Fiber optic spectrometer and spectral signal demodulation method

Abstract

The invention provides an optical fiber spectrometer and a spectral signal demodulation method. The optical fiber spectrometer comprises a light source, a first optical fiber coupler, a second optical fiber coupler, an optical fiber delay line, a first photoelectric detector, a second photoelectric detector, a laser and a controller. The first optical fiber coupler, the optical fiber delay line, the second optical fiber coupler and the first photoelectric detector form a first path, and the second optical fiber coupler, the first optical fiber coupler and the second photoelectric detector form a second path; light waves emitted by the light source are transmitted in the first path and the second path and output electrical time domain signals through the first photoelectric detector, and light waves emitted by the laser are transmitted in the first path and the second path and output time domain interference signals through the second photoelectric detector. And the controller is connected with the first photoelectric detector and the second photoelectric detector and is used for determining a spectral signal of the light wave according to the electric time domain signal and the time domain interference signal. According to the invention, the accuracy and reliability of spectral analysis results are improved.

Description

Technical Field

[0001] The present application relates to the field of measurement and analysis technology, and in particular to an optical fiber spectrometer and a demodulation method for spectral signals. Background Art

[0002] Fiber optic spectrometer is an instrument that uses optical fiber to transmit optical signals and perform spectral analysis. It often uses optical fiber as a signal coupling device to couple the measured light into the spectrometer for spectral analysis. Demodulation of spectral signals is a step in spectral analysis, which is used to extract useful information from complex spectral signals. Spectral signals usually contain light intensity information of multiple wavelengths, which can reflect the chemical composition and physical characteristics of the sample. The demodulation process of spectral signals involves steps such as separation, filtering and analysis of spectral signals to extract specific spectral features.

[0003] In some scenarios, in large systems such as converter stations and substations, fiber optic spectrometers are affected by harsh electromagnetic environments and severe mechanical disturbance environments, which can cause serious distortion in the spectral analysis of the measured light by the fiber optic spectrometer. This is because it is difficult to accurately obtain the moving speed of the moving mirror of the fiber optic spectrometer in harsh electromagnetic environments and severe mechanical disturbance environments, and thus it is difficult to obtain the optical path difference corresponding to different moments, which affects the accuracy and reliability of the spectral analysis results. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a fiber optic spectrometer and a demodulation method for spectral signals to solve the problem of low accuracy and reliability of spectral analysis results.

[0005] In order to solve the above technical problems, the embodiments of the present application are implemented as follows:

[0006] In a first aspect, an embodiment of the present application provides a fiber spectrometer, comprising: a light source, a first fiber coupler, a second fiber coupler, a fiber delay line, a first photodetector, a second photodetector, a laser, and a controller; the first fiber coupler, the fiber delay line, the second fiber coupler, and the first photodetector form a first path, the second fiber coupler, the first fiber coupler, and the second photodetector form a second path, and the transmission directions of the light waves emitted by the light source and the laser are opposite; the light waves emitted by the light source are transmitted in the first path and the second path and output electrical time domain signals through the first photodetector, and the light waves emitted by the laser are transmitted in the first path and the second path and output time domain interference signals through the second photodetector; the controller is respectively connected to the first photodetector and the second photodetector, and is used to determine the spectral signal of the light wave according to the electrical time domain signal and the time domain interference signal.

[0007] Optionally, the light source includes a broadband light source, and the laser includes a narrowband laser.

[0008] Optionally, the controller is also used to determine the optical path difference at any time based on the time domain interference signal; determine the interference signal of the light wave based on the optical path difference at any time and the electrical time domain signal; and demodulate the interference signal to obtain the spectral signal of the light wave.

[0009] Optionally, the controller is also used to determine the first light intensity and the first time domain signal corresponding to the wave number of the light wave emitted by the laser; construct an equation between the time domain interference signal and the first light intensity, the first time domain signal and the optical path difference; and determine the optical path difference using the time domain interference signal, the first light intensity and the first time domain signal as known quantities.

[0010] Optionally, the controller is also used to determine the corresponding phase difference based on the optical path difference; determine the interference signal of the light wave based on the phase difference, the second light intensity corresponding to the wave number of the light wave emitted by the light source in the electrical time domain signal, and the first light intensity corresponding to the wave number of the light wave emitted by the laser.

