CN115307567A - Curvature sensor based on multi-core optical fiber tapering and preparation method thereof - Google Patents
Curvature sensor based on multi-core optical fiber tapering and preparation method thereof Download PDFInfo
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- CN115307567A CN115307567A CN202110536619.4A CN202110536619A CN115307567A CN 115307567 A CN115307567 A CN 115307567A CN 202110536619 A CN202110536619 A CN 202110536619A CN 115307567 A CN115307567 A CN 115307567A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/255—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures for measuring radius of curvature
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02042—Multicore optical fibres
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/255—Splicing of light guides, e.g. by fusion or bonding
Abstract
The application provides a curvature sensor based on multicore optic fibre tapering and preparation method, this curvature sensor includes: the optical fiber comprises a first single-mode fiber area, a multi-core fiber area, a tapered micro-fiber area and a second single-mode fiber area; the first single mode fiber section includes: a first core, and an outside of the first core is clad with a first cladding, the second single mode fiber region including: a second core, and an exterior of the second core is clad with a second cladding, the multicore fiber region including: the multi-fiber core is configured to take one fiber core as a central fiber core, the rest fiber cores are arranged on the circumference of the side wall of the central fiber core in a surrounding mode, the multi-core fiber area is of a conical structure which shrinks from one end to the other end along the axial direction of the central fiber core, the first fiber core is connected with the central fiber core of the multi-core fiber area, and the side, far away from the first fiber core, of the multi-core fiber area is welded with the second single-mode fiber area through the tapered micro-fiber area. The curvature sensor is insensitive to temperature within the range of 30-140 ℃ and has extremely high sensitivity to curvature.
Description
Technical Field
The application relates to the technical field of sensors, in particular to a curvature sensor based on multi-core optical fiber tapering and a preparation method thereof.
Background
In recent years, accurate measurement of object curvature plays a crucial role in numerous applications such as medical instruments, engineering structure monitoring, aerospace engineering and the like. Among many curvature sensors, the optical fiber curvature sensor has been widely researched and applied due to its characteristics of electromagnetic interference resistance, simple structure and low cost. Various fiber optic curvature sensing devices have been proposed, such as Mach-Zehnder interferometers (MZIs), sagnac interferometers, fiber Bragg Gratings (FBGs), long-period gratings (LPFGs), and the like. The sensor based on the Sagnac interferometer has a complex structure; the preparation of the sensor based on the FBG and the LPFG requires laser etching, and the preparation difficulty and the cost are high; the MZI-based sensor is focused on the characteristics of small volume, simple preparation and high sensitivity.
Currently, MZI sensors for curvature measurement are mainly based on wires of different types of optical fibersType Mach-Zehnder Interferometer (IMZI) structures. The IMZI concentrates two transmission arms of the traditional MZI into one optical fiber, further reduces the volume and the cost of the MZI, and enables the structure of the MZI to be more compact and convenient to integrate. 2016, jingkong, xiaoweieiouyang et al proposed a high-sensitivity directional bending sensor based on an eccentric fiber Mach-Zehnder modal interferometer with a bending sensitivity of 13.49nm/m -1 However, IMZI sensors based on eccentric structures are typically not only sensitive to curvature, but also to temperature or external refractive index, which makes it difficult to separate the signal responses from each other. In 2017, meng-Zhu Zhang, yu-Ming Ge et al propose an ultra-sensitive curvature sensor based on a liquid crystal penetration fiber interferometer, and the maximum curvature sensitivity of the ultra-sensitive curvature sensor can reach 724.3nm/m -1 But greatly increases the difficulty and cost of manufacturing the sensor. In 2018, qi Wang and Yu Liu reported a curvature sensor based on a multimode fiber-seven-core fiber-multimode fiber (MMF-SCF-MMF) structure with a maximum curvature sensitivity of 41.46453nm/m -1 . In 2020, rui Zhou, xueguangQiao et al proposed a bending strain optical fiber sensor based on a lateral bias fusion seven-core optical fiber with a curvature sensitivity of 25.96nm/m -1 . Although the curvature sensitivity of the sensor is improved by the sensor based on the MMF-SCF-MMF structure, the attenuation of light is extremely large and is more than 15-25dB, and the sensor is not beneficial to practical application.
The MZI prepared by the existing structure is connected with the end face of the seven-core optical fiber through either a fused sphere or an eccentric fiber, so that the prepared device has the following defects: (1) the attenuation to light is large; (2) The problem of cross sensitivity of external environments such as temperature, curvature and the like is difficult to avoid; and (3) the structure is complex.
