CN118190818A - All-fiber coupling type integrating cavity device - Google Patents
All-fiber coupling type integrating cavity device Download PDFInfo
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- CN118190818A CN118190818A CN202410393547.6A CN202410393547A CN118190818A CN 118190818 A CN118190818 A CN 118190818A CN 202410393547 A CN202410393547 A CN 202410393547A CN 118190818 A CN118190818 A CN 118190818A
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- 230000008878 coupling Effects 0.000 title claims abstract description 84
- 238000010168 coupling process Methods 0.000 title claims abstract description 84
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- 239000000835 fiber Substances 0.000 title claims abstract description 27
- 239000013307 optical fiber Substances 0.000 claims abstract description 64
- 230000003287 optical effect Effects 0.000 claims abstract description 25
- 239000004065 semiconductor Substances 0.000 claims abstract description 10
- 230000000149 penetrating effect Effects 0.000 claims description 4
- 230000001427 coherent effect Effects 0.000 claims description 3
- 238000002310 reflectometry Methods 0.000 claims description 3
- 238000010521 absorption reaction Methods 0.000 claims description 2
- 230000003321 amplification Effects 0.000 claims description 2
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 2
- 238000005259 measurement Methods 0.000 abstract description 10
- 238000001514 detection method Methods 0.000 abstract description 8
- 230000005540 biological transmission Effects 0.000 abstract description 5
- 230000010354 integration Effects 0.000 description 5
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000000862 absorption spectrum Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
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Abstract
The invention relates to the technical field of optical detection devices, in particular to an all-fiber coupling type integrating cavity device; the optical fiber coupling boosting optical amplifier is applied to the incidence end of the integrating cavity, and can directly amplify the laser emitted by the optical fiber coupling semiconductor laser, so that the power loss in the laser transmission process is compensated, the effective optical path length of the laser in the integrating cavity is increased to the theoretical optical path, the signal-to-noise ratio of measurement is improved, and the lower limit of measurement is reduced; meanwhile, the optical fiber coupling booster optical amplifier is added, so that the coupling output light intensity of the integrating cavity is improved, and the detection precision of the gas concentration is improved. In addition, a large numerical aperture optical fiber coupling lens with the diameter larger than the light spot distribution diameter is connected to the emergent end of the integrating cavity through a multidimensional adjusting frame, and the other end of the coupling lens is converged to the photoelectric detector through multimode optical fibers to form a complete all-optical fiber coupling type integrating cavity device, so that the integrating cavity is suitable for multi-point distributed measurement.
Description
Technical Field
The invention relates to the technical field of optical detection devices, in particular to an all-fiber coupling type integrating cavity device.
Background
In industrial production, a tunable semiconductor laser absorption spectrum technology is generally adopted to detect gas, namely, after light passes through an integrating cavity filled with gas to be detected, light with a certain single frequency is absorbed by the gas to be detected in the integrating cavity, and the attenuation degree of the absorbed light can reflect the concentration of the gas to be detected. The integration cavity commonly used is mostly composed of two reflecting plates, and the detection of the gas concentration is performed through diffuse reflection.
A specific application form of the integrating cavity is disclosed in patent CN 217443635U. The patent builds an optical probe based on an integrating cavity technology, after a laser emitter generates a light beam in the integrating cavity to enter from an off-axis position of a first high-reflection lens, the light beam forms multiple reflections between the first high-reflection lens and a second high-reflection lens, the reflected light beam passing through the second high-reflection lens simultaneously generates transmission, and the transmitted light beam is converged on a detector through a converging lens; and then the concentration of methane isotope gas in the cavity is calculated through the intensity value of the light beam converged on the detector. However, when the integrating cavity is used, the laser emitted by the laser emitter is attenuated before entering the integrating cavity, so that the diffuse reflection times and the diffuse reflection intensity of the laser in the integrating cavity are reduced, the signals received by the detector are weaker, even the signal intensity of some signals transmitted to the detector is too weak to be identified, further, the accuracy of gas concentration detection is obviously reduced, and the detection requirement cannot be met.
Disclosure of Invention
In order to avoid and overcome the technical problems in the prior art, the invention provides an all-fiber coupling type integrating cavity device.
In order to achieve the above purpose, the present invention provides the following technical solutions:
The all-fiber coupling type integrating cavity device comprises a fiber coupling semiconductor laser used for generating laser, wherein an optical fiber coupling boosting optical amplifier used for receiving the laser and amplifying the received laser is arranged at an emergent port of the fiber coupling semiconductor laser; the optical fiber coupling booster optical amplifier comprises an optical fiber coupling collimator, an integrating cavity and a photoelectric detector, wherein the optical fiber coupling collimator is used for receiving laser after signal amplification and converting the laser into collimated light, the integrating cavity is arranged at the exit of the optical fiber coupling collimator and used for enabling the collimated light to be reflected for multiple times and filled with specified gas, and the photoelectric detector is arranged at the exit of the integrating cavity and used for detecting the output light intensity of the integrating cavity.
