Optical fiber coupling monitoring device and design method thereof

Abstract

The invention relates to the technical field of pollution monitoring, in particular to an optical fiber coupling monitoring device and a design method thereof. According to the characteristic that substances such as petroleum can reflect fluorescence under irradiation of exciting light, the exciting light is distributed on the surface of underground water after being transmitted by the optical fiber and reflected by the concave mirror, when underground water petroleum pollution occurs, pollutants are irradiated by the exciting light to reflect fluorescence, and the fluorescence is coupled into the optical fiber after being reflected and converged by the concave mirror. And after the spectrograph receives the fluorescent light, the fluorescent light is decomposed into different wave bands, and whether a specific fluorescent substance is contained or not and the content of the specific fluorescent substance are judged from a characteristic spectral line. According to the invention, whether oil gas leakage occurs in underground water or not can be monitored in real time underground, the complex process of sampling in a water quality monitoring hole is omitted, a small oil film can be formed on the surface of the underground water even if oil gas leakage in a small range occurs, so that fluorescence is reflected, and the progress of underground water pollutant monitoring is obviously improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pollution monitoring, and particularly relates to a fiber coupling monitoring device and a design method thereof. BACKGROUND

[0002] The underground water-sealed cave is used for forming a water pressure barrier by using a water level, so as to prevent oil and gas from leaking in the cave. However, if the oil height exceeds the water level or the surrounding rock fissures develop, the oil may seep into the rock mass and pollute the underground water.

[0003] At present, the underground water oil pollution monitoring mainly relies on manual sampling and laboratory analysis. For the detection of the oil concentration in the underground water, the traditional method mainly adopts the mass method to analyze the water sample after sampling, for example, water quality monitoring holes are arranged around the underground water-sealed cave, a PVC sleeve and a screen pipe are installed in the hole to filter the water sample. However, due to the fact that the hole spacing of the water quality monitoring hole in the underground water-sealed cave is usually 50-100 meters, the depth is 10-30 meters, and the hole has the characteristics of deep depth and small diameter, a technician uses a bailer or a submersible pump to regularly extract the water sample from the water quality monitoring hole, and the sampling difficulty in the hole is relatively large. At the same time, due to the fact that the hole sites are relatively dispersed, manual observation is not convenient. The water sample is sent to a laboratory to detect the total oil hydrocarbon concentration by a gas chromatography method or an ultraviolet fluorescence method, and the oil concentration detection process is relatively complex. The traditional method is time-consuming and has low spatial resolution, and it is difficult to capture small-range leakage. SUMMARY

[0004] The main purpose of the present application is to provide a fiber coupling monitoring device and a design method thereof, so as to solve the technical problems that the traditional underground water oil pollution monitoring method has sampling difficulty, is time-consuming, and is difficult to capture small-range oil leakage.

[0005] To achieve the above-mentioned purpose, the present application provides a fiber coupling monitoring device, which comprises a light source, an optical fiber, a ferrule, a spectrometer and a concave mirror, wherein: The optical fiber is a Y-shaped structure, the optical fiber comprises a first end, a second end and a third end, the first end and the second end are oppositely arranged on both sides of the first end, the second end and the third end are both away from the ferrule, and the first end is fixedly connected with the ferrule; The light source is used for emitting excitation light, and the light source is opposite to the end face of the second end; The ferrule has an inner hole extending along the extension direction of the ferrule, the first end is fixed in the inner hole, and the end face of the first end is exposedly arranged from the inner hole; The spectrometer is used for receiving fluorescence reflected by the pollutants and analyzing the spectrum of the fluorescence, and the third end is connected with the spectrometer; The mirror surface of the concave mirror is correspondingly arranged with the end face of the first end.

[0006] Further, the end face of the first end deviates from the plane where the optical axis of the concave mirror is located, so that the excitation light is not reflected back to the first end by the concave mirror after being emitted.

[0007] Further preferably, the fluorescence converges to form a light spot after being reflected by the concave mirror, the diameter of the light spot is the same as the diameter of the end face of the first end, and the end face of the first end is located at the position of the light spot.

[0008] Further preferably, the first end of the optical fiber is provided with a first branch and a second branch, the first branch is connected with the second end, the second branch is connected with the third end, and the ends of the fiber cores in the first branch and the second branch are uniformly distributed on the end face of the first end.