Therefore, a curvature sensor and a preparation method for improving the existing optical fiber tapering are needed.
Disclosure of Invention
In order to overcome the above-mentioned defect point, the present application aims at: a curvature sensor is provided, which is simple in manufacturing method, insensitive to temperature in a wide range, and has extremely high sensitivity to curvature.
In order to achieve the purpose, the following technical scheme is adopted in the application:
the utility model provides a curvature sensor based on multicore optic fibre tapering which characterized in that includes in proper order:
the optical fiber comprises a first single-mode optical fiber area, a multi-core optical fiber area, a tapered micro-optical fiber area and a second single-mode optical fiber area;
the first single-mode fiber section includes: a first core, and the outside of the first core is clad with a first cladding,
the second single-mode fiber section includes: a second core externally clad with a second cladding,
the multicore fiber section includes: a plurality of fiber cores, wherein one of the fiber cores is used as a central fiber core, the rest fiber cores are arranged on the circumference of the side wall of the central fiber core in a surrounding way, and the multi-core fiber area is a conical structure which is contracted from one end to the other end along the axial direction of the central fiber core,
the first fiber core is connected with the central fiber core of the multi-core fiber area, and the side, far away from the first fiber core, of the multi-core fiber area is in fusion connection with the second single-mode fiber area through the tapered micro-fiber area.
Preferably, the multi-strand core is arranged such that one of the cores serves as a central core, and the remaining cores are parallel to the central core. The conical shape is formed after the conical drawing.
Preferably, the multi-core fiber area is in a conical structure, and the diameter of the conical head side is larger than that of the conical tail.
Preferably, the first core is connected to the central core from the tapered side.
Preferably, the side of the second single mode fiber region, which is welded with the tapered micro fiber region, is in a tapered structure.
Preferably, the tapered microfiber region is configured with a cladding and no core.
Preferably, the first cladding has an outer diameter greater than the diameter of the plurality of cores arranged in the plurality of cores.
The embodiment of the application provides a preparation method of a curvature sensor based on multi-core optical fiber tapering, which is characterized by comprising the following steps:
placing the first single-mode fiber, the multi-core fiber and the second single-mode fiber in an optical fiber fusion splicer,
aligning a first fiber core of the first single-mode fiber with one end of a central fiber core of the multi-core fiber, and aligning a second fiber core of the second single-mode fiber with the other end of the central fiber core of the multi-core fiber;
the alignment position of the first fiber core and one end of the central fiber core of the multi-core fiber is a first welding point, the alignment position of the second fiber core of the second single-mode fiber and the other end of the central fiber core of the multi-core fiber is a second welding point, and an optical fiber welding machine is used for welding to form an optical fiber welding body;
and placing the optical fiber fusion splicer on an oxyhydrogen tapering device, wherein a second fusion point is placed at the center of a tapering of the oxyhydrogen tapering machine, adjusting the proportion of oxyhydrogen to oxygen in the oxyhydrogen tapering machine to adjust the tapering speed, tapering the multi-core optical fiber into a tapered structure and forming a tapered micro-optical fiber area between a taper tail and second single-mode light.
Advantageous effects
Compared with the prior art, the curvature sensor provided by the embodiment of the application has the advantages that the attenuation of light in the sensor is greatly reduced in a tapering mode based on the linear Mach-Zehnder interferometer (IMZI) principle, the attenuation is 8-12dB, the maximum curvature sensitivity can reach 174.02957nm/m & lt-1 & gt, and the sensitivity of the optical fiber curvature sensor is greatly improved. In addition, the sensor is insensitive to temperature within the range of 30-140 ℃, so that the problem of cross sensitivity of temperature and curvature is avoided, and the sensor is beneficial to practical application.
Drawings
FIG. 1 is a spliced exposure light path diagram of a holographic lens according to an embodiment of the present disclosure.
Fig. 2 is a schematic cross-sectional view of a seven-core optical fiber according to an embodiment of the present application.
Fig. 3a is a transmission spectrum of IMZI according to an embodiment of the present application, and fig. 3b is a schematic diagram of FFT transformation of the transmission spectrum.
Fig. 4 is a schematic diagram of a temperature sensing experiment system according to an embodiment of the present application.
Fig. 5a shows the change of the transmission spectrum measured by curvature, and fig. 5b shows the experimental and fitting curves of wavelength and curvature.
