CN108254100B - Optical fiber sensing liquid refractive index and temperature simultaneous measurement system and measurement method - Google Patents
Optical fiber sensing liquid refractive index and temperature simultaneous measurement system and measurement method Download PDFInfo
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- 239000007788 liquid Substances 0.000 title claims abstract description 120
- 239000013307 optical fiber Substances 0.000 title claims abstract description 118
- 238000005259 measurement Methods 0.000 title claims abstract description 19
- 238000000691 measurement method Methods 0.000 title description 2
- 238000000034 method Methods 0.000 claims abstract description 23
- 238000001069 Raman spectroscopy Methods 0.000 claims description 56
- 230000003287 optical effect Effects 0.000 claims description 12
- 238000002310 reflectometry Methods 0.000 claims description 8
- 239000012153 distilled water Substances 0.000 claims description 5
- 238000001914 filtration Methods 0.000 claims description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- 238000005253 cladding Methods 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 238000001514 detection method Methods 0.000 abstract description 2
- 238000005452 bending Methods 0.000 description 2
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- 238000005516 engineering process Methods 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 238000012742 biochemical analysis Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
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- 238000003912 environmental pollution Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
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- 230000004048 modification Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35383—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using multiple sensor devices using multiplexing techniques
- G01D5/35387—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using multiple sensor devices using multiplexing techniques using wavelength division multiplexing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N21/4133—Refractometers, e.g. differential
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Abstract
A system and a method for simultaneously measuring the refractive index and the temperature of optical fiber sensing liquid belong to the field of optical fiber sensing detection. The device is used for solving the problem of simultaneous remote online measurement of the refractive index and the temperature of the liquid. The invention relates to a system and a method for simultaneously measuring the refractive index and the temperature of optical fiber sensing liquid, wherein the system comprises: the device comprises a light source (1), a wavelength division multiplexer (2), a photoelectric detector (3), a collection card (4), a computer (5), an optical fiber thermostatic bath (6), a sensing optical fiber (7) and a sensing head (8). The sensing head is made of only one sensing optical fiber and comprises a liquid refractive index sensing part and a liquid temperature sensing part, the sensing head has the characteristics of small volume, simplicity in manufacturing and electromagnetic interference resistance, and the limitation that in the prior art, the sensor is complex in manufacturing, short in measuring distance and incapable of measuring the liquid refractive index and the temperature at the same time is overcome. The invention is suitable for the field of the requirement of long-distance simultaneous online measurement of the refractive index and the temperature of the liquid.
Description
Technical Field
the invention relates to the field of optical fiber sensing detection, in particular to a system and a method for simultaneously measuring the refractive index and the temperature of optical fiber sensing liquid.
Background
The refractive index is one of the important physical parameters of the liquid medium, and has a great significance in various aspects of daily production and life, and in addition, many properties of the liquid medium can be reflected on the refractive index, such as liquid concentration, temperature, mixture components, pH value and the like. Therefore, the method has wide application in the fields of biochemical analysis, environmental pollution monitoring, medical food and the like for measuring the liquid refractive index. There are many methods for measuring refractive index, and the commonly used refractive index measuring instrument is abbe's measuring instrument, and this method needs to put the measured object into the instrument for measurement, and cannot meet the requirement of remote on-line automatic measurement. With the rapid development of optical fiber sensing technology, the optical fiber sensor has the characteristics of small volume, corrosion resistance, electromagnetic interference resistance and the like, and the method and the technology for measuring the liquid refractive index by adopting the optical fiber sensing method are gradually concerned. In addition, since the refractive index of a liquid is affected by factors such as the concentration of the liquid and the temperature, it is only meaningful to measure the refractive index at a certain temperature. Therefore, the refractive index and the temperature need to be measured simultaneously.
disclosure of Invention
The invention provides a system and a method for simultaneously measuring the refractive index and the temperature of liquid by optical fiber sensing, aiming at solving the problem of simultaneously measuring the refractive index and the temperature of the liquid on line at a long distance.
