A probe optical fiber and a probe optical fiber sensor

Abstract

The application provides a detection optical fiber and a detection optical fiber sensor, and relates to the field of sensing. The detection optical fiber comprises: an optical fiber body; a first through hole penetrating an end face is arranged along a central axis of the optical fiber body; a plurality of third through holes penetrating the end face of the optical fiber body in an axial direction are arranged on the outer periphery of the first through hole; a semicircular through hole and a plurality of second through holes are arranged in the region between the first through hole and the third through hole; the circular arc surface of the semicircular through hole is away from the first through hole; a plating layer is arranged on the diameter surface of the semicircular through hole; the first through hole and the semicircular through hole are both used for placing a sample to be detected; when light irradiates the first through hole, the sample to be detected in the first through hole generates refracted light; the refracted light irradiates the sample to be detected in the semicircular through hole through the plating layer, and generates resonant light; and the application can enhance the coupling degree and improve the detection performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sensing, in particular to a detection optical fiber and a detection optical fiber sensor. BACKGROUND

[0002] Microstructure optical fiber sensors based on surface plasmon resonance are widely used in petroleum and chemical industry, biomedicine, aerospace, environmental detection, national defense technology and many other industries because they are very sensitive to changes in temperature, stress, refractive index and the like. Compared with visible light and near-infrared waveband, using mid-infrared waveband as the working wavelength of the microstructure optical fiber sensor has the following two advantages:

[0003] First, the longer working wavelength can penetrate deeper into the sample to be measured, thereby greatly improving the detection sensitivity and accuracy of the sensor for larger samples such as living cells.

[0004] Second, most biological samples have high transparency in the mid-infrared waveband, which can avoid light damage or light toxicity to the biological sample during detection.

[0005] Therefore, mid-infrared sensors based on microstructure optical fibers have attracted widespread attention from researchers. The current microstructure optical fiber sensors based on surface plasmon resonance in the mid-infrared waveband still have the following shortcomings:

[0006] First, the structure of the optical fiber in the existing sensor is too complex to be drawn, which greatly limits its practicality. Second, in order to excite the surface plasmon resonance effect in the microstructure optical fiber sensor, a gold film is selected to be plated in the sample channel of the optical fiber, which results in the sensor using the optical fiber being too expensive. Third, the existing sensors using mid-infrared microstructure optical fibers can only be used for low refractive index sensing (1.12-1.39), which will greatly limit the application range of such sensors. Finally, the detection sensitivity and accuracy of the sensor using the optical fiber in the prior art are not high enough to meet the current demand for high-precision and ultra-sensitive optical fiber sensing technology in the field of biochemical detection. SUMMARY

[0007] The purpose of the present application is to provide a detection optical fiber and a detection optical fiber sensor to enhance the coupling degree and improve the detection performance.

[0008] To achieve the above purpose, the present application provides the following solutions:

[0009] A detection optical fiber, comprising: an optical fiber body;

[0010] A first through-hole is formed along the central axis of the optical fiber body, penetrating the end face; multiple third through-holes are provided axially around the outer periphery of the first through-hole, penetrating the end face of the optical fiber body; a semi-circular through-hole and multiple second through-holes are formed in the region between the first through-hole and the third through-holes; the arc surface of the semi-circular through-hole is away from the first through-hole; a coating is provided on the diameter surface of the semi-circular through-hole; both the first through-hole and the semi-circular through-hole are used to place the sample to be tested;

[0011] When light shines on the first through hole, the sample under test inside the first through hole generates refracted light; the refracted light shines on the sample under test in the semi-circular through hole through the coating, generating resonant light.

[0012] Optionally, the diameter surface of the semi-circular through-hole is perpendicular to the radial direction of the optical fiber body.

[0013] Optionally, the center of each of the third through holes is equal to the center of the first through hole.

[0014] Optionally, the distance from the center of each of the second through holes to the center of the first through hole is greater than the distance from the center of the semi-circular through hole to the center of the first through hole.

[0015] Optionally, the coating material is indium tin oxide.

[0016] Optionally, the material of the optical fiber body is quartz.

[0017] Optionally, the end face of the optical fiber body is circular; the radius of the end face of the optical fiber body is 12.5um-14um.