Fig. 6 is an experimental and fitting curve of the wavelength and curvature of the curvature sensor based on the multi-core fiber tapering of the seven-core fibers with different lengths.
FIG. 7 is an experimental and fitting curve of the wavelength and curvature of a curvature sensor based on multi-core fiber tapering for different tapered micro-fiber zone lengths.
FIG. 8 is a schematic diagram of a temperature sensing experimental system.
FIGS. 9a-c are corresponding relationship between wavelength values of wave troughs and temperature of curvature sensors based on multi-core fiber tapering for different seven-core fiber lengths.
Detailed Description
The above-described scheme is further illustrated below with reference to specific examples. It should be understood that these examples are for illustrative purposes and are not intended to limit the scope of the present application. The conditions employed in the examples may be further adjusted as determined by the particular manufacturer, and the conditions not specified are generally those used in routine experimentation.
The curvature sensor greatly reduces the light attenuation in the sensor in a tapering mode based on the linear Mach-Zehnder interferometer (IMZI) principle, the attenuation is between 8 and 12dB, the maximum curvature sensitivity can reach 174.02957nm/m & lt-1 & gt, and the sensitivity of the optical fiber curvature sensor is greatly improved. In addition, the sensor is insensitive to temperature within the range of 30-140 ℃, so that the problem of cross sensitivity of temperature and curvature is avoided, and the sensor is beneficial to practical application.
The curvature sensor based on multi-core fiber tapering proposed by the present application is described next with reference to the accompanying drawings.
The first embodiment is as follows:
figure 1 shows a curvature sensor based on multi-core fiber tapering according to an embodiment of the present application,
this curvature sensor based on multicore optic fibre draws awl includes in proper order: the optical fiber comprises a first single-mode fiber area 1, a multi-core fiber area 2, a tapered micro-fiber area 3 and a second single-mode fiber area 4;
the first single-mode fiber section is composed of a first core 5 and a first cladding 6 externally clad thereto,
the second single-mode fiber area consists of a second fiber core 10 and a second cladding 11 coated outside the second fiber core;
the multicore optical fiber area consists of a plurality of fiber cores and a cladding layer coated outside the outermost side of the plurality of fiber cores,
wherein, the arrangement mode of the multi-strand fiber core is as follows: one of the fiber cores is used as a central fiber core 7, and the other fiber cores are uniformly arranged on the circumference of the side wall of the central fiber core in a surrounding manner;
the multi-core optical fiber area is in a conical structure which shrinks from one end to the other end along the axis direction of the central optical fiber core, the end with the larger diameter is a conical head 8, the end with the smaller diameter is a conical tail 9, and the first optical fiber core of the first single-mode optical fiber area is connected with the central optical fiber core of the multi-core optical fiber area from one end of the conical head; and one end of the cone tail of the multi-core optical fiber area is welded with the second single-mode optical fiber area through the tapered micro-optical fiber area. The rest fiber cores of the plurality of fiber cores before tapering are parallel to the central fiber core.
The working mechanism of the curvature sensor is as follows:
light is input from the second single-mode fiber area, and light in a second fiber core of the second single-mode fiber area is coupled into the multi-core fiber area through the tapered micro-fiber area. Since the diameter of the multi-core fiber is smaller than the mode field diameter in the multi-core fiber region, light is not limited to be transmitted in the central fiber core of the multi-core fiber any more, but enters the cladding and the rest of the fiber cores to be transmitted and excite a high-order mode, and is finally coupled into the single-mode fiber. Because the relative refractive indexes of the fundamental mode and the high-order mode are different, the light transmission direction of the central fiber core of the multi-core fiber is unchanged in the transmission process, the shape of the multi-core fiber region is contracted into a conical structure from one end to the other end along the axial direction of the central fiber core of the multi-core fiber, light transmitted in the rest fiber cores deviates from the axial direction of the central fiber core, corresponding optical path difference is generated between the light transmitted in the rest fiber cores and the central fiber core in the climbing process along the conical surface of the conical structure, and therefore interference is generated when the high-order mode is coupled back to the first single-mode fiber again.
