CN111537485A - In-situ water quality fluorescence monitoring system based on all-fiber and application thereof - Google Patents
In-situ water quality fluorescence monitoring system based on all-fiber and application thereof Download PDFInfo
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 41
- 239000000835 fiber Substances 0.000 title claims abstract description 39
- 238000012544 monitoring process Methods 0.000 title claims abstract description 38
- 238000011065 in-situ storage Methods 0.000 title claims abstract description 27
- 239000013307 optical fiber Substances 0.000 claims abstract description 96
- 230000003287 optical effect Effects 0.000 claims abstract description 49
- 238000012360 testing method Methods 0.000 claims abstract description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 31
- 229910052760 oxygen Inorganic materials 0.000 claims description 31
- 239000001301 oxygen Substances 0.000 claims description 31
- 230000005284 excitation Effects 0.000 claims description 23
- 229930002868 chlorophyll a Natural products 0.000 claims description 12
- ATNHDLDRLWWWCB-AENOIHSZSA-M chlorophyll a Chemical compound C1([C@@H](C(=O)OC)C(=O)C2=C3C)=C2N2C3=CC(C(CC)=C3C)=[N+]4C3=CC3=C(C=C)C(C)=C5N3[Mg-2]42[N+]2=C1[C@@H](CCC(=O)OC\C=C(/C)CCC[C@H](C)CCC[C@H](C)CCCC(C)C)[C@H](C)C2=C5 ATNHDLDRLWWWCB-AENOIHSZSA-M 0.000 claims description 12
- 230000010363 phase shift Effects 0.000 claims description 12
- 238000010791 quenching Methods 0.000 claims description 6
- 238000012545 processing Methods 0.000 claims description 5
- 238000011896 sensitive detection Methods 0.000 claims description 5
- 238000004364 calculation method Methods 0.000 claims description 4
- 230000000171 quenching effect Effects 0.000 claims description 4
- 238000012921 fluorescence analysis Methods 0.000 claims description 3
- 239000000126 substance Substances 0.000 claims description 3
- 238000005259 measurement Methods 0.000 abstract description 2
- 238000002834 transmittance Methods 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 3
- 230000008054 signal transmission Effects 0.000 description 3
- 238000013461 design Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000002795 fluorescence method Methods 0.000 description 1
- 230000036284 oxygen consumption Effects 0.000 description 1
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- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/6428—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes"
- G01N21/643—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" non-biological material
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- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N2021/6417—Spectrofluorimetric devices
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- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/6428—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes"
- G01N2021/6432—Quenching
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Abstract
The invention provides an in-situ water quality fluorescence monitoring system based on all-fiber and application thereof, wherein the system comprises an LED light source, a first straight-through optical fiber, a first optical filter, a first branch end of a first Y-shaped optical fiber, a second straight-through optical fiber, a sample cell, a third straight-through optical fiber, a second optical filter, a first branch end of a second Y-shaped optical fiber and a photocell which are sequentially connected from front to back; the second furcation end of the first Y-shaped optical fiber and the second furcation end of the second Y-shaped optical fiber are connected by a first flange adapter. The invention has high measurement precision, is not influenced by ambient light, has high test speed and does not generate secondary pollution.
Description
Technical Field
The invention relates to the technical field of water quality fluorescence monitoring, in particular to an in-situ water quality fluorescence monitoring system based on all-fiber and application thereof.
Background
Water is the source of life and the root of all things. Through modern optical science and technology means, the fluorescence method monitoring of the relevant parameters of the water quality is a novel water quality monitoring technology, and has the advantages of no need of pretreatment, no need of chemical reagents, no oxygen consumption, high response speed, high precision, realization of in-situ real-time monitoring and the like.
