A U-shaped ultra-fine optical fiber and an optical fiber sensor
Patent Information
- Application Number
- CN202522409827.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-13
- Publication Date
- 2026-10-16
- Estimated Expiration
- 2035-11-13
AI Technical Summary
[0003]然而当前U型光纤技术仍面临体积与灵敏度的双重瓶颈，严重制约其在高集成、高精度场景中的落地应用；在体积控制方面，传统U型光纤腰区直径多维持在30μm以上，弯曲半径则普遍大于5mm，部分U型液芯光纤的外径甚至可达300~2000μm，这种大体积特性使其无法适配小型化应用场景（例如微流控芯片的微米级通道、内窥镜微创检测中对小型化探头、随身携带的葡萄糖传感器等），极大限制了其在高密度集成系统中的应用；而灵敏度不足的问题根源在于腰区表面倏逝场强度低、透射深度小，导致倏逝场与外界分析物的作用强度薄弱，即便结合表面等离子体共振（SPR）等增敏技术，U型光纤的探测灵敏度仍多低于3500nm/RIU
[0018]本实用新型提出的U型超细光纤将腰区的光纤直径设置为预设色散转折点对应的特征直径，当预设色散转折点相应波长的光在腰区传输时，由于材料色散与波导色散相互抵消，使得光纤总色散降至最低，光的传输模式稳定，弯曲损耗低，这种光场特性提升了U型超细光纤腰区倏逝场与功能化敏感材料、目标介质的相互作用效率，进而提高了U型超细光纤的灵敏度；同时光纤的色散转折点对应的特征直径通常在数微米的超细尺寸，超细直径的U型光纤具有更大的可弯曲程度，从而有利于U型光纤传感器的小型化。
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Figure CN224861770U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of sensor technology, and in particular to a U-shaped ultra-fine optical fiber and an optical fiber sensor. Background Technology
[0002] U-shaped optical fibers, as a type of special optical fiber device based on the evanescent field enhancement effect, occupy a key position in fields such as sensing, optical communication and biomedicine due to their unique bending structure and optical properties. Their core value comes from the significant enhancement effect of the evanescent field in the bending waist region. That is, when light propagates in the waist region, a large amount of optical field energy penetrates into the surface of the optical fiber and can form a strong interaction with the surrounding medium. This characteristic makes it an ideal carrier for high-sensitivity sensing.
[0003] However, current U-shaped fiber technology still faces dual bottlenecks in size and sensitivity, which severely restricts its application in highly integrated and high-precision scenarios. In terms of size control, the waist diameter of traditional U-shaped fibers is mostly maintained above 30μm, and the bending radius is generally greater than 5mm. The outer diameter of some U-shaped liquid-core fibers can even reach 300~2000μm. This large size characteristic makes it unsuitable for miniaturized application scenarios (such as micron-level channels in microfluidic chips, miniaturized probes in minimally invasive endoscopic detection, and portable glucose sensors), which greatly limits its application in high-density integrated systems. The root cause of the insufficient sensitivity is the low evanescent field intensity and small transmission depth on the waist surface, resulting in weak interaction between the evanescent field and external analytes. Even with the combination of surface plasmon resonance (SPR) and other sensitization techniques, the detection sensitivity of U-shaped fibers is still mostly below 3500nm / RIU. Utility Model Content
[0004] This utility model embodiment provides a small-sized, highly sensitive U-shaped ultra-fine optical fiber and an optical fiber sensor.
[0005] The U-shaped ultra-fine optical fiber provided by this utility model is made of micro-nano optical fiber and includes a curved section and straight sections located at both ends of the curved section. The curved section includes a waist region, and the optical fiber diameter of the waist region is set as the characteristic diameter corresponding to a preset dispersion inflection point.
[0006] Optionally, the diameter of the optical fiber in the waist region is 3~5μm.
[0007] Optionally, the fiber diameter in the waist region is 3.5 μm.
[0008] Optionally, the bending radius of the waist region is 900~1500μm.
[0009] Optionally, the preset dispersion inflection point is 1550~1580nm.