[0011] Optionally, the controller is also used to determine a second time domain signal corresponding to the wave number of the light wave emitted by the light source; construct an equation between the interference signal, the optical path difference, the second time domain signal and the electrical time domain signal; and use the equation to perform Fourier transform on the interference signal to obtain a spectral signal of the light wave.

[0012] In the second aspect, an embodiment of the present application provides a demodulation method for a spectral signal, including: acquiring an electrical time domain signal output by a first photodetector and a time domain interference signal output by a second photodetector; determining the optical path difference at any time based on the time domain interference signal; determining the interference signal of the light wave based on the optical path difference and the electrical time domain signal at any time; and demodulating the interference signal to obtain a spectral signal of the light wave.

[0013] Optionally, determining the optical path difference at any time based on the time domain interference signal includes: determining a first light intensity and a first time domain signal corresponding to the wave number of the light wave emitted by the laser; constructing an equation between the time domain interference signal and the first light intensity, the first time domain signal and the optical path difference; and determining the optical path difference using the time domain interference signal, the first light intensity and the first time domain signal as known quantities.

[0014] Optionally, determining the interference signal of the light wave based on the optical path difference and the electrical time domain signal at any moment includes: determining the corresponding phase difference based on the optical path difference; determining the interference signal of the light wave based on the phase difference, a second light intensity corresponding to the wave number of the light wave emitted by the light source in the electrical time domain signal, and a first light intensity corresponding to the wave number of the light wave emitted by the laser.

[0015] Optionally, demodulating the interference signal to obtain the spectral signal of the light wave includes: determining a second time domain signal corresponding to the wave number of the light wave emitted by the light source; constructing an equation among the interference signal, the optical path difference, the second time domain signal and the electrical time domain signal; and using the equation to perform Fourier transform on the interference signal to obtain the spectral signal of the light wave.

[0016] Through the technical solution disclosed in the embodiment of the present application, the first fiber coupler, the fiber delay line, the second fiber coupler and the first photodetector form a first path, the second fiber coupler, the first fiber coupler and the second photodetector form a second path, and the transmission directions of the light waves emitted by the light source and the laser are opposite; the light waves emitted by the light source are transmitted in the first path and the second path and output electrical time domain signals through the first photodetector, and the light waves emitted by the laser are transmitted in the first path and the second path and output time domain interference signals through the second photodetector; the controller is connected to the first photodetector and the second photodetector respectively, and is used to determine the spectral signal of the light wave according to the electrical time domain signal and the time domain interference signal. In this way, the second photodetector can capture the reverse time domain interference signal, and determine the spectral signal of the light wave according to the time domain interference signal and the electrical time domain signal detected by the first photodetector. Even in a harsh electromagnetic environment and a severe mechanical disturbance environment, it will not affect the capture of the time domain interference signal by the second photodetector and the capture of the electrical time domain signal by the first photodetector. Therefore, according to the time domain interference signal and the electrical time domain signal detected by the first photodetector, the spectral signal of the light wave is determined, which can improve the accuracy and reliability of the spectral analysis results. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0018] Figure 1 A schematic diagram of the structure of a fiber optic spectrometer provided in an embodiment of the present application;

[0019] Figure 2 A schematic diagram of an electrical time domain signal collected by a first photodetector of a fiber optic spectrometer provided in an embodiment of the present application under four different violent fluctuation environments;

[0020] Figure 3 A schematic diagram of a time domain interference signal collected by a second photodetector of a fiber optic spectrometer under four different violent fluctuation environments provided in an embodiment of the present application;

[0021] Figure 4 A schematic diagram of a curve showing the change of optical path difference over time provided in an embodiment of the present application;

[0022] Figure 5 A schematic diagram of a curve showing the change of optical path difference with interference intensity provided in an embodiment of the present application;

[0023] Figure 6 Schematic diagram of spectral signals obtained in different ways provided in the embodiments of the present application;

[0024] Figure 7 A schematic flow chart of a method for demodulating a spectral signal provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] The purpose of the embodiments of the present application is to provide a fiber optic spectrometer and a demodulation method for spectral signals, thereby improving the accuracy and reliability of spectral analysis results.