Let the electric field strength of the incident light be:
E in ＝Aexp[i(ωt-β 0 n 0 x)] (1)
wherein A is the amplitude of the light wave; omega is the frequency; t is time; beta is a 0 Is the propagation constant; n is a radical of an alkyl radical 0 Is the effective refractive index of the core; and x is the optical path length. The total light intensity is:
the high-order mode light intensity excited by the tapered cone is as follows:
I f ＝ξ f I (3)
in which ξ f Is the proportionality coefficient of the light intensity of the high-order mode and the input light intensity. Interference is generated when the high-order mode is coupled back to the fundamental mode, and the light intensity at the moment is as follows:
wherein λ is the wavelength of light, Δ n eff Is the difference between the effective refractive index of the fundamental mode and the high-order mode, and L is the optical path length.
In the mode, the mode of directly welding and tapering a single mode and a multi-core fiber is utilized, so that the transmission filter with low loss and high contrast is realized. The method comprises the following steps: the multi-core fiber and the single-mode fiber are directly welded, so that the problem of discontinuous connection of the fibers is solved; in addition, after the multi-core fiber and the single-mode fiber are subjected to tapering, the optical field after the tapering is directly leaked from the micro-fiber core to the cladding and then is directly coupled into the multi-core fiber, so that the optical field coupled into the multi-core fiber is much smaller than the structural loss in the prior art. Because the light field can form interference in the first single mode fiber area of the other end through multicore fiber transmission, because the energy that gets into multicore fiber is compared in other structures and is strong a lot, consequently the interference fringe has better contrast, easily carries out the sensing experiment.
Example two
The preparation of the above-described sensor will be described next, taking a seven-core fiber as an example,
the preparation method of the curvature sensor based on the multi-core optical fiber tapering comprises the following steps:
firstly, a first single mode fiber, a seven-core fiber with a certain length (such as 2.1cm long) and a second single mode fiber are placed in an optical fiber fusion splicer,
aligning a first fiber core of a first single mode fiber with one end of a central fiber core of a seven-core fiber, and aligning a second fiber core of a second single mode fiber with the other end of the central fiber core of the seven-core fiber;
the first welding point is arranged at the position where the first fiber core is aligned with one end of the central fiber core of the seven-core optical fiber,
a second fusion point is formed at the aligned position of a second fiber core of the second single-mode fiber and the other end of the central fiber core of the seven-core fiber, and an optical fiber fusion body is formed by using an optical fiber fusion machine for fusion;
placing the optical fiber fusion connector on an oxyhydrogen tapering machine, placing a second fusion point at the tapering center of the oxyhydrogen tapering machine, adjusting the proportion of oxyhydrogen and oxygen in the oxyhydrogen tapering machine to adjust the tapering speed, tapering the seven-core optical fiber into a tapered structure through tapering, and forming a tapered micro-optical fiber area between the tapered tail and the second single-mode light; in the embodiment, the flame sweeping speed of the tapering machine is 0.5-3.0mm/s during tapering, and the moving speed of the fixed station is 0-0.5mm/s during tapering; preferably, the flame sweep speed of the tapering machine and the moving speed of the fixed station are respectively 2.5mm/s and 0.08mm/s, the length of the tapering micro-optical fiber area is 3.164mm, and the diameter of the tapering micro-optical fiber area is 2 mu m. In the present embodiment, the first and second liquid crystal display panels are,
the cross section of the seven-core fiber is shown in FIG. 2, with a cladding diameter of 150 μm, a core diameter of 8 μm, and a core pitch of 42 μm. At this time, the transmission spectrum of the spectrometer and the FFT transformation of the transmission spectrum are as shown in fig. 3a, showing strong interference at the wavelength, and the highest extinction ratio is 10.563dB.
Fig. 3b is a FFT plot of the transmission spectrum, and it can be seen that the higher order modes are excited, and the coupling efficiency from the fundamental mode to the higher order modes is calculated to be 41.88%. The curvature sensor prepared by the method is not sensitive to temperature and has extremely high sensitivity to curvature. The curvature sensor based on the multicore optical fiber tapering is manufactured by combining an arc discharge method and an oxyhydrogen flame tapering methodThe sensors belong to the linear mach-zehnder interferometer with low loss. In the tapering process of the fusion splice of the multi-core fiber and the Single Mode Fiber (SMF), light in each fiber core in the multi-core fiber interferes due to optical path difference when being coupled into the single mode fiber, and a comb-shaped peak is formed. The curvature sensor based on the multi-core fiber tapering is used for measuring the temperature and the curvature, the highest sensitivity of the curvature sensor to the temperature within the range of 30-140 ℃ is 0.01771 nm/DEG C, and the curvature sensitivity can reach 174.02957nm/m -1 The problem of cross-influence of the two is avoided, and the curvature sensitivity is the highest in the known multi-core optical fiber sensor.