At present, most of existing in-situ water quality fluorescence monitoring systems are developed based on a single-wavelength light source without reference light or based on two double light sources with unequal wavelengths of the reference light source and the monitoring light source, the light source is spread in a natural environment and is easily disturbed by the natural environment to the light source, the single light source cannot eliminate the influence of light source attenuation or the light attenuation caused by the inconsistent wavelengths of the double light sources is different, the light path is not equal and related, and the influence of photoelectric signal transmission instability caused by the external environment causes the problems of signal instability, influence on subsequent signal processing precision and the like, so that the fluctuation error of signals far exceeds the standard and cannot meet the monitoring requirement.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the art described above. Therefore, one objective of the present invention is to provide an in-situ water quality fluorescence monitoring system using all optical fibers.
The second purpose of the invention is to provide an application of the in-situ water quality fluorescence monitoring system based on the all-optical fiber.
In order to achieve the above object, an embodiment of a first aspect of the present invention provides an in-situ water quality fluorescence monitoring system based on all-fiber, including an LED light source, a first through fiber, a first optical filter, a first branch end of a first Y-shaped fiber, a second through fiber, a sample cell, a third through fiber, a second optical filter, a first branch end of a second Y-shaped fiber, and a photocell, which are connected in sequence from front to back; the second furcation end of the first Y-shaped optical fiber and the second furcation end of the second Y-shaped optical fiber are connected by a first flange adapter.
Based on the design, the reference light source and the excitation light source can be transmitted in a closed loop in the optical fiber, and the influence on the transmission of light in the natural environment is avoided.
In addition, the in-situ water quality fluorescence monitoring system based on the all-fiber provided by the embodiment of the invention can also have the following additional technical characteristics:
the first branch end of the first Y-shaped optical fiber is connected with the second straight-through optical fiber through a second flange adapter;
the distance between the first branch end of the first Y-shaped optical fiber and the second flange adapter is L3；
The distance between the second forked end of the first Y-shaped optical fiber and the first flange adapter is L4；
The length of the second straight-through optical fiber is L5；
The distance between the second forked end of the second Y-shaped optical fiber and the first flange adapter is L8；
The distance from the second Y-shaped optical fiber to the photocell is L9；
Said L3+L5＝L4+L8+L9。
The central wavelength of the first optical filter is equal to that of the LED light source, and the central thickness of the first optical filter is 2 mm.
The central wavelength of the second optical filter is equal to the central wavelength of the fluorescence signal emitted by the sample cell, and the central thickness of the second optical filter is 2 mm.
And an oxygen sensing film is attached to the surface of the sample cell.
In order to achieve the above object, a second aspect of the present invention provides an application of the in-situ water quality fluorescence monitoring system based on all-fiber, wherein during testing, an LED light source emits light, and the light is transmitted to a first Y-shaped fiber through a first straight-through fiber and a first optical filter in sequence, and then is divided into two light sources, wherein one light source is used as a reference light source and is transmitted to a photocell through a second Y-shaped fiber; the other light source is used as an excitation light source and is transmitted to the sample cell through the second straight-through optical fiber, a corresponding substance in the sample cell is irradiated by the excitation light source to generate a fluorescence signal with a specific wavelength, the fluorescence signal is transmitted to the photocell from the sample cell through the third straight-through optical fiber, the second optical filter and the second Y-shaped optical fiber in sequence, the reference light source and the fluorescence signal are transmitted to the photocell in sequence, the photocell converts the light signal into an electric signal and transmits the electric signal to the upper computer for signal processing operation, and the concentration value of the water quality parameter is obtained according to the corresponding fluorescence theory; the specific calculation method is as follows:
(1) calculating the value (such as the value of light intensity or the value of phase shift) of the parameter change when the reference light source is transmitted to the photocell through the LED light source, the first straight-through optical fiber, the first optical filter, the first Y-shaped optical fiber and the second Y-shaped optical fiber;
(2) calculating the value of parameter change (such as the attenuation value of light intensity or the value of phase shift) when an excitation light source is transmitted to the photocell through the LED light source, the first straight-through optical fiber, the first optical filter, the first Y-shaped optical fiber, the second straight-through optical fiber, the sample cell, the third straight-through optical fiber, the second optical filter and the second Y-shaped optical fiber;
(3) and (3) converting the value of the water quality parameter by the parameter change value obtained in the steps (1) to (2).
