CN107907491B - An optical fiber sensor and its detection platform and method - Google Patents

Abstract

The invention discloses an optical fiber sensor, a detection platform and a detection method thereof, which belong to the technical field of optical fiber sensing. It may increase the sensitivity of the sensor. The platform comprises a support, the support is composed of a vertical surface and a horizontal surface, the vertical surface is provided with a fixing part for fixing the optical fiber probe, and the horizontal surface is provided with a cavity for bearing a container. Aiming at the problem of low detection sensitivity of the optical fiber sensor in the prior art, the common tapered optical fiber string is processed, so that the sensitivity of the tapered optical fiber sensor can be improved.

Description

An optical fiber sensor and its detection platform and method

technical field

The invention relates to the technical field of optical fiber sensing, in particular to an optical fiber sensor and its detection platform and method.

Background technique

The detection and analysis of temperature and liquid parameters are widely used in petroleum, chemical, pharmaceutical, food, and environmental monitoring industries. Among them, liquid detection includes multiple parameters, such as liquid composition, refractive index, concentration, surface tension, turbidity, etc. degree, pH value and viscosity etc. There are many methods for detecting liquid components. In addition to traditional physical and chemical methods, methods such as spectrophotometry and liquid chromatography are also widely used. However, most of these liquid detection methods have single functions and low detection efficiency. And the cost is higher. Fiber optic sensors have become a more practical way to measure the refractive index and concentration of liquids, as microfibers have similar sensitivity to fiber grating-based sensors while being less expensive to manufacture and relatively easier to fabricate (often only requiring a fusion splicer to do so). Realized), gradually discovered and widely used. Recently, many microfiber structures have been reported, such as microfiber loop resonator (MLR), microfiber coil resonator (MCR), microfiber knot resonator, microfiber Mach-Zehnder interferometer (MMZI )wait.

In the existing detection platforms, the sensitivity of fiber optic sensors is mostly improved by appropriately changing the structure of the fiber optics. Research has found that when changing the fiber structure, there are many methods used: taper the ordinary fiber, increase the length of the evanescent field, or add multiple cone structures (evanescent field), or change the straight-line tapered fiber The structure is a U-shaped probe structure, and the transmission mode of the light wave in the optical fiber is changed to the reflection mode, etc., which can improve the sensitivity of the optical fiber sensor to a certain extent.

In the paper "Refractive Index Sensing With Mach–Zehnder Interferometer Based on Concatenating Two Single-Mode Fiber Tapers" published on IEEE PHOTONICS TECHNOLOGY LETTERS, VOL.20, NO.8 on April 15, 2008, Zhaobing Tian et al. The high-sensitivity characteristics of the tapered optical fiber string are used to detect the refractive index of liquids.

In the paper "InlineMicrofiber Mach-Zehnder Interferometer for High Temperature Sensing" published in IEEE SENSORS JOURNAL, VOL.13, NO.2 in February 2013, AliAbdulhadi Jasim, etc. studied the performance of the tapered optical fiber string sensor based on Mach-Zehnder interference. High-temperature sensitive characteristics, first taper the ordinary optical fiber to make a cone structure, and then taper on the cone structure.

In the paper "Microcontroller-based instrumentation system for measurement of refractive index of liquid using bare,tapered and bent fiber as sensor" published on 10.1049/iet-opt on September 17, 2013, Shakuntala Laskar et al. , use the curved tapered multimode fiber sensor with the cladding removed, bend it into a U shape on the tapered section, and make a probe to detect the refractive index of the liquid; this paper mainly involves the design of the circuit, the selection of components and connect.

