Optical fiber spectrum demodulation device and demodulation method based on virtual slit

Abstract

The invention discloses an optical fiber spectrum demodulation device and demodulation method based on a virtual slit. The optical fiber spectrum demodulation device comprises a light source, an optical fiber microcavity sensor, an optical fiber emergent port, a virtual slit generator, a collimating mirror, a light beam width adjusting module, a diffraction grating, a convergence mirror, a photoelectric detection array and a signal collecting and processing module. An optical signal emitted by the light source enters the optical fiber micro-cavity sensor for modulation, the optical signal carrying micro-cavity length change information is output, the optical signal is shrunk into a strip-shaped light spot through the virtual slit generator and then enters the light beam width adjusting module through the collimating mirror, and the diameter of the light spot is dynamically adjusted. And then the voltage signals enter a signal acquisition and processing module through a convergence reflector and a photoelectric detection array, after analog-to-digital conversion is carried out on the voltage signals, the peak position of interference signals is extracted, and the cavity length variation of the microcavity is calculated.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sensing and detection, and particularly relates to a high-throughput and high-resolution fiber spectrum demodulation device and method based on a virtual slit. BACKGROUND

[0002] The fiber microcavity sensing technology has the advantages of small size, light weight, anti-electromagnetic interference, large dynamic range, high precision, fast response speed, etc., and has a very wide application prospect in the fields of aerospace, ship and other extreme environment testing. For example, the fiber high-temperature sensing system based on sapphire microcavity is one of the main fiber high-temperature sensing technologies at present. The sapphire microcavity converts the temperature information into a slight change in the microcavity length, so that the change value of the microcavity can be demodulated to obtain the temperature.

[0003] The spectrum demodulation method is the main method for demodulating the microcavity length, which requires a high-throughput and high-resolution spectrum demodulation module. The factors affecting the resolution mainly include the incident slit, the grating and the detector. Generally, a spectrum demodulation module needs to use a slit with adjustable or fixed width to limit the incident light, because the width of the slit directly affects the resolution of the spectrum demodulation module, i.e. its ability to distinguish two similar spectral lines. The narrower the slit, the higher the resolution, and the better the ability to distinguish different wavelengths of light. However, the slit will block the outgoing light of the large-core fiber, and the light signal in the blocked area will be lost, so too narrow a slit will result in a loss of light intensity, making it necessary to take a longer integration time to detect the weak microcavity sensing light signal, limiting the demodulation speed, and even making it impossible to detect when the signal is too weak. At the same time, the resolution of the spectrum demodulation module is also affected by the diffraction grating. The more grating lines covered by the incident light signal on the grating surface, the higher the degree of dispersion and the higher the optical resolution, and vice versa. The detector, as the signal acquisition part of the spectrometer, directly determines the spectral coverage, sensitivity, resolution and signal-to-noise ratio of the fiber spectrometer. Generally, the smaller the pixel size of the detector, the more the number of pixels, the stronger the resolution, and the faster the response speed. Through a pixel merging method, the resolution of the detector can be dynamically adjusted. The principle is to combine multiple pixels into a "super-pixel" technology, which is usually synthesized in the form of 2x2 or 3x3, which can improve the signal-to-noise ratio but reduce the resolution of the image. Meanwhile, the super-pixel can be split to obtain more pixel units to meet the use requirements of high-resolution occasions. SUMMARY