[0010] Optionally, the refractive index sensitivity of the U-shaped ultrafine optical fiber is 5000~37000nm / RIU.
[0011] Optionally, the U-shaped ultrafine optical fiber is a single-mode optical fiber.
[0012] The fiber optic sensor provided by this utility model includes the U-shaped ultra-fine optical fiber described above, and:
[0013] A functionalized sensitive material is disposed on the waist region surface of the U-shaped ultra-thin 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 U-shaped ultra-thin optical fiber.
[0014] Optionally, the functionalized sensitive material includes at least one of biological enzymes, antibodies, single-stranded nucleic acids, pH-sensitive materials, temperature-sensitive materials, humidity-sensitive materials, and molecularly imprinted polymers.
[0015] 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 U-shaped ultra-fine optical fiber.
[0016] Optionally, the functionalized sensitive material is glucose oxidase.
[0017] This utility model has the following beneficial effects:
[0018] The U-shaped ultra-thin optical fiber proposed in this invention sets the fiber diameter in the waist region to the characteristic diameter corresponding to the preset dispersion inflection point. When light of the wavelength corresponding to the preset dispersion inflection point propagates in the waist region, the material dispersion and waveguide dispersion cancel each other out, minimizing the total dispersion of the optical fiber, stabilizing the light transmission mode, and reducing bending loss. This optical field characteristic improves the interaction efficiency between the evanescent field in the waist region of the U-shaped ultra-thin optical fiber and the functionalized sensitive material and target medium, thereby improving the sensitivity of the U-shaped ultra-thin optical fiber. At the same time, the characteristic diameter corresponding to the dispersion inflection point of the optical fiber is usually in an ultra-thin size of several micrometers. The ultra-thin diameter U-shaped optical fiber has a greater degree of flexibility, which is beneficial to the miniaturization of U-shaped optical fiber sensors. Attached Figure Description
[0019] 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.
[0020] Figure 1 This is an optical micrograph of the waist region of the U-shaped ultrafine optical fiber prepared in Embodiment 1 of this utility model;
[0021] Figure 2 These are schematic diagrams of some embodiments of the U-shaped ultrafine optical fiber of this utility model;
[0022] Figure 3 The simulation results of the refractive index sensitivity of micro / nano optical fibers of different diameters in Embodiment 1 of this utility model are shown.
[0023] Figure 4 The above are the simulation results of light field leakage for linear micro / nano optical fibers and U-shaped ultra-fine optical fibers in Embodiment 1 of this utility model;
[0024] Figure 5 The graph shows the interference wavelength of the U-shaped ultrafine optical fiber with a waist region bending radius of 900 μm prepared according to Embodiment 1 of this utility model as a function of refractive index. Detailed Implementation
[0025] 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.
[0026] 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.
[0027] See Figure 1 , 2 The U-shaped ultra-fine optical fiber provided by this utility model is made of micro-nano optical fiber and includes a curved section and straight sections located at both ends of the curved section. The curved section has a waist region, and the optical fiber diameter of the waist region is set as the characteristic diameter corresponding to the preset dispersion inflection point.
[0028] The waist region refers to the middle section of the U-shaped fiber where the bending degree is the greatest and the cross-section is the narrowest. The optical transmission characteristics of the U-shaped fiber (such as mode coupling, loss, and evanescent field enhancement) mainly occur in the waist region, which is the core area for the U-shaped fiber to realize sensing and other functions.
[0029] The dispersion inflection point (also known as the zero dispersion wavelength) refers to the point at which the material dispersion of the fiber and the waveguide dispersion are equal in magnitude but opposite in sign when the fiber diameter is at a certain value. The two cancel each other out, so that the total dispersion of the fiber is reduced to a minimum (or even close to zero dispersion). At this point, the broadening effect of the optical signal of the corresponding wavelength is greatly suppressed when it is transmitted in the fiber, and the optical field distribution and transmission characteristics reach a balanced and stable state.