As still further aspects of the invention:
according to the coherent superposition principle of light, the output light intensity of the integrating cavity is superposition of the light intensity of the integrating cavity transmitted each time, namely
Wherein I o is the output light intensity; i on is the light intensity transmitted out of the integrating cavity after the light incident into the integrating cavity is reflected n times in the integrating cavity. Light entering the integrating cavity is reflected back and forth between two plano-concave lenses serving as the cavity mirrors of the integrating cavity, when each time the light is reflected to the plano-concave lenses at the exit end of the integrating cavity, the light is reflected on the plano-concave lenses, meanwhile, the light is transmitted out of the plano-concave lenses, and the transmitted light enters the photoelectric detector to calculate the light intensity. I i is the intensity of the light incident into the integrating cavity. T represents the transmittance of the integrating cavity mirror. R represents the reflectivity of the integrating cavity mirror. Alpha represents the absorption loss coefficient of the gas in the integrating cavity for absorbing laser light. L is the fundamental length of the integrating cavity.
As still further aspects of the invention: the integration cavity is a cylindrical cavity, the entrance port and the exit port of the integration cavity are both coaxially and hermetically provided with plano-concave lenses, and the concave mirror surfaces of the two plano-concave lenses are arranged opposite to each other.
As still further aspects of the invention: and a large numerical aperture optical fiber coupling lens is coaxially arranged at the outer side of the emergent port of the integrating cavity, and laser passing through the large numerical aperture optical fiber coupling lens is transmitted to the photoelectric detector by a multimode optical fiber.
As still further aspects of the invention: a collimator adjusting frame for adjusting the emergent angle of the optical fiber coupling collimator is arranged at the entrance port of the integrating cavity; the collimator adjusting frame comprises a positioning sleeve coaxially sleeved on the outer side of an entrance port of the integrating cavity, and a spherical cavity penetrating through the two ends of the integrating cavity along the axial direction is formed in the positioning sleeve; a spherical joint is arranged in the spherical cavity to form a spherical pair; the ball joint is provided with a mounting hole penetrating through the center of the ball, the optical fiber coupling collimator is mounted in the mounting hole, and laser emitted by the optical fiber coupling collimator is emitted into the integrating cavity.
As still further aspects of the invention: a multidimensional coupling lens adjusting frame for adjusting the position of the large numerical aperture optical fiber coupling lens is arranged at the exit of the integrating cavity; the multidimensional coupling lens adjusting frame comprises a supporting seat capable of moving along the axial direction of the integrating cavity, and a lens sleeve which is coaxially arranged with the integrating cavity and is used for coaxially sleeving a large-numerical-aperture optical fiber coupling lens is arranged on the supporting seat.
As still further aspects of the invention: the high numerical aperture optical fiber coupling lens is arranged at the front end of the lens sleeve, the multimode optical fiber is arranged at the tail end of the lens sleeve, and the incidence point of the multimode optical fiber is overlapped with the focal point of the high numerical aperture optical fiber coupling lens.
As still further aspects of the invention: the large numerical aperture optical fiber coupling lens is a convex lens, and the diameter of the large numerical aperture optical fiber coupling lens is not smaller than that of the plano-concave lens.
Compared with the prior art, the invention has the beneficial effects that:
1. The optical fiber coupling boosting optical amplifier is applied to the incidence end of the integrating cavity, and can directly amplify the laser emitted by the optical fiber coupling semiconductor laser, so that the power loss in the laser transmission process is compensated, the effective optical path length of the laser in the integrating cavity is increased to the theoretical optical path, the signal-to-noise ratio of measurement is improved, and the lower limit of measurement is reduced; meanwhile, the optical fiber coupling booster optical amplifier is added, so that the coupling output light intensity of the integrating cavity is improved, the detection precision of the gas concentration is improved, and the integrating cavity is suitable for multi-point position distributed measurement.
2. The invention uses the large numerical aperture optical fiber coupling lens and the multimode optical fiber to effectively couple the transmission light beam of the integrating cavity into the photoelectric detector, thereby realizing all-fiber coupling.
Drawings
Fig. 1 is a schematic diagram of the overall structure of the present invention.
