CN113446962B - Temperature-insensitive curvature sensor based on strong-coupling multi-core fiber, curvature measuring device and method - Google Patents

Abstract

The invention discloses a temperature insensitive curvature sensor based on a strong coupling multi-core optical fiber, a curvature measuring device and a method, wherein the curvature sensor comprises: the strong coupling multi-core optical fiber comprises a central fiber core and six peripheral fiber cores which are arranged at the periphery of the central fiber core in a regular hexagon shape, wherein the outlines of the central fiber core and the peripheral fiber cores are regular hexagons; seven FBGs with the same central wavelength are respectively written into the same positions of the central fiber core and the six peripheral fiber cores; and the first single-mode fiber and the second single-mode fiber are respectively aligned and welded with two ends of the central fiber core. When the strongly coupled multi-core optical fiber is bent, the reflection spectrum of the strongly coupled multi-core optical fiber does not have obvious wavelength shift; along with the bending of the optical fiber, the mode distribution of two supermodes can be changed, and the effective refractive index difference can be changed; the size of the curvature radius determines the accumulated phase difference variable quantity between the two supermodes participating in interference; so that the two supermodes interfere to cause a change in the depth of the notch, while the temperature is hardly affected.

Description

A temperature-insensitive curvature sensor and curvature measurement based on strongly coupled multi-core optical fiber Measuring device and method

technical field

The invention relates to the field of curvature detection, in particular to a temperature-insensitive curvature sensor based on a strongly coupled multi-core optical fiber, a curvature measurement device and a method.

Background technique

Curvature is an important parameter to describe the shape of an object. The curvature of a curve is the rotation rate of the tangent direction angle to the arc length at a point on the curve. It is defined by differentiation, indicating the degree to which the curve deviates from a straight line. A numerical value that mathematically indicates how curved a curve is at a certain point. The greater the curvature, the more curved the curve. By measuring the curvature, the change trend of the shape of the object can be understood. Curvature sensors have broad application prospects in structural health monitoring, aerospace, robotics, surface shape measurement, etc. Among them, curvature sensors based on fiber gratings have small size, light weight, strong anti-electromagnetic interference, and quasi-distributed measurement. The advantages are favored by scholars at home and abroad.

Fiber grating is one of the most rapidly developed fiber passive components in recent years. Because it has many unique advantages, it has broad application prospects in the fields of optical fiber communication and optical fiber sensing. It is considered to be another major breakthrough in the development of optical fiber technology after the Erbium-doped fiber amplifier (EDFA) technology. With the continuous improvement of fiber grating manufacturing technology and the increasing application results, fiber grating has become one of the most promising and representative fiber passive devices. The emergence of fiber gratings has greatly broadened the application range of fiber optic technology. Fiber Ragg grating (FBG), as a very important sensing element, is also widely used in many fields of optical fiber sensing.

Y.P.Wang et al. proposed a cascaded long-period fiber grating (Long Period Fiber Grating, LPG) curvature sensor. The LPG written by ultraviolet exposure is only affected by the curvature, while the LPG written by two carbon dioxide lasers is used for Demodulate the bending direction (Y.P.Wang, Y.J.Rao. "A Novel Long Period Fiber GratingSensor Measuring Curvature and Determining Bend-Direction Simultaneously," IEEE Sensors Journal, 2005, 5(5):839～843.). In addition, J. Kong et al. proposed a two-dimensional bending sensor based on orthogonal cascaded eccentric fiber Bragg gratings, which demodulates the curvature and bending direction by comparing the central wavelength shift of two eccentric fibers. (J. Kong, A. Zhou, C. Cheng, et al. "Two-Axis Bending Sensor Based on Cascaded Eccentric Core Fiber Bragg Gratings," IEEE Photonics Technology Letters, 2016, 28(11): 1237～1240.).

However, in practical applications, the curvature sensor is often accompanied by temperature changes while measuring the curvature. The sensing signal collected by the sensor is the result of the joint action of the bending curvature and the temperature change. Existing demodulation schemes for curvature sensors cannot distinguish between curvature and temperature, so there are errors in curvature demodulation.

