Multi-reflection cavity enhanced Raman system and use method

Abstract

The invention discloses a multi-reflection cavity enhanced Raman system and a use method. The multi-reflection cavity enhanced Raman system comprises a concave mirror, a converging lens and an optical fiber bundle, the optical fiber bundle comprises a plurality of optical fibers which are horizontally arranged, a converging lens, a parallel lens, a reaction part and a concave mirror are distributed at the input end of each optical fiber, and a first lens and a first retroreflector as well as a second lens and a second retroreflector are arranged at the two ends of the reaction part. Then the laser signal reacts with the to-be-detected gas to generate a Raman signal, a part of the Raman signal is reflected by the concave mirror, and then the Raman signal is converged in the optical fiber by the converging lens and the parallel lens to be received; raman signals excited on the horizontal plane are matched with the horizontally arranged optical fibers, so that the receiving effect is good; the intensity of the laser signal at the reaction position is high, so that the intensity of the generated Raman signal is high. Therefore, the design has a relatively good receiving effect on the Raman signal, and the intensity of the received Raman signal is relatively high.

Description

Technical Field

[0001] The invention relates to an enhanced Raman system, belongs to the field of Raman gas detection, and in particular to a multi-reflection cavity enhanced Raman system and a use method thereof. Background Art

[0002] Raman spectroscopy is a powerful gas sensing method that can overcome the weaknesses of traditional non-spectral methods such as long detection time and poor repeatability, and can also make up for the defect that absorption spectroscopy cannot directly measure homonuclear diatomic molecules; at the same time, it can also use a single-frequency laser to perform qualitative and quantitative analysis on multi-component mixed gases, which is relatively convenient. However, in the detection process of Raman spectroscopy, due to the inherent weak Raman effect of the substance, and the fact that the Raman effect of gas is usually much lower than that of solids and liquids, the detection performance of Raman spectroscopy is greatly limited in the application of gas sensing.

[0003] In recent years, in order to enhance the detection performance of gas Raman spectroscopy, many studies have proposed corresponding enhancement technologies. However, in the current enhancement technologies, the shape of the optical fiber in the optical fiber bundle cannot match the shape of the Raman signal well, so the optical fiber has a poor reception effect on the Raman signal.

[0004] The information disclosed in this background technology section is only intended to increase the understanding of the overall background of the application, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to ordinary technicians in this field. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects and problems of poor Raman signal reception effect in the prior art, and to provide a reflection cavity enhanced Raman system with better Raman signal reception effect and a use method thereof.

[0006] To achieve the above objectives, the technical solution of the present invention is: A multi-reflection cavity enhanced Raman system, the system comprising a concave mirror, a converging lens and an optical fiber bundle; The optical fiber bundle includes a plurality of optical fibers arranged horizontally, the input ends of all the optical fibers are located at the focus of one side of a converging lens, the side of the converging lens away from the optical fiber faces one side of a parallel lens, the other side of the parallel lens faces the concave end of the concave mirror, and a reaction point is provided between the concave end and the parallel lens; A first lens is arranged at one side of the reaction site, a first retro-reflecting mirror is arranged on the extension line of the first lens in a direction away from the reaction site, a laser emitter is arranged at a position away from the first lens on the first retro-reflecting mirror, and an output end of the laser emitter is aligned with one end of the first lens; a second lens is arranged at one side of the reaction site away from the first lens, and a second retro-reflecting mirror is arranged at a position away from the reaction site on the second lens; The output ends of all optical fibers are connected to one end of the spectrometer.

[0007] The number of optical fibers in the optical fiber bundle is six to ninety-six, and the numerical aperture of the spectrometer ranges from 0.05 to 0.2.

[0008] The core diameter of the optical fiber is ten to two hundred microns, and the numerical aperture of the optical fiber ranges from 0.1 to 0.4.

[0009] The distance from the concave end to the reaction point is twice the focal length of the concave mirror.

[0010] The focal length ratio of the parallel lens to the convergent lens ranges from one half to two times.

[0011] The width of the first retroreflective mirror and the second retroreflective mirror is between one-half inch and two inches.

[0012] The optical axis of the converging lens and the optical axis of the parallel lens are located on the same horizontal line.