[0009] Further preferably, the concave mirror comprises a first edge line and a second edge line, the first edge line and the second edge line are located at both ends of the bending direction of the concave mirror, the first edge line is away from the ferrule, the second edge line is close to the ferrule, and the arc length of the cross-sectional circular arc between the first edge line and the second edge line is less than 1 / 4 of the arc length of the circle where the cross-sectional circular arc is located.

[0010] Further, the coupling assembly comprises a light collecting port, a mounting groove and a ferrule hole, the mounting groove and the ferrule hole are located on both sides of the light collecting port, the mounting groove and the ferrule hole are opposite, the ferrule is fixed in the ferrule hole, the end face of the first end faces the concave mirror, the concave mirror is fixed in the mounting groove, and the optical axis of the concave mirror is inclined to the outside of the light collecting port.

[0011] The application also provides a design method of an optical fiber coupling monitoring device, which is applied to the optical fiber coupling monitoring device and comprises the following steps: S1, obtaining the optical axis of the concave mirror; wherein the optical axis is inclined relative to the horizontal plane; S2, obtaining the curvature radius of the concave mirror and the inclination angle of the optical axis, and deriving the focal length of the concave mirror according to the curvature radius and the inclination angle of the optical axis; S3, obtaining the offset height of the midpoint of the concave mirror relative to the plane where the bottom edge of the concave mirror is located, and deriving the current design distance from the midpoint of the concave mirror to the end face of the first end according to the focal length, the offset height and the inclination angle of the optical axis; S4, deriving the focal point position of the concave mirror according to the inclination angle of the optical axis, the current design distance and the offset height; S5, setting the ferrule at the focal point position; wherein the first end in the ferrule faces the concave mirror, and the fluorescence reflected by the concave mirror forms a light spot on the first end; S6, obtaining the diameter of the light spot, and determining whether the diameter of the light spot is equal to the diameter of the optical fiber. S71, when the spot diameter is equal to the fiber diameter, then the second end is directly opposite the light source, and the third end is connected with the spectrometer, thereby completing the design of the fiber coupling monitoring device; S72, when the spot diameter is not equal to the fiber diameter, the current design distance is adjusted by a preset adjustment increment to obtain an adjusted current design distance, and then returning to step S6.

[0012] Further, the step S2 specifically comprises the following steps: The focal length f of the concave mirror is calculated by the formula , wherein R is the radius of curvature of the concave mirror, is the optical axis inclination angle.

[0013] Further, the step S3 specifically comprises the following steps: The current design distance from the midpoint of the concave mirror to the end face of the first end is calculated by the formula , wherein is the current design distance, is the offset height of the midpoint of the concave mirror relative to the plane on which the bottom edge of the concave mirror is located.

[0014] Further, the step S72 specifically comprises the following steps: If the spot diameter is greater than the fiber diameter, then the current design distance is increased by a preset adjustment increment to reduce the spot diameter; If the spot diameter is less than the fiber diameter, then the current design distance is reduced by a preset adjustment increment to increase the spot diameter.

[0015] Compared with the prior art, the present application has the following beneficial effects: The present application utilizes the characteristics that petroleum and other substances will reflect fluorescence under the irradiation of excitation light. After the excitation light is transmitted through the optical fiber and then reflected by the concave mirror, the excitation light is distributed on the surface of underground water. When underground water is contaminated by petroleum, the contaminants are irradiated by the excitation light and then reflect fluorescence. After the fluorescence is reflected and converged by the concave mirror, it is coupled into the optical fiber. After being transmitted through the optical fiber, it reaches the spectrometer. After the spectrometer receives the fluorescence, it is decomposed into different wave bands. Whether the fluorescence contains specific fluorescent substances and the content thereof are determined from the characteristic spectrum. The present application can monitor whether oil and gas leakage occurs in underground water in real time, and the complex sampling process in the water quality monitoring hole is avoided. Moreover, even small-scale oil and gas leakage will form small oil films on the surface of underground water and then reflect fluorescence, thereby significantly improving the progress of monitoring of underground water contaminants. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below only illustrate some of the embodiments of the present application, and all other drawings obtained by those of ordinary skill in the art without creative effort based on these drawings also belong to the protection scope of the present application.

