SNS superfine optical fiber and optical fiber sensor

Abstract

The utility model discloses a kind of SNS superfine optical fiber and optical fiber sensor, it is related to sensor technical field;SNS superfine optical fiber includes two single-mode optical fibers and the hollow core fiber fused between two single-mode optical fibers, the diameter of hollow core fiber is less than single-mode optical fiber, after light enters hollow core fiber from single-mode optical fiber, light will propagate in the hollow core fiber without cladding in the mode of multimode transmission, and strong evanescent wave will be generated and extended into the medium around optical fiber, the penetration depth of evanescent wave is substantially increased compared with single-mode optical fiber, and the interaction with external environment is significantly enhanced, so as to significantly improve the sensitivity of optical fiber sensor.

Description

Technical Field

[0001] This utility model relates to the field of sensor technology, and in particular to an SNS ultra-fine optical fiber and an optical fiber sensor. Background Technology

[0002] As a key technology in the field of intelligent sensing, fiber optic sensors have become an indispensable monitoring support tool for many critical industries due to their resistance to electromagnetic interference, corrosion resistance, small size, and long-distance transmission capabilities. In the biomedical field, scenarios such as non-invasive blood glucose monitoring and tumor marker detection rely on fiber optic sensors to accurately capture trace biological signals. For example, the detection of pg / mL level molecules in blood can directly affect the efficiency of early disease diagnosis. In environmental monitoring and industrial production, it can track the concentration of heavy metal ions in complex waters in real time and continuously monitor reactor parameters in high-risk chemical environments, building a data defense line for ecological protection and safe production. In addition, in fields such as bridge health monitoring and smart grid operation and maintenance, the distributed measurement capabilities of fiber optic sensors can achieve long-distance, high-resolution state perception, making them a key basic component for promoting the intelligent upgrading of various industries.

[0003] However, existing fiber optic sensors have always faced the dual bottlenecks of response capability and detection sensitivity due to insufficient light field leakage. Traditional single-mode fiber relies on the refractive index difference between the core and cladding to achieve light confinement. The core mode field is strongly confined, and the light field leakage is less than 5%. The interaction with the external environment is limited to the surface of the fiber, resulting in low detection sensitivity of target substances. In fact, it may even lead to missed detection due to insufficient signal capture, which greatly restricts the application of fiber optic sensors in micro-volume and rapid detection scenarios. Utility Model Content

[0004] This invention provides a highly sensitive SNS ultrafine optical fiber and optical fiber sensor.

[0005] The SNS ultra-fine optical fiber provided by this utility model includes two single-mode optical fibers and a coreless optical fiber fused between the two single-mode optical fibers. The diameter of the coreless optical fiber is smaller than that of the single-mode optical fiber.

[0006] Optionally, the diameter of the coreless optical fiber is 1~10μm.

[0007] Optionally, the coreless optical fiber has a diameter of 7.2 μm.

[0008] Optionally, the coreless optical fiber is made of the same material as the cladding material of the single-mode optical fiber.

[0009] Optionally, the coreless optical fiber is made of quartz glass or fluorine-doped quartz glass.

[0010] Optionally, the length of the coreless optical fiber is 15~75mm.

[0011] Optionally, the single-mode fiber and the coreless fiber are linear fibers.

[0012] This invention also provides an optical fiber sensor, including the SNS ultrafine optical fiber described above, and: a functionalized sensitive material disposed on the coreless surface of the SNS ultrafine optical fiber; the functionalized sensitive material can respond to changes in external substances or environmental physical quantities to change the optical transmission characteristics of the SNS ultrafine optical fiber.

[0013] Optionally, the functionalized sensitive material includes at least one of biological enzymes, antibodies, nucleic acid single chains, pH-sensitive materials, temperature-sensitive materials, humidity-sensitive materials, and molecularly imprinted polymers.

[0014] Optionally, it also includes a light source and a spectrometer; the light source and the spectrometer are respectively connected to the two ends of the SNS ultrafine optical fiber.