[0013] The first retroreflective mirror includes a first transverse surface and a first vertical surface, one end of the first vertical surface is vertically connected to one end of the first transverse surface, and the angle between the first transverse surface and the vertical surface is forty-five degrees.

[0014] The second retroreflective mirror includes a second transverse surface and a second vertical surface, one end of the second vertical surface is vertically connected to one end of the second transverse surface, and the included angle between the second transverse surface and the vertical surface is forty-five degrees.

[0015] A method for using a multi-reflection cavity enhanced Raman system, the method comprising the following steps: Step 1: Make the laser transmitter emit a laser signal; Step 2: The laser signal is converged to the reaction site by the first lens, and then the laser signal is transformed into a parallel laser signal through the second lens. Then the laser signal is reflected multiple times in the second retroreflector and the first retroreflector, so the laser signal will pass through the reaction site multiple times. Step 3: The laser signal at the reaction site reacts with the gas to be measured at the reaction site to generate a Raman signal. A portion of the Raman signal is directed toward the parallel lens, and a portion of the Raman signal is directed toward the concave end. The Raman signal toward the concave end is reflected by the concave end, and then the Raman signal toward the concave end is converted into a Raman signal toward the parallel lens. Step 4: Since the focus of the parallel lens coincides with the focus of the laser reflected multiple times at the reaction site, the parallel lens converts the Raman signal into a parallel Raman signal. The parallel Raman signal is then re-imaged by the converging lens and converged in multiple optical fibers on the focal plane of the converging lens. The Raman signal is then received by the optical fiber and introduced into the spectrometer for analysis.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. In a multiple reflection cavity enhanced Raman system and a method of using the same, the system comprises a concave mirror, a converging lens and an optical fiber bundle, the optical fiber bundle comprises a plurality of optical fibers arranged horizontally, a converging lens, a parallel lens and a concave mirror are sequentially arranged on the front side of the input end of the optical fiber, a reaction site is arranged between the parallel lens and the concave mirror, a first lens, a first retro-reflecting mirror and a laser transmitter are arranged on one side of the reaction site, a second lens and a second retro-reflecting mirror are arranged on the other side of the reaction site, the output end of the optical fiber is connected to a spectrometer, when used, the laser signal is converged at the reaction site multiple times under the action of the first lens and the second lens, then the laser signal at the reaction site reacts with the gas to be measured to generate a Raman signal, the Raman signal is then gradually reduced by the parallel lens and the converging lens, and finally converged at the input end of the wider horizontally arranged optical fiber, and then the spectrometer processes the Raman signal to obtain the type of the gas to be measured, the advantages of the present invention also include: First point: Raman signals are excited in the horizontal plane at the reaction site, and the horizontally arranged optical fibers are aligned with the Raman signals on the horizontal plane, so the shapes of the optical fibers and the Raman signals form a good match; compared with the prior art, the optical fibers are arranged in a horizontal manner, which increases the width of the optical fiber range, and the Raman signals located at and near the focus of the laser light path can also be effectively received, which increases the range of receiving Raman signals, and the optical fiber has a better reception effect on Raman signals; Second point: the first lens and the second lens make the laser signal converge at the reaction point for many times, so the laser signal intensity at the reaction point is the largest, and the intensity of the Raman signal generated at the reaction point is the largest, which improves the intensity of the Raman signal; part of the Raman signal is scattered in the direction of the parallel lens, and part of the Raman signal is scattered in the direction of the reflector. The reflector reflects the Raman signal scattered in the direction of the reflector into the parallel lens, which also improves the intensity of the Raman signal; Third point: The present invention has a high efficiency in receiving Raman signals, so when the content of the gas to be detected is low, the gas to be detected can also be detected, so the present invention can improve the limit of gas detection; Fourth point: During the detection process, due to the inclusion of optical elements such as the first lens, spherical noise will be generated, but the spherical noise is outside the receiving range of the optical fiber and will not be received by the optical fiber, so the signal-to-noise ratio of the present invention is relatively high; Therefore, the present invention has a better receiving effect on the Raman signal, and the intensity of the received Raman signal is relatively large.