Since the optical fiber itself is very easy to break, and the evanescent field part of the optical fiber is more slender and sensitive; therefore, no matter the linear tapered structure or the U-shaped probe structure, the long evanescent field of the sensor will exist after a liquid detection is completed. The problem of inconvenient cleaning will cause damage to the tapered area during cleaning, which will affect the next liquid detection. However, adding a U-line structure to the tapered section has high processing difficulty, high requirements for the consistency of the tapered areas on both sides, and complex structure, which makes the packaging and use of this type of sensor more difficult, which is difficult to achieve in actual operation. It is not meaningful to popularize and use, and the cost is high; in addition, when the tapered optical fiber with linear structure is used to detect small-scale trace liquid, it cannot fully contact with the liquid, and the detection is also difficult; the optical fiber sensor with the above structure has a high sensitivity. It cannot be promoted and used in occasions with higher requirements.

Contents of the invention

1. The technical problem to be solved by the invention

Aiming at the problem of low detection sensitivity of the optical fiber sensor in the prior art, the present invention provides an optical fiber sensor and its detection platform and method. It processes ordinary tapered optical fiber strings, which can improve the sensitivity of tapered optical fiber sensors.

2. Technical solution

In order to solve the above problems, the technical solution provided by the invention is:

An optical fiber sensor is composed of an optical fiber probe, including an incident area, a sensing area, and an end section of an optical fiber, and also includes a tapered area, one end of the sensing area is connected with a tapered area and the incident area in sequence, and the sensing area The other end of the sensing area is sequentially connected with another tapered area and one end of the fiber end section. It can increase the sensitivity of the sensor.

Preferably, the said tapered region includes a tapered region I and a tapered region II, one end of the tapered region I is connected to one end of the sensing region, and the other end of the tapered region I is connected to the incident region, so One end of the said tapered region II is connected to the other end of the sensing region, and the other end of said tapered region II is connected to the end section of the optical fiber.

Preferably, the optical fiber probe includes a cladding and a fiber core, and the cladding is provided with a fiber core.

Preferably, a metal film is provided on the end surface of the optical fiber end section, and a metal film is provided on the tapered region. It can significantly enhance the light intensity in the sensing area, which is beneficial to improve the sensitivity.

Preferably, the sensing area is U-shaped.

Preferably, the sensing area includes a sensing area I and a sensing area II, the sensing area II is U-shaped, and one end of the sensing area II is connected to a sensing area I, a tapered area and an incident area in sequence connected, the other end of the sensing area II is sequentially connected with another sensing area I and the end of the optical fiber.

Preferably, the metal film is a gold film or a palladium-gold film.

An optical fiber sensor detection platform includes a bracket, the bracket is composed of a vertical surface and a horizontal surface, the vertical surface is provided with a fixing part for fixing the above-mentioned optical fiber probe, and the horizontal surface is provided with a cavity for carrying the container .

Preferably, the container is located in the cavity, and the bottom of the container communicates with both the water injection port and the water outlet.

A kind of optical fiber sensor detection method, its step:

A, the two ends of above-mentioned a kind of optical fiber sensor are respectively fixed on the support of above-mentioned a kind of optical fiber sensor detection platform;

B. The incident area of the fiber optic probe is connected to the broadband light source and the spectrum analyzer through the fiber coupler; The path returns, and finally reaches the spectrum analyzer through the fiber coupler, and the spectrum analyzer measures the data of the light source;

C. Temperature detection: place the detection platform in the environment to be detected, and calculate the temperature according to the measurement results of the spectrum analyzer;

D. Liquid detection: close the water outlet, pass the liquid to be detected into the container through the water injection port until it covers the sensing area of the optical fiber probe, and calculate the liquid parameters according to the measurement results of the spectrum analyzer.

3. Beneficial effect

Compared with the prior art, the technical solution provided by the invention has the following beneficial effects:

(1) a kind of optical fiber sensor of the present invention, common tapered optical fiber string is processed, can improve the sensitivity of tapered optical fiber sensor;

(2) a kind of optical fiber sensor detection platform of the present invention, the setting of the water injection port and the water outlet on the transparent container, is convenient in detection process, avoids that the liquid to be measured settles down, guarantees the accuracy of detection result; The U-shaped probe is cleaned in time to detect the liquid to be tested more efficiently; therefore, the platform has a simple operation process, can quickly realize multiple samplings, has strong practicability, and is easy to clean;