[0015] This utility model has the following beneficial effects:

[0016] This invention utilizes SNS ultrafine optical fiber to fabricate a glucose sensor. The SNS ultrafine optical fiber comprises two single-mode optical fibers and a coreless optical fiber fused between the two single-mode optical fibers. After light enters the coreless optical fiber from the single-mode optical fiber, it propagates in a multimode mode within the unclad coreless optical fiber, generating a strong evanescent wave that extends into the surrounding medium. The penetration depth of the evanescent wave is significantly increased compared to the single-mode optical fiber, resulting in a significantly enhanced interaction with the external environment, thereby significantly improving the sensitivity of the optical fiber sensor. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 These are schematic diagrams illustrating the structure of some embodiments of the SNS ultrafine optical fiber of this utility model;

[0019] Figure 2 The image shows the microstructure of the coreless fiber portion of the SNS ultrafine optical fiber prepared in Embodiment 1 of this utility model.

[0020] Figure 3 This is a simulation diagram of the light field distribution and normalized light intensity of the linear single-mode fiber and the SNS ultrafine fiber in Embodiment 2 of this utility model.

[0021] Figure 4The simulated spectra of SNS micro / nano fibers with different coreless fiber lengths in Embodiment 2 of this utility model, as well as the comparison of free spectral range and wavelength shift;

[0022] Figure 5 The figure shows the simulation results of the spectral shift of the SNS micro-nano fiber with a coreless fiber length of 15 mm in Embodiment 2 of this utility model under different glucose concentrations and temperature environments. Detailed Implementation

[0023] To make the utility model's objectives, features, and advantages more apparent and understandable, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present utility model.

[0024] The terms “first” and “second” (if present) in this utility model are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as “first” or “second” may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, “multiple” means two or more.

[0025] See Figure 1 , 2 This utility model provides an SNS ultra-thin optical fiber, wherein "SNS" refers to "SMF-NCF-SMF". The SNS ultra-thin optical fiber includes two single-mode fibers (SMF) and a coreless fiber (NCF) spliced ​​between the two single-mode fibers. The diameter of the coreless fiber is smaller than that of the single-mode fiber. The connection between the coreless fiber and the single-mode fiber presents a tapered region. Both the single-mode fiber and the coreless fiber are straight optical fibers. The material of the coreless fiber is the same as the cladding material of the single-mode fiber.

[0026] In some embodiments, the diameter of the coreless optical fiber is 1~10μm, for example, 1μm, 3μm, 5μm, 7μm or 10μm can be selected, and other values ​​within the range are also applicable to this utility model. The specific lengths of the coreless optical fiber and the two single-mode optical fibers can be set according to mechanical strength requirements and testing needs.

[0027] In some embodiments, the coreless optical fiber is made of quartz glass or fluorine-doped quartz glass.

[0028] In some preferred embodiments, the coreless optical fiber has a diameter of 7.2 μm.

[0029] In some preferred embodiments, the length of the coreless fiber is 15~75mm. As the length of the coreless fiber increases, the sensing resolution of the SNS ultrafine fiber increases, while the sensitivity decreases.

[0030] The sensing principle of SNS ultra-thin optical fiber is as follows:

[0031] The input single-mode fiber stably transmits the fundamental mode optical signal to the coreless fiber in the middle. Because the coreless fiber lacks the optical confinement capability of the core layer and has a smaller diameter than the single-mode fiber, the input fundamental mode optical field cannot be confined inside the fiber and will diffuse significantly along the outer periphery of the coreless fiber, forming an evanescent field covering the fiber surface. The evanescent field comes into direct contact with target parameters in the external environment (physical quantities: temperature, stress, etc.; chemical quantities: heavy metal ions, gas concentration, etc.; biological quantities: tumor markers, antibodies, glucose, etc.). When the target parameters change, the local refractive index of the evanescent field propagation will change, resulting in a phase shift of the evanescent field. The evanescent field modulated by the external parameters (the phase, intensity, polarization state, or spectral characteristics have undergone quantitative changes) will be transmitted to the output single-mode fiber. The output single-mode fiber stably couples the modulated optical field out through mode field matching. By detecting the change in the interference spectrum at the output end, the change in the optical field can be converted into specific target parameter values, realizing the quantitative detection of the target analyte.

[0032] This invention utilizes SNS ultrafine optical fiber to fabricate a glucose sensor. The SNS ultrafine optical fiber comprises two single-mode optical fibers and a coreless optical fiber fused between the two single-mode optical fibers. After light enters the coreless optical fiber from the single-mode optical fiber, it propagates in a multimode mode within the unclad coreless optical fiber, generating a strong evanescent wave that extends into the surrounding medium. The penetration depth of the evanescent wave is significantly increased compared to the single-mode optical fiber, resulting in a significantly enhanced interaction with the external environment, thereby significantly improving the sensitivity of the optical fiber sensor.