[0017] 2. In a multiple reflection cavity enhanced Raman system and use method of the present invention, the distance from the concave mirror to the reaction site is twice the focal length of the concave mirror, the focal length ratio of the parallel lens to the convergent lens is one to one, and the width of the first retroreflector and the second retroreflector is one inch. When used, since the focal length ratio of the parallel lens to the convergent lens is one to one, the parallel lens, the convergent lens and the optical fiber are well matched, so the optical fiber has a better reception effect on the Raman signal; when the distance from the concave mirror to the reaction site is twice the focal length of the concave mirror, the Raman signal can be returned to the original path, and at this time, the optical fiber has the highest efficiency in receiving the Raman signal; the width of the first retroreflector and the second retroreflector is large, which can enable the laser to achieve the effect of multiple reflections. Therefore, the Raman signal reception efficiency of the present invention is high.

[0018] 3. In a multiple reflection cavity enhanced Raman system and use method of the present invention, the first retroreflector includes a first horizontal surface and a first vertical surface, and the second retroreflector includes a second horizontal surface and a second vertical surface. When used, the laser signal is reflected by the first horizontal surface and the first vertical surface and reaches the first lens, and the laser signal is reflected by the second horizontal surface and the second vertical surface and reaches the second lens. The first lens and the second lens are then used to realize the convergence of the laser signal, and the utilization rate of the laser signal is improved. Therefore, the present invention has a better convergence effect on the laser signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the present invention.

[0020] Figure 2 yes Figure 1 Path diagram of the laser signal.

[0021] Figure 3 yes Figure 1 Schematic diagram of the Raman signal being reflected.

[0022] Figure 4 yes Figure 1 Magnified view of the reaction site.

[0023] Figure 5 yes Figure 1 Schematic diagram of the structure of the optical fiber bundle.

[0024] Figure 6 yes Figure 5 Schematic diagram of the structure of optical fiber.

[0025] Figure 7 yes Figure 4 Schematic diagram of the laser signal at the reaction.

[0026] Figure 8 yes Figure 4 Schematic diagram of optical fiber receiving Raman signals.

[0027] Fig. 9 It is a schematic diagram of the application effect of the present invention.

[0028] In the figure: concave mirror 1, concave end 11, converging lens 2, parallel lens 21, optical fiber bundle 3, optical fiber 31, reaction site 4, first lens 5, first retroreflective mirror 51, first transverse surface 511, first vertical surface 512, laser transmitter 6, spectrometer 7, second lens 8, second retroreflective mirror 81, second transverse surface 811, second vertical surface 812, receiving range 9, Raman signal shape 91, laser signal shape 92. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0030] See also Figure 1 — Fig. 9 , a multi-reflection cavity enhanced Raman system, the system comprising a concave mirror 1, a converging lens 2 and an optical fiber bundle 3; The optical fiber bundle 3 includes a plurality of optical fibers 31 arranged horizontally, and the input ends of all the optical fibers 31 are located at the focus of one side of the converging lens 2, and the side of the converging lens 2 away from the optical fiber 31 faces one side of the parallel lens 21, and the other side of the parallel lens 21 faces the concave end 11 of the concave mirror 1, and a reaction site 4 is provided between the concave end 11 and the parallel lens 21; A first lens 5 is provided at one side of the reaction site 4, a first retro-reflecting mirror 51 is provided at the extension line of the first lens 5 in the direction away from the reaction site 4, a laser emitter 6 is provided at the first retro-reflecting mirror 51 at a position away from the first lens 5, and an output end of the laser emitter 6 is aligned with one end of the first lens 5; a second lens 8 is provided at one side of the reaction site 4 away from the first lens 5, and a second retro-reflecting mirror 81 is provided at the second lens 8 at a position away from the reaction site 4; The output ends of all optical fibers 31 are connected to one end of the spectrometer 7 .

[0031] The number of optical fibers 31 in the optical fiber bundle 3 is six to ninety-six, and the numerical aperture of the spectrometer 7 ranges from 0.05 to 0.2.

[0032] The core diameter of the optical fiber 31 is 10 to 200 microns, and the numerical aperture of the optical fiber 31 ranges from 0.1 to 0.4.

[0033] The distance from the concave end 11 to the reaction site 4 is twice the focal length of the concave mirror 1 .

