Spiral solution concentration optical fiber sensor and solution concentration detection device

Abstract

The invention relates to an optical fiber sensor, in particular to a spiral solution concentration optical fiber sensor and a solution concentration detection device.The spiral solution concentration optical fiber sensor comprises an optical fiber core which comprises an input section, a fiber core body and an output section which are sequentially connected, and the fiber core body is in a spiral shape; the wrapping shell is integrally in a spiral shape and is arranged outside the optical fiber core in a sleeving mode, at least two inlets are formed in one end of the wrapping shell, and at least one outlet is formed in the other end of the wrapping shell; the outer surface of the wrapping shell is covered with a total reflection layer so as to realize efficient reflection of optical signals; a certain gap is kept between the wrapping shell and the optical fiber core so that liquid to be detected can flow. The invention has the advantages of high sensitivity, quick response, outstanding stability and extremely low liquid consumption.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber concentration sensing, and in particular relates to a spiral type solution concentration optical fiber sensor and a solution concentration detection device. Background Art

[0002] In the field of fiber optic concentration sensing, fiber optic evanescent field sensor and hollow core fiber concentration sensor are two common measurement technologies, both of which rely on the absorption characteristics of the solution to the light signal to measure the concentration. However, both technologies have certain limitations in practical applications.

[0003] Traditional fiber optic evanescent field sensors mainly infer the concentration of solutions by measuring the absorption of light signals in the evanescent field on the fiber surface and the transmission loss. However, when the refractive index and absorbance of the solution change asynchronously, such as when the refractive index reaches an extreme value while the absorbance is still increasing in some solutions, the transmission loss may far exceed the evanescent field absorption, resulting in a significant decrease in the sensitivity of the sensor to subsequent concentration changes. This limitation restricts the application of traditional fiber optic evanescent field sensors in complex solution systems.

[0004] On the other hand, hollow-core fiber concentration sensors directly use the solution's absorption of light signals for measurement. Since the liquid's refractive index is usually smaller than that of the optical fiber, this measurement method places extremely high demands on the fully reflective material on the optical fiber surface, which significantly increases the manufacturing cost. In addition, the sensitivity of hollow-core optical fibers is also limited by their structural characteristics, making it difficult to accurately measure small changes in solution concentration.

[0005] Therefore, it is necessary to develop a new spiral solution concentration optical fiber sensor and a solution concentration detection device. Summary of the invention

[0006] The purpose of the present invention is to provide a spiral solution concentration optical fiber sensor and a solution concentration detection device which have high sensitivity, fast response, outstanding stability and extremely low liquid consumption.

[0007] In a first aspect, a spiral solution concentration optical fiber sensor according to the present invention comprises: An optical fiber core, comprising an input section, a core body and an output section connected in sequence, wherein the core body is in a spiral shape; The wrapping shell is spiral-shaped as a whole and is sleeved on the outside of the optical fiber core. One end of the wrapping shell is provided with at least two entrances, and the other end of the wrapping shell is provided with at least one exit. The outer surface of the wrapping shell is covered with a total reflection layer to achieve efficient reflection of the optical signal. A certain gap is maintained between the wrapping shell and the optical fiber core to allow the liquid to flow.

[0008] Optionally, an isolation structure is provided between the optical fiber core and the wrapping shell. The present invention uses the isolation structure to prevent the optical fiber core from directly contacting the wrapping shell, thereby ensuring the stability of the optical fiber core and the measurement accuracy.

[0009] Optionally, the isolation structure is composed of a plurality of support ribs, one end of which is connected to the inner wall of the wrapping shell, and the other end is connected to the outer surface of the optical fiber core, so as to provide stable support and maintain the gap between the optical fiber core and the wrapping shell. The present invention can provide stable support and maintain the gap between the optical fiber core and the wrapping shell through a plurality of support ribs.

[0010] Optionally, the total reflection layer is made of silver or gold, which has extremely high reflectivity.

[0011] Optionally, the encapsulating shell is a glass tube or a silica tube.

