CN102279438A - Optical fiber evanescent field sensing optical fiber with novel micro-nano structure - Google Patents

Abstract

The invention relates to a novel optical fiber evanescent field sensing optical fiber with a micro-nano structure, which comprises an optical fiber evanescent field sensing optical fiber with a reserved cladding and a cladding replaced, wherein micro-nano holes are drilled on the optical fiber cladding, the size characteristics, the distribution mode and the distance between the hole bottom and the fiber core interface of the micro-nano holes are controlled, and a substance to be measured is filled in the micro-nano holes for refractive index modulation. The cladding of the fiber section to be processed is removed, a replacing medium layer is filled, the refractive index of the fiber section to be processed is controlled, a micro-nano hole is modified on the replacing medium layer, a substance to be detected is filled in the micro-nano hole, and the refractive index of the substance to be detected is regulated. The invention adopts the method of reserving the sensing optical fiber cladding and drilling the micro-nano holes on the cladding, replacing the cladding with the medium layer and drilling the micro-nano holes on the cladding, and manufactures the optical fiber evanescent field sensing optical fiber with a novel micro-nano structure, thereby leading the evanescent field energy of a high-order mode to participate in the reaction to the maximum extent, improving the sensitivity of the sensor and being beneficial to the development of miniaturization and integration of the optical fiber evanescent field sensor.

Description

Optical fiber evanescent field sensing fiber with novel micro-nano structure

technical field

The invention belongs to the technical field of optical fiber biochemical sensors, and relates to the manufacture of optical fiber biochemical sensors used in the fields of medical detection, environmental monitoring, biochemical anti-terrorism, etc., and specifically relates to a new type of optical fiber evanescent field sensor with a new micro-nano structure for cladding retention and cladding replacement. Sensitive fiber.

Background technique

The optical fiber evanescent field sensor is a new type of functional optical fiber sensor proposed in the 1980s. It utilizes the evanescent field energy excited by the sensing fiber to interact with the measured substance within the range of energy action, causing the transmission of energy in the optical fiber. absorption to achieve the sensing effect. The more energy of the evanescent field involved in the reaction, the higher the sensitivity of the corresponding optical fiber sensor. Its core component is the optical fiber evanescent field sensing fiber. In the traditional sensing optical fiber, the cladding of the optical fiber is usually removed, so that the measured substance interacts with the evanescent field energy of the optical fiber to complete the sensing process. The amount of evanescent field energy excited by the sensing fiber plays a decisive role in the sensitivity of the sensor, and has a crucial impact on the performance of the sensor.

By exciting the optical waveguide of the high-order mode, more evanescent field energy is encouraged to participate in the interaction with the measured substance, which can effectively improve the sensitivity of the sensor. In order to obtain the optical waveguide of high-order mode, many scholars have improved the sensor by making the sensing fiber into a tapered, combined tapered, U-shaped structure or by adjusting the angle of the incident light. Such as literature [B.D.Gupta, H.Dodeja, A.K.Tomar, Fiber-optic evanescent field absorption sensor based on a U-shaped probe (U-shaped optical fiber evanescent field sensor based on energy absorption), 1996, Optical and Quantum Electronics 28: 1629-1639 and Anna Grazia Mignani, Riccardo Falciai, Leonardo Ciaccheri, Evanescent wave absorption spectroscopy by means of bi-tapered multimode optical fibers, 1998, 52(4): 546-551 and Yihui Wu, Xiaohong Deng, Feng Li, Xuye Zhuang, Less-mode optic fiber evanescent wave absorbing sensor: Parameter design for high sensitivity liquid detection (parameter design for high sensitivity solution detection of few-mode fiber evanescent field sensor based on energy absorption), 2007, Sensors and Actuators B 122:127-133] and so on. Although the optical waveguide of the high-order mode in the sensing fiber can be better excited by making the sensing fiber into a tapered shape, a combined tapered shape, a U shape, etc., there is a mode loss when the light propagates in the sensing fiber , reduces the signal-to-noise ratio of the sensor, and the evanescent field energy in the high-order optical waveguide excited by them is at most only 30% of the total energy transmitted in the optical fiber. There is also the problem of low sensing energy, and the ability to improve the sensitivity of the sensor is limited. The method of exciting the high-order mode optical waveguide by modulating the angle of the incident light increases the complexity of the sensor system, which is not conducive to the development of miniaturization and integration of the sensor.