[0034] The focal length ratio of the parallel lens 21 to the convergent lens 2 is in a range of one half to two times.

[0035] The width of the first retro-reflective mirror 51 and the second retro-reflective mirror 81 is between one-half inch and two inches.

[0036] The optical axis of the converging lens 2 and the optical axis of the parallel lens 21 are located on the same horizontal line.

[0037] The first retroreflective mirror 51 includes a first transverse surface 511 and a first vertical surface 512 . One end of the first vertical surface 512 is vertically connected to one end of the first transverse surface 511 . The angle between the first transverse surface 511 and the vertical surface is 45 degrees.

[0038] The second retroreflective mirror 81 includes a second transverse surface 811 and a second vertical surface 812 . One end of the second vertical surface 812 is vertically connected to one end of the second transverse surface 811 . The included angle between the second transverse surface 811 and the vertical surface is 45 degrees.

[0039] A method for using a multi-reflection cavity enhanced Raman system, the method comprising the following steps: The first step: enabling the laser transmitter 6 to emit a laser signal; Step 2: The laser signal is converged to the reaction site 4 by the first lens 5, and then the laser signal is transformed into a parallel laser signal by the second lens 8. Then, the laser signal is reflected multiple times in the second retroreflective mirror 81 and the first retroreflective mirror 51, so the laser signal passes through the reaction site 4 multiple times. Step 3: The laser signal at the reaction location 4 reacts with the gas to be measured at the reaction location 4 to generate a Raman signal. A portion of the Raman signal is directed toward the parallel lens 21, and a portion of the Raman signal is directed toward the concave end 11. The Raman signal directed toward the concave end 11 is reflected by the concave end 11, and then the Raman signal directed toward the concave end 11 is converted into a Raman signal directed toward the parallel lens 21. Step 4: Since the focus of the parallel lens 21 coincides with the focus of the laser reflected multiple times at the reaction site 4, the parallel lens 21 converts the Raman signal into a parallel Raman signal, and then the parallel Raman signal is re-imaged by the converging lens 2 and converged in the multiple optical fibers 31 on the focal plane of the converging lens 2. The Raman signal is then received by the optical fiber 31 and introduced into the spectrometer 7 for analysis.

[0040] The supplementary description of the present invention is as follows: The application of the present invention is to increase the receiving efficiency of Raman signals to improve the gas detection limit; the optical fiber 31 is located on the focal plane of the converging lens 2, so that the Raman signal at the focus of the laser light path and the vicinity can be received; when the number of optical fibers 31 increases, the distribution of the optical fibers 31 on the focal plane is also wider, the range of receiving Raman signals is increased, and therefore the intensity of the received Raman signals is also increased, see Figure 7The intensity of the Raman signal received by the eight optical fibers 31 is about six times that of the Raman signal received by one optical fiber 31 ; the receiving efficiency of the Raman signal is relatively high, that is, the gas to be tested can be detected even when the content of the gas to be tested is weak, which can improve the limit of gas detection.

[0041] The laser signal shape 92 of the present invention is: Figure 7 — Figure 8 Due to the convergence effect of the first lens 5 and the second lens 8 on the laser signal, the diameter of the laser signal at the reaction site 4 gradually decreases along the direction approaching the reaction site 4, so the laser signal shape 92 is two opposite triangles centered on the center of the reaction site 4, and the Raman signal shape 91 is the same as the laser signal shape 92.