[0004] The purpose of the present application is to overcome the deficiencies of the prior art, and provide a high-throughput high-resolution fiber spectrum demodulation device and method based on a virtual slit. The demodulation device is provided with a virtual slit generator behind the fiber exit end face to form a high-throughput virtual slit. While ensuring the spectral resolution remains unchanged, the use of the physical slit is eliminated to improve the light throughput of the demodulation device. Meanwhile, a beam width adjustment module is provided in front of the diffraction grating. The relative distance between the mirror groups is adjusted to dynamically adjust the size of the light spot diameter incident on the grating surface, so as to adjust the number of engraved lines covered by the light spot to achieve dynamic adjustment of the resolution of the demodulation device, break the mutual restriction between the light throughput and the resolution of the spectrometer, and improve the signal-to-noise ratio. Meanwhile, the selected detector adopts a pixel merging technology, and the number and size of the pixel units can be adjusted to adjust the resolution and response speed within a certain dynamic range, so as to realize high-speed and stable demodulation of the fiber high-temperature sensing optical signal. This method provides a high-stability, high-speed and high-precision microcavity demodulation technical solution for the fields of aviation, aerospace and ocean, and especially provides a stable demodulation method for a fiber high-temperature sensing system based on a sapphire microcavity.

[0005] The first aspect of the present application provides a fiber spectrum demodulation device based on a virtual slit, which comprises a light source, a fiber microcavity sensor, a fiber exit port, a virtual slit generator, a collimating mirror, a beam width adjustment module, a diffraction grating, a converging mirror, a photoelectric detection array and a signal acquisition and processing module.

[0006] The light source emits light signals to the fiber microcavity sensor. The fiber microcavity sensor modulates the laser from the light source, converts the temperature change into a change in the microcavity length, and outputs an optical signal carrying the microcavity length change information. The optical signal is output through a multimode fiber via the fiber exit port and is incident on the virtual slit generator. The optical signal carrying the microcavity length change information is shrunk into a 5-25 wide strip-shaped light spot. The shrunk strip-shaped light spot is incident on the collimating mirror, and the reflected light signal is incident on the beam width adjustment module. The diameter size of the light spot is adjusted in the beam width adjustment module, and the number of engraved lines covered by the exit light incident on the diffraction grating is dynamically adjusted. The light signal is split by the diffraction grating and is incident on the converging mirror. The converging mirror reflects the light signal to the receiving surface of the photoelectric detection array. The photoelectric detection array integrates / splits the received light signal, generates a voltage signal, and transmits the voltage signal to the signal acquisition and processing module. The signal acquisition and processing module extracts the interference signal peak position after the voltage signal output by the photoelectric detection array is analog-to-digital converted, and calculates the microcavity length change amount.

[0007] The photoelectric detection array is electrically connected with the signal acquisition and processing module.

[0008] The light source wavelength range is 400-1200 nm.

[0009] Further, the virtual slit generator comprises a first focusing lens and a second focusing lens, and the long axes of the first focusing lens and the second focusing lens are arranged orthogonally to each other to converge the light signals in the horizontal direction and the vertical direction respectively.

[0010] Further, the light beam width adjusting module comprises a first light beam width adjusting mirror and a second light beam width adjusting mirror, and the relative distance between the first light beam width adjusting mirror and the second light beam width adjusting mirror is changed to realize beam expansion / beam contraction of the light spot diameter.

[0011] Further, the diameter of the multi-mode optical fiber connected to the optical fiber exit port in the optical fiber microcavity sensor is 105 and the above.

[0012] Further, the optical fiber microcavity sensor is an F-P microcavity sensor; more preferably, the F-P microcavity sensor adopts a sapphire F-P microcavity or a photonic crystal fiber F-P cavity. When the optical fiber microcavity sensor adopts a sapphire F-P microcavity, it is a sapphire optical microcavity high-temperature sensor, which utilizes the thermal expansion effect of sapphire, and the change of temperature causes the change of grating period; when the optical fiber microcavity sensor adopts a photonic crystal fiber F-P cavity, it utilizes the band gap characteristics of the photonic crystal, and the change of temperature causes the change of band gap displacement or transmission spectrum.

[0013] More preferably, the optical fiber microcavity sensor adopts a full sapphire material.