[0026] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application.

[0027] For example, Figure 1 As shown, an embodiment of the present application provides a fiber optic spectrometer, which may specifically include: a light source 1, a first fiber optic coupler 2, a second fiber optic coupler 4, a fiber optic delay line 3, a first photodetector 5, a second photodetector 6, a laser 7 and a controller (not shown in the figure).

[0028] The first fiber coupler 2, the fiber delay line 3, the second fiber coupler 4 and the first photodetector 5 form a first path, the second fiber coupler 4, the first fiber coupler 2 and the second photodetector 6 form a second path, and the transmission directions of the light waves emitted by the light source 1 and the laser 7 are opposite.

[0029] The light waves emitted by the light source 1 are transmitted in the first path and the second path and output electrical time domain signals through the first photodetector 5 . The light waves emitted by the laser 7 are transmitted in the first path and the second path and output time domain interference signals through the second photodetector 6 .

[0030] The controller is connected to the first photodetector 5 and the second photodetector 6 respectively, and is used to determine the spectrum signal of the light wave according to the electrical time domain signal and the time domain interference signal.

[0031] Specifically, the controller and the first photodetector 5 and the second photodetector 6 can be connected by wire or by wireless connection, which is not limited in the present embodiment. The light source 1 can be a broadband light source, and the laser 7 can be a narrowband laser.

[0032] Furthermore, the first fiber coupler 2 and the second fiber coupler 4 can both be 2*2 fiber couplers. The light waves emitted by the broadband light source form a measured spectrum after passing through the measured substance, and enter the first path and the second path through the first fiber coupler 2, and form interference at the first photodetector 5. The ultra-narrow linewidth laser emitted by the narrow-band laser 7 is reversely injected into the first path and the second path by the second fiber coupler 4, and forms interference at the second photodetector 6. The interference optical path difference in the optical path structure is scanned by the optical fiber delay line 3, and an electrical time domain signal and a time domain interference signal that are correlated with the measured spectrum and the spectrum emitted by the narrow-band laser are formed at the first photodetector 5 and the second photodetector 6, respectively. By analyzing the electrical time domain signal and the time domain interference signal captured by the first photodetector 5 and the second photodetector 6, the analysis of the spectral signal caused by environmental disturbances can be suppressed, and the spectral signal can be accurately obtained.

[0033] Furthermore, the broadband light emitted by the broadband light source passes through the measured material to form a measured spectrum which is divided into two paths by the first fiber coupler 2, and an MZ interferometer is formed through the fiber delay line 3 and the second fiber coupler 4. The light output by the MZ interferometer is converted into an electrical time domain signal I1(t) by the first photodetector 5. The light emitted by the narrowband laser is divided into two paths by the second fiber coupler 4, and is transmitted in reverse to the second photodetector 6 to form a time domain interference signal I2(t). Among them, the forward and reverse light emitted by the broadband light source and the narrowband laser share an MZ interferometer. Since the frequency and wavelength of the light emitted by the narrowband laser are fixed, the time domain interference signal of the reverse light can be captured by the second photodetector 6, thereby obtaining the optical path difference δ(t) of the interferometer at any time, and parsing the interference signal I1(δ) of the measured spectrum, and then inverting the measured spectrum signal.

[0034] For example, Figure 2 and Figure 3 As shown, Figure 2 A schematic diagram of an electrical time domain signal collected by a first photodetector of a fiber optic spectrometer under four different violent fluctuation environments provided in an embodiment of the present application, Figure 3 A schematic diagram of a time domain interference signal collected by a second photodetector of a fiber optic spectrometer in four different violent fluctuation environments provided in an embodiment of the present application. Figure 2 and Figure 3 It can be seen that in the operation of the fiber optic spectrometer, even if the measured spectra are consistent, due to the influence of environmental fluctuations, there is a large difference between the electrical time domain signal collected by the first photodetector and the time domain interference signal collected by the second photodetector.