A fiber optic sensing system for simultaneously measuring refractive index and temperature of a liquid, comprising: the device comprises a light source, a wavelength division multiplexer, a photoelectric detector, a collection card, a computer, an optical fiber thermostatic bath, a sensing optical fiber and a sensing head;
the wavelength division multiplexer is provided with four ports, namely ports a, b, c and d; the pulse output by the light source is input from the port a of the wavelength division multiplexer, the port b of the wavelength division multiplexer is connected with the sensing optical fiber through the optical fiber thermostatic bath, and the other end of the sensing optical fiber is connected with a sensing head immersed in the liquid to be measured; the c port and the d port of the wavelength division multiplexer are connected with a photoelectric detector together, and the signal output end of the photoelectric detector is connected with the signal input end of the acquisition card; the signal output end of the acquisition card is connected with the signal input end of the computer; the temperature information of the optical fiber thermostatic bath is transmitted to a computer through a serial port; the wavelength division multiplexer has a filtering function, can filter the light input from the port b and detected by the sensing head to obtain Raman anti-Stokes light and Raman Stokes light, and outputs the Raman anti-Stokes light and the Raman Stokes light to the photoelectric detector from the ports c and d respectively.
Pulse light emitted by a light source enters the wavelength division multiplexer through the port a, is output and transmitted to the optical fiber thermostatic bath through the port b, is transmitted to the sensing head through the sensing optical fiber, the sensing head is immersed in liquid to be detected, a signal detected by the sensing head returns along the sensing optical fiber, enters the wavelength division multiplexer through the port b, is filtered by the wavelength division multiplexer to obtain Raman Stokes light, and is output from the port c, Raman anti-Stokes light is output from the port d, the Raman Stokes light and the Raman anti-Stokes light are converted into electric signals through the photoelectric detector and then are transmitted to the acquisition card, and the acquisition card transmits the acquired signals to the computer for demodulation and display of liquid refractive index and temperature information. And the temperature information of the optical fiber thermostatic bath is transmitted to a computer through a serial port.
a system for simultaneously measuring the refractive index and the temperature of optical fiber sensing liquid comprises a light source, a wavelength division multiplexer, a photoelectric detector, a collection card, a computer, an optical fiber thermostatic bath, a sensing optical fiber, a sensing head and a multi-channel optical switch; the sensing optical fibers and the sensing heads are multiple;
The wavelength division multiplexer is provided with four ports, namely ports a, b, c and d; the pulse output by the light source is input from the port a of the wavelength division multiplexer, the port b of the wavelength division multiplexer is connected with the multichannel optical switch through the optical fiber thermostatic bath, the multichannel optical switch is connected with a plurality of sensing optical fibers, and the other end of each sensing optical fiber is connected with a sensing head immersed in the liquid to be measured; the c port and the d port of the wavelength division multiplexer are connected with a photoelectric detector together, and the signal output end of the photoelectric detector is connected with the signal input end of the acquisition card; the signal output end of the acquisition card is connected with the signal input end of the computer; the temperature information of the optical fiber thermostatic bath is transmitted to a computer through a serial port; the wavelength division multiplexer has a filtering function, can filter the light input from the port b and detected by the sensing head to obtain Raman anti-Stokes light and Raman Stokes light, and outputs the Raman anti-Stokes light and the Raman Stokes light to the photoelectric detector from the ports c and d respectively.
Pulse light emitted by a light source enters the wavelength division multiplexer through the port a, is output and transmitted to the optical fiber thermostatic bath through the port b, then enters the multichannel optical switch, selects a sensing channel through the multichannel optical switch, then is transmitted to the sensing head through the sensing optical fiber, the sensing head is immersed in liquid to be detected, a signal detected by the sensing head returns along the sensing optical fiber, enters the wavelength division multiplexer through the port b, the returned signal is filtered by the wavelength division multiplexer to obtain Raman Stokes light, the Raman Stokes light is output from the port c, the Raman anti-Stokes light is output from the port d, the Raman Stokes light and the Raman Stokes light are converted into electric signals through the photoelectric detector and then are transmitted to the acquisition card, and the acquisition card transmits the acquired signals to the computer to demodulate and display liquid refractive index and temperature information. And the temperature information of the optical fiber thermostatic bath is transmitted to a computer through a serial port.