Due to its specific physical characteristics, especially the hollow-core photonic crystal fiber (hollow-core photonic bandgap fiber), there is a large amount of light energy in the hollow region, which provides a carrier for the development of high-sensitivity optical fiber evanescent field sensors. By filling the measured substance into the hollow of the photonic crystal fiber, a new type of optical fiber evanescent field sensor can be obtained, but the process is very complicated, the design and analysis of the sensor is heavy, the detection time is long, and it is difficult to react with the measured substance. The sensitive film or feature of the fiber is modified on the hollow wall of the fiber, which limits the sensitivity of the sensor and restricts the application and development of this type of sensor. For example, Jian Sun, Chi-ChiuChan, Yi-Fan Zhang, Analysis of hollow-core photonic bandgap fibers forevanescent wave biosensing (analysis of hollow-core photonic crystal bandgap fiber applied to evanescent field biosensing), Journal of Biomedical Optics, 2008, 13(5): 054048 and Y.Y.Huang, Y.Xu, and A.Yariv, Fabrication of functional microstructured optical fibers through a selective-filling technique (process method for making micro-nano structured functional optical fibers by selective filling), Appl.Phys. Lett., 2004, 85:5182-5184.

Contents of the invention

In order to solve the problems of low energy of the evanescent field excited by the sensing fiber and complicated manufacturing process in the technical background, the purpose of the present invention is to provide a novel micro-nano structure optical fiber evanescent field sensing fiber.

In order to achieve the stated purpose, the present invention provides a technical solution for the optical fiber evanescent field sensing fiber with novel micro-nano structure: the optical fiber evanescent field sensing optical fiber with the micro-nano structure of the fiber cladding and the optical fiber with the micro-nano structure replaced by the cladding Evanescent field sensing optical fiber; the optical fiber evanescent field sensing optical fiber of the novel micro-nano structure that retains the optical fiber cladding includes: retaining the optical fiber cladding of the fiber section to be processed on the optical fiber, and radially arranged on the optical fiber cladding Micro-nano hole, the micro-nano hole is set with a hole distance along the axial direction of the optical fiber section to be processed, and the bottom of each micro-nano hole is set at a certain distance from the interface of the fiber core. Refractive index modulation; the characteristics of the optical fiber evanescent field sensing fiber of the novel micro-nano structure replaced by the cladding include: removing a part of the cladding of the optical fiber section of the optical fiber to be processed to form a residual cladding, and the residual cladding and the optical fiber There is a certain distance between the core interfaces, and a replacement medium layer is covered on the residual cladding, and radial micro-nanoholes are arranged on the replacement medium layer, and the hole distance is set along the axial direction of the fiber segment to be processed; The measured substance is filled in the micro-nano hole to modulate the refractive index.

In a preferred embodiment, the distance is between -10λ˜10λ, where λ is the longest wavelength of the light source, and the negative sign indicates that the micro-nano holes go deep into the fiber core.

In a preferred embodiment, the axial pitch is between 0.001λ˜1000λ.

In a preferred embodiment, the size of the micro-nanopores is in the range of 0.001λ˜1000λ.

In a preferred embodiment, the refractive index of the measured substance is controlled between 0.5n ₂ and 2n ₁ , where n ₁ is the refractive index of the fiber core, and n ₂ is the refractive index of the fiber cladding.