[0017] Figure 1 The connection diagram of the overall structure in an embodiment of the present application; Figure 2 The cross-sectional view of the coupling assembly in an embodiment of the present application; Figure 3 The fluorescent reflection diagram of the concave mirror and the optical fiber in an embodiment of the present application; Figure 4 The flow diagram of the design method of the optical fiber coupling monitoring device in an embodiment of the present application.

[0018] The purposes, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings.

[0019] Explanation of the reference signs: 1, concave mirror; 11, first side line; 12, second side line; 2, ferrule; 3, optical fiber; 31, first end; 32, second end; 33, third end; 4, light source; 5, spectrometer; 6, coupling assembly; 61, light inlet; 62, mounting groove; 63, ferrule hole. DETAILED DESCRIPTION

[0020] It should be understood that the specific embodiments described herein are merely used to explain the present application, and are not used to limit the present application.

[0021] The technical solutions in the embodiments of the present application will be described clearly and completely with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0022] It should be noted that all the directionality indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative position relationship, movement condition, etc. between the components in a certain specific posture (as described in the drawings). If the specific posture changes, the directionality indications also change accordingly.

[0023] In addition, the description related to "first", "second" and the like in the present application is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can be explicitly or implicitly included at least one of the features. In addition, the technical solutions of various embodiments can be combined with each other, but it must be based on the realization of ordinary skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, nor within the protection scope required by the present application.

[0024] Please refer to Figures 1 to 3 The embodiment provides a kind of optical fiber coupling monitoring device, including light source 4, optical fiber 3, ferrule 2, spectrometer 5 and concave mirror 1, wherein: The optical fiber 3 is Y type structure, the optical fiber 3 includes first end 31, second end 32 and third end 33, the first end 31 and second end 32 are oppositely arranged on the two sides of the first end 31, the second end 32 and third end 33 are both away from the ferrule 2, the first end 31 is fixedly connected with the ferrule 2; The light source 4 is used to emit excitation light, and the light source 4 is opposite to the end face of the second end 32; The ferrule 2 has an inner hole extending along the extension direction of itself, the first end 31 is fixed in the inner hole, and the end face of the first end 31 is exposedly arranged from the inner hole; The spectrometer 5 is used for receiving fluorescence reflected from pollutants and analyzing the spectrum of the fluorescence, and the third end 33 is connected with the spectrometer 5; The mirror surface of the concave mirror 1 is arranged corresponding to the end face of the first end 31.

[0025] The embodiment utilizes the characteristics that petroleum and other substances will reflect fluorescence under the irradiation of excitation light. The light source 4 of the embodiment emits excitation light, the excitation light enters the optical fiber 3 from the second end 32, is transmitted to the first end 31 through the optical fiber 3, is emitted after being reflected by the concave mirror 1, and irradiates the underground water. When the underground water is polluted by petroleum, the pollutants reflect fluorescence after being irradiated by the excitation light, the fluorescence is coupled into the first end 31 of the optical fiber 3 after being reflected and converged by the concave mirror 1, is transmitted to the spectrometer 5 from the third end 33 of the optical fiber 3, is decomposed into different wave bands after being received by the spectrometer 5, and the spectrometer 5 judges whether specific fluorescent substances and the content thereof are contained according to characteristic spectral lines.

[0026] The embodiment can monitor whether oil and gas leakage occurs in underground water in real time, avoids the complex sampling process in the water quality monitoring hole, and even a small range of oil and gas leakage can form a small oil film on the surface of underground water to reflect fluorescence, thereby significantly improving the progress of underground water pollution monitoring. In the embodiment, the Y-shaped optical fiber can ensure that the received fluorescence is transmitted to the spectrometer 5 during the continuous transmission of the excitation light, so that the excitation light emission and the fluorescence reception are performed synchronously, thereby ensuring the real-time of underground water monitoring. Moreover, the condensing effect of the concave mirror 1 makes more fluorescence gather on the optical fiber 3, thereby improving the response accuracy of the embodiment in response to small range oil and gas leakage. Since the concave mirror 1 is based on reflection principle, the anti-pollution ability is stronger than that of glass lens, and there is no need to consider the waterproof problem, so the adaptability is stronger.