In the figure: 1. an optical fiber coupled semiconductor laser; 2. an optical fiber coupling booster optical amplifier; 3. a collimator adjustment frame; 4. an optical fiber coupling collimator; 5. an integrating cavity; 6. a multidimensional coupling lens adjusting frame; 7. a large numerical aperture fiber coupling lens; 8. a multimode optical fiber; 9. a photodetector.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, the device of the present invention includes an optical fiber coupled semiconductor laser 1, an optical fiber coupled booster amplifier 2, a collimator adjustment frame 3, an optical fiber coupled collimator 4, an integrating cavity 5, a multidimensional coupling lens adjustment frame 6, a large numerical aperture optical fiber coupling lens 7, a multimode optical fiber 8, and a photodetector 9.
The integrating cavity 5 is formed inside a rectangular parallelepiped case, and the integrating cavity 5 is cylindrical. Plano-concave lenses are hermetically mounted at both the entrance and exit of the integrating cavity 5, and the concave mirror surfaces of the two plano-concave lenses are arranged opposite to each other. The purpose of the sealing installation is that when gas is introduced into the integrating cavity 5, the gas cannot leak out, and the gas in the integrating cavity 5 can reach the set pressure.
On the optical fiber coupling boosting optical amplifier 2 for amplifying optical signals, the optical fiber coupling boosting optical amplifier 2 strongly amplifies laser emitted by the optical fiber coupling semiconductor laser 1 and then transmits the amplified laser to the optical fiber coupling collimator 4, and then the collimator adjusting frame 3 is used for fixing and adjusting the position and angle of the optical fiber coupling collimator 4, so that the laser beam entering the integrating cavity 5 forms stable multiple reflections in the integrating cavity 5. The collimator adjusting frame 3 is a five-degree-of-freedom structure, and can adjust the position of the optical fiber coupling collimator 4 in a three-dimensional space besides adjusting the incident angle of the optical fiber coupling collimator 4 through a spherical pair, and two rotational degrees of freedom and three movement degrees of freedom, thereby forming the five-degree-of-freedom structure.
The laser beam is eccentrically incident into the integrating cavity 5, reflected between the two plano-concave lenses, and at each reflection, the laser beam is transmitted through the plano-concave lens on the right. The transmitted light beam enters the large numerical aperture optical fiber coupling lens 7, the light beam is coupled through the convex lens type large numerical aperture optical fiber coupling lens 7, and then the coupled light beam is transmitted to the photoelectric detector 9 through the multimode optical fiber 8, and the photoelectric detector 9 detects the energy of the coupled light beam. After the light beam is reflected for many times in the integrating cavity 5, the light beam is converged on a photosensitive surface of the photoelectric detector 9 through the large-numerical-aperture optical fiber coupling lens 7, the photoelectric detector 9 performs photoelectric conversion on the collected optical signal, and the obtained electric signal is subjected to analog-to-digital conversion through the data acquisition card and is uploaded to upper computer software through the USB serial port, so that inversion of the concentration of the to-be-treated gas is realized. In the detection process, the position of the supporting seat is adjusted up, down, left, right, front and back through the multidimensional coupling lens adjusting frame 6 similar to the collimator adjusting frame 3, and meanwhile, the inclination angle of the large numerical aperture optical fiber coupling lens 7 is changed through the adjusting lens sleeve, so that the coupling efficiency is optimal.
According to the coherent superposition principle of light, the output light intensity of the integrating cavity 5 is superposition of the light intensity of the integrating cavity 5 output by each transmission, namely:
When the number of integration approaches positive infinity, the effective optical path length L eff of the integrating cavity 5 is only related to the reflectivity R of the integrating cavity mirror, i.e. L eff =l/(1-R). However, in the actual measurement process, the used photodetector 9 has noise equivalent power NEP, and nep=2.5× -14 w@1550nm generally, so that the number of reflection times n of light in the light intensity range which can be detected by the photodetector 9 is far less than positive infinity. When the number of reflections reaches the upper limit of integration, the corresponding outgoing light intensity is the NEP value of the photodetector 9. For a fixed NEP value, the greater the incident light intensity I i; the larger the number of reflections n, the longer the effective optical path length of the integrating cavity 5. When the incident light intensity is large enough, the effective light path reaches the theoretical light path L eff =L/(1-R), the light intensity is continuously increased, the effective light path is not increased any more, but the light intensity of the transmitted integrating cavity 5 is continuously increased, and the coupling efficiency of the transmitted light of the integrating cavity 5 is improved.
Therefore, the optical fiber coupling boosting optical amplifier 2 is beneficial to increasing the effective optical path length of the integrating cavity 5 to the theoretical optical path, improving the signal-to-noise ratio of measurement, reducing the lower limit of measurement, and improving the coupling output light intensity of the integrating cavity 5, and is suitable for multi-point distributed measurement.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.