In a preferred embodiment, the thickness of the residual cladding is between -0.4d~d, d is the outer diameter of the optical fiber, which varies according to the type of optical fiber selected, and the negative sign indicates that the core of the optical fiber is also removed.

In a preferred embodiment, the refractive index of the replacement medium layer is between 1.3 and 2.0, and the thickness of the replacement medium layer is between 1 nm and 2d, where d is the outer diameter of the optical fiber and is determined according to the type of optical fiber used.

Beneficial effects of the present invention: In the optical fiber evanescent field sensing fiber of the novel micro-nano structure of the present invention, by processing the radial micro-nano hole structure on the sensing fiber retaining the fiber cladding and the sensing fiber replacing the cladding, no It is necessary to remove the cladding of the optical fiber, and the high strength of the optical fiber makes the sensor more resistant to impact and is more suitable for use in complex and harsh physical environments. By controlling the size, circumferential layout, axial layout and the distance between the bottom of the hole and the fiber core interface of the micro-nano hole, and filling the measured substance in the micro-nano hole for matching modulation of the refractive index, the high The energy of the order mode optical waveguide is induced to form an evanescent field in the micro-nano hole on the surface of the optical fiber, which can participate in the sensing more effectively and improve the sensitivity of the sensor. The manufacturing process of the sensing optical fiber is simple and the cost is low, which provides a new way for the further development of the optical fiber evanescent field sensor.

Description of drawings

Figure 1a is a schematic diagram of the fabrication of the optical fiber evanescent field sensing optical fiber with the novel micro-nano structure of the present invention.

Fig. 1b is a schematic diagram of an experimental optical fiber used in the present invention.

2a to 2b are cross-sectional schematic diagrams of modified optical fibers.

3a to 3c are schematic diagrams of micro-nano holes arranged in the axial direction of an optical fiber.

Fig. 4 is a schematic cross-sectional view of a novel micro-nano-structure optical fiber evanescent field sensing fiber that retains the fiber cladding.

5a to 5c are schematic diagrams of processing cladding-replaced optical fiber evanescent field sensing fibers.

Fig. 6a to Fig. 6b are mode electric field cloud diagrams of the optical evanescent field sensing optical fiber with novel micro-nano structure retained in the optical fiber cladding.

Fig. 7a to Fig. 7b are the model electric field cloud diagrams of the optical evanescent field sensing fiber with the new micro-nano structure replaced by the cladding.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

Fig. 1 a shows the schematic diagram of making the optical fiber evanescent field sensing fiber of the novel micro-nano structure of the present invention, and Fig. 1 b shows that an experimental optical fiber 1 used in the present invention includes the fiber segment 2 to be processed and the fiber segment 3 that does not need to be processed; The optical fiber evanescent field sensing fiber with novel micro-nano structure of the present invention includes two kinds of optical fiber evanescent field sensing optical fibers with micro-nano structure: the optical fiber evanescent field sensing fiber 16 with micro-nano structure retaining the fiber cladding and the cladding-replaced micro Nano-structured optical fiber evanescent field sensing fiber 23; it is a process of retaining the cladding and setting a micro-nano hole structure on the to-be-processed fiber section 2 of an experimental optical fiber 1; a new micro-nano structure for cladding replacement The optical fiber evanescent field sensing optical fiber 23 is treated by replacing the cladding with a dielectric layer on the fiber segment 2 to be processed of an experimental optical fiber 1 and setting a micro-nano hole structure thereon.

