A n-octadecane phase transition detection sensor based on anti-resonant hollow core fiber

Abstract

The application discloses a n-octadecane phase change detection sensor based on an anti-resonance hollow-core optical fiber, relates to the technical field of optical fiber sensors, and comprises input single-mode optical fibers, tubular hollow-core optical fibers and output single-mode optical fibers which are sequentially connected, and the sensor realizes phase change detection of n-octadecane materials by comparing the change of resonance peak intensity. The application further discloses a manufacturing method and a using method of the n-octadecane phase change detection sensor based on the anti-resonance hollow-core optical fiber. The application realizes liquid-solid phase change detection of the phase change material n-octadecane by using anti-resonance. Experimental verification shows that when the n-octadecane has liquid-solid phase change, the resonance peak of the transmission spectrum of the sensor will have a mutation of more than 10 dB. The proposed phase change detection sensor has the advantages of simple structure, small size, easy-to-obtain material and high repeatability, and has important application value in the fields of material detection and thermal energy storage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical fiber sensors, in particular to a n-octadecane phase change detection sensor based on anti-resonant hollow core fiber. BACKGROUND

[0002] Phase change materials absorb or release a large amount of energy during melting or solidification, which plays an important role in thermal energy storage applications. In order to improve the energy efficiency of the energy storage process, it is necessary to accurately detect the phase change of the phase change material. As a simple and low-cost temperature sensor, thermocouples are often used to detect material temperature to indirectly detect material phase change, but they also have obvious defects. When the thermocouple is immersed in the material, the thermocouple may become a heat source and affect the phase state of the surrounding material, and the phase change temperature will also change under different conditions, which will eventually lead to detection errors.

[0003] There are also different degrees of defects in the commonly used direct detection methods. Direct observation method to observe the phase change phenomenon is only suitable for optically transparent materials; X-ray tomography and radiography can be applied to opaque materials. Both of these two methods can detect the change of material density related to phase change, but both of these two methods are based on laboratory and high cost, and both of these two methods will involve human exposure to radiation; Differential scanning calorimetry can be used to characterize phase change materials and can also be used to determine the phase state in very small bulk material samples. However, this method cannot determine the phase state at a specific location within the sample volume, so it is not suitable for energy storage conditions of large volume phase change materials.

[0004] Therefore, the skilled in the art is committed to developing a n-octadecane phase change detection sensor based on anti-resonant hollow core fiber, which is based on optical sensing, safe, small in size, high in precision, resistant to electromagnetic interference, resistant to corrosion and remote measurement, and is expected to make up for the defects of the existing methods. SUMMARY

[0005] In view of the above defects of the prior art, the technical problem to be solved by the present application is how to provide a fiber phase change detection sensor which is simple in structure, easy to manufacture and convenient to use.

[0006] To achieve the above-mentioned purpose, the present application provides a n-octadecane phase change detection sensor based on anti-resonant hollow core fiber, which comprises input single-mode optical fiber, tubular hollow core fiber and output single-mode optical fiber connected in sequence, and the sensor is configured to realize phase change detection of n-octadecane material by comparing the change of resonance peak intensity.

[0007] Further, the tubular hollow core fiber is connected between the input single-mode optical fiber and the output single-mode optical fiber in a coaxial fusion splicing manner.

[0008] Further, the cladding diameter of the input single-mode optical fiber and the output single-mode optical fiber is 125 μm, and the core diameter is 4-10 μm.

[0009] Further, the outer diameter of the tubular hollow-core optical fiber is 125 μm, and the inner diameter is 20-40 μm.

[0010] Further, the length of the tubular hollow-core optical fiber is 0.5-5 cm.