(3) A kind of optical fiber sensor detection method of the present invention, the test temperature of detection liquid parameter is 25 ℃, because the tapered optical fiber string is very sensitive to temperature, the change of temperature can affect detection result, selects in the test at constant temperature condition (generally The detection of liquids at room temperature (about 25°C) can better obtain ideal results and greatly reduce the sensitivity of the interferometer to temperature;

(4) A kind of optical fiber sensor detection method of the present invention, two fixed clips on the bracket fix the two free ends of the optical fiber probe (i.e. the optical fiber incident area and the end section of the optical fiber), to ensure that the force is even and reduce the stress factor The effect of cross-sensitivity on the sensor's liquid concentration detection;

(5) A kind of optical fiber sensor detection method of the present invention, optical fiber probe size is little, manufacturing process is simple, has higher sensitivity to temperature, pressure, refractive index etc.; Simplified; less expensive to make.

Description of drawings

Fig. 1 is one of structural schematic diagrams of optical fiber probe;

Figure 2 is the second schematic diagram of the optical fiber probe structure;

Fig. 3 is a kind of optical fiber sensor detection platform schematic diagram of the present invention;

Figure 4 is a schematic diagram of the container.

Explanation of the labels in the schematic diagram:

100, optical fiber probe; 11, incident area; 101, cladding; 102, fiber core; 12, sensing area; 13, end section of optical fiber; 14; tapered area; 121, sensing area I; 122, sensing area II; 141, tapered area I; 142, tapered area II; 1, bracket; 2, fixed part; 3, container; 4, breadboard; 5, broadband light source; 6, spectrum analyzer; 8, concave hole; 9. Water injection port; 10. Water outlet; 15. Optical fiber coupler.

Detailed ways

In order to further understand the content of the present invention, the present invention will be described in detail in conjunction with the accompanying drawings and embodiments.

Example 1

An optical fiber sensor is composed of an optical fiber probe 100, including an incident area 11, a sensing area 12 and an optical fiber end section 13, and also includes a tapered area 14, and one end of the sensing area 12 is connected with a tapered area 14 and an incident area 11 are sequentially connected, and the other end of the sensing region 12 is connected with another tapered region 14 and one end of the fiber end section 13 in sequence.

Both the incident area 11 and the end section 13 of the optical fiber belong to the unprocessed optical fiber structure, and the tapered area 14 and the sensing area 12 are obtained through processing. When the liquid medium is placed in the sensing area 12, the evanescent field (the tapered area 14 surrounding and itself) interacts with the medium through absorption and scattering. In a tapered fiber, most of the evanescent wave travels in the cladding region and is therefore more sensitive to changes in the surrounding medium. The penetration depth of the evanescent wave, the sensing core diameter and the sensing length of the uniform sensing area are the main influencing factors of the tapered optical fiber evanescent wave sensor. The sensitivity of the sensor depends on the amount of light reflection and the penetration depth of the evanescent field in the sensing area. In order to improve the sensitivity of the sensor, the structure of the tapered optical fiber string is changed to a U-shaped probe shape. When the light enters the bending region, the angle between the outer surface of the bending region and the normal line of the core/cladding interface decreases. A reduction in the value of the ray angle in the sensing area increases the penetration depth and the number of evanescent ray reflections per unit length N, increasing the sensitivity of the sensor.

Example 2

An optical fiber sensor, further improved on the basis of Embodiment 1, the tapered area 14 includes a tapered area I141 and a tapered area II142, one end of the tapered area I141 is connected to one end of the sensing area 12, and the tapered area I141 is connected to one end of the sensing area 12. The other end of the tapered region I141 is connected to the incident region 11 , one end of the tapered region II142 is connected to the other end of the sensing region 12 , and the other end of the tapered region II142 is connected to the end section 13 of the optical fiber.

The optical fiber probe 100 includes a cladding 101 and a fiber core 102, the cladding 101 is provided with a fiber core 102; the end surface of the optical fiber end section 13 is provided with a layer of metal film, and the said tapered region 14 is provided with a layer of metal film , both the tapered region I141 and the tapered region II142 are provided with a layer of metal film.