[0012] Optionally, the input section and the output section of the optical fiber core are both in a straight line, so as to ensure the stability and low loss of the optical signal when it reaches the sensing area.

[0013] In a second aspect, a solution concentration detection device according to the present invention comprises: A laser transmitter, used for emitting laser; In the spiral solution concentration optical fiber sensor of the present invention, one inlet is used to introduce the solution to be tested during detection, and the other inlet is used to introduce the cleaning solution during cleaning. After the laser interacts with the solution during transmission in the optical fiber core, it is reflected by the total reflection layer and output from the output end carrying the solution concentration information. The infrared light detection module is arranged at the output end of the spiral solution concentration optical fiber sensor and is used to detect the infrared light signal and convert it into an electrical signal; A signal amplifier, connected to the infrared light detection module, for receiving and amplifying the electrical signal output by the infrared light detection module; A signal receiving terminal is connected to the signal amplifier and is used to receive and process the amplified electrical signal to analyze and display the concentration information of the solution to be tested; The power module is connected to the signal amplifier to provide the signal amplifier with required power supply.

[0014] Optionally, it also includes: The temperature feedback module is used to monitor and feedback the temperature information in the detection device in real time. The temperature feedback module is connected to the signal receiving terminal to monitor the temperature of the system in real time to ensure the stability of the device operation.

[0015] Optionally, the infrared light detection module uses an infrared photoelectric detector, or a power meter.

[0016] The present invention has the following advantages: (1) In traditional fiber optic sensing technology, the solution absorbs light signals mainly in two ways: evanescent field absorption and transmission loss (i.e., attenuation when light passes directly through the solution). The innovation of the present invention lies in that it combines these two absorption mechanisms and enhances the sensitivity of the sensor to the solution concentration by designing a wrapping tube and setting a total reflection layer on the outer surface of the wrapping shell. When the concentration of the solution changes, its refractive index will also change accordingly. When the refractive index and absorbance of the solution change asynchronously (such as when the refractive index reaches an extreme value while the absorbance is still increasing), the traditional sensor may be insensitive to subsequent concentration changes due to the significant increase in transmission loss. The present invention can convert this part of the refractive energy that may have been lost into evanescent field absorption and direct absorption of the solution by setting a wrapping tube and setting a total reflection layer on the outer surface of the wrapping shell, thereby improving the measurement accuracy and range. The present invention can measure the concentration of the solution more accurately, especially when dealing with liquids such as alcohol solutions whose refractive index and absorbance change asynchronously. Its advantages are more obvious. Theoretically, the spiral solution concentration optical fiber sensor can measure the solution concentration from 0 to the saturated absorbance range, greatly broadening the measurement range.

[0017] (2) The present invention effectively increases the propagation path of the optical signal in the solution by physically bending the optical fiber and the wrapping shell. This design allows the optical signal to have more opportunities to interact with the solution when passing through the solution, thereby improving the sensor's response sensitivity to changes in solution concentration.

[0018] (3) The present invention provides an inlet at one end of the encapsulating shell and an outlet at the other end. When in use, a micro water pump is used to pump liquid into the encapsulating shell and finally discharge it through the outlet, thereby effectively solving the problem of device contamination.

[0019] (4) The present invention uses an isolation structure to prevent the optical fiber core from directly contacting the sheath, making the sensor less susceptible to external vibration disturbances.

[0020] In summary, the present invention achieves high sensitivity, rapid response and accurate measurement of solution concentration by combining evanescent field absorption with solution absorption, increasing the optical path, and converting refraction loss into absorption loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the spiral solution concentration optical fiber sensor described in the embodiment of the present application; Figure 2 This is one of the internal structure schematic diagrams of the spiral solution concentration optical fiber sensor described in the embodiment of the present application; Figure 3 This is the second schematic diagram of the internal structure of the spiral solution concentration optical fiber sensor described in the embodiment of the present application; Figure 4 This is the third schematic diagram of the internal structure of the spiral solution concentration optical fiber sensor described in the embodiment of the present application; Figure 5 Schematic diagram of the internal structure of the solution concentration detection device described in the embodiment of the present application; In the figure: 1. entrance, 2. optical fiber core, 2a. core body, 3. wrapping shell, 3a. isolation structure, 3b. total reflection layer, 4. exit, 5. temperature feedback module, 6. power module, 7. signal receiving terminal, 8. signal amplifier, 9. infrared light detection module, 10. waste liquid barrel, 11-cleaning liquid barrel, 12. laser transmitter, 13-solution barrel. DETAILED DESCRIPTION

[0022] The following will describe the embodiments of the present invention with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention, not for limiting the scope of protection of the present invention.