1. The optical fiber evanescent field sensing fiber 16 of the novel micro-nano structure of retaining the optical fiber cladding comprises: retain the optical fiber cladding 7 of the fiber section 2 to be processed on the optical fiber 1, and the optical fiber cladding 7 is provided with radial The micro-nano hole 8, the micro-nano hole 8 is set with a hole distance 15 along the axial direction of the optical fiber section 2 to be processed, and the hole bottom 10 of each micro-nano hole 8 is set with a distance 11 from the interface of the optical fiber core 6, The micro-nano hole 8 is filled with the measured substance 9 for refractive index modulation;

The technical scheme of the optical fiber evanescent field sensing fiber 16 with a novel micro-nano structure that retains the fiber cladding 7 is as follows: Figure 2a shows that a plurality of micro-nano holes 8 are evenly arranged 4 in the circumferential direction of the optical fiber 1, and Figure 2b shows that multiple Micro-nanoholes 8 are non-uniformly arranged 5 in the circumferential direction of the optical fiber 1 , and the fiber core 6 , cladding 7 , micro-nanoholes 8 , analyte 9 and hole bottom 10 are also shown.

Take a section of experimental optical fiber 1 with a length of 0.2-100m, which can be single-mode optical fiber, multi-mode optical fiber for communication, or plastic optical fiber or other special optical fiber, and divide experimental optical fiber 1 into optical fiber section 2 to be processed and Segment 3 of fiber that does not require treatment. First, the fiber section 2 to be processed of an experimental optical fiber 1 is processed, the processing is to carry out the modification process of punching micro-nano holes 8 on the fiber section 2 to be processed on the optical fiber 1 for the experiment, and the fiber section 2 to be processed The length is between 5cm and 100cm. Firstly, the fiber segment 2 to be treated is drilled with micro-nano holes 8, the distance 11 between the bottom of the hole 10 and the fiber core 6 is controlled between -10λ～10λ, λ is the longest wavelength of the incident light source, and the negative sign indicates the micro-nano holes 8 It can go deep into the optical fiber core 6, the type of the optical fiber 1 used in the experiment is determined, and the depth of the micro-nano hole 8 can be determined after the specific value of the hole bottom 10 is determined. The shape of the micro-nano hole 8 can be cylindrical, square or other regular polygonal or irregular shapes.

Figure 3a shows a schematic diagram of micro-nanoholes 8 uniformly distributed 12 in the axial direction of optical fiber 1, Figure 3b shows a schematic diagram of micro-nanoholes 8 staggered distribution 13 in the axial direction of optical fiber 1, and Figure 3c shows micro-nanoholes 8 is a schematic diagram of the axial disorder distribution 14 of the optical fiber 1, and the cross-sectional view of the optical fiber evanescent field sensing optical fiber 16 with a novel micro-nano structure retaining the optical fiber cladding 7 is shown in Fig. 4 below, and the cylindrical micro-nano hole 8 As an example to illustrate the content of the present invention, a plurality of circles are arranged on the fiber segment 2 to be processed of the optical fiber 1, and the number of cylindrical micro-nano holes 8 perforated on each circle is controlled at 2 to 50, and the number is uniform according to the circumferential direction. The distribution 4 or non-uniform distribution 5 is on each circumference of the fiber section 2 to be treated of the fiber 1 . The size of the axial spacing 15 of the cylindrical micro-nanoholes 8 is controlled between 0.01λ˜1000λ, and the arrangement of the cylindrical micro-nanoholes 8 can be in a regular arrangement 12 , a staggered arrangement 13 or a random arrangement 14 . The size of the cylindrical micro-nano hole 8 is controlled within the range of 0.001λ-1000λ, and the specific size can be freely changed within this range. The diameter of the cylindrical micro-nano hole 8 is controlled within the range of 0.001λ-1000λ. The length of the optical fiber section 2 to be processed is controlled between 1 cm and 100 cm, and the total length of the optical fiber 1 is controlled between 0.1 m and 100 m. The optical fiber segment 3 does not need to be processed because the micro-nano hole 8 is not punched and the optical fiber cladding 7 is retained. The optical fiber segment 3 does not need to be processed to transmit light in the present invention. The completed fiber cladding is retained as shown in Figure 4 7's novel micro-nano-structure optical fiber evanescent field sensing fiber 16.