The performance of the curvature sensor is described next in connection with experimental data.
When the curvature sensor measures curvature change, the curvature sensor based on the multicore optical fiber tapering is fixed on two mobile stations, wherein the mobile station on the right side is fixed, and the distance between the two mobile stations is adjusted by adjusting a micrometer screw on the mobile station on the left side, so that the change of the optical fiber curvature is realized, as shown in fig. 4.
The equation for the fiber curvature is:
wherein l 0 Is the distance between two mobile stations, R is the radius of curvature, x is the displacement of the left mobile station, and C is the curvature.
FIG. 5a shows the change of the transmission spectrum measured by the curvature when the seven-core optical fiber has a length of 2.1 cm. The 1547.8nm wave trough is selected as the detection wavelength, and the bending curvature is 0.04702m -1 The corresponding trough wavelength is 1543.18nm, and the trough undergoes a blue shift as the bending curvature increases.
Fig. 5b is a corresponding relationship between the wavelength value of the trough and the curvature, and it can be seen from the curve that the wavelength and the curvature satisfy the relationship:
λ＝-98.06988C+1547.86764
the wavelength value also has a linear relationship with curvature, R 2 =0.9987. The measurement precision is 98.06988nm/m -1 。
In order to verify the curvature sensitivity, the influence of the length of the seven-core optical fiber and the length of the tapered micro-optical fiber area on the curvature sensitivity is respectively tested.
Firstly, the lengths of the seven-core optical fiber are respectively changed to be 1.0cm, 1.5cm, 2.1cm and 2.5cm, the length of the tapered micro-optical fiber area is between 3.1mm and 3.2mm, and the experiment result is shown in fig. 6, and the fact that the length of the seven-core optical fiber has no obvious relation with the sensitivity of the curvature sensor based on the multi-core optical fiber tapering can be found. When the length of the seven-core optical fiber is 2.5cm, the highest curvature sensitivity is 105.58707nm/m -1 . The length of the seven-core optical fiber is kept to be 2.1cm, the lengths of the tapered micro optical fiber areas are respectively 3.164mm, 3.52mm and 3.862mm, and the experimental result is shown in fig. 7, so that the curvature sensitivity of the IMZI is obviously improved along with the increase of the length of the tapered micro optical fiber area. When the length of the tapered micro-optical fiber area is 3.862mm, the curvature sensitivity is 174.02957nm/m -1 . However, in an actual preparation experiment, the length of the tapered micro-optical fiber area is too short, so that obvious interference cannot be generated, and the length of the tapered micro-optical fiber area is too long, so that the curvature sensor based on multi-core optical fiber tapering is easy to break, and is not beneficial to practical application. FIG. 6 is an experimental and fitting curve of the wavelength and curvature of a curvature sensor based on multi-core fiber tapering of seven-core fibers with different lengths.
FIG. 7 is an experimental and fitting curve of the wavelength and curvature of a curvature sensor based on multi-core fiber tapering for different tapered micro-fiber zone lengths.
FIG. 8 is a schematic diagram of a temperature sensing experiment system, in which a broadband light source of 1525-1575 nm is used as an experiment light source when measuring temperature, the change of the ambient temperature is realized by a thermostat, and the change of the transmission spectrum is monitored in real time by spectral analysis. Setting the initial temperature to be 140 ℃, gradually reducing the temperature to 30 ℃, and recording the corresponding transmission spectra at different temperatures.
FIGS. 9a-9c are graphs of the wavelength values of the valleys of the curvature sensor based on the tapering of the multi-core optical fiber according to the lengths of the seven-core optical fibers and the temperature. The lengths of the seven-core optical fiber are 1.1cm, 1.5cm and 2.1cm respectively, and the lengths of the tapered micro-optical fiber areas are 3.1mm-3.2mm. Wave troughs with different wavelengths are selected for detection, and the wavelength value corresponding to the wave trough generates red shift along with the reduction of temperature. Experiments show that the curvature sensor based on the multi-core fiber tapering is not sensitive to temperature, and the highest temperature sensitivity is only 0.01771 nm/DEG C under different seven-core fiber lengths.