The metal film is a gold film or a palladium-gold film, and a gold-plated film is used. When the tapered optical fiber is coated with a gold film, the original projection measurement method becomes a reflection measurement method, and the electromagnetic field in the sensing area 12 can be more effectively utilized. The enhancement effect makes the light output by the optical fiber sensing head be reflected and then pass through the sensing area again, return to the original optical fiber and finally be received by the photodetector, which means that the sensing length of the sensing area 12 is doubled, and at the same time, the sensing area can be significantly enhanced. The light intensity of the sensitive area 12 is beneficial to improve the sensitivity.

A method of making an optical fiber sensor:

A. Remove the cladding 101 and clean the surface of the common standard single-mode optical fiber (SMF, core 102 and cladding 101 diameters are 60um and 125um respectively), heat the desired tapered part of the optical fiber, and pull the optical fiber Taper until the desired structure of the tapered region 14 is obtained, and the taper parameters of the tapered fiber are controlled by special operating software.

B. Coating the tapered optical fiber.

C. Structurally bending the tapered optical fiber after coating to form a U-shaped structure, and make the optical fiber probe 100 .

Example 3

An optical fiber sensor is further improved on the basis of Embodiment 1 or 2, and the sensing area 12 is U-shaped. As shown in Figure 1. Compared with the optical fiber sensor using the tapered structure as the sensing area 12 in the prior art, the U-shaped of the present application is used as the sensing area 12, which is convenient for cleaning, and will not damage the tapered structure (the tapered area I141 of the application and tapered area II142), can be used repeatedly.

Example 4

An optical fiber sensor, further improved on the basis of any one of embodiments 1-3, the sensing area 12 includes a sensing area I121 and a sensing area II122, the sensing area II122 is U-shaped, and the sensing area One end of II122 is connected with one sensing region I121, the tapered region 14 and the incident region 11 in sequence, and the other end of the sensing region II122 is connected with another sensing region I121 and the end section of optical fiber 13 in sequence. As shown in FIG. 2, the sensing region I121 is an unprocessed optical fiber structure.

The principle of detecting liquid parameters and temperature in this embodiment:

When the medium is placed in the sensing region 12, the evanescent field (constituted around and by the tapered region 14) interacts with the medium through absorption and scattering. In the tapered region 14, most of the evanescent wave travels in the cladding 11, so it is more sensitive to the change of the surrounding medium. The penetration depth of the evanescent wave, the sensing core diameter and the sensing length of the uniform sensing area are the main factors affecting the sensitivity of the fiber optic probe 100 .

The penetration depth is:

Where λ is the wavelength of the light source, θ is the angle between the normal line of the interface between the surface of the core 102 and the cladding 101 , n _co is the refractive index of the core 102 , and n _cl is the refractive index of the cladding 101 . Define the distance from the surface of the fiber core 102 to the place where the electromagnetic field amplitude drops to 1/e of the electromagnetic field amplitude on the surface of the fiber core 102 as the penetration depth d _p of the evanescent wave of the fiber optic probe 100 .

It can be seen from Equation 1 that when the value of θ decreases, the penetration depth d _p will increase; the number of ray reflections per unit length N is defined as:

For a given type of fiber, N depends on the value of θ. Under the condition of total reflection, a standing wave field is generated in the core 102 and decays exponentially to the cladding 101, and the intensity E(x) of the evanescent field is:

Wherein, x is the distance from the surface of the core 102 to the boundary of the penetration depth, and E ₀ is the field intensity at the junction of the core 102 and the cladding 101 .

The common optical fiber is tapered into a tapered optical fiber with a smaller diameter by tapering technology, that is, the tapered region 14 in this application. The tapered optical fiber string includes two tapered regions 14, which are separated by a few centimeters from a tapered body. The production of the second cone is seamlessly connected. Wherein the taper has a uniform waist of a few millimeters long, and at the same time has the characteristic of less loss (<0.1dB).