Based on the design, the single LED light source is adopted, the LED light source is divided into two parts through the Y-shaped optical fiber, the two parts are divided into two beams of light with the same state, the reference light source and the excitation light source can be transmitted in the optical fiber in a closed loop mode and are not influenced by ambient light, the reference light path is provided, the light source attenuation can be eliminated, the stability of photoelectric signal transmission caused by the outside world can be improved, the measurement precision is high, the test speed is high, and secondary pollution cannot be generated.
In addition, the application of the all-fiber-based in-situ water quality fluorescence monitoring system provided by the above embodiment of the invention may further have the following additional technical features:
when the concentration of dissolved oxygen in water is monitored, an oxygen sensing film is attached to the surface of the sample pool, the oxygen sensing film can generate a fluorescent signal when an LED light source is excited, and oxygen can quench the excited fluorescent signal on the oxygen sensing film.
When the concentration of the dissolved oxygen in the water is monitored, the range of the phase shift difference between the excitation light source and the reference light source is as follows:
(J)
wherein, delta phi is the phase shift difference between the excitation light source and the reference light source;
λ is the central wavelength of the fluorescence signal, nm (nanometers);
n is the refractive index of the optical fiber and is dimensionless;
L6is the length of the third straight-through fiber, mm (millimeters);
L7is the distance, mm (millimeters), between the second Y-shaped optical fiber and the second optical filter;
L9is the distance, mm (millimeters), between the second Y-shaped optical fiber and the photovoltaic cell;
2πfτ0is modulated by modulated light with frequency f to obtain maximum fluorescence lifetime0Phase lag, radian, in the appearance of the fluorescence signal;
τ0maximum fluorescence lifetime in the absence of oxygen, ns (nanoseconds);
f is the modulation light modulation frequency, kHz (kilohertz);
according to the formula (J), the fluorescence quenching principle and the phase-sensitive detection principle, the concentration of the dissolved oxygen in the water can be obtained.
When in-situ chlorophyll a is monitored, the chlorophyll a exists in the sample pool, and a fluorescence signal is generated under the irradiation of an excitation light source;
(4) the light of the reference light source is emitted to the photocell to be received through the LED light source, and the light intensity I received by the photocellin；
(5) The light of the excitation light source is emitted to the photocell to be received through the LED light source, and the light intensity I received by the photocellout；
(6) According to the principle of fluorescence analysis, the concentration of chlorophyll a and Iin、IoutThe relationship of the values of (A) can be represented as Iout＝k0cIinSubstituting into I obtained in steps (4) and (5)in、IoutThe concentration of chlorophyll a can be solved as follows: c is ═ Iout/k0Iin(ii) a Wherein k is0Is a constant of the monitoring system.
Drawings
FIG. 1 is a schematic structural diagram of an in-situ water quality fluorescence monitoring system according to the present invention.
Detailed Description
In order to better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
Referring to fig. 1, an in-situ water quality fluorescence monitoring system based on all-fiber comprises an LED light source 1, a first straight-through fiber 2, a first optical filter 3, a first branch end 41 of a first Y-shaped fiber 4, a second straight-through fiber 5, a sample cell 6, a third straight-through fiber 7, a second optical filter 8, a first branch end 91 of a second Y-shaped fiber 9, and a photocell 10, which are connected in sequence from front to back; the second furcation end 42 of the first Y-fiber 4 and the second furcation end 92 of the second Y-fiber 9 are connected by a first flange adapter 11.
Wherein the refractive index of all the fibers is the same.