[0011] The application also provides a manufacturing method of the n-octadecane phase change detection sensor based on the anti-resonant hollow-core optical fiber, comprising the following steps:

[0012] Step one: the coating layer of the input single-mode optical fiber is stripped with a fiber stripping pliers, and the end face is cut flat with a fiber cutting knife;

[0013] Step two: the coating layer of the tubular hollow-core optical fiber is scraped off with a blade, and the end face is cut flat with a fiber cutting knife;

[0014] Step three: the input single-mode optical fiber with the cut flat end face and the head end of the tubular hollow-core optical fiber are placed in a fiber fusion splicer for fusion splicing, the position of the fusion splicer fire head is adjusted to be deviated to the input single-mode optical fiber, and the discharge parameters of the fusion splicer are changed, so that the large-scale collapse of the hollow-core optical fiber or the false welding of the optical fiber is avoided;

[0015] Step four: the tubular hollow-core optical fiber is cut off at a distance of 0.5-5 cm from the welding point with a fiber cutting knife;

[0016] Step five: the coating layer of the output single-mode optical fiber is stripped with a fiber stripping pliers, and the end face is cut flat with a fiber cutting knife;

[0017] Step six: the output single-mode optical fiber with the cut flat end face and the tail end of the tubular hollow-core optical fiber are placed in a fiber fusion splicer for fusion splicing, the position of the fusion splicer fire head is adjusted to be deviated to the output single-mode optical fiber, and the discharge parameters of the fusion splicer are changed, so that the large-scale collapse of the hollow-core optical fiber or the false welding of the optical fiber is avoided.

[0018] Further, the cladding diameter of the input single-mode optical fiber in the step one and the output single-mode optical fiber in the step five is 125 μm, and the core diameter is 4-10 μm.

[0019] Further, the outer diameter of the tubular hollow-core optical fiber in the step two is 125 μm, and the inner diameter is 20-40 μm.

[0020] The application also provides a use method of the n-octadecane phase change detection sensor based on the anti-resonant hollow-core optical fiber, comprising the following steps:

[0021] Step 1, connecting the tubular hollow core optical fiber between the input single-mode optical fiber and the output single-mode optical fiber in a coaxial fusion manner to obtain a phase change detection sensor;

[0022] Step 2, immersing the phase change detection sensor in n-octadecane material;

[0023] Step 3, connecting the input single-mode optical fiber to the super-continuous light source and connecting the output single-mode optical fiber to the optical spectrum analyzer;

[0024] Step 4, controlling the temperature of the n-octadecane by the ceramic heating sheet to change the phase change state of the n-octadecane;

[0025] Step 5, measuring the real-time temperature of the material by the thermocouple and the temperature measuring instrument, and directly observing the phase state transition state of the n-octadecane by the image sensor;

[0026] Step 6, recording the transmission spectrum of the phase change detection sensor at different temperatures and corresponding phase states.

[0027] Further, the cladding diameters of the input single-mode optical fiber and the output single-mode optical fiber in the step 1 are both 125 μm, the core diameters are both 4-10 μm, the outer diameter of the tubular hollow core optical fiber is 125 μm, and the inner diameter is 20-40 μm.

[0028] The present application has the following beneficial effects:

[0029] (1) The basic structure of the present application is simple, only single-mode optical fiber and tubular hollow core optical fiber are needed;

[0030] (2) The phase change detection of the phase change material can be realized by comparing the resonance peak intensity change.

[0031] The concept, specific structure and generated technical effects of the present application will be further described below with reference to the accompanying drawings to fully understand the purpose, features and effects of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a structure schematic diagram of a preferred embodiment of the present application;

[0033] Figure 2 is a physical cross-sectional view of a preferred embodiment of the present application;

[0034] Figure 3 is a light beam propagation path schematic diagram of a preferred embodiment of the present application;

[0035] Figure 4 is a transmission spectrum of a preferred embodiment of the present application;

[0036] Figure 5 is a detection spectrum of a preferred embodiment of the present application for phase state change;

[0037] Figure 6 is the strength of the resonance peak when the material phase changes.

[0038] Wherein, 1-input single-mode optical fiber, 2-tubular hollow optical fiber, 3-output single-mode optical fiber, 4-outer cladding, 5-air core. DETAILED DESCRIPTION

[0039] The technical content of the present application will be more clearly understood and facilitated to be understood by introducing the preferred embodiments of the present application with reference to the accompanying drawings of the specification. The present application can be embodied in many different forms, and the scope of protection of the present application is not limited to the embodiments mentioned herein.

[0040] In the drawings, the same components have the same reference numerals, and components having similar structures or functions are denoted by similar reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present application is not limited to the size and thickness of each component. In order to make the drawing clearer, the thickness of some components is appropriately exaggerated in some places in the drawing.