As shown in Figures 1 and 2, when the transmitted light enters the tapered region I141, the small component light in the evanescent field of the fiber will no longer be guided by the core 102 because the cladding mode is excited and propagated in the cladding 101 region , and the turn is guided by the cladding 101 . The portion that is not tapered is an interference region that enables interference between the core 102 and the cladding 101 . Since the reference path of transmitted light is along the core 102, and the sensing path is associated with a particular excited cladding mode, the need to have two physical fiber branches is reduced. When the guided mode kept traveling in the core 102 and the guided mode propagated through the cladding 101 as an unguided mode meet, interference occurs, and the two modes accumulate a difference to generate an optical path delay. A portion of the transmitted light in the cladding mode is coupled back into the core 102 at the tapered region II 142 .

The sensitivity of the fiber optic sensor depends on the number of light reflections and the penetration depth of the evanescent field in the sensing region 12 . In order to further improve the sensitivity of the sensor, the present embodiment changes the unprocessed section of two adjacent tapered regions 14 to be U-shaped, as shown in Figures 1 and 2, the sensing region 12 of the optical fiber sensor has a semicircular shape with a fixed curvature . In the case of a U-shaped probe, when light enters the bending region of the sensing region 12 of the fiber optic sensor, the angle at the outer surface of the bending region with the normal to the core 102/cladding 102 interface decreases. The meridians are:

Where θ represents the angle at which the transmitted light hits the outer surface of the curved core 102, h is the distance from the core 102/cladding 101 interface to the entrance of the U-shaped structure, and R is the bending radius of the U-shaped structure . According to formulas (1), (2), the reduction of the angle value of the light in the sensing area 12 increases the penetration depth and the number of light reflections per unit length N of evanescence.

For those of ordinary skill in the art, the U-shaped structure is directly made on the unprocessed optical fiber, and the formed optical fiber sensor has low sensitivity, poor performance, and low cost performance. Optical fiber sensors with this structure, and there are few optical fiber sensors with this structure in the field, so the idea of directly processing the unprocessed optical fiber sensor into a U-shaped structure is an existing technology for those of ordinary skill in the art. bias.

The angle of ray propagation in a straight-line configuration probe is constant and the amount of ray reflection is inversely proportional to the core 102 radius and depends only on the radius. However, in a U-shaped structure, the angle at which the ray propagates is not constant but decreasing. A decrease in the angle of propagation will therefore result in an increase in the penetration depth. Fiber bending will cause light loss and evanescent field penetration depth to increase. In U-shaped structure, the absorption coefficient is larger and the fiber sensitivity is higher.

The operation process of this platform is simple, it can quickly realize multiple sampling, it has strong practicability, it is easy to clean, and it can better realize the relevant detection of small volume liquid.

Example 5

An optical fiber sensor detection platform, including a bracket 1, the bracket 1 is composed of a vertical plane and a horizontal plane, and the vertical plane is provided with a fixing part 2 for fixing the fiber optic probe 100 described in any one of Embodiments 1-3 , the horizontal plane is provided with a cavity 8 for carrying the container 3 .

As a further improvement of this embodiment, the container 3 is located in the cavity 8 , and the bottom of the container 3 communicates with both the water injection port 9 and the water outlet 10 .

The fixing part 2 is a fixing clip, and the fixing clip fixes the fiber optic probe 100 on the vertical surface of the bracket 1. The container 3 is a transparent vessel, which is placed in the concave hole 8. The inside of the transparent vessel is engraved with a horizontal line, and at the bottom Both are equipped with a water injection port 9 and a water outlet port 10; by observing the transparent vessel, the amount of the solution can be intuitively known, and it can be judged whether the liquid to be tested is fully in contact with the sensing area 12.