The first furcation end 41 of the first Y-fiber 4 is connected to the second pass-through fiber 5 via a second flange adapter 12;
the first straight-through optical fiber 2 has a length L1；
The distance between the first optical filter 3 and the first Y-shaped optical fiber 4 is L2
The distance between the first furcation end 41 of the first Y-shaped optical fiber 4 and the second flange adapter 12 is L3；
The second furcation end 42 of the first Y-shaped optical fiber 4 is spaced from the first flange adapter 11 by a distance L4；
The second through optical fiber 5 has a length L5；
The third straight-through optical fibre 7 has a length L6；
The distance between the second Y-shaped optical fiber 9 and the second optical filter 8 is L7；
The second furcation end 92 of the second Y-shaped optical fiber 9 is spaced from the first flange adapter 11 by a distance L8；
The distance between the second Y-shaped optical fiber 9 and the photocell 10 is L9；
And the light path interval satisfies: l is3+L5＝L4+L8+L9。
The central wavelength of the first optical filter 3 is equal to the central wavelength of the LED light source 1, and the central thickness of the first optical filter 3 is 2 mm. The central wavelength of the second optical filter 8 is equal to the central wavelength of the fluorescence signal emitted by the sample cell 6, and the central thickness of the second optical filter 8 is 2 mm.
Example 1
Referring to fig. 1 again, an in-situ dissolved oxygen monitoring system based on all-fiber transmits a test instruction through an upper computer, so that an LED light source 1 emits light, the light emitted by the LED light source 1 is a green LED light source, and a central wavelength λ is 530+/-5 nm; the light is transmitted to a first Y-shaped optical fiber 4 through a first straight-through optical fiber 2 and a first optical filter 3 in sequence (the central wavelength of the first optical filter 3 is consistent with the center of an LED light source 1, namely lambda is 530+/-5nm, and the transmittance OD is more than 4) and then is divided into two light sources in the same state, and one light source is used as a reference light source and is transmitted to a photocell 10 through a second Y-shaped optical fiber 9; the other path of light source is used as an excitation light source and is transmitted to the sample cell 6 through the second straight optical fiber 5, so that a corresponding substance in the oxygen-sensitive film on the surface of the sample cell is irradiated by the excitation light source to generate a fluorescent signal with a specific wavelength, a layer of oxygen sensing film is attached to the surface of the sample cell, and the oxygen sensing film has the characteristics that when the oxygen sensing film is excited by the LED light source 1 with the central wavelength lambda being 530+/-5nm, a red fluorescent signal can be generated (the central wavelength lambda being 650+/-5nm), and the oxygen can be quenched by the fluorescent signal excited on the oxygen sensing film. The fluorescence signal is transmitted to a second Y-shaped optical fiber 9 through a third straight-through optical fiber 7 and a second optical filter 8 (the central wavelength of the second optical filter 8 is consistent with the fluorescence signal, namely, lambda is 650+/-5nm, and the transmittance OD is more than 4) in sequence from the sample cell 6, the fluorescence is transmitted to a photocell 10 through the second Y-shaped optical fiber 9, a reference light source and the fluorescence signal are sequentially transmitted to the photocell 10, the photocell 10 converts the optical signal into an electrical signal in sequence and transmits the electrical signal to an upper computer for corresponding signal processing operation, and the specific calculation method is as follows:
A. at a central wavelength of λ0Light of nm passing through a segment of refractive index n0Distance, distanceIs L0The phase shift generated by passing through the optical fiber is:
B. under the condition of no oxygen, the maximum fluorescence lifetime is tau0ns is obtained by analyzing the phase-sensitive detection theory, and the relation between the phase lag and the fluorescence lifetime is as follows:
tan(φ0)＝2πfτ0……(2)；
C. formula (1) is recycled, light in the reference light path is emitted to photocell 10 through green LED light source 1 and received, and the generated phase shift is as follows:
D. formula (1) is recycled, and the light of monitoring light path is emergent to photocell 10 and is received through green glow LED light source 1, and the phase place that produces moves and is:
E. and obtaining the phase shift difference between the monitoring optical path and the reference optical path as follows: Δ φ ═ phi (φ)Monitoring-φ)-φReference toSubstituting the values into phi obtained in the above formulas (2) to (4)Monitoring、φReference toThe range of phase shift difference obtained by the values of φ is:
wherein, in the above formulas (2) to (5),
λ530the center wavelength of the LED light source 1, nm (nanometers);
λ650the central wavelength of the fluorescence signal, nm (nanometers);
delta phi is the phase shift difference and radian of the excitation light source and the reference light source;
n is the refractive index of the optical fiber and is dimensionless;
L6the length of the third straight-through optical fiber 7, mm (millimeters);
L7is the distance, mm (millimeters), between the second Y-shaped optical fiber 9 and the second optical filter 8;
L9is the distance, in mm (millimeters), between the second Y-shaped optical fiber 9 and the photovoltaic cell 10;
2πfτ0is modulated by modulated light with frequency f to obtain maximum fluorescence lifetime0Phase lag, radian, in the appearance of the fluorescence signal;
τ0maximum fluorescence lifetime in the absence of oxygen, ns (nanoseconds);
f is the modulation light modulation frequency, kHz (kilohertz);
F. according to the phase difference obtained by the formula (5), the concentration of the dissolved oxygen in the water can be obtained according to the fluorescence quenching principle and the phase-sensitive detection principle, and the method comprises the following specific steps:
according to the phase-sensitive detection principle, the phase difference and fluorescence life relationship is as follows: tan (Δ Φ) ═ 2 pi f τ … … (6);
according to the principle of fluorescence quenching and according to the Stern-Volmer equation:
from the equations (2), (6) and (7), the dissolved oxygen concentration in water can be derived as follows:
wherein, in the above formulas (6) to (8),
k is the concentration coefficient of dissolved oxygen in water and is dimensionless;
delta phi is the phase shift difference and radian of the excitation light source and the reference light source;
pi is the circumference ratio and is dimensionless;
τ0maximum fluorescence lifetime in the absence of oxygen, ns (nanoseconds);
f is the modulation light modulation frequency, kHz (kilohertz);
example 2
Referring to fig. 1 again, an in-situ chlorophyll a monitoring method based on all-fiber is characterized in that an upper computer sends a test instruction to enable an LED light source 1 to emit light, the light emitted by the LED light source 1 is a blue LED light source, and the central wavelength λ is 460+/-5nm, the light is transmitted to a first Y-type optical fiber 4 through a first straight-through optical fiber 2 and a first optical filter 3 (the central wavelength of the first optical filter 3 is consistent with that of the LED light source 1, i.e., λ is 460+/-5nm, and the transmittance OD is greater than 4) in sequence, and then is divided into two light sources in the same state, one light source is used as a reference light source and transmitted to a photocell 10 through a second Y-type optical fiber 9, the other light source is used as an excitation light source and transmitted to a sample cell 6 through a second straight-through optical fiber 5, so that chlorophyll a in the sample cell is irradiated by the excitation light source to generate a fluorescence signal with a specific wavelength, and the fluorescence signal passes through the sample cell 6 through a third The wavelength is consistent with the fluorescence signal, that is, λ is 680+/-5nm, and the cutoff transmittance OD is greater than 4) is transmitted to the second Y-shaped optical fiber 9, the fluorescence is transmitted to the photocell 10 through the second Y-shaped optical fiber 9, the reference light source and the fluorescence signal are sequentially transmitted to the photocell 10, the photocell 10 converts the optical signal into an electrical signal in sequence, and transmits the electrical signal to the upper computer for corresponding signal processing operation, and according to a corresponding fluorescence theory, the concentration value of the required water quality parameter can be obtained, and the specific calculation method is as follows:
G. the light on the reference light path is emitted to the photocell 10 through the blue LED light source 1 and received by the photocell 10, and the light intensity I received by the photocell 10in；
H. The light on the monitoring light path is emitted to the photocell 10 through the blue LED light source 1 to be received, and the light intensity I received by the photocell 10out；
I. According to the principle of fluorescence analysis, the concentration of chlorophyll a and Iin、IoutHas a value of Iout＝k0cIinSubstituted into I obtained in step G, Hin、IoutThe concentration of chlorophyll a can be calculated as follows: c is ═ Iout/k0Iin。
Wherein k is0Is a constant of the monitoring system.