[0035] Furthermore, when the controller determines the spectral signal according to the electrical time domain signal and the interference time domain signal, the optical path difference at any time is first determined according to the time domain interference signal; then the interference signal of the light wave is determined according to the optical path difference at any time and the electrical time domain signal; finally, the interference signal is demodulated to obtain the spectral signal of the light wave. Wherein, when determining the optical path difference at any time according to the time domain interference signal, the first light intensity and the first time domain signal corresponding to the wave number of the light wave emitted by the laser are first determined; then an equation is constructed between the time domain interference signal and the first light intensity, the first time domain signal and the optical path difference; finally, the optical path difference is determined with the time domain interference signal, the first light intensity and the first time domain signal as known quantities.

[0036] Specifically, the time domain interference signal collected by the second photodetector can be expressed as follows:

[0037]

[0038] In the above formula, I2(t) represents the time domain interference signal collected by the second photodetector. FBG is the wave number corresponding to the light wave emitted by the narrow-band laser. FBG ) represents the first light intensity corresponding to the light with wave number k emitted by the narrowband laser. η1(t) and η2(t) represent the first time domain signal. δ(t) is the optical path difference that changes with time.

[0039] For example, Figure 4 As shown, Figure 4 A curve diagram of the optical path difference changing with time provided in the embodiment of the present application shows that the optical path difference is also changing with time. Figure 2 By transforming the horizontal axis of Figure 2 The curve of the optical path difference after the horizontal coordinate is transformed as the interference intensity changes is as follows Figure 5 As shown, Figure 5 The following is a schematic diagram of the curve of the optical path difference as the interference intensity changes according to the embodiment of the present application. Since the relationship between the optical path difference and time is not a linear relationship, Figure 5 The projection of the sampling point on the horizontal axis does not change uniformly, that is, the curve of the interference intensity changing with the optical path difference is a curve obtained by non-uniform sampling.

[0040] Furthermore, when determining the spectral signal, the controller is also used to determine the second time domain signal corresponding to the wave number of the light wave emitted by the light source; construct an equation between the interference signal, the optical path difference, the second time domain signal and the electrical time domain signal; and use the equation to perform Fourier transform on the interference signal to obtain the spectral signal of the light wave.

[0041] Specifically, the electrical time domain signal collected by the first photodetector can be expressed as follows:

[0042]

[0043] In the above formula, I1(t) represents the electrical time domain signal collected by the first photodetector. k is the wave number of the light in the measured light, where k = 2π / λ, λ is the wavelength. δ(t) is the optical path difference that changes with time. I(k) represents the second light intensity corresponding to the light with wave number k in the measured light, that is, the interference signal. η1(t) and η2(t) represent the second time domain signal, and the second time domain signal can be the same as the first time domain signal. It can be seen from the above formula that ∫I(k)η1(t)dk and ∫I(k)η2(t)dk are low-frequency slowly varying signals, is the real part of the Fourier transform.

[0044] Furthermore, when determining the interference signal of the light wave, the corresponding phase difference is first determined based on the optical path difference; then the interference signal of the light wave is determined based on the phase difference, the second light intensity corresponding to the wave number of the light wave emitted by the light source in the electrical time domain signal, and the first light intensity corresponding to the wave number of the light wave emitted by the laser.

[0045] Specifically, the phase difference can be calculated by the following formula:

[0046]

[0047] In the above formula, represents the phase difference, ΔL represents the optical path difference, and λ represents the wavelength.

[0048] The interference signal of the light wave is then determined by the following formula:

[0049]

[0050] In the above formula, I represents the interference signal of the light wave, I1 represents the first light intensity, and I2 represents the second light intensity.

[0051] Furthermore, the following is combined Figure 6 The spectral signal obtained by the optical fiber spectrometer of the embodiment of the present application and the spectral signal obtained by the traditional desktop spectrometer are described. Figure 6 Schematic diagram of spectral signals obtained in different ways provided in the embodiments of the present application. Figure 6 In FIG. 1 , the solid line portion is a spectrum signal obtained by the optical fiber spectrometer in the embodiment of the present application, and the dotted line portion is a spectrum signal obtained by a conventional desktop spectrometer. Figure 6 It can be seen that the accuracy difference between the spectral signal obtained by the optical fiber spectrometer provided in the embodiment of the present application and the spectral signal obtained by the desktop spectrometer is relatively small.