The sensor head comprises two parts: an optical fiber loop and an optical fiber tip; the optical fiber ring is used as a liquid temperature sensor, the tail end of the optical fiber is used as a liquid refractive index sensor, the cladding is required to be stripped at the tail end of the optical fiber, the optical fiber ring is cut into a vertical and smooth surface, and in order to avoid bending loss of the optical fiber, the diameter of the optical fiber ring is larger than 5 cm.
A method for simultaneously measuring the refractive index and the temperature of optical fiber sensing liquid is realized based on the system and comprises the following steps:
The method comprises the following steps: the sensor head was immersed in distilled water and the raman anti-stokes light intensity (I) was obtained using the system described above0as) As a liquid refractive index sensing reference value, Raman anti-Stokes light intensity (I) is obtained by using the system0as) And Raman Stokes light intensity (I)0s) Ratio R (T)0) Taking the liquid temperature as a liquid temperature sensing reference value, and then executing a step two;
step two: immersing the sensing head in the liquid to be measured, and obtaining the Raman anti-Stokes light intensity (I) by using the systemas) Raman anti-Stokes light intensity (I) is obtained as a liquid refractive index sensing measurement value by using the systemas) And Raman Stokes light intensity (I)s) Taking the ratio R (T) as a liquid temperature sensing measurement value, and then executing a third step;
step three: sensing fiducials using liquid refractive indexValue I0asAnd liquid refractive index sensing measurement IasObtaining the reflectivity R of the contact surface of the optical fiber end and the liquid to be detected, and utilizing the liquid temperature sensing reference value R (T)0) And the liquid temperature sensing measured value R (T) to obtain the indicated quantity M of the liquid temperature to be measured, and then executing the step four;
Step four: obtaining the refractive index n of the liquid to be detected by utilizing the reflectivity R of the contact surface of the optical fiber tail end and the liquid to be detected, which is obtained in the step threes(ii) a And D, obtaining the temperature T of the liquid to be measured by using the indication quantity M of the temperature of the liquid to be measured obtained in the step three.
the system and the method for simultaneously measuring the refractive index and the temperature of the liquid by the optical fiber sensing overcome the defects that the sensor is complex to manufacture, the measuring distance is short, and the refractive index and the temperature of the liquid cannot be simultaneously measured in the prior art, and are suitable for realizing remote simultaneous online measurement of the refractive index and the temperature of the liquid.
Drawings
FIG. 1 is a schematic diagram of a configuration of a system for simultaneously measuring refractive index and temperature of a liquid using fiber optics;
FIG. 2 is a schematic diagram of another configuration of a system for simultaneously measuring refractive index and temperature of a liquid using optical fiber sensing;
FIG. 3 is a schematic view of an optical fiber sensor structure;
FIG. 4 is a flow chart of a method for simultaneously measuring the refractive index and temperature of a liquid by optical fiber sensing.
1-light source, 2-wavelength division multiplexer, 3-photoelectric detector, 4-collecting card, 5-computer, 6-optical fiber thermostatic bath, 7-sensing optical fiber, 8-sensing head and 9-multichannel optical switch.
Detailed Description
the first embodiment is as follows: referring to fig. 1, the present embodiment is specifically described, and the system for simultaneously measuring the refractive index and the temperature of the optical fiber sensing liquid according to the present embodiment includes: the system comprises a light source 1, a wavelength division multiplexer 2, a photoelectric detector 3, a collection card 4, a computer 5, an optical fiber thermostatic bath 6, a sensing optical fiber 7 and a sensing head 8;
pulse light emitted by a light source enters the wavelength division multiplexer through the port a, is output and transmitted to the optical fiber thermostatic bath through the port b, is transmitted to the sensing head through the sensing optical fiber, the sensing head is immersed in liquid to be detected, a signal detected by the sensing head returns along the sensing optical fiber, enters the wavelength division multiplexer through the port b, is filtered by the wavelength division multiplexer to obtain Raman Stokes light, and is output from the port c, Raman anti-Stokes light is output from the port d, the Raman Stokes light and the Raman anti-Stokes light are converted into electric signals through the photoelectric detector and then are transmitted to the acquisition card, and the acquisition card transmits the acquired signals to the computer for demodulation and display of liquid refractive index and temperature information. And the temperature information of the optical fiber thermostatic bath is transmitted to a computer through a serial port.