The water quality fluorescence monitoring system adopts a single LED light source, divides the LED light source into two parts through the Y-shaped optical fiber, divides the two parts into two beams of light with the same state, enables the reference light source and the excitation light source to be capable of closed-loop transmission in the optical fiber, avoids the influence of the light in the transmission of the natural environment, and has the reference light path capable of eliminating the light source attenuation and improving the stability of photoelectric signal transmission caused by the outside. The invention considers the equal optical path and combines the influence of the relation between the optical speed and the optical wavelength, thereby improving the stability of the monitored data (such as intensity and phase) and improving the monitoring accuracy and precision.
Claims (9)
1. An in-situ water quality fluorescence monitoring system based on all-fiber is characterized in that: the device comprises an LED light source (1), a first straight-through optical fiber (2), a first optical filter (3), a first branch end (41) of a first Y-shaped optical fiber (4), a second straight-through optical fiber (5), a sample cell (6), a third straight-through optical fiber (7), a second optical filter (8), a first branch end (91) of a second Y-shaped optical fiber (9) and a photocell (10) which are sequentially connected from front to back; the second bifurcated end (42) of the first Y-shaped optical fiber (4) and the second bifurcated end (92) of the second Y-shaped optical fiber (9) are connected through a first flange adapter (11).
2. The all-fiber based in-situ water quality fluorescence monitoring system of claim 1, wherein: the first branch end (41) of the first Y-shaped optical fiber (4) is connected with the second straight-through optical fiber (5) through a second flange adapter (12);
the distance between the first branch end (41) of the first Y-shaped optical fiber (4) and the second flange adapter (12) is L3；
The distance between the second forked end (42) of the first Y-shaped optical fiber (4) and the first flange adapter (11) is L4；
The length of the second straight-through optical fiber (5) is L5；
The distance between the second forked end (92) of the second Y-shaped optical fiber (9) and the first flange adapter (11) is L8；
The distance from the second Y-shaped optical fiber (9) to the photocell (10) is L9；
Said L3+L5＝L4+L8+L9。
3. The all-fiber based in-situ water quality fluorescence monitoring system of claim 1, wherein: the central wavelength of the first optical filter (3) is equal to that of the LED light source (1), and the central thickness of the first optical filter (3) is 2 mm.
4. The all-fiber based in-situ water quality fluorescence monitoring system of claim 1, wherein: the central wavelength of the second optical filter (8) is equal to the central wavelength of the fluorescence signal emitted by the sample cell (6), and the central thickness of the second optical filter (8) is 2 mm.
5. The all-fiber based in-situ water quality fluorescence monitoring system of claim 1, wherein: and an oxygen sensing film is attached to the surface of the sample cell (6).