[0023] like Figures 1 to 4 As shown, in an embodiment of the present application, a spiral solution concentration optical fiber sensor includes an optical fiber core 2 and a wrapping shell 3.

[0024] like Figure 1 As shown, the optical fiber core 2 includes an input section, a core body 2a and an output section connected in sequence, and the core body 2a is spiral. The wrapping shell 3 is spiral as a whole and is sleeved on the outside of the optical fiber core 2. One end of the wrapping shell 3 is provided with at least two openings, which serve as a light input port and a liquid inlet 1 respectively, and the other end of the wrapping shell 3 is provided with at least one outlet 4 for discharging liquid. A total reflection layer 3b is covered on the outer surface of the wrapping shell 3 to achieve efficient reflection of the optical signal; a certain gap is maintained between the wrapping shell 3 and the optical fiber core 2 to allow the liquid to flow.

[0025] like Figure 2 and Figure 3 As shown, in a possible embodiment, the isolation structure 3a is disposed between the optical fiber core 2 and the encapsulating shell 3 to prevent the optical fiber core 2 from directly contacting the encapsulating shell 3, thereby ensuring the stability of the optical fiber core 2 and the measurement accuracy.

[0026] like Figure 2As shown, in a possible embodiment, the isolation structure 3a is composed of a plurality of supporting ribs, one end of the supporting ribs is connected to the inner wall of the encapsulating shell 3, and the other end is connected to the outer surface of the optical fiber core 2 to provide stable support and maintain the gap between the optical fiber core 2 and the encapsulating shell 3.

[0027] like Figure 3 As shown, in a possible embodiment, the isolation structure 3a is composed of a plurality of supporting ribs, one end of the supporting rib is connected to the inner wall of the wrapping shell 3, and a fixing ring is provided at the other end of the supporting rib, and the fixing ring is mounted on the fiber core body 2a, so as to prevent the optical fiber core 2 from directly contacting the wrapping shell 3.

[0028] In a possible embodiment, the total reflection layer 3b is made of silver or gold, both of which have extremely high light reflectivity.

[0029] In a possible embodiment, the encapsulating shell 3 is a glass tube or a silicon dioxide tube.

[0030] like Figure 1 As shown, in a possible embodiment, the input section and the output section of the optical fiber core 2 are both straight lines, so as to ensure the stability and low loss of the optical signal when it reaches the sensing area.