[0042] Embodiment 1: See also Figure 1 — Fig. 9 A multiple reflection cavity enhanced Raman system, the system comprises a concave mirror 1, a converging lens 2 and an optical fiber bundle 3; the optical fiber bundle 3 comprises a plurality of optical fibers 31 arranged horizontally, the input ends of all the optical fibers 31 are located at the focus of one side of the converging lens 2, the side of the converging lens 2 away from the optical fiber 31 faces the side of the parallel lens 21, the other side of the parallel lens 21 faces the concave end 11 of the concave mirror 1, and a reaction site 4 is arranged between the concave end 11 and the parallel lens 21; a first lens 5 is arranged on one side of the reaction site 4, a first retro-reflecting mirror 51 is arranged on the extension line of the first lens 5 along the direction away from the reaction site 4, a laser emitter 6 is arranged on the first retro-reflecting mirror 51 along the position away from the first lens 5, and the output end of the laser emitter 6 is aligned with one end of the first lens 5; a second lens 8 is arranged on the side of the reaction site 4 away from the first lens 5, and a second retro-reflecting mirror 81 is arranged on the second lens 8 along the position away from the reaction site 4; the output ends of all the optical fibers 31 are connected to one end of a spectrometer 7. The number of optical fibers 31 in the optical fiber bundle 3 is six to ninety-six, and the numerical aperture of the spectrometer 7 ranges from 0.05 to 0.2. The core diameter of the optical fiber 31 is ten to two hundred microns, and the numerical aperture of the optical fiber 31 ranges from 0.1 to 0.4. Preferably, the numerical aperture of the spectrometer 7 is 0.2. Preferably, the optical fiber diameter is one hundred and five microns, and the numerical aperture of the optical fiber 31 is 0.2.

[0043] A method for using a multi-reflection cavity enhanced Raman system, the method comprising the following steps: The first step: enabling the laser transmitter 6 to emit a laser signal; Step 2: The laser signal is converged to the reaction site 4 by the first lens 5, and then the laser signal is transformed into a parallel laser signal by the second lens 8. Then, the laser signal is reflected multiple times in the second retroreflective mirror 81 and the first retroreflective mirror 51, so the laser signal passes through the reaction site 4 multiple times. Step 3: The laser signal at the reaction location 4 reacts with the gas to be measured at the reaction location 4 to generate a Raman signal. A portion of the Raman signal is directed toward the parallel lens 21, and a portion of the Raman signal is directed toward the concave end 11. The Raman signal directed toward the concave end 11 is reflected by the concave end 11, and then the Raman signal directed toward the concave end 11 is converted into a Raman signal directed toward the parallel lens 21. Step 4: Since the focus of the parallel lens 21 coincides with the focus of the laser reflected multiple times at the reaction site 4, the parallel lens 21 converts the Raman signal into a parallel Raman signal, and then the parallel Raman signal is re-imaged by the converging lens 2 and converged in the multiple optical fibers 31 on the focal plane of the converging lens 2. The Raman signal is then received by the optical fiber 31 and introduced into the spectrometer 7 for analysis.

[0044] Embodiment 2: The basic content is the same as that of Example 1, except that: See also Figure 1 — Figure 4 , the distance from the concave end 11 to the reaction point 4 is twice the focal length value of the concave mirror 1. The focal length ratio of the parallel lens 21 to the converging lens 2 ranges from one-half to two times. The width of the first retroreflective mirror 51 and the second retroreflective mirror 81 is from one-half inch to two inches. The optical axis of the converging lens 2 and the optical axis of the parallel lens 21 are located on the same horizontal line. Preferably, the focal length ratio of the parallel lens 21 to the converging lens 2 is one to one. Preferably, the width of the first retroreflective mirror 51 and the second retroreflective mirror 81 is one inch.

[0045] When used, the parallel lens 21 converts the Raman signal into a parallel Raman signal, and then the converging lens 2 re-images the Raman signal and converges it in multiple optical fibers on the focal plane of the converging lens, so the receiving effect of the Raman signal is better; when the focal length ratio of the parallel lens and the converging lens 2 is one to one, it cooperates well with the parameters such as the numerical aperture of the optical fiber 31, which can improve the effect of receiving the Raman signal; the concave end 11 can reflect the Raman signal toward the concave end 11 to the parallel lens 21, and the distance from the concave end 11 to the reaction point 4 is twice the focal length value of the concave mirror 1. At this time, the concave end 11 has the best reflection effect on the Raman signal, so the receiving efficiency of the Raman signal can be increased; when the optical axis of the converging lens 2 and the optical axis of the parallel lens 21 are located on the same horizontal line, the effect of converging the Raman signal on the optical fiber 31 is better; the width of the first retroreflector 51 and the second retroreflector 81 is large, so the number of reflections of the laser signal can be increased, thereby increasing the laser intensity at the reaction point 4.