The second embodiment is as follows: referring to fig. 2, the present embodiment is specifically described, and the system for simultaneously measuring the refractive index and the temperature of the optical fiber sensing liquid according to the present embodiment includes: the system comprises a light source 1, a wavelength division multiplexer 2, a photoelectric detector 3, a collection card 4, a computer 5, an optical fiber thermostatic bath 6, a multi-channel optical switch 9, a sensing optical fiber 7 and a sensing head 8;
Pulse light emitted by a light source enters the wavelength division multiplexer through the port a, is output and transmitted to the optical fiber thermostatic bath through the port b, then enters the multichannel optical switch, selects a sensing channel through the multichannel optical switch, then is transmitted to the sensing head through the sensing optical fiber, the sensing head is immersed in liquid to be detected, a signal detected by the sensing head returns along the sensing optical fiber, enters the wavelength division multiplexer through the port b, the returned signal is filtered by the wavelength division multiplexer to obtain Raman Stokes light, the Raman Stokes light is output from the port c, the Raman anti-Stokes light is output from the port d, the Raman Stokes light and the Raman Stokes light are converted into electric signals through the photoelectric detector and then are transmitted to the acquisition card, and the acquisition card transmits the acquired signals to the computer to demodulate and display liquid refractive index and temperature information. And the temperature information of the optical fiber thermostatic bath is transmitted to a computer through a serial port.
The third concrete implementation mode: in this embodiment, the wavelength division multiplexer has four ports, i.e., a port, b port, c port and d port, and the wavelength division multiplexer has a filtering function and can filter light input from the d port to obtain raman anti-stokes light and raman stokes light.
The fourth concrete implementation mode: this embodiment is specifically described with reference to fig. 3, and is further described with reference to the sensor head according to one or two embodiments, in this embodiment, the sensor head includes two parts: an optical fiber end and an optical fiber ring; the optical fiber ring is used as a liquid temperature sensor, the tail end of the optical fiber is used as a liquid refractive index sensor, the cladding is required to be stripped at the tail end of the optical fiber, the optical fiber ring is cut into a vertical and smooth surface, and in order to avoid bending loss of the optical fiber, the diameter of the optical fiber ring is larger than 5 cm.
the fifth concrete implementation mode: referring to fig. 4, the embodiment is specifically described, and the method for simultaneously measuring the refractive index and the temperature of the optical fiber sensing liquid according to the embodiment is implemented based on the above system, and the implementation includes the following steps:
the method comprises the following steps: the sensor head was immersed in distilled water and the raman anti-stokes light intensity (I) was obtained using the system described above0as) As a liquid refractive index sensing reference value, Raman anti-Stokes light intensity (I) is obtained by using the system0as) And Raman Stokes light intensity (I)0s) Ratio R (T)0) Taking the liquid temperature as a liquid temperature sensing reference value, and then executing a step two;
Step two: immersing the sensing head in the liquid to be measured, and obtaining the Raman anti-Stokes light intensity (I) by using the systemas) Raman anti-Stokes light intensity (I) is obtained as a liquid refractive index sensing measurement value by using the systemas) And Raman Stokes light intensity (I)s) Taking the ratio R (T) as a liquid temperature sensing measurement value, and then executing a third step;
step three: sensing reference value I by using liquid refractive index0asAnd liquid refractive index sensing measurement IasObtaining the reflectivity R of the contact surface of the optical fiber end and the liquid to be detected, and utilizing the liquid temperature sensing reference value R (T)0) And the liquid temperature sensing measured value R (T) to obtain the indicated quantity M of the liquid temperature to be measured, and then executing the step four;
step four: obtaining the refractive index n of the liquid to be detected by utilizing the reflectivity R of the contact surface of the optical fiber tail end and the liquid to be detected, which is obtained in the step threes(ii) a Obtained by the third stepand obtaining the temperature T of the liquid to be measured according to the indication quantity M of the temperature of the liquid to be measured.