In order to solve the problems existing in the existing solutions, a sensor based on strongly coupled multi-core fiber Bragg gratings is proposed, which can realize a temperature-insensitive curvature sensor, which is an urgent problem to be solved in this field.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, to provide a temperature-insensitive curvature sensor, curvature measurement device and method based on strongly coupled multi-core optical fiber, and to solve the problem that the prior art cannot distinguish between bending curvature and temperature change and cause curvature demodulation There is a problem of error.

The purpose of the present invention is achieved through the following technical solutions:

The first aspect of the present invention provides a temperature-insensitive curvature sensor based on strongly coupled multi-core optical fiber, including:

Strongly coupled multi-core optical fiber, comprising a central core and six peripheral cores arranged in a regular hexagonal shape on the periphery of the central core, and the outlines of the central core and the peripheral cores are regular hexagons;

Seven FBGs with the same central wavelength are written in the same positions of the central core and six peripheral cores respectively;

The first single-mode optical fiber and the second single-mode optical fiber are respectively aligned and welded to the two ends of the central fiber core.

Further, the six sides of the central core are aligned with one side of the six peripheral cores.

Further, the writing method of the FBG includes a phase mask method, a femtosecond laser direct writing method or an arc discharge preparation method.

Further, the FBG is located in the middle of the central core and the six peripheral cores.

A second aspect of the present invention provides a method for preparing a temperature-insensitive curvature sensor based on a strongly coupled multi-core optical fiber, comprising the following steps:

The first single-mode fiber and the second single-mode fiber are respectively aligned and welded at both ends of a strongly coupled multi-core fiber with a central core; the peripheral of the central core of the strong-coupled multi-core fiber includes a peripheral fiber core, the contours of the central fiber core and the peripheral fiber core are both regular hexagons;

Seven FBGs with the same central wavelength are respectively written in the same positions of the central core and six peripheral cores.

A third aspect of the present invention provides a curvature measurement device based on a temperature-insensitive curvature sensor, the device comprising:

said curvature sensor;

A light source connected to the input end of the curvature sensor;

The spectrum analyzer is connected to the output terminal of the curvature sensor, and is used to calculate the spectrum according to the output of the curvature sensor;

The curvature calculating device is connected with the spectrum analyzer, and is used to calculate and obtain the curvature value according to the gap depth between the two resonance peaks in the spectrum.

Further, the calculating the curvature value according to the gap depth between the two resonance peaks in the spectrum includes: using the depth-curvature curve and the gap depth between the two resonance peaks in the spectrum to calculate the actual curvature value .

Further, the curvature measuring device also includes:

The experimental fixture is used to fix the curvature sensor in different experimental curvatures; the spectrum analyzer is also used to calculate the experimental spectra under different curvatures fixed by the experimental fixture;

The curvature calculation device is also used to obtain the experimental curvature value according to the experimental fixture, and to obtain the experimental notch depth by using the experimental spectrum; the curvature calculation device is also used to calculate the experimental notch depth under different experimental curvature values to obtain the depth- curvature curve.

In a fourth aspect of the present invention, a method for measuring curvature based on a temperature-insensitive curvature sensor is provided, using the output data of the curvature sensor; the method includes the following steps:

Obtain the spectrum converted from the output data of the curvature sensor to be measured;

Curvature values are calculated from the depth of the gap between two resonance peaks in the spectrum.

Further, the curvature value calculated according to the gap depth between two resonance peaks in the spectrum includes:

Using the depth-curvature curve and the gap depth between two resonance peaks in the spectrum, the actual curvature value is calculated.

Further, the acquisition method of the depth-curvature curve includes:

Obtain the experimental spectrum when the curvature sensor is in different experimental curvatures;

Calculate the experimental notch depth for each experimental spectrum;

Calculate the experimental notch depth under different experimental curvature values to obtain the depth-curvature curve.

According to the fifth aspect of the present invention, based on the implementation of the curvature measurement method, a storage medium is also provided, on which computer instructions are stored, and when the computer instructions are run, the above-mentioned temperature-insensitive curvature sensor-based Curvature measurement method.

The sixth aspect of the present invention, based on the implementation of the curvature measurement method, also provides a terminal (that is, a curvature calculation device), including a memory and a processor, and the memory stores a program that can run on the processor A computer instruction, the processor executes the curvature measurement method based on a temperature-insensitive curvature sensor when running the computer instruction.