[0046] Embodiment 3: The basic content is the same as that of Example 1, except that: See also Figure 1 — Figure 3 The first retro-reflecting mirror 51 includes a first transverse surface 511 and a first vertical surface 512, one end of the first vertical surface 512 is vertically connected to one end of the first transverse surface 511, and the angle between the first transverse surface 511 and the vertical surface is 45 degrees. The second retro-reflecting mirror 81 includes a second transverse surface 811 and a second vertical surface 812, one end of the second vertical surface 812 is vertically connected to one end of the second transverse surface 811, and the angle between the second transverse surface 811 and the vertical surface is 45 degrees.

[0047] When used, the laser emitter 6 first generates a laser signal, which is then converged at the reaction location 4 by the first lens 5, and then the laser signal passes through the reaction location 4, and then the laser signal is converted into parallel light by the second lens 8, and then the laser signal is reflected by the second horizontal surface 811 to the second vertical surface 812, and then the laser signal is reflected by the second vertical surface 812 to the second lens 8, and then the laser signal is converged at the reaction location 4 by the second lens 8, and then the laser signal passes through the reaction location 4, and then the laser signal is converted into parallel light by the first lens 5, and then the laser signal is reflected by the first horizontal surface 511 to the first vertical surface 512, and then the laser signal is converged at the reaction location 4 by the first lens 5, thereby realizing multiple reflections of the laser signal; in the aforementioned process, the laser signal passes through the reaction location 4 multiple times, so the laser signal intensity at the reaction location 4 is the largest, that is, the intensity of the generated Raman signal is the largest.

[0048] Embodiment 4: The basic content is the same as that of Example 1, except that: See also Figure 1 — Fig. 9 , a method for using a multi-reflection cavity enhanced Raman system, the method comprising the following steps: The first step: enabling the laser transmitter 6 to emit a laser signal; Step 2: First, the first lens 5 converges the laser signal toward the reaction location 4, and the laser signal reacts with the gas to be measured at the reaction location 4 to generate a Raman signal. Then, a portion of the Raman signal is directed toward the parallel lens 21, and a portion of the Raman signal is directed toward the concave end 11. The Raman signal moving toward the concave end 11 is reflected by the concave end 11, and then the Raman signal toward the concave end 11 is converted into a Raman signal toward the parallel lens 21. The Raman signal toward the parallel lens 21 is converted into a parallel Raman signal by the parallel lens 21, and then the parallel Raman signals are converted into converged Raman signals by the convergent lens 2. The converged Raman signals are collected by the optical fiber 31, and then the optical fiber 31 guides the Raman signal into the spectrometer 7; Step 3: The laser signal at the reaction location 4 moves toward the second lens 8 again, and then the second lens 8 makes the laser signal move toward the second retroreflective mirror 81, and then the second retroreflective mirror 81 makes the laser signal move toward the second lens 8, and then the second lens 8 makes the laser signal move toward the reaction location 4, and the laser signal reacts with the gas to be measured at the reaction location 4 to generate a Raman signal, and then a part of the Raman signal moves toward the parallel lens 21, and a part of the Raman signal moves toward the concave end 11, and the Raman signal moving toward the concave end 11 is reflected by the concave end 11, and then the Raman signal moving toward the concave end 11 becomes a Raman signal toward the parallel lens 21, and the Raman signal toward the parallel lens 21 is converted into a parallel Raman signal by the parallel lens 21, and then the parallel Raman signal is converted into a converged Raman signal by the converging lens 2, and the converged Raman signal is collected by the optical fiber 31, and then the optical fiber 31 introduces the Raman signal into the spectrometer 7; Step 4: The laser signal at the reaction site 4 moves toward the first lens 5, and then the first lens 5 moves the laser signal toward the first retroreflective mirror 51, and then the first retroreflective mirror 51 moves the laser signal toward the first lens 5; Step 5: Repeat steps 2, 3, and 4 in sequence until the laser signal reaches the reflection limit.

[0049] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modifications or changes made by ordinary technicians in this field based on the contents disclosed by the present invention should be included in the protection scope recorded in the claims.