[0041] The working principle of the present application is based on the anti-resonance effect of the hollow optical fiber itself. When the n-octadecane phase changes, its own refractive index will change greatly, which will change the Fresnel reflection coefficient between the cladding of the hollow optical fiber and the outside, thereby affecting the resonance strength of the structure transmission spectrum. The phase state of the surrounding n-octadecane can be detected by detecting the change in peak intensity.

[0042] Example 1

[0043] As shown in Figure 1 , the n-octadecane phase change detection sensor of the hollow optical fiber is composed of an input single-mode optical fiber 1, a tubular hollow optical fiber 2 and an output single-mode optical fiber 3. The tubular hollow optical fiber 2 is fused to the input single-mode optical fiber 1 and the output single-mode optical fiber 3 along the axis. When fusing, the parameters of the fusion machine should be adjusted to avoid the occurrence of large-scale collapse of the hollow optical fiber or the situation of optical fiber false welding caused by improper power. The core diameter of the input and output single-mode optical fiber 1 is 8.2 μm, and the cladding diameter is 125 μm.

[0044] As shown in Figure 2 , the outer cladding 4 of the tubular hollow optical fiber 2 has a diameter of 125 μm, the air core 5 inside the tubular hollow optical fiber has a diameter of 25 μm, and the length of the tubular hollow optical fiber 2 is selected to be 0.5 to 5 cm.

[0045] Example 2

[0046] The present embodiment provides a method for manufacturing a hollow optical fiber n-octadecane phase change detection sensor, and the specific steps are as follows:

[0047] Step one: use the optical fiber stripper to remove the coating of the input single-mode optical fiber, and use the optical fiber cutter to cut the end face flat;

[0048] Step two: use the blade to scrape off the coating of the tubular hollow-core optical fiber, and use the optical fiber cutter to cut the end face flat;

[0049] Step three: place the flat end face of the input single-mode optical fiber and the leading end of the tubular hollow-core optical fiber in the optical fiber fusion splicer, adjust the position of the fusion splicer's flame to be biased towards the input single-mode optical fiber, and change the discharge parameters of the fusion splicer to ensure that the hollow-core optical fiber does not collapse or the optical fiber is not virtually welded;

[0050] Step four: use the optical fiber cutter to cut the tubular hollow-core optical fiber at a distance of 0.5 to 5 cm from the weld point;

[0051] Step five: use the optical fiber stripper to remove the coating of the output single-mode optical fiber, and use the optical fiber cutter to cut the end face flat;

[0052] Step six: place the flat end face of the output single-mode optical fiber and the trailing end of the tubular hollow-core optical fiber in the optical fiber fusion splicer, adjust the position of the fusion splicer's flame to be biased towards the output single-mode optical fiber, and change the discharge parameters of the fusion splicer to ensure that the hollow-core optical fiber does not collapse or the optical fiber is not virtually welded.

[0053] Example 3

[0054] The present embodiment provides a use method of a n-octadecane phase change detection sensor based on a reverse resonant hollow-core optical fiber, the specific steps are as follows:

[0055] Step 1: connect the tubular hollow-core optical fiber between the input single-mode optical fiber and the output single-mode optical fiber in a coaxial fusion splicing manner to obtain a phase change detection sensor;

[0056] Step 2: immerse the phase change detection sensor in n-octadecane material;

[0057] Step 3: connect the input single-mode optical fiber to the super-continuous light source, and connect the output single-mode optical fiber to the optical spectrum analyzer;

[0058] Step 4: control the temperature of the n-octadecane by the ceramic heating sheet, so as to change the phase change state of the n-octadecane;

[0059] Step 5: measure the real-time temperature of the material by using the thermocouple and the temperature measuring instrument, and directly observe the phase state transition state of the n-octadecane by using the charge-coupled device (CCD) image sensor;

[0060] Step 6: record the transmission spectrum of the phase change detection sensor at different temperatures and corresponding phase states.