[0027] Specifically, the plug core 2 is made of finished stainless steel material, and the coupling assembly 6 is made of aluminum material processed by CNC. The corrosion resistance of aluminum material and stainless steel material can better adapt to the harsh conditions of underground water environment. In the embodiment, the concave mirror 1 is still polished by using a wool ball after being processed by the CNC process, so as to form a mirror surface, and the reflectivity of the mirror surface is increased from 50% to more than 90%. The wool ball polishing process not only significantly enhances the fluorescence signal intensity, but also can be polished again if the mirror surface is polluted after a period of use, so that the maintenance is relatively simple.

[0028] In one embodiment, the end face of the first end 31 deviates from the plane where the optical axis of the concave mirror 1 is located. Preferably, the excitation light emitted in the first end 31 is reflected by the concave mirror 1 in the form of parallel light and irradiated to the underground water after deviating from the first end 31, thereby reducing the adverse effects caused by the direct reflection of the excitation light to the monitoring of the first end 31.

[0029] As a further preferred, the fluorescence is converged to form a light spot after being reflected by the concave mirror 1, the diameter of the light spot is the same as the diameter of the end face of the first end 31, and the end face of the first end 31 is located at the position of the light spot, so that the fluorescence is uniformly distributed on the end face of the first end 31, thereby improving the utilization rate of the optical fiber 3.

[0030] As a further preferred in the embodiment, the optical fiber 3 in the prior art includes a fiber core, the first end 31 of the optical fiber 3 includes a first branch and a second branch, the first branch is connected with the second end 32, the second branch is connected with the third end 33, and the fiber core ends in the first branch and the second branch are uniformly distributed on the end face of the first end 31, so that the fluorescence can be uniformly transmitted from the second branch to the spectrometer 5, and the excitation light from the second branch is uniformly distributed on the first end 31 of the optical fiber 3.

[0031] As Figure 1As shown, further preferably, the concave mirror 1 comprises a first edge line 11 and a second edge line 12, the first edge line 11 and the second edge line 12 are located at both ends of the bending direction of the concave mirror 1, the first edge line 11 is away from the ferrule 2, the second edge line 12 is close to the ferrule 2, and the arc length of the cross section of the curved surface between the first edge line 11 and the second edge line 12 is less than 1 / 4 of the arc length of the circle on which the cross section of the curved surface is located.

[0032] In one embodiment, as shown in Figure 2 Further comprising a coupling assembly 6, the coupling assembly 6 comprises a light inlet 61, a mounting groove 62 and a ferrule hole 63, the mounting groove 62 and the ferrule hole 63 are located on both sides of the light inlet 61, the mounting groove 62 and the ferrule hole 63 are opposite, the ferrule 2 is fixed in the ferrule hole 63, the end face of the first end 31 faces the concave mirror 1, the concave mirror 1 is fixed in the mounting groove 62, and the optical axis of the concave mirror 1 is inclined to the outside of the light inlet 61. The light inlet 61 faces the underground water surface, and the fluorescence is emitted from the light inlet 61, reflected by the concave mirror 1, and then converged on the first end 31 of the optical fiber 3 in the ferrule 2. The coupling assembly 6 fixes the concave mirror 1 and the ferrule 2 together, so that the distance between the concave mirror 1 and the first end 31 is always consistent, thereby improving the convenience of underground installation of the embodiment.

[0033] Further, the coupling assembly 6 further comprises a light-transmitting cover, which is wrapped outside the light inlet, so as to avoid pollution of the concave mirror 1 and the optical fiber 3 by the underground water environment, thereby affecting the monitoring effect of the embodiment.

[0034] In the embodiment, the concave mirror 1 and the mounting groove 62 are further detachably connected in a buckle type. Specifically, the edge part of the mounting groove 62 connected with the first edge line 11 and the second edge line 12 of the concave mirror 1 is provided with a bayonet, and the first edge line 11 and the second edge line 12 are inserted into the bayonet to complete the fixation. When the concave mirror 1 is polluted or broken, the concave mirror 1 can be taken out from the mounting groove 62 for replacement.