[0031] In the embodiment of the present application, the working principle of a spiral solution concentration optical fiber sensor is as follows: The present spiral solution concentration optical fiber sensor is based on the existing spiral single-mode optical fiber sensor, with a wrapping shell 3 added to the core body 2a, and the input end of the wrapping shell 3 is provided with two entrances 1, the output end of the wrapping shell 3 is provided with an exit 4, and the outer surface of the wrapping shell 3 is covered with a total reflection layer 3b. According to the principle of evanescent field absorption of optical signals in optical fiber transmission and Fresnel's refraction law, when the optical signal is incident from the straight part (i.e. the input section of the optical fiber core) to the curved part (i.e. the core body 2a), it will be totally reflected or refracted to the outside world according to the different incident angles. When total reflection occurs, the optical signal will be lost due to the interaction with the evanescent field of the solution, and refraction will also cause loss. For the traditional solution evanescent wave sensor, when measuring the concentration, at the beginning, due to the large difference between the refractive index of the solution and the refractive index of the core, the loss generated mostly comes from the absorption of the evanescent field. When the solution As the concentration increases, the critical value of the total reflection angle increases, and more and more light is refracted. At this time, the loss mainly depends on the refraction of light, which makes it difficult to continuously measure the solution concentration from extremely low (ppm) to extremely high (such as %). In addition, the optical fiber material used is inevitably flawed, such as gaps and uneven material distribution, which will have a greater impact on the measurement of solution concentration, especially small changes in concentration. The spiral solution concentration optical fiber sensor can make the loss of the incident light signal depend only on the evanescent field absorption and direct absorption of the solution. Its principle is The light signal is refracted or transmitted from the core by the coating shell 3. After being absorbed by the solution, it contacts the coating shell 3, undergoes another absorption and refraction of the evanescent field, encounters the total reflection material of the outer layer, and is returned. It undergoes another absorption and refraction of the evanescent field of the light, contacts the solution again and reaches the core, undergoes reflection and refraction. What is finally detected at the output end is the light signal that is not completely absorbed by the solution and is still transmitted in the optical fiber. That is, the change of the refractive index is converted into the absorption of the solution and the absorption of the evanescent field. The light source is very sensitive to small changes in liquid concentration. In order to achieve more accurate measurement of the solubility of liquids such as alcohol, whose refractive index and absorbance do not reach their extreme values ​​synchronously during the change process and have a nonlinear relationship, the following key characteristics are used for optimization: Given that the refractive index and absorbance of alcohol do not change synchronously, even when the refractive index has increased to near the maximum value, the absorbance still increases with the increase in concentration, and the "binding" effect of the light signal in the medium, it is still possible to continuously monitor the slight changes in the light signal with the increase in concentration until the absorbance itself reaches its extreme point. On the contrary, if the absorbance reaches saturation first, and the refractive index continues to increase with the increase in concentration, the light signal will contact the solution more and be absorbed more, so the change of the light signal under small concentration changes can still be detected, thereby significantly broadening the concentration range of the measurement, ensuring high precision and wide adaptability of the measurement, and theoretically measuring the concentration of the solution from 0 concentration to the saturated absorbance or maximum refractive index.

[0032] like Figure 5 As shown, in the embodiment of the present application, a solution concentration detection device includes a laser emitter 12, a spiral solution concentration optical fiber sensor such as in the embodiment of the present application, an infrared light detection module 9, a signal amplifier 8, a signal receiving terminal 7 and a power module 6. The laser emitter 12 is used to emit laser light. One inlet 1 of the spiral solution concentration optical fiber sensor is used to introduce the solution to be tested during inspection, and the other inlet 1 is used to enter the cleaning solution during cleaning. After the laser interacts with the solution during transmission in the optical fiber core 2, it is reflected by the total reflection layer 3b and output from the output end carrying the solution concentration information. The infrared light detection module 9 is arranged at the output end of the spiral solution concentration optical fiber sensor, and is used to detect the infrared light signal and convert it into an electrical signal. The signal amplifier 8 is connected to the infrared light detection module 9, and is used to receive and amplify the electrical signal output by the infrared light detection module 9. The signal receiving terminal 7 is connected to the signal amplifier 8, and is used to receive and process the amplified electrical signal to analyze and display the concentration information of the solution to be tested. The power module 6 is connected to the signal amplifier 8 to provide the required power supply for the signal amplifier 8.

[0033] like Figure 5 As shown, in a possible embodiment, a solution concentration detection device further includes a temperature feedback module 5 for real-time monitoring and feedback of temperature information in the detection device, and the temperature feedback module 5 is connected to a signal receiving terminal 7. It is used to monitor the temperature of the system in real time to ensure the stability of the device operation.

[0034] In a specific embodiment, the laser transmitter 12 is a 1550 nm laser.

[0035] In a specific embodiment, the infrared light detection module 9 adopts an infrared photoelectric detector, and may also adopt a power meter.