6. Use of an all-fiber based in-situ water quality fluorescence monitoring system according to claims 1-5, wherein:
when in test, the LED light source (1) emits light, the light is transmitted to the first Y-shaped optical fiber (4) through the first straight-through optical fiber (2) and the first optical filter (3) in sequence and then is divided into two light sources, wherein one light source is used as a reference light source and is transmitted to the photocell (10) through the second Y-shaped optical fiber (9); the other light source is used as an excitation light source and is transmitted to the sample cell (6) through the second straight-through optical fiber (5), corresponding substances in the sample cell (6) are irradiated by the excitation light source to generate fluorescence signals with specific wavelengths, the fluorescence signals are transmitted to the photocell (10) through the third straight-through optical fiber (7), the second optical filter (8) and the second Y-shaped optical fiber (9) in sequence from the sample cell (6), the reference light source and the fluorescence signals are transmitted to the photocell (10) in sequence, the photocell (10) converts the light signals into electric signals and transmits the electric signals to the upper computer for signal processing operation, and the concentration value of the water quality parameter is obtained according to the corresponding fluorescence theory; the specific calculation method is as follows:
(1) calculating the value of parameter change when the reference light source is transmitted to the photocell (10) through the LED light source (1), the first straight-through optical fiber (2), the first optical filter (3), the first Y-shaped optical fiber (4) and the second Y-shaped optical fiber (9);
(2) solving the numerical value of parameter change when an excitation light source is transmitted to a photocell (10) through an LED light source (1), a first straight-through optical fiber (2), a first optical filter (3), a first Y-shaped optical fiber (4), a second straight-through optical fiber (5), a sample cell (6), a third straight-through optical fiber (7), a second optical filter (8) and a second Y-shaped optical fiber (9);
(3) and (3) converting the value of the water quality parameter by the parameter change value obtained in the steps (1) to (2).
7. The use of the all-fiber based in-situ water quality fluorescence monitoring system of claim 6, wherein: when the concentration of dissolved oxygen in water is monitored, an oxygen sensing film is attached to the surface of the sample cell (6), the oxygen sensing film can generate a fluorescent signal when the LED light source (1) is excited, and the oxygen can quench the excited fluorescent signal on the oxygen sensing film.
8. The use of the all-fiber based in-situ water quality fluorescence monitoring system of claim 7, wherein: when the concentration of the dissolved oxygen in the water is monitored, the range of the phase shift difference between the excitation light source and the reference light source is as follows:
(J)
to
Wherein, delta phi is the phase shift difference between the excitation light source and the reference light source;
λ is the central wavelength of the fluorescence signal, nm;
n is the refractive index of the optical fiber;
L6is the length of the third straight-through optical fiber (7), mm;
L7the distance between the second Y-shaped optical fiber (9) and the second optical filter (8) is mm;
L9is the distance, mm, between the second Y-shaped optical fiber (9) and the photocell (10);
2πfτ0is modulated by modulated light with frequency f to obtain maximum fluorescence lifetime0Phase lag, radian, in the appearance of the fluorescence signal;
τ0maximum fluorescence lifetime, ns, in the absence of oxygen;
f is modulation light modulation frequency, kHz;
according to the formula (J), the fluorescence quenching principle and the phase-sensitive detection principle, the concentration of the dissolved oxygen in the water can be obtained.
9. The use of the all-fiber based in-situ water quality fluorescence monitoring system of claim 6, wherein: when in-situ chlorophyll a is monitored, the sample pool (6) contains the chlorophyll a, and a fluorescence signal is generated by irradiation of an excitation light source;
(4) the light of the reference light source is emitted to the photocell (10) to be received through the LED light source (1), and the light intensity I received by the photocell (10) is obtainedin；
(5) The light of the excitation light source is emitted to the photocell (10) to be received through the LED light source (1), and the light intensity I received by the photocell (10)out；
(6) According to the principle of fluorescence analysis, the concentration of chlorophyll a and Iin、IoutThe relationship of the values of (A) can be represented as Iout＝k0cIinSubstituting into I obtained in steps (4) and (5)in、IoutThe concentration of chlorophyll a can be solved as follows: c is ═ Iout/k0Iin。
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| US6207961B1 (en) * | 1996-10-15 | 2001-03-27 | American Research Corporation Of Virginia | Loss compensation using digital-signal processing in fiber-optic fluorescence sensors |
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| US6207961B1 (en) * | 1996-10-15 | 2001-03-27 | American Research Corporation Of Virginia | Loss compensation using digital-signal processing in fiber-optic fluorescence sensors |
| CN101082584A (en) * | 2007-06-28 | 2007-12-05 | 大连海事大学 | Optical fiber biological sensor |
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