[0018] A detection fiber optic sensor, the sensor comprising: a laser source, a polarizer, a coupling lens, a spectrometer, and the detection fiber described in any one of the above;

[0019] The laser source is used to emit laser light;

[0020] The polarizer is disposed in the output optical path of the laser source, and the polarizer is used to modulate the laser to obtain modulated light;

[0021] The coupling lens is disposed in the output optical path of the polarizer. The coupling lens is used to couple and focus the modulated light into the first through hole of the probe optical fiber. The sample under test in the first through hole generates refracted light under the illumination of the modulated light. The refracted light is irradiated onto the sample under test in the semi-circular through hole of the probe optical fiber through the coating, generating resonant light.

[0022] The spectrometer is positioned in the output light path of the resonant light and is used to monitor the resonant light in real time.

[0023] Optionally, the detection fiber sensor further includes: a fiber adjustment frame; the fiber adjustment frame is used to set the detection fiber so that the first through hole of the detection fiber and the output light path of the coupling lens are on the same straight line.

[0024] Optionally, the fiber optic adjustment frame is a three-dimensional fiber optic adjustment frame.

[0025] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0026] The detection optical fiber and detection optical fiber sensor provided in this embodiment of the invention include an optical fiber body with a first through-hole penetrating the end face along the central axis of the optical fiber body; a plurality of third through-holes penetrating the end face of the optical fiber body along the axial direction are provided on the outer periphery of the first through-hole; a semi-circular through-hole and a plurality of second through-holes are provided in the region between the first and third through-holes, with the arc surface of the semi-circular through-holes being away from the first through-hole; a coating is provided on the diameter surface of the semi-circular through-holes; both the first through-hole and the semi-circular through-holes are used to place the sample to be tested; when light shines on the first through-hole, the sample to be tested in the first through-hole generates refracted light; the refracted light shines through the coating onto the sample to be tested in the semi-circular through-holes, generating resonant light. The first through-hole serves as the fiber core, the semi-circular through-hole as the sample channel, and the second and third through-holes as air holes. Because this detection fiber uses a core and sample channel structure, and includes air holes, the structure is simple and easy to draw. Furthermore, the sample channel's diameter is coated to excite surface plasma waves, reducing manufacturing costs. Additionally, the core and sample channel hold the sample to be tested. The structure of this detection fiber enhances the coupling between the core mode and the plasma mode on the sample channel surface, resulting in resonant light. This improves detection accuracy and sensitivity, thereby enhancing detection performance. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a structural diagram of the detection optical fiber provided in an embodiment of the present invention;

[0029] Figure 2 This is a structural diagram of the optical fiber sensor provided in an embodiment of the present invention.

[0030] Symbol explanation:

[0031] Fiber body-1, fiber core-2, air hole-3, sample channel-4, coating-5, laser source-6, polarizer-7, coupling lens-8, spectrometer-9, detection fiber-10. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] The purpose of this invention is to provide a detection optical fiber and a detection optical fiber sensor. The detection optical fiber includes an optical fiber body, with a first through-hole extending through the end face along the central axis of the optical fiber body; multiple third through-holes extending axially through the end face of the optical fiber body are provided around the outer periphery of the first through-hole; a semi-circular through-hole and multiple second through-holes are provided in the region between the first and third through-holes, with the arc surface of the semi-circular through-holes being away from the first through-hole; a coating is provided on the diameter surface of the semi-circular through-holes; both the first through-hole and the semi-circular through-holes are used to place the sample to be tested; when light shines on the first through-hole, the sample to be tested in the first through-hole generates refracted light; the refracted light shines through the coating onto the sample to be tested in the semi-circular through-hole, generating resonant light; the first through-hole is used as... The fiber core and semi-circular through-hole serve as the sample channel, while the second and third through-holes serve as air holes. Because this detection fiber employs a core and sample channel structure, and includes air holes, the structure is simple and easy to draw. Furthermore, the sample channel's diameter is coated to excite surface plasma waves, reducing manufacturing costs. Additionally, the core and sample channel hold the sample to be tested. Under the structural effect of this detection fiber, the coupling strength between the core mode of the core and the plasma mode on the sample channel surface is enhanced, resulting in resonant light. This improves detection accuracy and sensitivity, i.e., enhances detection performance. Therefore, this invention enhances coupling and thus improves detection performance.

