Water Mie, Rayleigh and Brillouin scattering measurement technology based on Add-Drop filter

Abstract

Based on a water body Mie scattering (Mie scattering), Rayleigh scattering (Rayleigh scattering) and Brillouin scattering (Brillouin scattering) measurement technology of an Add-Drop type filter, the device is correspondingly formed by a narrow linewidth laser, a laser frequency stabilization system, an optical emission system, an optical receiving system, the cascaded Add-Drop type filter, a multi-channel photoelectric detection system and a data acquisition and processing system. An Add-Drop type filter is used as a narrow-band optical filter, and Mie scattering in water, Rayleigh scattering of water molecules and Brillouin scattering of the water can be separated, so that the Mie scattering intensity, the Rayleigh scattering intensity and the Brillouin scattering intensity of the water can be directly measured, and corresponding high-precision parameters can be obtained.

Description

Technical Field

[0001] The present invention relates to a water body Mie scattering, Rayleigh scattering and Brillouin scattering measurement technology and implementation method based on an Add-Drop filter, and more specifically to a water body Mie scattering, Rayleigh scattering and Brillouin scattering measurement technology using an Add-Drop filter as a narrow-band optical filter. Background Art

[0002] When the laser is incident on the water, it will generate Mie scattering with the suspended particles in the water, Rayleigh scattering with the water molecules, and Brillouin scattering by the interaction with the phonons in the water. Mie scattering and Rayleigh scattering are elastic scattering. The spectral width of Mie scattering of particles in water is basically the same as the line width of the incident laser; the spectral width of Rayleigh scattering of water molecules is about 1GHz. Brillouin scattering in water consists of two parts: Stokes Brillouin scattering and anti-Stokes Brillouin scattering. In the temperature range of 0~40℃ and salinity of 35‰ (seawater salinity), Stokes Brillouin scattering and anti-Stokes Brillouin scattering are approximately located on both sides of the excitation wavelength in the range of ±6.5GHz~±8.5GHz, and the spectral width is approximately in the range of 0.4GHz~2GHz.

[0003] According to the spectral characteristics of the three scatterings, a laser with a line width smaller than the Rayleigh scattering spectrum width is used as the light source, and a narrow-band optical filter can be used to separate the Mie scattering, Rayleigh scattering and Brillouin scattering of water bodies in the spectrum. In the measurement technology of Mie scattering, Rayleigh scattering and Brillouin scattering of water bodies, the narrow-band optical filters currently used include Fabry-Pérot interferometers, molecular (atomic) filters, etc.

[0004] The Add-Drop filter consists of three parts: Bus waveguide, Dropping waveguide, and coupling unit between Bus waveguide and Dropping waveguide. Light is input from the input port of Bus waveguide, and most of the light is output from the output port of Bus waveguide with almost no attenuation. When the wavelength of light meets the resonance wavelength of the coupling unit, the light of this wavelength is coupled from Bus waveguide to Dropping waveguide and output from the forward or backward port of Dropping waveguide. Therefore, the output of Bus waveguide is equivalent to optical band-stop filter, and the output of Dropping waveguide is equivalent to optical bandpass filter.

[0005] Add-Drop filters are currently mainly used in optical communications, biosensors and other fields. Summary of the invention

[0006] The purpose of the present invention is to provide a water body Mie scattering, Rayleigh scattering and Brillouin scattering measurement technology based on Add-Drop type filter, wherein the Add-Drop type filter is used as a narrow-band optical filter.

[0007] The invention comprises a narrow line width laser, a laser frequency stabilization system, an optical transmitting system, an optical receiving system, a cascaded Add-Drop filter, a multi-channel photoelectric detection system, and a data acquisition and processing system.

[0008] The cascaded Add-Drop filters are divided into three groups, corresponding to Mie scattering and Rayleigh scattering of water, Stokes Brillouin scattering of water, and anti-Stokes Brillouin scattering of water.

[0009] The output wavelength of the narrow linewidth laser is locked by a laser frequency stabilization system, and the locked wavelength is selected from the group of Add-Drop filters corresponding to Mie scattering and Rayleigh scattering of water bodies, and the peak wavelength of the optical bandpass filter of the Add-Drop filter located in the middle of the spectral characteristics of the group.

[0010] The stabilized laser is emitted into the water body through the optical transmitting system, and the water body echo is received by the optical receiving system and coupled into the cascaded Add-Drop filter. The output of the cascaded Add-Drop filter is converted into an electrical signal by a multi-channel photoelectric detection system and imported into the data acquisition and processing system.

[0011] The Mie scattering and Rayleigh scattering, Stokes Brillouin scattering and anti-Stokes Brillouin scattering models of water bodies are all accurately known. By filtering out the corresponding signals using three sets of cascaded Add-Drop filters, the parameters of Mie scattering in water, Rayleigh scattering in water, and Brillouin scattering in water can be calculated.