[0036] like Figure 5 As shown, when the spiral solution concentration optical fiber sensor is used to detect the liquid concentration, the inlet 1 for introducing the solution to be tested (the inlet 1 is connected to the solution barrel 13 through a pipeline) and the outlet 4 for removing the waste liquid are opened, the outlet 4 is connected to the waste liquid barrel 10 through a pipeline, and the waste liquid is introduced into the waste liquid barrel 10 through the outlet 4. The input end of the optical fiber core 2 is connected to the laser transmitter 12, and the infrared light detection module 9 is set at the output end of the optical fiber core 2. The infrared signal detected by the infrared light detection module 9 is converted into a voltage signal through the signal amplifier 8, and the data is read and recorded in real time on the signal receiving terminal 7.

[0037] like Figure 5As shown, when the spiral solution concentration optical fiber sensor needs to be cleaned, the inlet 1 for introducing the cleaning liquid (connected to the cleaning liquid barrel 11 through a pipeline) and the outlet 4 for discharging the waste liquid are opened, and the spiral solution concentration optical fiber sensor is cleaned by introducing the cleaning liquid.

[0038] The above-mentioned embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above-mentioned embodiments. Any other changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement modes and shall be included in the protection scope of the present invention.

Claims

1. A spiral solution concentration optical fiber sensor, characterized in that: include: An optical fiber core (2), comprising an input section, a fiber core body (2a) and an output section which are connected in sequence, wherein the fiber core body (2a) is in a spiral shape; The wrapping shell (3) is spiral-shaped as a whole and is sleeved outside the optical fiber core (2); one end of the wrapping shell (3) is provided with at least two inlets (1), and the other end of the wrapping shell (3) is provided with at least one outlet (4); the outer surface of the wrapping shell (3) is covered with a total reflection layer (3b) to achieve efficient reflection of optical signals; a certain gap is maintained between the wrapping shell (3) and the optical fiber core (2) to allow the flow of liquid to be measured.

2. The spiral solution concentration optical fiber sensor according to claim 1, characterized in that: An isolation structure (3a) is provided between the optical fiber core (2) and the wrapping shell (3).

3. The spiral type solution concentration optical fiber sensor according to claim 2, characterized in that: The isolation structure (3a) is composed of a plurality of support ribs, one end of each support rib is connected to the inner wall of the wrapping shell (3), and the other end of each support rib is connected to the outer surface of the optical fiber core (2).

4. The spiral type solution concentration optical fiber sensor according to claim 1, characterized in that: The total reflection layer (3b) is made of silver or gold.

5. The spiral solution concentration optical fiber sensor according to claim 1, characterized in that: The encapsulating shell (3) is a glass tube or a silica tube.

6. The spiral type solution concentration optical fiber sensor according to claim 1, characterized in that: The input section and the output section of the optical fiber core (2) are both in a straight line shape.

7. A solution concentration detection device, characterized in that: include: A laser transmitter (12), used for transmitting laser light; The spiral solution concentration optical fiber sensor according to any one of claims 1 to 6, wherein one inlet (1) is used to introduce a solution to be tested during detection, and the other inlet (1) is used to introduce a cleaning solution during cleaning, and after the laser interacts with the solution during transmission in the optical fiber core (2), it is reflected by the total reflection layer (3b) and output from the output end carrying the solution concentration information; An infrared light detection module (9) is arranged at the output end of the spiral solution concentration optical fiber sensor and is used to detect infrared light signals and convert them into electrical signals; A signal amplifier (8) connected to the infrared light detection module (9) and used to receive and amplify the electrical signal output by the infrared light detection module (9); A signal receiving terminal (7) is connected to the signal amplifier (8) and is used to receive and process the amplified electrical signal to analyze and display the concentration information of the solution to be tested; The power module (6) is connected to the signal amplifier (8) to provide the signal amplifier (8) with the required power supply.

8. The solution concentration detection device according to claim 7, characterized in that: Also includes: The temperature feedback module (5) is used for real-time monitoring and feeding back temperature information in the detection device, and the temperature feedback module (5) is connected to the signal receiving terminal (7).

9. The solution concentration detection device according to claim 7, characterized in that: The infrared light detection module (9) adopts an infrared photoelectric detector, or adopts a power meter.

Images