[0061] AsFigure 3 The propagation path of the light beam in the n-octadecane phase change detection sensor is shown in the figure, and the arrow is used to demonstrate the propagation mechanism of the light beam in the tubular hollow core fiber 2. The outer cladding 4 of the tubular hollow core fiber 2 can be regarded as a set of Fabry-Perot (FP) etalons, only the wavelengths satisfying the anti-resonance condition can be confined in the air core 5 (shown by the solid arrow and the dashed arrow in the figure), and the other wavelengths satisfying the resonance condition will leak to the surrounding environment (shown by the dotted arrow in the figure), thereby causing the transmission spectrum to produce periodic resonance peaks. The resonance wavelength λ m and its free spectral range (FSR) can be calculated by the following formula:

[0062]

[0063]

[0064] Where d is the outer cladding 4 thickness of the tubular hollow core fiber 2, n0 and n1 are the refractive indexes of the air core and the outer cladding 4 respectively, and m is the resonance order of the non-negative integer. From the formula, it can be seen that the resonance wavelength λ m and its FSR only depend on the outer cladding 4 thickness and the outer cladding 4 refractive index of the tubular hollow core fiber 2.

[0065] The resonance peak intensity I r can be calculated by the following formula:

[0066] I r = |A r | 2 (3)

[0067]

[0068]

[0069] Where A is the amplitude of the incident light, r1 and r2 are the Fresnel reflection coefficients of the air core 5 and the outer cladding 4, and the outer cladding 4 and the surrounding environment, and θ is the refraction angle of the incident light at the air core 5 and the outer cladding 4. It can be seen that the resonance peak intensity I r is related to the Fresnel reflection coefficients inside and outside the tubular hollow core fiber 2. Since the tubular hollow core fiber 2 is fixed and does not change, the internal Fresnel reflection coefficient r1 does not change, only the external reflection coefficient r2 will change with the surrounding environment, thereby causing the resonance peak intensity I r to change. When the material phase changes, its refractive index will change significantly, causing r2 to change, which will cause the resonance peak intensity I r of the transmission spectrum to change significantly, so as to detect the phase change of the phase change material.

[0070] like Figure 4 The image shows the transmission spectrum of an octadecane phase transition detection sensor constructed from a 1cm hollow fiber. It exhibits a clear and consistent FSR and a large extinction ratio. The minor internal resonances are caused by slight collapse of the hollow fiber during fusion splicing and interference of higher-order modes, and do not affect subsequent phase change detection.

[0071] When detecting phase transitions in materials, the sensor is immersed in n-octadecane. When n-octadecane is in a liquid state, the resonance peak of the transmission spectrum almost completely disappears. As the temperature is gradually lowered, the resonance peak reappears when the temperature approaches the critical value for the n-octadecane phase transition (approximately 27.5℃ under experimental conditions). When the n-octadecane phase transitions to a solid state, the intensity of the resonance peak in the transmission spectrum increases sharply. Due to the extremely short phase transition time of n-octadecane, the resonance peak of the sensor's transmission spectrum changes abruptly. Figure 5 To detect the spectral changes of n-octadecane as it changes from a liquid to a solid state, Figure 6 This refers to the intensity change of the resonance peak at 1500.9 nm during the phase transition detection process. It is noteworthy that when n-octadecane is stable in either a solid or liquid state, the transmission spectrum remains constant, and the resonance intensity differs by more than 10 dB between the two states—a very significant difference. Therefore, it can be determined that when the resonance intensity of the transmission spectrum changes, its overall phase state is changing.

[0072] In summary, the present invention provides a solution for the detection of octadecane phase transition based on anti-resonant hollow optical fiber. This sensor can detect the phase change of octadecane in the environment by observing the intensity change of the resonance peak, thus providing a solution for achieving rapid, safe, and sensitive material phase transition detection.

[0073] The sensor proposed in this invention is based on single-mode optical fibers for input and output and tubular hollow optical fibers. It utilizes anti-resonance to detect the liquid-solid phase transition of the phase change material n-octadecane. Experiments have verified that when n-octadecane undergoes a liquid-solid phase change, the resonance peak of its transmission spectrum will experience a sudden change of more than 10 dB. The phase transition detection sensor proposed in this invention has a simple and compact structure, uses readily available materials, and exhibits high repeatability. It has significant application value in fields such as materials detection and thermal energy storage.