[0014] The second aspect of the present application provides a high-throughput high-resolution optical fiber spectrum demodulation device and method based on a virtual slit, comprising:

[0015] The light source outputs a multi-channel light signal with a wavelength range of 400-1200 nm, which is incident on the optical fiber microcavity sensor. The optical fiber microcavity sensor modulates the laser from the light source, and then the optical sensing signal carrying the microcavity length change information after modulation is incident on the virtual slit generator through the optical fiber exit port, and the light signal is shrunk to a 5-25 wide strip-shaped light spot, which is then incident on the collimating mirror, off-axis reflects the shaped strip-shaped light spot to generate a parallel light beam; the parallel light beam passes through the light beam width adjusting module, dynamically adjusts the diameter of the light spot to a range of 1-50 , and is incident on the diffraction grating for light splitting; the converging mirror causes the light-splitting parallel light beam to be incident on different positions of the photodetector array receiving surface according to different wavelengths; the analog electrical signal output by the photodetector array is converted into a digital signal for analysis and processing, the peak position of the interference signal is extracted, and the microcavity length change amount is calculated.

[0016] Compared with the prior art, the present application has the following advantages:

[0017] 1. The high-throughput high-resolution fiber spectrum demodulation device based on virtual slit of the present application adopts a virtual slit generator, eliminates the physical slit, breaks through the limitation between light flux and resolution, increases the utilization of light energy of the output light of the large-core fiber, reduces the light intensity loss, and improves the resolution.

[0018] 2. The demodulation device adopts a light beam width adjusting system to adjust the spot diameter size of the light incident to the surface of the diffraction grating to realize dynamic adjustment of the resolution.

[0019] 3. The demodulation device adopts a pixel merging technology, which can adjust the number and size of the pixel units, ensures the dynamic adjustment of the resolution, and at the same time, the design of the spectrum demodulation module is miniaturized and the structure is compact, which is suitable for the size and weight limitation and the multi-channel sensing system requirement in extreme environments such as aerospace and ships.

[0020] 4. The light path structure of the demodulation device is simple, the light beam shaping and collimation, dispersion, focusing, and signal acquisition system are integrated together, and the device is more miniaturized and integrated. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a structural schematic diagram of the high-throughput high-resolution fiber spectrum demodulation device based on virtual slit of the present application;

[0022] Figure 2 is a structural schematic diagram of the virtual slit generator in the demodulation device;

[0023] Figure 3 is a structural schematic diagram of the light beam width adjusting module in the demodulation device.

[0024] Figure 4 is a schematic diagram of the pixel merging technology of the photodetector array in the demodulation device.

[0025] In the drawings:

[0026] 1: light source; 2: fiber microcavity sensor; 3: fiber exit port; 4: first focusing lens; 5: second focusing lens; 6: collimating mirror; 7: first light beam width adjusting mirror; 8: second light beam width adjusting mirror; 9: diffraction grating; 10: converging mirror; 11: photodetector array; 12: signal acquisition and processing module. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, beneficial effects, and significant advancements of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings provided in the examples of the present invention. Obviously, all the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] like Figure 1 As shown, a high-throughput, high-resolution fiber optic spectral demodulation device based on a virtual slit includes: a light source 1, a fiber optic microcavity sensor 2, a fiber optic output port 3, a first focusing lens 4, a second focusing lens 5, a collimating mirror 6, a first beam width adjustment mirror 7, a second beam width adjustment mirror 8, a diffraction grating 9, a converging mirror 10, a photoelectric detection array 11, and a signal acquisition and processing module 12.

[0029] The wavelength range of the light source 1 is 400nm-1200nm.

[0030] One end of the fiber optic microcavity sensor 2 is connected to a light source 1 for inputting the light source into the fiber optic microcavity sensor 2 for modulation, and the other end is connected to a fiber optic output port 3 for receiving the optical signal carrying information about the microcavity length change after modulation by the fiber optic microcavity sensor. The fiber optic microcavity sensor 2 is at least partially disposed inside the mechanical equipment whose temperature is to be monitored.