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] Example 1

[0036] like Figure 1 As shown, this embodiment of the invention provides a detection optical fiber, which includes an optical fiber body 1; the material of the optical fiber body is quartz. The end face of the optical fiber body is circular; the radius of the end face of the optical fiber body is 12.5um-14um.

[0037] A first through-hole is formed along the central axis of the optical fiber body 1, penetrating the end face; the first through-hole serves as the core 2 of the probe optical fiber. Multiple third through-holes are formed axially around the outer periphery of the first through-hole, penetrating the end face of the optical fiber body; the third through-holes can serve as air holes 3 for the probe optical fiber. A semi-circular through-hole and multiple second through-holes are formed in the region between the first and third through-holes; the second through-holes have the same dimensions as the third through-holes and can also serve as air holes 3 for the probe optical fiber. The arc surface of the semi-circular through-hole is away from the first through-hole; a coating 5 is applied to the diametrical surface of the semi-circular through-hole; specifically, the coating material is indium tin oxide. The diametrical surface of the semi-circular through-hole is perpendicular to the radial direction of the optical fiber body.

[0038] Both the first through-hole and the semi-circular through-hole are used to place the sample to be tested. The semi-circular through-hole can serve as the sample channel 4 for the probe fiber.

[0039] When light shines on the first through hole, the sample under test inside the first through hole generates refracted light; the refracted light shines through the coating onto the sample under test in the semi-circular through hole, generating resonant light.

[0040] The center of each third through hole is equal to the center of the first through hole. The distance from the center of each second through hole to the center of the first through hole is greater than the distance from the center of the semi-circular through hole to the center of the first through hole.

[0041] like Figure 1 As shown, multiple third through-holes form a circle along the circular end face; a semi-circular through-hole and multiple second through-holes also form a circle along the circular end face. That is, on the end face of the fiber body 1 of the probe fiber, two layers of air holes are formed: multiple third through-holes forming a circle along the circular end face constitute the second layer of air holes; multiple second through-holes forming a circle along the circular end face constitute the first layer of air holes. The semi-circular through-hole and multiple second through-holes are located within a circle on one end face. The semi-circular through-hole serves as the sample channel 4.

[0042] This embodiment provides a detection optical fiber, the specific structure of which is as follows:

[0043] The detection fiber uses pure quartz as the substrate material, i.e., the fiber body 1. A semi-circular sample channel 4 with a radius of 3.0-3.4 μm is located at the corresponding position of the first layer of air holes 3 in the detection fiber, and the distance from its bottom to the center of the fiber core 2 is 4.0 μm. In order to generate surface plasmon waves in the detection fiber, a coating layer 5 with a thickness of 90-110 nm is deposited on the bottom of the sample channel 4. This coating layer 5 is made of indium tin oxide. In addition, the detection fiber also contains two layers of circular air holes 3 with a radius of 1.9 μm, arranged in a circular pattern. The distance from the first layer of air holes 3 to the center of the fiber core 2 is 5.3 μm, and the distance from the second layer of air holes 3 to the center of the fiber core 2 is 9.5 μm. In order to enhance the coupling between the surface plasmon mode and the fiber core fundamental mode in the coating layer 5 in the sample channel 4, the fiber core 2 of the detection fiber is located at the exact center of the fiber cross-section (this fiber core 2 is a circular channel formed on the substrate material, i.e., the fiber body, which serves to generate the fiber core fundamental mode, and has a radius of 1.95-2.05 μm). Finally, the sample to be tested, which is a liquid, was injected into both sample channel 4 and fiber core 2. The radius of the cross-section of the entire probe photonic crystal fiber (also known as the fiber body) is 12.5-14 μm. This probe fiber can overcome the shortcomings of existing mid-infrared surface plasmon resonance fiber sensors, such as high cost, low detection accuracy, and difficulty in drawing. This probe fiber is a highly sensitive single-liquid-core, single-sample-channel probe fiber based on surface plasmon resonance.