[0030] The U-shaped ultra-thin optical fiber proposed in this invention sets the fiber diameter in the waist region to the characteristic diameter corresponding to the preset dispersion inflection point. When light of the wavelength corresponding to the preset dispersion inflection point propagates in the waist region, the material dispersion and waveguide dispersion cancel each other out, minimizing the total dispersion of the optical fiber, stabilizing the light transmission mode, and reducing bending loss. This optical field characteristic improves the interaction efficiency between the evanescent field in the waist region of the U-shaped ultra-thin optical fiber and the functionalized sensitive material and target medium, thereby improving the sensitivity of the U-shaped ultra-thin optical fiber. At the same time, the characteristic diameter corresponding to the dispersion inflection point of the optical fiber is usually in an ultra-thin size of several micrometers. The ultra-thin diameter U-shaped optical fiber has a greater degree of flexibility, which is beneficial to the miniaturization of U-shaped optical fiber sensors.
[0031] In some specific embodiments, the preset dispersion inflection point is 1550~1580nm (i.e., the zero dispersion wavelength is 1550~1580nm). Based on the dispersion inflection point, the required fiber diameter is deduced to be 3~5μm. Thus, the waist region fiber diameter of the U-shaped ultrafine fiber is set to 3~5μm.
[0032] In some specific embodiments, the bending radius of the waist region can be set to 900~1500μm. A smaller bending radius is beneficial to improving the sensitivity of the U-shaped ultrafine optical fiber.
[0033] In some preferred embodiments, the U-shaped ultra-thin optical fiber is a single-mode optical fiber. Due to the controllability of its fundamental mode transmission and the concentration of its mode field distribution, the penetration depth and energy distribution of the evanescent wave can be precisely adjusted through the optical fiber structure, thereby improving the detection sensitivity.
[0034] The U-shaped ultrafine optical fiber provided by this invention can be prepared by the following method:
[0035] U-shaped ultra-fine optical fibers are prepared using an optical fiber taper machine, which includes an oxy-hydrogen lamp heating device and a displacement platform stretching device. The single-mode optical fiber is heated by the oxy-hydrogen lamp heating device and stretched to a preset length at a uniform speed to obtain an ultra-fine fiber with a target diameter. Subsequently, the ultra-fine optical fiber is fixed in a capillary glass tube using UV photoresist to obtain a U-shaped ultra-fine optical fiber with a preset bending radius.
[0036] Based on the U-shaped ultra-thin optical fiber provided in the above embodiments, this utility model also proposes an optical fiber sensor. The optical fiber sensor includes a U-shaped ultra-thin optical fiber and a functionalized sensitive material disposed on the waist region surface of the U-shaped ultra-thin optical fiber. The functionalized sensitive material can respond to changes in external substances or environmental physical quantities, thereby changing the optical transmission characteristics of the U-shaped ultra-thin optical fiber.
[0037] 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.
[0038] In some embodiments, the functionalized sensitive material is an antibody, such as an anti-carcinoembryonic antigen polyclonal antibody for tumor marker detection.
[0039] 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.
[0040] 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.
[0041] 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.
[0042] In some embodiments, the functionalized sensitive material is a humidity-sensitive material, such as graphene oxide (GO) / chitosan composite film, silica (SiO2) aerogel, etc.
[0043] 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.
[0044] In the above embodiments of the fiber optic sensor, when light passes through the curved section of the U-shaped ultra-thin fiber, due to the destruction of the total internal reflection condition, some light energy leaks into the external environment in the form of evanescent waves. When the functionalized sensitive material modified on the fiber surface combines with the target analyte, it will cause a local refractive index change, resulting in a change in the phase of the evanescent wave. The concentration of the target analyte can be calculated by detecting the shift in the interference spectrum at the output end.
[0045] In some specific embodiments, the fiber optic sensor also includes a light source and a spectrometer; the light source and the spectrometer are respectively connected to the two ends of the U-shaped ultra-thin optical fiber. The light source emits light of a preset wavelength, which is converted into a new optical signal carrying the concentration information of the target analyte after passing through the U-shaped ultra-thin optical fiber. The spectrometer receives the optical signal transmitted by the U-shaped ultra-thin optical fiber and generates a corresponding detection spectrum. The concentration information of the analyte can be obtained by analyzing the detection spectrum.
[0046] 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.
