell is connected with a high-pressure gas source and a vacuum pump.

10. A method for pretreatment of hollow core optical fiber preform rods with micro-concentration gas, characterized in that Using any one of the devices in claims 1-9, the hollow core optical fiber preform is installed and connected in place, The carbon dioxide concentration of the gas in the cavity of the optical fiber preform is detected: the light wavelength of the detection light source is adjusted to the characteristic wavelength of the carbon dioxide absorption peak, and the optical signal is passed through the optical fiber preform and the reference unit by an optical fiber beam splitter, and then received by the carbon dioxide detector, and the converted signal is transmitted to the data analysis and processing module. The data analysis and processing module uses the carbon dioxide concentration obtained after processing the optical signal of the reference unit as a calibration, and then compares and analyzes the converted signal of the optical fiber preform with it to obtain the initial carbon dioxide concentration V0 in the preform. Pre-treat the gas in the cavity of the hollow-core optical fiber preform rod: open the vacuum pump and the gas circuit control valve, evacuate the cavity until the vacuum degree is less than 10pa, then close the vacuum pump and the gas circuit control valve, and then open the high-pressure gas source and the gas circuit control valve to inflate the cavity until the pressure in the cavity reaches 0.2Mpa, and then close the high-pressure gas source and the gas circuit control valve.

11. The method for pretreatment of hollow core optical fiber preform with micro-concentration gas according to claim 10, characterized in that The pretreatment vacuuming and inflation are repeated multiple times, so that the carbon dioxide concentration V1 of the gas in the preform cavity after pretreatment is lower than 0.1 ppm; the optical fiber beam splitter has a splitting ratio of 1:

1.

12. The method for pretreating hollow core optical fiber preform with micro-concentration gas according to claim 10 or 11, characterized in that One end of the hollow-core optical fiber preform is a tapered end, a front capillary is placed in a central through hole and connected by melting, the front capillary is connected to a beam splitter through a single-mode optical fiber, the other end of the hollow-core optical fiber preform is a tail end, a sealing end cover is arranged on the tail end face, an inlet and outlet gas joint is arranged on the sealing end cover, and the inlet and outlet gas joints are respectively connected to a high-pressure gas source and a vacuum pump, a central through hole is opened on the sealing end cover, a rear capillary is placed in a central through hole and connected by melting, and the rear capillary is connected to a carbon dioxide detector through a single-mode optical fiber.

13. The method for pretreatment of hollow core optical fiber preform with micro-concentration gas according to claim 12, characterized in that The circumferential side of the hollow-core optical fiber preform is provided with a through hole identical to the inner cavity, and a pressure gauge and a vacuum gauge are respectively installed thereon. A porous capillary connected to the inlet and outlet gas joints is installed in the inner cavity of the preform; the outer diameter of the porous capillary is 3 to 5 mm, the inner diameter is 1.0 to 2.0 mm, and the length is 600 to 800 mm. The porous capillary is provided with equidistant circular holes, the hole spacing is 40 to 60 mm, and the hole diameter is 0.7 to 1.2 mm.

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