Example 6

A kind of optical fiber sensor detection method, its steps are:

A, the two ends of a kind of optical fiber sensor described in any one of embodiment 1-4 are respectively fixed on the support 1 of a kind of optical fiber sensor detection platform described in embodiment 5;

B, the incidence area 11 of fiber optic probe 100 is connected with broadband light source 5 and spectrum analyzer 6 through fiber coupler 15; and the end section 13 of the optical fiber, reflected by the end face of the end section 13 of the optical fiber, return to the original path, pass through the end section 13 of the optical fiber, the sensing area 12 and the incident area 11 of the optical fiber probe 100 in turn, and then reach the spectrum analyzer 6 through the optical fiber coupler 15 , the spectrum analyzer 6 measures light source data;

C, temperature detection: the detection platform is placed in the environment to be detected, and the temperature is calculated according to the measurement results of the spectrum analyzer 6;

D. Liquid detection: close the water outlet 10, pass the liquid to be detected into the container 3 through the water injection port 9 until it covers the sensing area 12 of the optical fiber probe 100, and calculate the liquid parameters according to the measurement results of the spectrum analyzer 6.

Example 7

A kind of optical fiber sensor detection platform, improves on the basis of embodiment 5, comprises breadboard 4, support 1, and breadboard 4 is solid aluminum breadboard, generally used in the board of experimental design and has two kinds: universal board and Breadboard, in which the universal board needs to be soldered, and the device cannot be moved after being fixed; while using the breadboard, the device can be inserted or pulled out at will, which is very suitable for assembly, debugging and training.

The breadboard 4 is provided with a bracket 1, and the bracket 1 has a fixed clip 2 for fixing the two free ends of the optical fiber probe 100 (incidence area 11 and the end section of the optical fiber 13), ensuring uniform force and reducing stress caused by factors cross-sensitivity effects. The incident end of the fiber optic probe 100 is connected to the broadband light source 5 and the spectrum analyzer 6 through the fiber coupler 15 , as shown in FIG. 3 .

In addition to being provided with the fixed clip 2 that can fix the fiber optic probe 100, the bracket 1 is also provided with a horizontal plane on which the container 3 can be placed, and a hole 8 with a diameter of 5 cm is opened on the horizontal plane. The size of the concave hole 8 is the same as that of the container 3 ( In the present embodiment, the size of the transparent container) is matched, that is, the transparent container can be fixedly embedded in the concave hole 8, and it is also possible to select other size values during specific design. The transparent vessel containing the liquid to be tested is embedded in it and fixed, and the liquid to be tested is placed in the transparent vessel. In order to control the amount of the liquid to be tested, a level line is engraved on the inside of the transparent container, and the setting of the water injection port 9 and the water outlet 10 is convenient to avoid the liquid to be tested from settling during the detection process, and at the same time facilitates the injection and discharge of the liquid, and can be used repeatedly , strong practicability.

The setting of the water injection port 9 and the water outlet 10 on the transparent vessel of the present invention facilitates timely cleaning of the sensing area 12 of the optical fiber probe 100 during the detection process, and more efficient detection of the liquid to be measured; therefore, the operating process of the platform It is simple, can quickly realize multiple sampling, has strong practicability, and is easy to clean.

Example 8

As shown in Fig. 1-4, further improvement on the basis of embodiment 7, a kind of optical fiber sensor detection method of the present embodiment, its steps are:

A. Choose a breadboard 4, and fix the bracket 1 on the breadboard 4;

B. Open a concave hole 8 on the bracket 1, insert the transparent container into the concave hole 8, and fix it, and close the water injection port 9 and the water outlet 10;

C. Fix the two free ends of the fiber optic probe 100 on the bracket 1 respectively with the fixing clips; move and fix the fiber optic probe 100 to a certain depth in the transparent vessel before the measurement. After the measurement starts, it will be fixed and at the same time Ensure that the volume of the solution to be tested in the transparent vessel is the same;

D. Open the water injection port 9 of the transparent container, inject the liquid to be tested to the inner level line; open the water outlet 10, adjust the flow rate of the two water ports, ensure that the amount of liquid in the transparent container remains constant and the liquid is in a flowing state during the detection process, so as to avoid Settlement; detection, after detecting the parameters of the liquid to be tested; close the water injection port 9, keep the water outlet 10 open, and discharge the liquid to be tested; open the water injection port 9, inject clean water for cleaning, after cleaning is completed, discharge clean water, close the injection Water port 9 and water outlet 10;

E. In step D, after the data detection of each liquid is completed, the signal of the optical fiber probe 100 will be transmitted to the spectrum analyzer 6 through the optical fiber connector;

F, repeat steps D, E to carry out the detection of multiple liquids;

As a further improvement, the test temperature for detecting liquid parameters is 25°C.