[0033] Based on the SNS ultra-thin optical fiber provided in the above embodiments, this utility model also provides an optical fiber sensor, which includes an SNS ultra-thin optical fiber and a functionalized sensitive material; the functionalized sensitive material is disposed on the coreless surface of the SNS ultra-thin optical fiber and can respond to changes in external substances or environmental physical quantities to change the optical transmission characteristics of the SNS ultra-thin optical fiber.

[0034] In some embodiments, the functionalized sensitive material is a biological enzyme, such as glucose oxidase that can monitor glucose concentration or alcohol dehydrogenase that can detect ethanol content.

[0035] In some embodiments, the functionalized sensitive material is an antibody, such as an anti-carcinoembryonic antigen polyclonal antibody for tumor marker detection.

[0036] In some embodiments, the functionalized sensitive material is a single-stranded nucleic acid, such as a complementary nucleic acid probe for the detection of a specific gene, or a specific aptamer for the detection of Escherichia coli rRNA in drinking water.

[0037] In some embodiments, the functionalized sensitive material is a pH-sensitive material, such as polymethacrylic acid-acrylic acid copolymer for dynamic monitoring of cell culture medium pH, or bromophenol blue-modified mesoporous SiO2 for soil pH detection.

[0038] In some embodiments, the functionalized sensitive material is a temperature-sensitive material, such as poly(N-isopropylacrylamide) hydrogel or vanadium oxide (VO2) nanofilm, used for monitoring local heat distribution in electronic chips and for minimally invasive temperature measurement of biological tissues.

[0039] In some embodiments, the functionalized sensitive material is a humidity-sensitive material, such as graphene oxide (GO) / chitosan composite film, silica (SiO2) aerogel, etc.

[0040] In some embodiments, the functionalized sensitive material is a specific molecularly imprinted polymer, such as a molecularly imprinted polymer for detecting pesticide residues in agricultural products, or an imprinted polymer for detecting specific chemicals in liquids such as fruit juice and blood, etc.

[0041] In the above embodiments of the fiber optic sensor, when the functionalized sensitive material modified on the surface of the coreless fiber is combined with the target analyte, the local refractive index change is enhanced, resulting in a change in the phase of the evanescent wave. The concentration of the target analyte can be calculated by detecting the change in the interference spectrum at the output end.

[0042] Based on the above embodiments, in order to illustrate the technical solution of this utility model in more detail, the following specific embodiments are also proposed. It should be noted that the following specific embodiments are merely exemplary and are not intended to limit the scope of protection of this utility model in any way.

[0043] Example 1

[0044] This embodiment demonstrates the fabrication of an SNS ultrafine optical fiber.

[0045] Two 30cm single-mode fibers and one 15mm coreless fiber were fused together using a fiber fusion splicer, with the coreless fiber positioned between the two single-mode fibers to obtain an SNS fiber. The SNS fiber was then heated and lengthened using a fiber tapering machine. Specifically, the SNS fiber was heated with an oxyhydrogen flame and lengthened by 1.2cm at a speed of 200μm / s, resulting in an ultrafine SNS fiber with a diameter of 7.2μm. The microstructure of the coreless fiber section is shown below. Figure 2 As shown.

[0046] Example 2

[0047] This embodiment simulates the optical field leakage characteristics and sensing sensitivity of SNS ultrafine optical fiber.

[0048] Simulation results are as follows Figure 3 As shown, the results indicate that, in the initial state, when light passes through a single-mode fiber, most of the light propagates within the fiber core via total internal reflection. However, in a straight single-mode ultrafine fiber, the light continues to propagate around the fiber core and interferes, with a slight penetration phenomenon in the fiber's tapered region, and some energy propagating outward in the form of evanescent waves. In contrast, when light passes through an SNS ultrafine fiber, the propagation of the light field after passing through the tapered region changes significantly, the interference phenomenon becomes more pronounced, and more energy leaks into the external environment in the form of evanescent waves, resulting in a substantial increase in penetration depth.