[0044] Example 2

[0045] like Figure 2 As shown, this embodiment of the invention provides a detection fiber sensor, which includes: a laser source 6, a polarizer 7, a coupling lens 8, a spectrum analyzer 9, and any one of the detection fibers 10 in Embodiment 1; the laser source 6 is used to emit laser light; the polarizer 7 is disposed in the output optical path of the laser source 6, and the polarizer 7 is used to modulate the laser light to obtain modulated light.

[0046] The coupling lens 8 is set in the output light path of the polarizer 7. The coupling lens 8 is used to couple and focus the modulated light into the first through hole of the probe fiber 10. The sample under test in the first through hole generates refracted light under the illumination of the modulated light. The refracted light is irradiated onto the sample under test in the semi-circular through hole of the probe fiber 10 through the coating, generating resonant light.

[0047] The spectrometer 9 is set in the output light path of the resonant light and is used to monitor the resonant light in real time.

[0048] Specifically, the fiber optic sensor also includes: a fiber optic adjustment frame; the fiber optic adjustment frame is used to set the detection fiber 10 so that the first through hole of the detection fiber 10 and the output light path of the coupling lens 8 are on the same straight line.

[0049] Furthermore, the fiber optic adjustment frame is a three-dimensional fiber optic adjustment frame.

[0050] The sensor includes a supercontinuum light source, i.e., a laser source 6 (such as an SC4500 supercontinuum light source), capable of providing stable output in the wavelength range of 1300–4500 nm; a polarizer 7 used to adjust the polarization state of the incident light wave (the polarizer 7 should be fixed on the optical platform, and the light wave emitted by the laser source 6 is directly incident on the polarizer 7; no other optical components are needed between them, and optical path modulation is mainly achieved by adjusting the position of the polarizer 7). In addition, a coupling optical lens, i.e., a coupling lens 8, is required to effectively couple the incident light into the fiber of the probe microstructure. Finally, a spectrometer 9 monitors the real-time changes in the surface plasmon resonance signal. The connection order of all optical components is as follows: Figure 2 As shown, the optical path connections between all optical devices are achieved using spatial light modulation, meaning that there are no other devices between any two adjacent optical devices.

[0051] The specific implementation process of this invention is as follows:

[0052] First, the liquid to be tested is injected into the core and sample channel of the probe fiber using the capillary effect of the liquid. Then, the probe fiber is placed horizontally on a three-dimensional fiber adjustment frame (the function of the three-dimensional fiber adjustment frame is to adjust the position of the probe microstructure fiber in three-dimensional space; the probe fiber needs to be fixed in the three-dimensional fiber adjustment frame. The fixing method is to first put the probe microstructure fiber into the fiber clamp and press it tightly, and then put it into the three-dimensional fiber adjustment frame for fixation), and make it coaxial with the coupling lens 8 (also called the coupling optical lens). Next, the incident light is adjusted to y-polarized light using the polarizer 7 (y-polarized light refers to light along the y-axis direction on the coordinate axis, that is, the vibration direction is perpendicular to the light propagation direction, and the light propagation direction is horizontal), and the central axis of the core of the probe microstructure fiber is made parallel to the polarization direction of the incident light. Finally, the incident light is efficiently coupled into the core 2 of the probe fiber using the coupling lens 8 (also called the coupling optical lens) (the method is to place the core 2 of the microstructure fiber at the focal point of the coupling lens 8), and the spectrometer 9 at the receiving end monitors it in real time.

[0053] The specific working principle is as follows: When the refractive index of the sample to be tested in sample channel 4 decreases, the effective refractive index of both the surface plasmon film (the film on the surface of the indium tin oxide layer in the sample channel) and the fiber core fundamental mode (the mode in the liquid being tested in the fiber core, whose energy also diffuses to the silicon dioxide in the fiber core region) also decreases. However, the decrease in the surface plasmon mode is greater than that of the fiber core fundamental mode, causing the coupled resonance wavelength to shift towards shorter wavelengths, resulting in a blue shift in the absorption peak of the transmitted light wave input to the spectrometer 9. Conversely, when the refractive index of the sample to be tested increases, the increase in the effective refractive index of the surface plasmon film is greater than that of the fiber core fundamental mode, causing the coupled resonance wavelength to shift towards longer wavelengths, resulting in a red shift in the transmission absorption peak of the spectrometer 8. Therefore, the sensor provided in this embodiment of the invention can monitor the change in the refractive index of the sample to be tested in real time.