[0012] The line width of the narrow line width laser is smaller than the spectral width of the Add-Drop filter. The free spectral range of the Add-Drop filter is larger than the spectral interval between Stokes Brillouin scattering and anti-Stokes Brillouin scattering of water. The spectral interval between two adjacent Add-Drop filters in each group of cascaded Add-Drop filters is smaller than the spectral width of the Rayleigh scattering of water and the spectral width of the Brillouin scattering of water. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention.

[0014] Figure 1, the Add-Drop filter structure diagram of the present invention Figure 2 , the Add-Drop filter spectrum characteristic diagram of the present invention Figure 3 , the structure diagram of the water Mie scattering, Rayleigh scattering and Brillouin scattering measurement system based on Add-Drop filter of the present invention Figure 4 The cascaded Add-Drop filter spectrum of the present invention and the Mie scattering, Rayleigh scattering and Brillouin scattering spectra of water Figure 5 The Mie scattering, Rayleigh scattering and Brillouin scattering spectra of water filtered out by the Add-Drop filter of the present invention are as follows: In the figure: 1. Bus waveguide of Add-Drop filter, 2. Dropping waveguide of Add-Drop filter, 3. Coupling unit of Add-Drop filter, 4. Bus waveguide input port of Add-Drop filter, 5. Bus waveguide output port of Add-Drop filter, 6. Dropping waveguide backward output port of Add-Drop filter, 7. Dropping waveguide forward output port of Add-Drop filter, 8. Bandpass spectrum output from Dropping waveguide backward or forward output port of Add-Drop filter, 9. Bandstop spectrum output from Bus waveguide output port of Add-Drop filter, 10. Spectral width (full width at half maximum) of Add-Drop filter, 11. Free spectral range of Add-Drop filter, 12. Narrow linewidth laser, 13. Laser frequency stabilization system, 14. Optical transmitting system, 15. Optical receiving system, 16. Cascaded Add-Drop filter, 17. Multi-channel photoelectric detection system, 18. Data acquisition and processing system, 19. Bandpass spectrum of cascaded Add-Drop filter, 20. Laser wavelength locking point, 21. Mie scattering in water, 22. Rayleigh scattering in water, 23. Stokes Brillouin scattering in water, 24. Anti-Stokes Brillouin scattering in water, 25. Spectral interval between two adjacent Add-Drop filters in each set of cascaded Add-Drop filters, 26. λ L 1. The filtered Mie scattering and Rayleigh scattering signals in water, 27. The filtered Rayleigh scattering signals in water, 28. The filtered Stokes Brillouin scattering signals in water, 29. The filtered anti-Stokes Brillouin scattering signals in water. DETAILED DESCRIPTION

[0015] The purpose of the present invention is to provide a water body Mie scattering, Rayleigh scattering and Brillouin scattering measurement technology and implementation method based on Add-Drop filter to solve the technical problems in the relevant fields. In order to make the technical problems and technical solutions to be solved by the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0016] The Add-Drop filter structure of the present invention is shown in FIG. Figure 1 As shown, the Add-Drop filter spectral characteristics are as follows Figure 2 shown.

[0017] The Add-Drop filter consists of three parts: a Bus waveguide (1), a Dropping waveguide (2), and a coupling unit (3) between the Bus waveguide and the Dropping waveguide. Light is input from the input port (4) of the Bus waveguide, and most of the light is output from the output port (5) of the Bus waveguide with almost no attenuation. When the wavelength of light meets the resonance wavelength of the coupling unit (3), the light of this wavelength is coupled from the Bus waveguide (1) to the Dropping waveguide (2) and output from the backward output port (5) or the forward output port (6) of the Dropping waveguide. Therefore, the backward output port (5) or the forward output port (6) of the Dropping waveguide is equivalent to an optical bandpass filter, and the corresponding spectral characteristic is (8); the output port (4) of the Bus waveguide is equivalent to an optical bandstop filter, and the corresponding spectral characteristic is (9). The spectral width of the Add-Drop filter corresponding to (8) and (9) is (10), and the free spectral range of the corresponding Add-Drop filter is (11).

[0018] The structure diagram of the water Mie scattering, Rayleigh scattering and Brillouin scattering measurement system based on Add-Drop filter of the present invention is as follows: Figure 3 shown.

[0019] A narrow linewidth laser (12) is used as a light source, and a laser frequency stabilization (13) system is used to lock the laser wavelength. The frequency-locked laser enters the measured water body through an optical transmitting system (14). The laser echo of the water body is received by an optical receiving system (15) and introduced into a cascaded Add-Drop filter optical discriminator (16). The output of the cascaded Add-Drop filter (16) is detected by a multi-channel photoelectric detection system (17) and introduced into a data acquisition and processing system (18).

[0020] The spectrum of the cascaded Add-Drop filter of the present invention and the spectrum of Mie scattering, Rayleigh scattering and Brillouin scattering of water are as follows: Figure 4 shown.

[0021] The cascaded Add-Drop filters are divided into three groups: corresponding to Mie scattering (21) and Rayleigh scattering (22) in water, with wavelength λ L centered; Stokes Brillouin scattering of water (23), with wavelength λ N centered; water anti-Stokes Brillouin scattering (24), with wavelength λ M λ is the center. N and λ M Located at λ L About 7.5GHz on both sides.