[0052] It is worth noting that when the optical path difference is obtained in the embodiment of the present application, it is different from the prior art that it is necessary to strictly know the moving speed of the moving mirror in the spectrometer at every moment to obtain the corresponding optical path difference at different moments. The optical path difference of the spectrometer in the embodiment of the present application is determined by the electrical time domain signal and the time domain interference signal formed by the reverse transmission of the light source and the laser. Therefore, the change of the optical path difference in the embodiment of the present application with time t is non-uniform and non-repeatable. No matter how the environmental fluctuations are, it does not affect the performance of the fiber optic spectrometer provided in the embodiment of the present application.

[0053] Through the technical solution disclosed in the embodiment of the present application, the second photodetector can capture the reverse time domain interference signal, and determine the spectral signal of the light wave according to the time domain interference signal and the electrical time domain signal detected by the first photodetector. Even in a harsh electromagnetic environment and a severe mechanical disturbance environment, it will not affect the capture of the time domain interference signal by the second photodetector and the capture of the electrical time domain signal by the first photodetector. Therefore, according to the time domain interference signal and the electrical time domain signal detected by the first photodetector, the spectral signal of the light wave is determined, which can improve the accuracy and reliability of the spectral analysis results.

[0054] Corresponding to the optical fiber spectrometer provided in the above embodiment, based on the same technical concept, the embodiment of the present application also provides a demodulation method for a spectral signal. Figure 7 The schematic flow chart of the demodulation method of the spectral signal provided in the embodiment of the present application includes:

[0055] In step S701, an electrical time domain signal output by the first photodetector and a time domain interference signal output by the second photodetector are acquired.

[0056] In step S702, the optical path difference at any time is determined according to the time domain interference signal.

[0057] Specifically, determining the optical path difference at any time based on the time domain interference signal includes: determining the first light intensity and the first time domain signal corresponding to the wave number of the light wave emitted by the laser; constructing an equation between the time domain interference signal and the first light intensity, the first time domain signal and the optical path difference; and determining the optical path difference using the time domain interference signal, the first light intensity and the first time domain signal as known quantities.

[0058] In step S703, the interference signal of the light wave is determined according to the optical path difference and the electrical time domain signal at any time.

[0059] Specifically, determining the interference signal of the light wave based on the optical path difference and the electrical time domain signal at any moment includes: determining the corresponding phase difference based on the optical path difference; determining the interference signal of the light wave based on the phase difference, the second light intensity corresponding to the wave number of the light wave emitted by the light source in the electrical time domain signal, and the first light intensity corresponding to the wave number of the light wave emitted by the laser.

[0060] In step S704, the interference signal is demodulated to obtain a spectrum signal of the light wave.

[0061] Specifically, demodulating the interference signal to obtain the spectral signal of the light wave includes: determining the second time domain signal corresponding to the wave number of the light wave emitted by the light source; constructing an equation among the interference signal, the optical path difference, the second time domain signal and the electrical time domain signal; and using the equation to perform Fourier transform on the interference signal to obtain the spectral signal of the light wave.

[0062] Through the technical solution disclosed in the embodiment of the present application, the second photodetector can capture the reverse time domain interference signal, and determine the spectral signal of the light wave according to the time domain interference signal and the electrical time domain signal detected by the first photodetector. Even in a harsh electromagnetic environment and a severe mechanical disturbance environment, it will not affect the capture of the time domain interference signal by the second photodetector and the capture of the electrical time domain signal by the first photodetector. Therefore, according to the time domain interference signal and the electrical time domain signal detected by the first photodetector, the spectral signal of the light wave is determined, which can improve the accuracy and reliability of the spectral analysis results.

[0063] It should be noted that the fiber optic spectrometer and the demodulation method of spectral signals provided in the embodiment of the present application are based on the same application concept, so the specific implementation of this embodiment can refer to the implementation of the aforementioned fiber optic spectrometer, and has the same or similar beneficial effects, and the repeated parts will not be repeated.