The refractive index of the fiber core 6 is n ₁ , and the refractive index of the fiber cladding 7 is n ₂ . During detection, the refractive index n ₉ of the measured substance 9 filled in the micro-nano hole 8 is adjusted so that n ₉ is controlled between 0.5n ₂ and 2n ₁ . The special optical fiber structure, combined with the precise control of the refractive index of the measured substance 9 filled in the micro-nano hole 8, forms a novel optical fiber evanescent field sensing fiber 16 with a new micro-nano structure that retains the fiber cladding 7.

2. The technical scheme of the optical fiber evanescent field sensing fiber 23 of the new micro-nano structure replacing the optical fiber cladding 7 is as follows: the characteristics of the optical fiber evanescent field sensing fiber 23 of the novel micro-nano structure replacing the cladding include: Removing a part of the fiber cladding 7 of the fiber segment 2 to be processed in the optical fiber 1 forms a residual cladding 20, there is a distance 19 between the residual cladding 20 and the interface of the optical fiber core 6, and a layer of replacement medium is covered on the residual cladding 20 layer 21, on which the replacement medium layer 21 is provided with radial micro-nanoholes 8, and the micro-nanoholes 8 are set with a hole distance 15 along the axial direction of the optical fiber segment 2 to be processed; the micro-nanoholes 8 are filled with the substance 9 to be tested Refractive index modulation.

Figure 5a is a schematic diagram of the optical fiber 1 removing the fiber cladding 7 of the fiber section 2 to be processed, Figure 5b is a schematic diagram of the optical fiber 1 removing the fiber cladding 7 of the fiber section 2 to be processed and filling the replacement medium layer 21, and Figure 5c is A schematic diagram of a novel micro-nano structured optical fiber evanescent field sensing optical fiber 23 after the optical fiber cladding 7 is replaced. The figure shows a tapered transition layer 17, a de-cladding region 18, a distance 19, a residual cladding 20, a replacement dielectric layer 21 and a replacement dielectric layer thickness 22;

The fiber cladding 7 of the fiber section 2 to be processed in the fiber 1 is removed. If the material of the optical fiber cladding 7 is doped silica, the method of wet etching with hydrofluoric acid (HF) is used to remove the optical fiber cladding 7. Silicon dioxide also has a corrosion effect, so there will be a tapered transition layer 17 at the place where the optical fiber cladding 7 is removed. When the selected optical fiber cladding 7 is other materials, such as plastic, the optical fiber cladding 7 is generally removed by cutting, so that there will be no tapered transition layer 17 . The control range of the interface distance 19 from the optical fiber core 6 of the residual cladding 20 is -0.4d-～d, and the outer diameter of the d optical fiber varies according to the type of optical fiber selected. The negative sign indicates that a part of the optical fiber core layer 6 is also removed. Then cover the replacement dielectric layer 21 on the part of the fiber section 2 to be treated from which the fiber cladding 7 has been removed, and the thickness 22 of the replacement dielectric layer is controlled between 1nm and 2d, where d is the outer diameter of the fiber and is determined according to the type of fiber used. The refractive index n of the replacement medium layer 21 is controlled between 1.3 and 2.0.

Then punch micro-nanoholes 8 on the replacement medium layer 21, the number of micro-nanoholes on the circumference of the optical fiber section 2 to be processed, and the distribution form of the micro-nanoholes 8 on the circumference and the axial direction of the optical fiber section 2 to be processed, the axial The hole pitch 15, the distance 11 between the bottom of the hole 10 and the interface of the fiber core 6, and the shape of the micro-nano hole 8 are the same as those of the novel micro-nano-structure optical fiber evanescent field sensing fiber 16 that retains the fiber cladding 7. The length of the optical fiber 1 and the length of the fiber segment 2 to be processed are also the same as those of the optical evanescent field sensing optical fiber 16 with a novel micro-nano structure that retains the optical fiber cladding 7 .