[0035] As shown in Figure 3 and Figure 4 The embodiment further provides a design method of the optical fiber coupling monitoring device, which is applied to the optical fiber coupling monitoring device as described above and comprises the following steps: S1, obtaining an optical axis of the concave mirror 1; wherein the optical axis is arranged to be inclined relative to a horizontal plane; S2, obtaining a curvature radius of the concave mirror 1 and an inclination angle of the optical axis, and obtaining a focal length of the concave mirror 1 according to the curvature radius and the inclination angle of the optical axis; The focal length f of the concave mirror 1 is calculated by using the formula ; wherein R is the curvature radius of the concave mirror 1, is the inclination angle of the optical axis.

[0036] S3. Obtain an offset height of the midpoint of the concave mirror 1 relative to the plane where the second edge of the concave mirror 1 is located, and determine a current design distance from the midpoint of the concave mirror 1 to the end face of the first end 31 based on the focal length, the offset height, and the optical axis inclination angle; Specifically, the formula , calculate the current design distance from the midpoint of the concave mirror 1 to the end face of the first end 31; wherein, is the current design distance, is the offset height of the midpoint of concave mirror 1.

[0037] S4. deriving the focal position of the concave mirror 1 according to the optical axis tilt angle, the current design distance, and the offset height; S5. Arrange the ferrule 2 at the focal position; wherein the first end 31 located in the ferrule 2 faces the concave mirror 1, and the fluorescence reflected by the concave mirror 1 forms a light spot on the first end 31; S6. Obtain the diameter of the light spot, and determine whether the diameter of the light spot is equal to the diameter of the optical fiber; S71. When the spot diameter is equal to the optical fiber diameter, the second end 32 is placed facing the light source 4 and the third end 33 is connected to the spectrometer 5, thereby completing the design of the optical fiber coupling monitoring device. S72: When the spot diameter is not equal to the optical fiber diameter, adjust the current design distance according to a preset adjustment increment to obtain an adjusted current design distance, and then return to step S6.

[0038] In this embodiment, step S72 specifically includes the following steps. In this embodiment, the preset adjustment increment is preferably 1mm, 2mm, or 5mm: If the spot diameter is larger than the optical fiber diameter, the current design distance is increased according to a preset adjustment increment to reduce the spot diameter; If the spot diameter is smaller than the optical fiber diameter, the current design distance is reduced according to a preset adjustment increment to increase the spot diameter.

[0039] On the other hand, it is possible to set whether the spot diameter is within a preset range of the optical fiber diameter. In this embodiment, the preset range of the optical fiber diameter is preferably ±1 mm. If the spot diameter is larger than the preset range of the optical fiber diameter, the current design distance is increased according to the preset adjustment increment to reduce the spot diameter; If the spot diameter is smaller than the preset range of the optical fiber diameter, the current design distance is reduced according to the preset adjustment increment to increase the spot diameter.

[0040] Further, the calculation formula of the spot diameter is: Wherein, d is the spot diameter. The fiber diameter D in the embodiment is equal to the spot diameter d.

[0041] In the embodiment, preferably, the first end 31 is positioned at the new focal point position of the inclined optical axis, and the coordinates satisfy the following formula: Wherein, x is the horizontal coordinate of the focal point in the sectional view, and y is the vertical coordinate of the focal point in the sectional view.

[0042] Through the design method of the fiber coupling monitoring device provided in the embodiment, the skilled person can quickly determine the optimal relative position of the first end 31 of the optical fiber 3 according to the existing concave mirror 1 and the installation angle, so as to facilitate the manufacture of the coupling assembly 6 to fix the relative distance between the concave mirror 1 and the ferrule 2, and facilitate the installation of the embodiment.

[0043] The above is only the preferred embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent flow transformation using the content of the specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A fiber coupling monitoring device, characterized by, The device comprises a light source, an optical fiber, a ferrule, a spectrometer and a concave mirror, wherein: The optical fiber has a Y-shaped structure, and comprises a first end, a second end and a third end. The first end and the second end are oppositely arranged on both sides of the first end. The second end and the third end are both arranged away from the ferrule. The first end is fixedly connected with the ferrule. The light source is used for emitting excitation light. The light source is opposite to the end face of the second end. The ferrule has an inner hole extending along the extending direction of the ferrule. The first end is fixed in the inner hole, and the end face of the first end is exposed from the inner hole. The spectrometer is used for receiving fluorescent light reflected by the contaminant and analyzing the spectrum of the fluorescent light. The third end is connected with the spectrometer. The mirror surface of the concave mirror is arranged corresponding to the end face of the first end.