Claims

1. A multi-reflection cavity enhanced Raman system, characterized in that: The system comprises a concave mirror (1), a converging lens (2) and an optical fiber bundle (3); The optical fiber bundle (3) comprises a plurality of optical fibers (31) arranged horizontally, the input ends of all the optical fibers (31) are located at the focal point of one side of a converging lens (2), the side of the converging lens (2) away from the optical fibers (31) faces one side of a parallel lens (21), the other side of the parallel lens (21) faces the concave end (11) of the concave mirror (1), and a reaction point (4) is provided between the concave end (11) and the parallel lens (21); A first lens (5) is arranged on one side of the reaction site (4); a first retro-reflecting mirror (51) is arranged on the extension line of the first lens (5) in a direction away from the reaction site (4); a laser emitter (6) is arranged on the first retro-reflecting mirror (51) at a position away from the first lens (5); an output end of the laser emitter (6) is aligned with one end of the first lens (5); a second lens (8) is arranged on the side of the reaction site (4) away from the first lens (5); a second retro-reflecting mirror (81) is arranged on the second lens (8) at a position away from the reaction site (4); The output ends of all optical fibers (31) are connected to one end of the spectrometer (7).

2. A multi-reflection cavity enhanced Raman system according to claim 1, characterized in that: The number of optical fibers (31) in the optical fiber bundle (3) is six to ninety-six, and the numerical aperture of the spectrometer (7) ranges from 0.05 to 0.

2.

3. A multi-reflection cavity enhanced Raman system according to claim 2, characterized in that: The core diameter of the optical fiber (31) is ten to two hundred micrometers, and the numerical aperture of the optical fiber (31) ranges from 0.1 to 0.

4.

4. A multi-reflection cavity enhanced Raman system according to claim 1, 2 or 3, characterized in that: The distance from the concave end (11) to the reaction point (4) is twice the focal length of the concave mirror (1).

5. A multi-reflection cavity enhanced Raman system according to claim 4, characterized in that: The focal length ratio of the parallel lens (21) to the convergent lens (2) ranges from one half to two times.

6. A multi-reflection cavity enhanced Raman system according to claim 5, characterized in that: The width of the first retroreflective mirror (51) and the second retroreflective mirror (81) is between one-half inch and two inches.

7. A multi-reflection cavity enhanced Raman system according to claim 6, characterized in that: The optical axis of the converging lens (2) and the optical axis of the parallel lens (21) are located on the same horizontal line.

8. A multi-reflection cavity enhanced Raman system according to claim 1, 2 or 3, characterized in that: The first retroreflective mirror (51) comprises a first transverse surface (511) and a first vertical surface (512); one end of the first vertical surface (512) is vertically connected to one end of the first transverse surface (511); and the angle between the first transverse surface (511) and the vertical surface is forty-five degrees.

9. A multi-reflection cavity enhanced Raman system according to claim 8, characterized in that: The second retroreflective mirror (81) comprises a second transverse surface (811) and a second vertical surface (812), one end of the second vertical surface (812) is vertically connected to one end of the second transverse surface (811), and the angle between the second transverse surface (811) and the vertical surface is forty-five degrees.

10. A method for using the multi-reflection cavity enhanced Raman system according to claim 1, characterized in that: The method of use comprises the following steps: The first step: enabling the laser transmitter (6) to emit a laser signal; Step 2: The laser signal is first converged by the first lens (5), and then the laser signal is transformed into a parallel laser signal through the second lens (8). The laser signal is then reflected multiple times in the second retroreflective mirror (81) and the first retroreflective mirror (51), so that the laser signal passes through the reaction point (4) multiple times. Step 3: The laser signal at the reaction location (4) reacts with the gas to be measured at the reaction location (4) to generate a Raman signal, a portion of the Raman signal is directed toward the parallel lens (21), and a portion of the Raman signal is directed toward the concave end (11), the Raman signal directed toward the concave end (11) is then reflected by the concave end (11), and then the Raman signal directed toward the concave end (11) is converted into a Raman signal directed toward the parallel lens (21); Step 4: Since the focus of the parallel lens (21) coincides with the focus of the laser light reflected multiple times at the reaction point (4), the parallel lens (21) converts the Raman signal into a parallel Raman signal. The parallel Raman signal is then re-imaged by the converging lens (2) and converged in the multiple optical fibers (31) on the focal plane of the converging lens (2). The Raman signal is then received by the optical fiber (31) and introduced into the spectrometer (7) for analysis.

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