Adjust the refractive index of the measured substance 9 and fill it into the micro-nano hole 8 . The refractive index of the measured substance 9 is controlled between 1.1 and 2.0. The combination of the special optical fiber structure of the present invention and the precise control of the refractive index of the measured substance 9 forms a novel micro-nano structured optical fiber evanescent field sensing optical fiber 23 that replaces the optical fiber cladding 7 .

The optical fiber evanescent field sensing fiber with novel micro-nano structure itself is a combination of a device and a detection method. The present invention requires controlling the refractive index of the measured substance filled in the micro-nano hole 8 . After processing a special micro-nano structure that meets the requirements on the sensing fiber, the refractive index of the fiber core layer 6, fiber cladding layer 7, replacement medium layer 21, and measured substance 9 are adjusted to match each other, and the sensor can be The energy of the high-order optical waveguide in the sensing fiber is induced into the micro-nano hole 8 on the surface of the fiber 1 for sensing, which meets the requirements of the invention.

1. A new type of micro-nano structure optical fiber evanescent field sensing fiber with cladding retention

Take a section of optical fiber 1 with a length of 35 cm, the diameter of the fiber core 6 is 18 μm, the diameter of the fiber cladding 7 is 80 μm, the length of the fiber section 2 to be processed is 10 cm, and the wavelength of the incident light is 1.554 μm. The distance between the hole bottom 10 and the fiber core interface is 1 μm, the refractive index of the optical fiber cladding 7 is 1.4378, the refractive index of the optical fiber core layer 6 is 1.4459, the refractive index of the measured substance 9 in the micro-nano hole 8 is 1.4475, and the refractive index of the micro-nano hole 8 is 1.4475. The hole diameter is 5 μm, and four micro-nano holes 8 are evenly distributed on the circumference of the fiber segment 2 to be processed. Taking an interface of an optical fiber with micro-nanohole 8, and analyzing the characteristics of the light propagation mode, it can be obtained that the energy of the high-order mode optical waveguide whose effective mode is less than 1.4443 is mainly distributed in the micro-nanohole 8 to participate in sensing, while the effective mode The energy of the low-order mode optical waveguide greater than 1.4443 mainly propagates in the optical fiber core 6 and plays the role of information transmission. Fig. 6a is a cloud diagram of the electric field component of the high-order mode optical waveguide with an effective modulus of 1.444297, and about 86.2% of the energy participates in sensing in the micro-nano hole. Fig. 6b is a cloud diagram of the electric field component of the low-order mode optical waveguide with an effective mode number of 1.444887, and about 97.5% of the energy is confined to propagate in the fiber core.

2. A new type of micro-nano structure optical fiber evanescent field sensing fiber with cladding replacement

Take another experimental optical fiber 1 with a length of 35 cm, the diameter of the fiber core 6 is 18 μm, the refractive index of the fiber core 6 is 1.445, the diameter of the fiber cladding 7 is 80 μm, and the refractive index of the fiber cladding 7 is 1.4378. The length of section 2 is 10 cm, the thickness of the remaining cladding after removing the fiber cladding 7 is 1 μm, the refractive index of the filling replacement medium layer is 1.4358, the filling thickness is 30 μm, and the incident light wavelength is 1.554 μm. Four micro-nanoholes 8 are evenly distributed on the circumference of the optical fiber 1 with a diameter of 5 μm. The distance between the hole bottom 10 and the interface of the fiber core 5 is 1 μm. The refractive index of the measured substance 9 in the micro-nanoholes 8 is 1.447. Taking a certain interface of the optical fiber section 2 to be treated with micro-nano holes, and analyzing the characteristics of the propagation mode, it can be obtained that the energy of the high-order mode optical waveguide whose effective mode number is less than 1.44362 is mainly distributed in the micro-nano holes to participate in sensing, while the effective mode number is less than 1.44362. The energy of the low-order mode optical waveguide with a modulus greater than 1.44362 mainly propagates in the fiber core 6 and plays the role of information transmission. Fig. 7a is the cloud diagram of the electric field component of the high-order mode optical waveguide with an effective modulus of 1.443615, and about 88.1% of the energy participates in sensing in the micro-nano hole. FIG. 7 b is a cloud diagram of the electric field component of the low-order mode optical waveguide with an effective mode number of 1.44401, and about 96.4% of the energy is confined to propagate in the fiber core 6 .