2. The optical fiber coupling monitoring device according to claim 1, characterized in that: The end face of the first end deviates from the plane where the optical axis of the concave mirror is located, so that the excitation light is not reflected back to the first end by the concave mirror after being emitted.

3. The optical fiber coupling monitoring device according to claim 2, characterized in that: The fluorescent light is converged to form a light spot after being reflected by the concave mirror. The diameter of the light spot is the same as the diameter of the end face of the first end. The end face of the first end is located at the position of the light spot.

4. The fiber-coupled monitoring device of claim 2, wherein, The first end of the optical fiber is provided with a first branch and a second branch. The first branch is connected with the second end, and the second branch is connected with the third end. The ends of the fiber cores in the first branch and the second branch are uniformly distributed on the end face of the first end.

5. The fiber-coupled monitoring device of claim 2, wherein, The concave mirror comprises a first edge line and a second edge line. The first edge line and the second edge line are located at both ends of the bending direction of the concave mirror. The first edge line is away from the ferrule, and the second edge line is close to the ferrule. The arc length of the cross-sectional circle of the curved surface between the first edge line and the second edge line is less than 1 / 4 of the arc length of the circle where the cross-sectional circle is located.

6. The fiber-coupled monitoring device of claim 2, wherein, The device further comprises a coupling assembly. The coupling assembly comprises a light collecting port, a mounting groove and a ferrule hole. The mounting groove and the ferrule hole are oppositely arranged on both sides of the light collecting port. The ferrule is fixed in the ferrule hole. The end face of the first end faces the concave mirror. The concave mirror is fixed in the mounting groove. The optical axis of the concave mirror is obliquely directed out of the light collecting port.

7. A method of designing a fiber coupling monitoring device, applied to the fiber coupling monitoring device according to any one of claims 1-6, characterized in that, The device comprises the following steps: S1, obtaining the optical axis of the concave mirror; wherein the optical axis is arranged obliquely relative to the horizontal plane; S2, obtaining the curvature radius of the concave mirror and the inclination angle of the optical axis. The focal length of the concave mirror is obtained according to the curvature radius and the inclination angle of the optical axis; S3, obtaining the offset height of the midpoint of the concave mirror relative to the plane where the bottom edge of the concave mirror is located. The current design distance from the midpoint of the concave mirror to the end face of the first end is obtained according to the focal length, the offset height and the inclination angle of the optical axis; S4, obtaining the focal point position of the concave mirror according to the inclination angle of the optical axis, the current design distance and the offset height; S5, arranging the ferrule at the focal point position; wherein the first end in the ferrule faces the concave mirror. The fluorescent light reflected by the concave mirror forms a light spot on the first end; S6, obtaining the diameter of the light spot, and determining whether the diameter of the light spot is equal to the diameter of the optical fiber. S71, when the spot diameter is equal to the fiber diameter, then the second end is directly opposite the light source, and the third end is connected with the spectrometer, thereby completing the design of the fiber coupling monitoring device; S72, when the spot diameter is not equal to the fiber diameter, the current design distance is adjusted according to a preset adjustment increment to obtain an adjusted current design distance, and then the step S6 is returned to.

8. The design method of claim 7, wherein, The step S2 specifically comprises the following steps: The focal length f of the concave mirror is calculated by the formula wherein R is the radius of curvature of the concave mirror, is the inclination angle of the optical axis.

9. The design method of claim 8, wherein, The step S3 specifically comprises the following steps: The current design distance of the midpoint of the concave mirror to the end surface of the first end is calculated by using the formula ; wherein, is the current design distance, is the offset height of the midpoint of the concave mirror relative to the plane where the bottom edge of the concave mirror is located.

10. The method of claim 7, wherein, The step S72 specifically comprises the following steps: If the spot diameter is greater than the fiber diameter, then the current design distance is expanded according to a preset adjustment increment, so as to reduce the spot diameter; If the spot diameter is less than the fiber diameter, then the current design distance is reduced according to a preset adjustment increment, so as to increase the spot diameter.

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