[0064] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0065] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, devices or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0066] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A fiber optic spectrometer, characterized in that: The fiber optic spectrometer comprises: a light source, a first fiber optic coupler, a second fiber optic coupler, a fiber optic delay line, a first photodetector, a second photodetector, a laser and a controller; The first fiber coupler, the fiber delay line, the second fiber coupler and the first photodetector form a first path, the second fiber coupler, the first fiber coupler and the second photodetector form a second path, and the transmission directions of the light waves emitted by the light source and the laser are opposite; The light wave emitted by the light source is transmitted in the first path and the second path and outputs an electrical time domain signal through the first photodetector, and the light wave emitted by the laser is transmitted in the first path and the second path and outputs a time domain interference signal through the second photodetector; The controller is connected to the first photodetector and the second photodetector respectively, and is used to determine the spectrum signal of the light wave according to the electrical time domain signal and the time domain interference signal.

2. The optical fiber spectrometer according to claim 1, characterized in that: The light source comprises a broadband light source, and the laser comprises a narrowband laser.

3. The optical fiber spectrometer according to claim 1, characterized in that: The controller is also used to determine the optical path difference at any time according to the time domain interference signal; Determine an interference signal of the light wave according to the optical path difference at any time and the electrical time domain signal; The interference signal is demodulated to obtain a spectrum signal of the light wave.

4. The optical fiber spectrometer according to claim 3, characterized in that: The controller is also used to determine a first light intensity and a first time domain signal corresponding to the wave number of the light wave emitted by the laser; constructing an equation between the time domain interference signal and the first light intensity, the first time domain signal and the optical path difference; The optical path difference is determined using the time domain interference signal, the first light intensity and the first time domain signal as known quantities.

5. The optical fiber spectrometer according to claim 3, characterized in that: The controller is also used to determine the corresponding phase difference according to the optical path difference; The interference signal of the light wave is determined according to the phase difference, the second light intensity corresponding to the wave number of the light wave emitted by the light source in the electrical time domain signal, and the first light intensity corresponding to the wave number of the light wave emitted by the laser.

6. The optical fiber spectrometer according to claim 3, characterized in that: The controller is also used to determine a second time domain signal corresponding to the wave number of the light wave emitted by the light source; constructing an equation between the interference signal, the optical path difference, the second time domain signal, and the electrical time domain signal; The interference signal is Fourier transformed using the equation to obtain a spectrum signal of the light wave.

7. A method for demodulating a spectrum signal, characterized in that: Based on the fiber optic spectrometer according to any one of claims 1 to 6, the method comprises: Acquire an electrical time domain signal output by the first photodetector and a time domain interference signal output by the second photodetector; Determine the optical path difference at any time according to the time domain interference signal; Determine an interference signal of the light wave according to the optical path difference at any time and the electrical time domain signal; The interference signal is demodulated to obtain a spectrum signal of the light wave.

8. The demodulation method of spectrum signal according to claim 7, characterized in that: Determining the optical path difference at any time according to the time domain interference signal comprises: Determine a first light intensity and a first time domain signal corresponding to the wave number of the light wave emitted by the laser; constructing an equation between the time domain interference signal and the first light intensity, the first time domain signal and the optical path difference; The optical path difference is determined using the time domain interference signal, the first light intensity and the first time domain signal as known quantities.

9. The demodulation method of spectrum signal according to claim 7, characterized in that: The determining of the interference signal of the light wave according to the optical path difference at any time and the electrical time domain signal comprises: Determine a corresponding phase difference according to the optical path difference; The interference signal of the light wave is determined according to the phase difference, the second light intensity corresponding to the wave number of the light wave emitted by the light source in the electrical time domain signal, and the first light intensity corresponding to the wave number of the light wave emitted by the laser.

10. The demodulation method of spectrum signal according to claim 7, characterized in that: The demodulating the interference signal to obtain the spectrum signal of the light wave comprises: Determine a second time domain signal corresponding to the wave number of the light wave emitted by the light source; constructing an equation between the interference signal, the optical path difference, the second time domain signal, and the electrical time domain signal; The interference signal is Fourier transformed using the equation to obtain a spectrum signal of the light wave.

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