[0074] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A reverse-hybrid octadecane phase transition detection sensor based on a reverse-hybrid hollow-core optical fiber, characterized in that, The sensor comprises an input single-mode optical fiber, a tubular hollow-core optical fiber and an output single-mode optical fiber connected in sequence, and is configured to detect phase transition of n-octadecane material by comparing changes in resonance peak intensity; the outer cladding of the tubular hollow-core optical fiber is regarded as a set of Fabry-Perot etalons, only the wavelengths satisfying the anti-resonance condition can be confined in the air core, and the other wavelengths satisfying the resonance condition will leak to the surrounding environment, thereby causing the transmission spectrum to have periodic resonance peaks; The method for manufacturing the n-octadecane phase transition detection sensor based on the anti-resonance hollow-core optical fiber comprises the following steps: Step one: use a fiber stripper to remove the coating of the input single-mode optical fiber, and use a fiber cutter to cut the end face flat; Step two: use a blade to remove the coating of the tubular hollow-core optical fiber, and use a fiber cutter to cut the end face flat; Step three: place the input single-mode optical fiber and the first end of the tubular hollow-core optical fiber with the flat end face in a fiber fusion splicer, adjust the position of the fusion splicer fire head to be biased towards the input single-mode optical fiber, and change the discharge parameters of the fusion splicer to ensure that no large-scale collapse of the hollow-core optical fiber or false welding of the optical fiber occurs; Step four: use a fiber cutter to cut the tubular hollow-core optical fiber at a distance of 0.5 to 5 cm from the welding point; Step five: use a fiber stripper to remove the coating of the output single-mode optical fiber, and use a fiber cutter to cut the end face flat; Step six: place the output single-mode optical fiber and the end of the tubular hollow-core optical fiber with the flat end face in a fiber fusion splicer, adjust the position of the fusion splicer fire head to be biased towards the output single-mode optical fiber, and change the discharge parameters of the fusion splicer to ensure that no large-scale collapse of the hollow-core optical fiber or false welding of the optical fiber occurs.

2. The anti-resonant hollow core optical fiber based n-octadecane phase transition detection sensor of claim 1, wherein, The tubular hollow-core optical fiber is connected between the input single-mode optical fiber and the output single-mode optical fiber in a coaxial fusion manner.

3. The anti-resonant hollow core optical fiber based n-octadecane phase transition detection sensor of claim 1, wherein, The cladding diameters of the input single-mode optical fiber and the output single-mode optical fiber are both 125 μm, and the core diameters are both 4 to 10 μm.

4. The anti-resonant hollow core optical fiber based n-octadecane phase transition detection sensor of claim 1, wherein, The outer diameter of the tubular hollow-core optical fiber is 125 μm, and the inner diameter is 20 to 40 μm.

5. The anti-resonant hollow core optical fiber based n-octadecane phase transition detection sensor of claim 1, wherein, The length of the tubular hollow-core optical fiber is 0.5 to 5 cm.

6. A method of using the n-octadecane phase transition detection sensor based on the anti-resonant hollow core optical fiber according to claim 1, characterized by, The method comprises the following steps: Step 1: connect the tubular hollow-core optical fiber between the input single-mode optical fiber and the output single-mode optical fiber in a coaxial fusion manner to obtain a phase transition detection sensor; Step 2: immerse the phase transition detection sensor in n-octadecane material; Step 3: connect the input single-mode optical fiber to an ultrashort pulse laser, and connect the output single-mode optical fiber to a spectrum analyzer; Step 4: control the temperature of the n-octadecane by using a ceramic heating sheet, so as to change the phase transition state of the n-octadecane; Step 5: measure the real-time temperature of the material by using a thermocouple and a temperature measuring instrument, and directly observe the phase state transition state of the n-octadecane by using an image sensor; Step 6: record the transmission spectrum of the phase transition detection sensor at different temperatures and corresponding phase states.

7. The method of using a reverse-resonator hollow-core photonic fiber based n-octadecane phase transition detection sensor according to claim 6, wherein, In step 1, the cladding diameters of the input single-mode optical fiber and the output single-mode optical fiber are both 125 μm, the core diameters are both 4 to 10 μm, the outer diameter of the tubular hollow-core optical fiber is 125 μm, and the inner diameter is 20 to 40 μm.

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