The sixth specific implementation mode: in this embodiment, the method for simultaneously measuring the refractive index and the temperature of the optical fiber sensing liquid according to the fifth embodiment is further described, in this embodiment, the reflectivity R of the contact surface of the optical fiber end and the liquid to be measured is obtained according to the following formula,
Wherein n isfIs the refractive index of the core of the optical fiber, n0the refractive index of distilled water.
The seventh embodiment: in this embodiment, a method for simultaneously measuring the refractive index and the temperature of the liquid by the optical fiber sensing is further described, in which the refractive index n of the liquid to be measured is obtained according to the following formulas，
The specific implementation mode is eight: in this embodiment, a method for simultaneously measuring refractive index and temperature of liquid by optical fiber sensing is further described, and in this embodiment, a liquid temperature sensing reference value R (T) is obtained according to the following formula0) And a liquid temperature sensing measurement R (T),
Wherein v isasAnd vsthe frequencies of the anti-stokes light and the stokes light are respectively, h is a Planckian constant, c is the speed of light, k is a Boltzmann constant, and Deltav is the Raman phonon frequency.
The specific implementation method nine: in this embodiment, the method for simultaneously measuring the refractive index and the temperature of the liquid by the optical fiber sensing is further described in the fifth embodiment, in this embodiment, the indication amount M of the temperature of the liquid to be measured is obtained according to the following formula,
The detailed implementation mode is ten: in this embodiment, the method for simultaneously measuring the refractive index and the temperature of the liquid by the optical fiber sensing is further described in the fifth embodiment, in this embodiment, the temperature T of the liquid to be measured is obtained according to the following formula,
the above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.
Claims (4)
1. An optical fiber sensing system for simultaneously measuring the refractive index and temperature of a liquid, comprising: the device comprises a light source (1), a wavelength division multiplexer (2), a photoelectric detector (3), a collection card (4), a computer (5), an optical fiber thermostatic bath (6), a sensing optical fiber (7) and a sensing head (8);
The wavelength division multiplexer (2) is provided with four ports, namely a port, b port, c port and d port; pulses output by the light source (1) are input from an a port of the wavelength division multiplexer (2), a b port of the wavelength division multiplexer (2) is connected with a sensing optical fiber (7) through an optical fiber thermostatic bath (6), and the other end of the sensing optical fiber (7) is connected with a sensing head (8) immersed in liquid to be measured; the ports c and d of the wavelength division multiplexer (2) are connected with the photoelectric detector (3) together, and the signal output end of the photoelectric detector (3) is connected with the signal input end of the acquisition card (4); the signal output end of the acquisition card (4) is connected with the signal input end of the computer (5); the temperature information of the optical fiber thermostatic bath (6) is transmitted to the computer (5) through a serial port; the wavelength division multiplexer (2) has a filtering function, can filter light which is input from a port b and detected by the sensing head (8) to obtain Raman anti-Stokes light and Raman Stokes light, and outputs the Raman anti-Stokes light and the Raman Stokes light to the photoelectric detector (3) from ports c and d respectively; the sensor head (8) comprises two parts: an optical fiber ring (8-1) and an optical fiber end (8-2); wherein the optical fiber ring (8-1) is used as a liquid temperature sensor, the optical fiber tail end (8-2) is used as a liquid refractive index sensor, and the cladding of the optical fiber tail end (8-2) needs to be stripped and cut into a vertical and smooth surface; the diameter of the optical fiber ring (8-1) is more than 5 cm.