Example 9

The optical fiber sensor detection method of this embodiment is improved on the basis of Embodiment 6, and the temperature detection range is: 5°C-45°C. Its detection principle is:

Spectrum analyzer 9 can measure the optical fiber output light intensity I, expressed as:

In the formula, I _co , I _cl , respectively represent the light intensity of the core 102, the cladding 101 and the phase difference between them, the phase difference can be expressed as:

In the formula, n _co , n _cl represent the effective refractive index of the core 102 and the cladding 101, and the difference between them is Δn _eff , when When the interference intensity is the smallest, the corresponding wavelength λ _n.min = 2Δn _eff L/(2n+1), n takes an integer, because L, Δn _eff is affected by the thermal expansion effect of the fiber and the thermo-optic effect, λ _n.min changes with the temperature Therefore, the sensing measurement of the ambient temperature can be realized according to the specific λ _n.min drift in the transmission spectrum.

Example 10

A kind of optical fiber sensor detection method of the present embodiment, its steps are:

A. Build an optical fiber sensor detection platform as described above. The test temperature for detecting liquid parameters is 25°C. The reason for this is that the tapered optical fiber is very sensitive to temperature, and changes in temperature will affect the detection results. In the test, choose Under constant temperature conditions, generally at room temperature of 25°C, the detection of liquids can better obtain ideal results and greatly reduce the sensitivity of the optical fiber probe 100 of the tapered optical fiber string to temperature;

B. Open a concave hole 8 on the bracket 1, embed the transparent vessel, and fix it, and close the water injection port 9 and the water outlet 10 of the transparent vessel;

C. Open the water injection port 9 of the transparent container, inject the liquid to be tested to the inner level line, then open the water outlet 10, strictly control the flow rate of the two water ports, and ensure that the amount of liquid in the transparent container is always maintained at the inner level line, and the liquid is stable at the same time dynamic;

D. Allow the sensor (sensing area 12) to fully contact the liquid, because as long as it touches the liquid, there will be hydraulic pressure, and the same standard ensures the same hydraulic pressure for detection; after the detection process has detected the parameters of the liquid to be measured, close the water injection port of the transparent vessel 9 , discharge the liquid, and then carry out cleaning work;

E. In step D, after the data detection for each liquid is completed, the signal on the fiber optic probe 100 will be transmitted to the spectrometer through the fiber optic connector. The optical fiber connector connects a free end (incidence region 11) of the sensor with the spectrum analyzer 6, and the spectrum analyzer 6 detects the sensor's spectrograms to different liquid concentrations, and the spectral change has a corresponding relationship with the refractive index, and the spectrum analyzer 6 will The data is transmitted to the computer, and the data is processed by the computer to obtain the concentration of the liquid;

F. Repeat steps D and E to detect multiple liquids.

Example 11

A kind of optical fiber sensor detection platform of the present embodiment comprises support 1, fixing clip, transparent vessel and bread board 4, and support 1 is arranged on bread board 4; Fixing clip groove; except being provided with fixing clip on support 1, also be provided with the experimental device of placing transparent container, get through a recess on the device, the diameter of recess 8 is 5cm, and the size of recess 8 is the same as that of transparent container The size of the transparent vessel matches the size, that is, the transparent vessel can be fixedly embedded in the concave hole 8, and other values can also be selected; the transparent vessel is placed in the concave hole 8, and the transparent vessel 3 is engraved with a horizontal line, and the bottom is provided with a water injection port 9 and water outlet 10.