[0031] The fiber optic microcavity sensor is an FP microcavity sensor that modulates the laser light from light source 1. When the temperature rises, the microcavity material undergoes thermal expansion, changing the cavity length. This converts the temperature information into a minute change in the microcavity length, modulates and outputs an optical signal carrying the information about the change in the microcavity length. Specifically, the fiber optic microcavity sensor uses the sapphire optical microcavity high-temperature sensor disclosed in CN119880186A, including a protective sleeve, a first ferrule, a multimode fiber, a sapphire fiber, and a sapphire optical microcavity. The sapphire optical microcavity includes a second ferrule and a sapphire wafer. The sapphire wafer is fixed to the end of the second ferrule using a glue-free bonding method. The second ferrule is made of sapphire material. One end of the multimode fiber and the sapphire fiber are aligned and fixed, and the connection point of the multimode fiber and the sapphire fiber is suspended inside the protective sleeve. The other end of the sapphire fiber extends into the interior of the sapphire optical microcavity and is 50-100 μm away from the sapphire wafer and perpendicular to the sapphire wafer. The protective sleeve is fitted onto the outer surface of part of the sapphire optical microcavity and part of the outer surface of the multimode fiber and the sapphire fiber. The end of the sapphire optical microcavity with the sapphire wafer is exposed outside the protective sleeve. Furthermore, the sapphire optical microcavity and sapphire optical fiber form a sapphire optical microcavity high-temperature probe, both made of sapphire material. Of course, other microcavity sensors can also be selected according to actual needs.

[0032] like Figure 2 As shown, the first focusing lens 4 and the second focusing lens 5 form a virtual slit generator, used to achieve beam shaping, reducing the optical signal carrying microcavity length variation information emitted from the fiber optic output port 3 to a beam width of 5. Up to 25 The design utilizes a strip-shaped light spot to concentrate light energy, thus achieving a high-throughput virtual slit structure. The first focusing lens 4 and the second focusing lens 5 are arranged in a spatial layout with their major axes orthogonal. The first focusing lens 4 is dedicated to converging horizontal light signals, while the second focusing lens 5 converges vertical light signals. This orthogonal optical design efficiently reduces the diverging beam from the fiber optic exit port 3 into a narrow strip-shaped light spot with a width between 5 μm and 25 μm. This design not only significantly improves energy density but also avoids the mechanical wear and diffraction losses inherent in physical slits, achieving a high-throughput, low-aberration virtual slit function and providing ideal optical input conditions for subsequent spectral dispersion.

[0033] The collimating mirror 6 is used to collimate the light beam incident on the mirror surface and generate a parallel light beam through off-axis reflection.

[0034] like Figure 3As shown, the first beam width adjustment mirror 7 and the second beam width adjustment mirror 8 constitute a beam width adjustment module. By adjusting the relative distance between the mirrors, the size of the light spot can be controlled, thereby adjusting the number of lines covered on the diffraction grating and achieving dynamic adjustment of the resolution. The first beam width adjustment mirror 7 and the second beam width adjustment mirror 8 are mounted on a precision linear slide to adjust the relative distance between the two mirrors. The beam width adjustment module achieves continuous adjustment of the light spot size by changing the beam expansion ratio. Its adjustment range covers ±20% of the light spot width change, thereby controlling the number of lines covered by the beam incident on the diffraction grating, thus dynamically adjusting the system's spectral resolution (adjustment range from 0.2nm to 1.5nm) to adapt to the resolution requirements of different measurement scenarios.

[0035] The diffraction grating 9 is used to split the parallel beam emitted from the second beam width adjustment mirror 8 to generate beams of different wavelengths. The number of grating line pairs of the diffraction grating 9 is 600 to 1800.

[0036] The converging reflector 10 is used to reflect light beams of different wavelengths to the receiving surface of the photoelectric detection array 11.