FIG. 9a is an experimental and fitted curve of wavelength versus temperature for a 1.1cm length of a seven-core fiber;
FIG. 9b is an experimental and fitted curve of wavelength versus temperature for a seven-core fiber length of 1.5 cm;
FIG. 9c is an experimental and fitted curve of wavelength versus temperature for a seven-core fiber length of 2.1 cm;
the curvature sensor based on the multi-core optical fiber tapering is not sensitive to temperature within the range of 30-140 ℃ and has extremely high sensitivity to curvature through experiments of curvature and temperature, the curvature sensitivity of the curvature sensor based on the multi-core optical fiber tapering can be further improved by increasing the length of the tapering area, and when the length of the tapering micro optical fiber area is 3.862mm, the curvature sensitivity can reach 174.02957 nm/DEG C. And because of the extremely low temperature sensitivity, the problem of cross influence of temperature and curvature in practical application is well avoided.
The above embodiments are merely illustrative of the technical concepts and features of the present application, and the purpose of the embodiments is to enable those skilled in the art to understand the content of the present application and implement the present application, and not to limit the protection scope of the present application. All equivalent changes and modifications made according to the spirit of the present application are intended to be covered by the scope of the present application.
Claims (10)
1. The utility model provides a curvature sensor based on multicore optic fibre tapering which characterized in that includes in proper order:
the optical fiber comprises a first single-mode optical fiber area, a multi-core optical fiber area, a tapered micro-optical fiber area and a second single-mode optical fiber area;
the first single mode fiber region includes: a first core, and the outside of the first core is clad with a first cladding,
the second single mode fiber region includes: a second core externally clad with a second cladding,
the multi-core fiber region includes: a plurality of cores, the plurality of cores being arranged such that one of the cores serves as a central core, the remaining cores being arranged around a circumference of a sidewall of the central core, and the multicore fiber section having a tapered structure converging from one end to the other end along an axial direction of the central core,
the first fiber core is connected with the central fiber core of the multi-core fiber area, and the side, far away from the first fiber core, of the multi-core fiber area is welded with the second single-mode fiber area through the tapered micro-fiber area.
2. The multi-core fiber taper-based curvature sensor of claim 1,
before tapering, the plurality of fiber cores are configured to use one of the fiber cores as a central fiber core, and the rest of the fiber cores are respectively parallel to the central fiber core.
3. The multi-core fiber taper-based curvature sensor of claim 1, wherein the multi-core fiber region has a tapered configuration, the diameter on the taper tip side being greater than the diameter on the taper tail.
4. The multi-core fiber taper-based curvature sensor of claim 3,
the first core is connected to the central core from the taper side.
5. The multi-core fiber taper-based curvature sensor of claim 1,
and the side of the second single-mode fiber area, which is welded with the tapered micro-fiber area, is of a tapered structure.
6. The multi-core fiber-based tapered curvature sensor of claim 1, wherein the tapered micro fiber region is configured with a cladding and no core.
7. The multi-core fiber taper-based curvature sensor of claim 1,
the first cladding has an outer diameter greater than a diameter of the multiple-strand core.
8. A method for preparing a curvature sensor based on multi-core optical fiber tapering is characterized by comprising the following steps:
placing the first single-mode fiber, the multi-core fiber and the second single-mode fiber in an optical fiber fusion splicer,
aligning a first fiber core of a first single-mode fiber with one end of a central fiber core of a multi-core fiber, and aligning a second fiber core of a second single-mode fiber with the other end of the central fiber core of the multi-core fiber;
the first welding point is arranged at the position where the first fiber core is aligned with one end of the central fiber core of the multi-core fiber,
A second welding point is formed at the aligned position of a second fiber core of the second single-mode fiber and the other end of the central fiber core of the multi-core fiber, and an optical fiber welding machine is used for welding to form an optical fiber welding body;
and placing the optical fiber fusion splicer on an oxyhydrogen tapering device, wherein a second fusion point is placed at the center of a tapering of the oxyhydrogen tapering machine, adjusting the proportion of oxyhydrogen to oxygen in the oxyhydrogen tapering machine to adjust the tapering speed, tapering the multi-core optical fiber into a tapered structure and forming a tapered micro-optical fiber area between a taper tail and second single-mode light.
9. The method for preparing a curvature sensor based on multi-core optical fiber tapering of claim 8, wherein a flame sweep speed of the tapering machine during tapering is 0.5-3.0mm/s.
10. The method for preparing a curvature sensor based on multi-core optical fiber tapering of claim 8, wherein the moving speed of the fixed stage is 0-0.5mm/s during tapering.
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