[0054] Compared with existing mid-infrared surface plasmon resonance refractive index guided microstructure fiber optic sensors, this invention has the following advantages:

[0055] 1. Novel structure, easy to draw. This sensor adopts a single-core, single-sample-channel structure, and the cladding has only two layers of air holes. This structure can greatly reduce the difficulty of drawing the sensor.

[0056] 2. Low cost. Because this sensor uses an indium tin oxide thin film to excite surface plasma waves, the manufacturing cost of the sensor can be greatly reduced.

[0057] 3. It can be used for high refractive index sensing (1.45~1.53), and can detect high refractive index objects such as fat.

[0058] 4. High detection accuracy, capable of achieving 1.57×10 4 The maximum wavelength sensitivity is 6.36 × 10 nm / RIU. -6 The RIU achieves maximum refractive index resolution. This is mainly due to the fiber structure used, which, with its single liquid core and single sample channel, effectively enhances the coupling strength between the core mode and the surface plasmon film, thereby improving the sensor's detection sensitivity.

[0059] This invention provides a high-precision, ultra-sensitive sensor that is simple in structure, inexpensive to manufacture, and can be used for high refractive index sensing.

[0060] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0061] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A detection optical fiber, characterized in that, The detection optical fiber includes: an optical fiber body; A first through-hole is formed along the central axis of the optical fiber body, penetrating the end face; multiple third through-holes are provided axially around the outer periphery of the first through-hole, penetrating the end face of the optical fiber body; a semi-circular through-hole and multiple second through-holes are formed in the region between the first through-hole and the third through-holes; the arc surface of the semi-circular through-hole is away from the first through-hole; a coating is provided on the diametrical surface of the semi-circular through-hole; both the first through-hole and the semi-circular through-hole are used to place the sample to be tested; the coating thickness is 90-110 nm. When light shines on the first through hole, the sample under test inside the first through hole generates refracted light; the refracted light shines on the sample under test in the semi-circular through hole through the coating, generating resonant light; The coating material is indium tin oxide; Multiple third through holes are arranged in a circle along the circular end face; a semi-circular through hole and multiple second through holes are arranged in a circle along the circular end face; The center of each of the third through holes is equal to the center of the first through hole; the distance from the center of each of the second through holes to the center of the first through hole is greater than the distance from the center of the semi-circular through hole to the center of the first through hole; Used for high refractive index sensing of 1.45–1.53; achieving 1.57 × 10⁻⁶ 4 The maximum wavelength sensitivity is 6.36 × 10 nm / RIU. - 6 RIU's maximum refractive index resolution.

2. The detection optical fiber according to claim 1, characterized in that, The diameter surface of the semi-circular through-hole is perpendicular to the radial direction of the optical fiber body.

3. The detection optical fiber according to claim 1, characterized in that, The material of the optical fiber body is quartz.

4. The detection optical fiber according to claim 1, characterized in that, The end face of the optical fiber body is circular; the radius of the end face of the optical fiber body is 12.5um-14um.

5. A fiber optic sensor for detection, characterized in that, The sensor includes: a laser source, a polarizer, a coupling lens, a spectrometer, and a detection optical fiber as described in any one of claims 1-4; The laser source is used to emit laser light; The polarizer is disposed in the output optical path of the laser source, and the polarizer is used to modulate the laser to obtain modulated light; The coupling lens is disposed in the output optical path of the polarizer. The coupling lens is used to couple and focus the modulated light into the first through hole of the probe optical fiber. The sample under test in the first through hole generates refracted light under the illumination of the modulated light. The refracted light is irradiated onto the sample under test in the semi-circular through hole of the probe optical fiber through the coating, generating resonant light. The spectrometer is positioned in the output light path of the resonant light and is used to monitor the resonant light in real time.

6. The optical fiber sensor according to claim 5, characterized in that, The detection fiber sensor further includes: a fiber adjustment frame; the fiber adjustment frame is used to set the detection fiber so that the first through hole of the detection fiber and the output light path of the coupling lens are on the same straight line.

7. The optical fiber sensor according to claim 6, characterized in that, The fiber optic adjustment frame is a three-dimensional fiber optic adjustment frame.

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