[0037] The photoelectric detection array 11 is used to receive light beams of different wavelengths and generate analog signals. It employs pixel merging technology, dynamically integrating and splitting pixels in a 2×2 or 3×3 programmable pixel merging mode. The array integrates a switched-capacitor network, which reduces noise interference per unit area and expands the detection range of a single pixel by merging the photoresponse signals of multiple pixel units. When high-resolution detection is required to capture subtle light intensity differences, the switched-capacitor network can disconnect the connections between units, allowing each photodiode to resume independent operation. Specifically, the photoelectric detection array includes multiple photodiodes arranged in a matrix, with each unit independently responding to local light intensity changes. Light beams of different wavelengths from the converging mirror 10 are captured by corresponding diodes for parallel detection. Subsequently, the current output by each photodiode is amplified, filtered, and converted into a voltage signal. Figure 4 The diagram shows a magnified and reduced resolution conversion of the photoelectric detection array 11. The receiving surface of the photoelectric detection array 11 is electrically connected to the signal acquisition and processing module.

[0038] The signal acquisition and processing module 12 performs analog-to-digital conversion on the voltage signal from the photoelectric detection array 11, extracts the peak position of the interference signal, and calculates the microcavity length variable. This module is used to acquire and process signals from the photoelectric detection array 11, generating corresponding digital voltage signals. The signal acquisition and processing module 12 includes an analog-to-digital conversion unit, a signal processing unit, and a cavity length calculation unit. The analog-to-digital conversion unit converts the voltage signal from the photoelectric detection array 11 into a digital signal. The signal processing unit implements a peak positioning algorithm on the converted digital signal using an FPGA and fits the interference envelope using cubic spline interpolation. The cavity length calculation unit calculates the cavity length change based on the wavelength-cavity length mapping relationship ΔL = (λ1λ2) / (2nΔλ), and combines this with a temperature compensation algorithm to eliminate thermal drift errors, thereby obtaining the microcavity length change and thus the temperature change.

[0039] The demodulation method of the high-throughput fiber optic spectral demodulation device based on a virtual slit is as follows:

[0040] The light source 1 outputs an optical signal with a wavelength range of 400nm to 1200nm, which is incident on the fiber optic microcavity sensor 2. The fiber optic microcavity sensor modulates and outputs an optical signal carrying information about the change in the microcavity length.

[0041] The optical signal carrying the microcavity length variation information is incident on the first focusing lens 4 through the optical fiber output port 3; the first focusing lens 4 and the second focusing lens 5 constitute a virtual slit generator, which reduces the optical signal carrying the microcavity length variation information into a smaller strip light spot, completes the setting of the high-throughput virtual slit structure, and increases the light throughput at the incident point.

[0042] The converged light signal, after being focused by the virtual slit generator, is incident on the collimating mirror 6, which reflects the strip-shaped light spot off-axis, generating a parallel beam. The parallel beam passes through the beam width adjustment system, and the size of the output light spot is adjusted by moving the relative distance between the first beam width adjustment mirror 7 and the second beam width adjustment mirror 8, thereby achieving dynamic adjustment of the resolution. After the light spot is incident on the diffraction grating 9, it is split by diffraction. The split parallel beam is incident on the converging focusing mirror 10, which directs the parallel beam at different positions on the receiving surface of the photodetector array 11 according to different wavelengths. The photodetector array 11 adopts pixel merging technology, which integrates and splits pixels in a 2×2 or 3×3 form, thereby achieving adjustable pixel number and size, and thus realizing dynamic adjustment of detector resolution and improvement of response speed. The signal acquisition and processing module 12 converts the analog electrical signal output by the photoelectric detection array 11 into a digital signal and performs system control and digital signal processing, thereby demodulating the peak position of the interference signal and calculating the change in the length of the microcavity to obtain the temperature change of the mechanical equipment where the fiber optic microcavity sensor 2 is located, thus realizing real-time monitoring of the temperature of the mechanical equipment.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. Non-essential improvements, adjustments or substitutions made by those skilled in the art based on the content of this specification are all within the scope of protection claimed by the present invention.