2. The utility model provides an optical fiber sensing liquid refracting index and temperature simultaneous measurement system which characterized in that: the device comprises a light source (1), a wavelength division multiplexer (2), a photoelectric detector (3), an acquisition card (4), a computer (5), an optical fiber thermostatic bath (6), a sensing optical fiber (7), a sensing head (8) and a multi-channel optical switch (9); the sensing optical fibers (7) and the sensing heads (8) are multiple;
The wavelength division multiplexer (2) is provided with four ports, namely a port, b port, c port and d port; pulses output by the light source (1) are input from an a port of the wavelength division multiplexer (2), a b port of the wavelength division multiplexer (2) is connected with a multi-channel optical switch (9) through an optical fiber thermostatic bath (6), the multi-channel optical switch (9) is connected with a plurality of sensing optical fibers (7), and the other end of each sensing optical fiber (7) is connected with a sensing head (8) immersed in liquid to be measured; the ports c and d of the wavelength division multiplexer (2) are connected with the photoelectric detector (3) together, and the signal output end of the photoelectric detector (3) is connected with the signal input end of the acquisition card (4); the signal output end of the acquisition card (4) is connected with the signal input end of the computer (5); the temperature information of the optical fiber thermostatic bath (6) is transmitted to the computer (5) through a serial port; the wavelength division multiplexer (2) has a filtering function, can filter light which is input from a port b and detected by the sensing head (8) to obtain Raman anti-Stokes light and Raman Stokes light, and outputs the Raman anti-Stokes light and the Raman Stokes light to the photoelectric detector (3) from ports c and d respectively; the sensor head (8) comprises two parts: an optical fiber ring (8-1) and an optical fiber end (8-2); wherein the optical fiber ring (8-1) is used as a liquid temperature sensor, the optical fiber tail end (8-2) is used as a liquid refractive index sensor, and the cladding of the optical fiber tail end (8-2) needs to be stripped and cut into a vertical and smooth surface; the diameter of the optical fiber ring (8-1) is more than 5 cm.
3. The system for simultaneously measuring the refractive index and the temperature of the liquid by the optical fiber sensing according to claim 1 or 2, wherein the light source (1) is connected with the acquisition card (4), and the signal output end of the computer (5) is connected with the signal input end of the light source (1).
4. A method for simultaneously measuring the refractive index and the temperature of a liquid by optical fiber sensing, which is realized by the system of any one of claims 1 to 3, and comprises the following steps:
The method comprises the following steps: the sensor head (8) is immersed in distilled water, and the Raman anti-Stokes light intensity I is obtained by using the system0asThe Raman anti-Stokes light intensity I is obtained by using the system as a liquid refractive index sensing reference value0asAnd Raman Stokes light intensity I0sratio R (T)0) Taking the liquid temperature as a liquid temperature sensing reference value, and then executing a step two;
Step two: the sensing head (8) is immersed in the liquid to be measured, and the Raman anti-Stokes light intensity I is obtained by using the systemasas a liquid refractive index sensing measurement value, the system is used for obtaining the Raman anti-Stokes light intensity Iasand Raman Stokes light intensity IsTaking the ratio R (T) as a liquid temperature sensing measurement value, and then executing a third step;
Step three: sensing reference value I by using liquid refractive index0asAnd liquid refractive index sensing measurement IasObtaining the reflectivity R of the contact surface of the optical fiber end (8-2) and the liquid to be detected, and utilizing the liquid temperature sensing reference value R (T)0) And the liquid temperature sensing measured value R (T) to obtain the indicated quantity M of the liquid temperature to be measured, and then executing the step four;
Step four: obtaining the refractive index n of the liquid to be detected by utilizing the reflectivity R of the contact surface of the optical fiber tail end (8-2) and the liquid to be detected obtained in the step threes(ii) a Obtaining the temperature T of the liquid to be measured by using the indication quantity M of the temperature of the liquid to be measured obtained in the step three;
The reflectivity R of the contact surface of the optical fiber tail end (8-2) and the liquid to be detected is obtained according to the following formula,
Wherein n isfIs the refractive index of the core of the optical fiber, n0Is the refractive index of distilled water; obtaining the refractive index n of the liquid to be measured according to the following formulas，
the liquid temperature sensing reference value R (T) is obtained according to the following formula0) And a liquid temperature sensing measurement R (T),
wherein v isasAnd vsThe frequencies of the anti-stokes light and the stokes light respectively, h is the Planck constant, c is the speed of light, k is the Boltzmann constant, Deltav is the Raman phonon frequency,
the indicated quantity M of the temperature of the liquid to be measured is obtained according to the following formula,
The temperature T of the liquid to be measured is obtained according to the following formula,
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| CN109709070B (en) * | 2018-12-29 | 2021-07-20 | 天津大学 | Refractive index and temperature double-parameter measuring method by using composite fiber grating sensor |
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