Aiming at the problem that the liquid detection platform in the prior art detects one kind of liquid at a time, the operation is relatively complicated, and the present invention provides an optical fiber sensor, a detection platform and a method thereof. By changing the structure of the tapered light string into a U-shaped probe, the tapered optical fiber structure becomes compact, so as to improve sensitivity and facilitate testing, thereby realizing the concentration change of small volume liquid.

The above schematically describes the present invention and its implementation, which is not restrictive, and what is shown in the drawings is only one of the implementations of the present invention, and the actual structure is not limited thereto. Therefore, if a person of ordinary skill in the art is inspired by it, without departing from the inventive concept of the present invention, without creatively designing a structural mode and embodiment similar to the technical solution, it shall all belong to the protection scope of the present invention .

Claims (5)

1. An optical fiber sensor is composed of an optical fiber probe (100) and comprises an incidence area (11), a sensing area (12) and an optical fiber end section (13), and is characterized by further comprising a tapering area (14), wherein one end of the sensing area (12) is sequentially connected with one tapering area (14) and the incidence area (11), and the other end of the sensing area (12) is sequentially connected with one end of the other tapering area (14) and one end of the optical fiber end section (13);

the cone pulling area (14) comprises a cone pulling area I (141) and a cone pulling area II (142), one end of the cone pulling area I (141) is connected with one end of the sensing area (12), the other end of the cone pulling area I (141) is connected with the incident area (11), one end of the cone pulling area II (142) is connected with the other end of the sensing area (12), and the other end of the cone pulling area II (142) is connected with the optical fiber end section (13);

the optical fiber probe (100) comprises a cladding (101) and a fiber core (102), wherein the fiber core (102) is arranged in the cladding (101);

a layer of metal film is arranged on the end face of the optical fiber end section (13), and a layer of metal film is arranged on the tapering region (14);

the sensing area (12) is U-shaped, the sensing area (12) comprises a sensing area I (121) and a sensing area II (122), the sensing area II (122) is U-shaped, one end of the sensing area II (122) is sequentially connected with one sensing area I (121), a tapering area (14) and an incidence area (11), and the other end of the sensing area II (122) is sequentially connected with the other sensing area I (121) and an optical fiber end section (13).

2. The optical fiber sensor according to claim 1, wherein the metal film is a gold film or a palladium-gold film.

3. The optical fiber sensor detection platform comprises a support (1), and is characterized in that the support (1) is composed of a vertical surface and a horizontal surface, the vertical surface is provided with a fixing part (2) for fixing the optical fiber probe (100) according to claim 1, and the horizontal surface is provided with a concave hole (8) for bearing a container (3).

4. A fiber sensor testing platform according to claim 3, wherein the container (3) is located in the cavity (8), and the bottom of the container (3) is communicated with the water filling port (9) and the water outlet (10).

5. The detection method of the optical fiber sensor is characterized by comprising the following steps of:

A. fixing both ends of an optical fiber sensor according to claim 1 on a bracket (1) of an optical fiber sensor detection platform according to claim 3;

B. the incidence area (11) of the optical fiber probe (100) is connected with the broadband light source (5) and the spectrum analyzer (6) through the optical fiber coupler (15); the broadband light source (5) emits light, the light passes through an incidence area (11), a sensing area (12) and an optical fiber end section (13) of the optical fiber probe (100), the light passes through the end face of the optical fiber end section (13) to form reflection, the light returns in the original path, and finally reaches the spectrum analyzer (6) through the optical fiber coupler (15), and the spectrum analyzer (6) measures the light source data;

C. and (3) temperature detection: placing the detection platform in an environment to be detected, and calculating the temperature according to the measurement result of the spectrum analyzer (6);

D. and (3) liquid detection: closing the water outlet (10), introducing liquid to be detected into the container (3) through the water filling port (9) until the liquid covers the sensing area (12) of the optical fiber probe (100), and calculating liquid parameters according to the measurement result of the spectrum analyzer (6).