[0022] The cascaded Add-Drop filter connects the Bus waveguide output port (5) of the previous Add-Drop filter to the Bus waveguide input port (4) of the next Add-Drop filter, and the backward port (6) or forward port (7) of the Dropping waveguide is used as the output of this stage.

[0023] The laser wavelength is locked to Figure 4 (20) in the figure corresponds to the wavelength λ L Add-Drop filter. The central wavelength of Mie scattering (21) and Rayleigh scattering (22) in water is also λ L The present invention requires that the line width of the narrow line width laser (12) is smaller than the spectral width (10) based on the Add-Drop filter, and the free spectral range (11) of the Add-Drop filter is larger than the wavelength interval between the Stokes Brillouin scattering (23) and the anti-Stokes Brillouin scattering (24) of the water body. The spectral interval (25) between two adjacent Add-Drop filters in each group of cascaded Add-Drop filters is smaller than the spectral width of the Rayleigh scattering of the water body and the spectral width of the Brillouin scattering of the water body.

[0024] Figure 4 Medium wavelength λ L The Add-Drop filter can filter out Mie scattering and part of Rayleigh scattering (26); wavelength λ L-2 , L-1 , L+1 , L+2 The corresponding Add-Drop filter can filter out part of the Rayleigh scattering (27); wavelength λ N-2 , N-1 , N , N+1 , N+2 The corresponding Add-Drop filter can filter out part of the Stokes Brillouin scattering (28); wavelength λ M-2 , M-1, M , M+1 , M+2 The corresponding Add-Drop filter can filter out part of the anti-Stokes Brillouin scattering (29).

[0025] Because the bandpass spectrum characteristics (8) of the Add-Drop filter are accurately known, and the Mie scattering and Rayleigh scattering models in water, Stokes Brillouin scattering and anti-Stokes Brillouin scattering models in water are also accurately known, the comprehensive Figure 5 The signal intensities of (26), (27), (28) and (29) can be used to calculate the parameters of Mie scattering in water, Rayleigh scattering in water and Brillouin scattering in water.

[0026] In conclusion, Figure 3 The water Mie scattering, Rayleigh scattering and Brillouin scattering measurement technology based on Add-Drop filter can directly measure the elastic scattering and Brillouin scattering of water and obtain the corresponding high-precision parameters.

[0027] It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Those skilled in the art should take the specification as a whole, and the technical solutions in the various embodiments can also be appropriately combined to form other implementations that can be understood by those skilled in the art.

Claims

1. A water Mie scattering, Rayleigh scattering and Brillouin scattering measurement technology based on Add-Drop filter, characterized by: It consists of a narrow linewidth laser, a laser frequency stabilization system, an optical transmitting system, an optical receiving system, a cascaded Add-Drop filter, a multi-channel photoelectric detection system, and a data acquisition and processing system. The cascaded Add-Drop filter is divided into three groups, corresponding to Mie scattering and Rayleigh scattering of water, Stokes Brillouin scattering of water, and anti-Stokes Brillouin scattering of water. The output wavelength of the narrow linewidth laser is locked by a laser frequency stabilization system. The locked wavelength is selected from the peak wavelength of the optical bandpass filter of the Add-Drop filter group corresponding to the Mie scattering and Rayleigh scattering of the water body and located in the middle of the spectral characteristics of the Add-Drop filter in the group. The stabilized frequency laser is emitted into the measured water body through the optical transmitting system, and the water body echo is received by the optical receiving system and coupled into the cascaded Add-Drop filter; the output of the cascaded Add-Drop filter is converted into an electrical signal by the multi-channel photoelectric detection system and imported into the data acquisition and processing system; The Mie scattering and Rayleigh scattering, Stokes Brillouin scattering and anti-Stokes Brillouin scattering models of water bodies are all accurately known. Using the corresponding signals filtered out by three sets of cascaded Add-Drop filters, the parameters of Mie scattering in water, Rayleigh scattering in water, and Brillouin scattering in water can be calculated.

2. The water Mie scattering, Rayleigh scattering and Brillouin scattering measurement technology based on Add-Drop filter as claimed in claim 1, characterized in that: The linewidth of a narrow-linewidth laser is smaller than the spectral width of an Add-Drop filter.

3. The water Mie scattering, Rayleigh scattering and Brillouin scattering measurement technology based on Add-Drop filter as claimed in claim 1, characterized in that: The free spectral range of the Add-Drop filter is larger than the spectral interval between Stokes Brillouin scattering and anti-Stokes Brillouin scattering of water.

4. The water Mie scattering, Rayleigh scattering and Brillouin scattering measurement technology based on Add-Drop filter as claimed in claim 1, characterized in that: The spectral interval between two adjacent Add-Drop filters in each group of cascaded Add-Drop filters is smaller than the spectral width of the Rayleigh scattering of water and the spectral width of the Brillouin scattering of water.

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