[0047] Example 1
[0048] This embodiment simulates the refractive index sensitivity of U-shaped ultrafine optical fibers fabricated from micro-nano optical fibers of different diameters, and fabricates a U-shaped ultrafine optical fiber with a waist region fiber diameter of 3.5 μm.
[0049] The refractive index of an ideal micro / nano optical fiber was measured. The operating wavelength of the fiber was 1550–1580 nm, and the corresponding characteristic diameter of the dispersion inflection point was 3.5 μm. Simulation results are as follows: Figure 3 As shown, as the diameter of the micro / nano fiber gradually decreases from 5.0 μm to 3.5 μm, the refractive index sensitivity increases significantly, reaching a maximum of 37000 nm / RIU. However, when the diameter continues to decrease to 2.5 μm, the refractive index sensitivity drops sharply to 0. It was further found that when the diameter of the micro / nano fiber is greater than 3.5 μm, the increase in the environmental refractive index causes a red shift in the interference wavelength, while when the diameter is less than 3.5 μm, the interference wavelength undergoes a blue shift.
[0050] Using 3.5 μm as the waist fiber diameter and 900 μm as the waist bending radius, the simulation results of light field leakage for U-shaped ultrafine fibers and linear micro / nano fibers are as follows: Figure 4 As shown, compared with linear micro / nano optical fibers, U-shaped ultrafine optical fibers exhibit significantly improved light field leakage. This means that the interaction between U-shaped ultrafine optical fibers as sensors and the external environment is enhanced, thereby improving the sensitivity of the sensors.
[0051] U-shaped ultrafine optical fibers were fabricated using an optical fiber taper machine, which included an oxy-hydrogen lamp heating device and a displacement platform stretching device. The single-mode fiber was heated by the oxy-hydrogen lamp heating device and stretched to a preset length at a uniform speed, resulting in an ultrafine fiber with a waist diameter of 3.5 μm. Subsequently, the ultrafine fiber was fixed in a capillary glass tube using UV photoresist, yielding a U-shaped ultrafine optical fiber with a waist bending radius of 900 μm. The waist morphology of the fabricated U-shaped ultrafine optical fiber is shown below. Figure 1 As shown.
[0052] The refractive index test results of U-shaped ultra-thin optical fiber are as follows: Figure 5 As shown, with the increase of refractive index (1.333 to 1.335), the interference wavelength exhibits a redshift phenomenon. Specifically, the interference wavelength shifts from 1562.9 nm to 1579.0 nm, with an overall shift of 16.1 nm and a sensitivity of 8050 nm / RIU.
[0053] The above-described embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model 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 utility model.
Claims
1. A U-shaped ultra-thin optical fiber, comprising a bent section and straight sections located at both ends of the bent section, characterized in that, The curved section includes a waist region, and the fiber diameter of the waist region is set to the characteristic diameter corresponding to a preset dispersion inflection point.
2. The U-shaped ultrafine optical fiber according to claim 1, characterized in that, The diameter of the optical fiber in the waist region is 3~5μm.
3. The U-shaped ultrafine optical fiber according to claim 1, characterized in that, The diameter of the optical fiber in the waist region is 3.5 μm.
4. The U-shaped ultrafine optical fiber according to claim 1, characterized in that, The bending radius of the waist region is 900~1500μm.
5. The U-shaped ultrafine optical fiber according to claim 1, characterized in that, The preset dispersion inflection point is 1550~1580nm.
6. The U-shaped ultrafine optical fiber according to claim 1, characterized in that, The U-shaped ultra-thin optical fiber is a single-mode optical fiber.
7. An optical fiber sensor, characterized in that, Including the U-shaped ultrafine optical fiber as described in any one of claims 1-6, and: A functionalized sensitive material is disposed on the waist region surface of the U-shaped ultra-thin 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 U-shaped ultra-thin optical fiber.
8. The fiber optic sensor according to claim 7, 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.
9. The fiber optic sensor according to claim 7, 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 U-shaped ultra-fine optical fiber.
10. The fiber optic sensor according to claim 7, characterized in that, The functionalized sensitive material is glucose oxidase.