[0049] Further comparison reveals that the transmission depth of SNS ultrafine fiber is significantly improved compared to linear single-mode ultrafine fiber, indicating a stronger interaction between SNS ultrafine fiber and the external environment, thus significantly enhancing the sensor's sensitivity. Specifically, from the perspective of optical power, the output power of linear single-mode ultrafine fiber is approximately 95%, meaning that most of the optical power is still retained within the fiber. In contrast, the output power of SNS ultrafine fiber is significantly reduced, remaining at only about 20%. This means that most of the optical power leaks to the outside world in the form of evanescent waves, with a small portion of energy returning to the single-mode fiber at the output end. This result demonstrates that SNS ultrafine fiber, through its stronger light field leakage characteristics, interacts more closely with the external environment, thereby greatly enhancing the sensor's response to external changes and its detection sensitivity.

[0050] Further, see Figure 4 In this embodiment, a comparative experiment was designed with SNS ultrafine optical fibers of different coreless fiber lengths. The lengths of the coreless optical fibers were set to 15mm, 45mm and 75mm respectively, and all optical fibers were SNS ultrafine optical fibers with an extension of 12000μm. Figure 4 In the figures (a)-(c), the simulation results are for coreless optical fibers of different lengths. Figure 4 Figure (d) shows a comparison of the free spectral range (FSR) and interference wavelength shift for coreless optical fibers of different lengths. Simulation results show that as the length of the coreless optical fiber increases from 15 mm to 45 mm, and finally to 75 mm, the free spectral range (FSR) gradually decreases, from 13.6 nm to 11.1 nm, and then to 10.1 nm. This trend indicates that as the length of the coreless optical fiber increases, the interference effect of the fiber becomes more significant, leading to a compression of the free spectral range. However, as the length of the coreless optical fiber increases, the offset distance of the interference wavelength gradually decreases. In summary, as the length of the coreless optical fiber increases, the detection resolution of the enhanced glucose sensor based on SNS ultrafine optical fiber improves, while the sensitivity decreases.

[0051] Subsequently, this embodiment conducted simulation tests on glucose concentration and temperature using a 15mm coreless SNS ultrafine optical fiber. The test results are as follows: Figure 5 As shown, in terms of concentration detection, the interference wavelength exhibits a redshift as glucose concentration increases, indicating that the effect of concentration change on the spectrum is measurable, and the concentration change can be inferred from the redshift of the spectrum. In terms of temperature detection, the interference wavelength undergoes a blueshift as temperature increases. This temperature-related spectral change enables the sensor to effectively respond to temperature changes and provide corresponding measurement results. Simulation results show that the 15mm coreless SNS ultrafine optical fiber not only ensures good measurement resolution and sensitivity but also provides reliable performance in glucose concentration and temperature detection.

[0052] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A type of SNS ultra-thin optical fiber, characterized in that, It includes two single-mode optical fibers and a coreless optical fiber fused between the two single-mode optical fibers, wherein the diameter of the coreless optical fiber is smaller than that of the single-mode optical fiber.

2. The SNS ultrafine optical fiber according to claim 1, characterized in that, The diameter of the coreless optical fiber is 1~10μm.

3. The SNS ultrafine optical fiber according to claim 1, characterized in that, The coreless optical fiber has a diameter of 7.2 μm.

4. The SNS ultrafine optical fiber according to claim 1, characterized in that, The coreless optical fiber is made of the same material as the cladding material of the single-mode optical fiber.

5. The SNS ultrafine optical fiber according to claim 4, characterized in that, The coreless optical fiber is made of quartz glass or fluorine-doped quartz glass.

6. The SNS ultrafine optical fiber according to claim 1, characterized in that, The coreless optical fiber has a length of 15~75mm.

7. The SNS ultrafine optical fiber according to claim 1, characterized in that, The single-mode fiber and the coreless fiber are linear fibers.

8. An optical fiber sensor, characterized in that, Including the SNS ultrafine optical fiber as described in any one of claims 1-7, and: A functionalized sensitive material is disposed on the coreless fiber surface of the SNS ultrafine optical fiber; the functionalized sensitive material can respond to changes in external substances or environmental physical quantities to change the optical transmission characteristics of the SNS ultrafine optical fiber.

9. The fiber optic sensor according to claim 8, characterized in that, The functionalized sensitive material is a biological enzyme, antibody, nucleic acid single chain, pH sensitive material, temperature sensitive material, humidity sensitive material, or molecularly imprinted polymer.

10. The fiber optic sensor according to claim 8, characterized in that, It also includes a light source and a spectrometer; the light source and the spectrometer are respectively connected to the two ends of the SNS ultrafine optical fiber.

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