The above is only a specific implementation mode in the present invention, but the scope of protection of the present invention is not limited thereto. Anyone familiar with the technology can understand the conceivable transformation or replacement within the technical scope disclosed in the present invention. All should be covered within the scope of the present invention.

Claims (7)

1. A kind of optical fiber evanescent field sensing fiber of novel micro-nano structure, it is characterized in that comprising: the optical fiber evanescent field sensing fiber (16) of the micro-nano structure of retaining fiber cladding and the optical fiber evanescence of the micro-nano structure of cladding replacement Field sensing optical fiber (23); The optical fiber evanescent field sensing fiber (16) of the novel micro-nano structure that retains the optical fiber cladding comprises: retaining the optical fiber cladding (7) of the fiber section (2) to be processed on the optical fiber (1), (7) is provided with radial micro-nanoholes (8), and the micro-nanoholes (8) are set with a hole distance (15) along the axial direction of the optical fiber section (2) to be processed, and each micro-nanohole (8) The bottom of the hole (10) is set at a distance (11) from the interface of the optical fiber core (6), and the micro-nano hole (8) is filled with a measured substance (9) for refractive index modulation; The characteristics of the optical fiber evanescent field sensing fiber (23) of the novel micro-nano structure replaced by the cladding include: removing a part of the fiber cladding (7) of the optical fiber section (2) to be processed in the optical fiber (1) to form a residual cladding layer (20), there is a distance (19) between the residual cladding (20) and the interface of the optical fiber core (6), and a replacement dielectric layer (21) is covered on the residual cladding (20), and the replacement dielectric layer (21) is provided with radial micro-nanoholes (8), and the micro-nanoholes (8) are set with a hole distance (15) along the axial direction of the optical fiber section (2) to be processed; the micro-nanoholes (8) are filled with The substance to be measured (9) undergoes refractive index modulation. 2. The optical fiber evanescent field sensing fiber of novel micro-nano structure as claimed in claim 1, is characterized in that, described distance (11) is between-10λ～10λ, and λ is the longest wavelength of light source, and negative sign represents micro The nanoholes go deep into the fiber core (6). 3. The optical fiber evanescent field sensing fiber with novel micro-nano structure according to claim 1, characterized in that, the axial pitch (15) is between 0.001λ˜1000λ. 4. The optical fiber evanescent field sensing fiber with novel micro-nano structure according to claim 1, characterized in that the size of the micro-nano hole (8) is 0.001λ˜1000λ. 5. The optical fiber evanescent field sensing fiber with novel micro-nano structure as claimed in claim 1, characterized in that the refractive index of the measured substance (9) is controlled between 0.5n ₂ and 2n ₁ , and n ₁ is the optical fiber The refractive index of the core (6), n ₂ is the refractive index of the fiber cladding (7). 6. The optical fiber evanescent field sensing fiber with novel micro-nano structure according to claim 1, characterized in that, the thickness (19) of the residual cladding (20) is between -0.4d～d, and d is the optical fiber The outer diameter varies according to the type of optical fiber selected, and the negative sign indicates that the core (6) of the optical fiber is also removed. 7. The optical fiber evanescent field sensing fiber of novel micro-nano structure as claimed in claim 1, is characterized in that, the refractive index of described replacement medium layer (21) is between 1.3～2.0, and the thickness of replacement medium layer is 1nm Between ～2d, d is the outer diameter of the optical fiber determined according to the type of optical fiber used.

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