Claims (8)
1. The all-fiber coupling type integrating cavity device is characterized by comprising a fiber coupling semiconductor laser (1) for generating laser, wherein an optical fiber coupling booster light amplifier (2) for receiving the laser and amplifying a signal of the received laser is arranged at an emergent port of the fiber coupling semiconductor laser (1); the optical fiber coupling booster optical amplifier is characterized in that an exit opening of the optical fiber coupling booster optical amplifier (2) is provided with an optical fiber coupling collimator (4) for receiving laser after signal amplification and converting the laser into collimated light, the exit opening of the optical fiber coupling collimator (4) is provided with an integrating cavity (5) for reflecting and diffusely reflecting the collimated light and filling specified gas, and the exit opening of the integrating cavity (5) is provided with a photoelectric detector (9) for detecting the output light intensity of the integrating cavity (5).
2. An all-fiber coupled integrating cavity device according to claim 1, characterized in that the output light intensity of the integrating cavity (5) is the superposition of the light intensity of the output integrating cavity (5) transmitted each time, according to the coherent superposition principle of light, namely:
Wherein I o is the output light intensity; i on is the light intensity transmitted out of the integrating cavity (5) after the light incident into the integrating cavity (5) is reflected n times in the integrating cavity (5); i i is the intensity of the light incident into the integrating cavity (5); t represents the transmissivity of the integrating cavity (5) cavity mirror; r represents the reflectivity of the cavity mirror of the integrating cavity (5); alpha represents the absorption loss coefficient of the gas in the integrating cavity (5) for absorbing laser; l is the base length of the integrating cavity (5).
3. An all-fiber coupled integrating cavity device according to claim 3, wherein the integrating cavity (5) is a cylindrical cavity, the entrance port and the exit port of the integrating cavity (5) are coaxially and hermetically provided with plano-concave lenses, and the concave mirror surfaces of the two plano-concave lenses are arranged opposite to each other.
4. A full optical fiber coupling type integrating cavity device according to claim 3, wherein a large numerical aperture optical fiber coupling lens (7) is coaxially installed on the outer side of the exit port of the integrating cavity (5), and laser light passing through the large numerical aperture optical fiber coupling lens (7) is transmitted to a photodetector (9) by a multimode optical fiber (8).
5. An all-fiber coupled integrating cavity device according to claim 1,2, 3 or 4, characterized in that a collimator adjusting frame (3) for adjusting the exit angle of the fiber coupled collimator (4) is installed at the entrance of the integrating cavity (5); the collimator adjusting frame (3) comprises a positioning sleeve coaxially sleeved on the outer side of an entrance port of the integrating cavity (5), and a spherical cavity penetrating along the two axial ends of the integrating cavity (5) is formed in the positioning sleeve; a spherical joint is arranged in the spherical cavity to form a spherical pair; the ball joint is provided with a mounting hole penetrating through the center of the ball, the optical fiber coupling collimator (4) is mounted in the mounting hole, and laser emitted by the optical fiber coupling collimator (4) is emitted into the integrating cavity (5).
6. An all-fiber coupled integrating cavity device according to claim 1 or 2 or 3 or 4, characterized in that a multidimensional coupling lens adjusting frame (6) for adjusting the position of a large numerical aperture fiber coupling lens (7) is mounted at the exit of the integrating cavity (5); the multidimensional coupling lens adjusting frame (6) comprises a supporting seat capable of axially moving along the integrating cavity (5), and a lens sleeve which is coaxially arranged with the integrating cavity (5) and is used for coaxially sleeving a large numerical aperture optical fiber coupling lens (7) is arranged on the supporting seat.
7. The all-fiber coupling type integrating cavity device according to claim 6, wherein the large-numerical-aperture fiber coupling lens (7) is mounted at the front end of the lens sleeve, the multimode fiber (8) is mounted at the tail end of the lens sleeve, and the incidence point of the multimode fiber (8) is arranged coincident with the focal point of the large-numerical-aperture fiber coupling lens (7).
8. The all-fiber coupling type integrating cavity device according to claim 7, wherein the large numerical aperture fiber coupling lens (7) is a convex lens, and the diameter of the large numerical aperture fiber coupling lens (7) is not smaller than the diameter of a plano-concave lens.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410393547.6A CN118190818A (en) | 2024-04-02 | 2024-04-02 | All-fiber coupling type integrating cavity device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410393547.6A CN118190818A (en) | 2024-04-02 | 2024-04-02 | All-fiber coupling type integrating cavity device |
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| Publication Number | Publication Date |
|---|---|
| CN118190818A true CN118190818A (en) | 2024-06-14 |
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|---|---|---|---|
| CN202410393547.6A Pending CN118190818A (en) | 2024-04-02 | 2024-04-02 | All-fiber coupling type integrating cavity device |
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| CN (1) | CN118190818A (en) |
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- 2024-04-02 CN CN202410393547.6A patent/CN118190818A/en active Pending
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