Claims

1. A fiber optic spectral demodulation device based on a virtual slit, characterized in that, It includes a light source (1), an optical fiber microcavity sensor (2), an optical fiber output port (3), a virtual slit generator, a collimating mirror (6), a beam width adjustment module, a diffraction grating (9), a converging mirror (10), a photoelectric detection array (11), and a signal acquisition and processing module (12). In this process, the light source (1) emits an optical signal that is incident on the fiber optic microcavity sensor (2). The fiber optic microcavity sensor modulates the laser from the light source (1), converting the temperature change into a change in the microcavity length, and outputs an optical signal carrying information about the change in the microcavity length. This optical signal is then output through a multimode fiber via the fiber optic output port (3) and incident on the virtual slit generator, which reduces the optical signal carrying the information about the change in the microcavity length to 5-25. A wide strip-shaped light spot; the beam-shrinking strip-shaped light spot is incident on the collimating mirror (6), and the light signal after reflection is incident on the beam width adjustment module, in which the diameter of the light spot is adjusted, thereby dynamically adjusting the number of lines covered on the diffraction grating (9) by the outgoing light; the light signal is incident on the converging mirror (10) after being split by the diffraction grating (9); the converging mirror (10) reflects the light signal to the receiving surface of the photoelectric detection array (11); the photoelectric detection array (11) integrates / splits the received light signal into pixels, generates a voltage signal, and transmits it to the signal acquisition and processing module (12). The signal acquisition and processing module (12) performs analog-to-digital conversion on the voltage signal output by the photoelectric detection array (11), extracts the peak position of the interference signal, and calculates the change in the microcavity length.

2. The fiber optic spectral demodulation device based on a virtual slit according to claim 1, characterized in that, The light source (1) has a wavelength range of 400nm-1200nm.

3. The fiber optic spectral demodulation device based on a virtual slit according to claim 1, characterized in that, The virtual slit generator includes a first focusing lens (4) and a second focusing lens (5), and the major axes of the first focusing lens (4) and the second focusing lens (5) are arranged orthogonally to each other, respectively converging the light signals in the horizontal and vertical directions.

4. The fiber optic spectral demodulation device based on a virtual slit according to claim 1, characterized in that, The beam width adjustment module includes a first beam width adjustment mirror (7) and a second beam width adjustment mirror (8). By changing the relative distance between the first beam width adjustment mirror (7) and the second beam width adjustment mirror (8), the beam diameter can be expanded / contracted.

5. The fiber optic spectral demodulation device based on a virtual slit according to claim 1, characterized in that, The multimode fiber connected to the fiber optic output port (3) in the fiber optic microcavity sensor has a diameter of 105 mm. and above.

6. The fiber optic spectral demodulation device based on a virtual slit according to claim 1, characterized in that, The fiber optic microcavity sensor is an FP microcavity sensor.

7. The fiber optic spectral demodulation device based on a virtual slit according to claim 6, characterized in that, The FP microcavity sensor uses a sapphire FP microcavity or a photonic crystal fiber FP cavity.

8. The fiber optic spectral demodulation device based on a virtual slit according to claim 6, characterized in that, The fiber optic microcavity sensor is made entirely of sapphire.

9. The demodulation method of the fiber optic spectral demodulation device based on a virtual slit according to claim 1, comprising: The light source (1) outputs multiple optical signals with a wavelength range of 400nm to 1200nm, which are then incident on the fiber optic microcavity sensor (2). The external fiber optic microcavity sensor modulates the laser from the light source (1), and then the modulated optical sensing signal carrying information on the microcavity length variation is incident on the virtual slit generator through the fiber optic output port (3), reducing the optical signal to 5 to 25 nm. A wide, strip-shaped light spot is then incident on the collimating mirror (6), where the shaped light spot is reflected off-axis to generate a parallel beam. The diameter of the parallel beam is dynamically adjusted from 1 to 50 mm via a beam width adjustment module. The beam is incident on the diffraction grating (9) for beam splitting; the converging mirror (10) directs the split parallel beam to different positions on the receiving surface of the photoelectric detection array (11) at different wavelengths; the analog electrical signal output by the photoelectric detection array (11) is then converted into a digital signal for analysis and processing, the peak position of the interference signal is extracted, and the change in the microcavity length is calculated.

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