The beneficial effects of the present invention are:

(1) In an exemplary embodiment of the present invention, when the single-mode fiber of the curvature sensor and the special fiber (strongly coupled multi-core fiber) are bent, due to the excitation conditions, the central core of the strong-coupled multi-core fiber has most of the of light intensity. Therefore, the FBG in this central core contributes more to the reflection spectrum than the FBG written in the peripheral core. Therefore, when the strongly coupled multi-core optical fiber 1 is bent, its reflection spectrum has no obvious wavelength shift. In addition, as the fiber is bent, the mode distribution of the two supermodes will change, so their effective refractive index difference will also change. The size of the radius of curvature determines the amount of cumulative phase difference change between the two supermodes participating in the interference. Thus, the interference of the two supermodes causes the variation of the notch depth, while the temperature is hardly affected. Therefore, the bending radius (ie, curvature) can be determined by monitoring the notch depth of the reflectance spectrum. Compared with the traditional wavelength reading method, the curvature sensor in this exemplary embodiment can effectively eliminate the cross-sensitivity problem caused by temperature, and at the same time reduce the requirement on the resolution of optical spectrum analyzers (OSA). At the same time, the sensor of the invention also has the advantages of compact structure, simple demodulation, low cross sensitivity and the like. In addition, a method for fabricating a temperature-insensitive curvature sensor based on strongly coupled multi-core optical fibers also has the same advantages.

(2) In yet another exemplary embodiment of the present invention, the curvature measurement device has a certain relationship with the curvature through the notch depth, so the curvature calculation device uses the spectrum output by the spectrum analyzer, according to the notch depth between the two resonance peaks in the spectrum Calculate the curvature value. In addition, the curvature measurement method, storage interpretation and terminal also have the same advantages.

(3) In yet another exemplary embodiment of the present invention, the curvature measurement device uses the depth-curvature curve and the gap depth between the two resonance peaks in the spectrum obtained by experiments to calculate the actual curvature value, so that The actual curvature value can be directly calculated when the notch depth is known; in addition, the curvature measurement method, storage interpretation and termination also have the same advantages.

(4) In yet another exemplary embodiment of the present invention, the specific structure of the experimental fixture is disclosed to facilitate the acquisition of multi-curvature data parameters.

Description of drawings

Fig. 1 is a schematic structural diagram of a temperature-insensitive curvature sensor disclosed in an exemplary embodiment of the present invention;

Figure 2 is a schematic diagram of one of the spectra disclosed in an exemplary embodiment of the present invention;

Fig. 3 is a schematic diagram of the connection of the curvature measuring device disclosed in an exemplary embodiment of the present invention;

Fig. 4 is a schematic structural diagram of an experimental fixture disclosed in an exemplary embodiment of the present invention;

Fig. 5 is a curvature sensor disclosed by an exemplary embodiment of the present invention at 0m ^-1 , 0.29m ^-1 , 0.51m ^-1 , 0.70m ^-1 , 0.87m ^-1 , 1.02m ^-1 , 1.15m ^-1 Schematic diagram of spectral data under curvature;

Fig. 6 is a schematic diagram of the depth-curvature curve obtained by calculating the experimental notch depth under different experimental curvature values disclosed in an exemplary embodiment of the present invention;

In the figure, 1-strongly coupled multi-core fiber, 101-central fiber core, 102-peripheral fiber core, 103-FBG, 201-first single-mode fiber, 202-second single-mode fiber, 301-curvature sensor input fixed Device, 302-curvature adjustment platform, 303-curvature sensor output end fixing device, 304-curvature adjustment steel belt, 305-load.

detailed description

The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Apparently, the described embodiments are part of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms belonging to "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" etc. The indicated direction or positional relationship is based on the direction or positional relationship described in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, or in a specific orientation. construction and operation, therefore, should not be construed as limiting the invention.

In the description of the present invention, it should be noted that, unless otherwise specified and limited, "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrally connected; it can be mechanically connected or electrically connected; it can be directly connected or indirectly connected through an intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations.

The terminology used in this application is for the purpose of describing particular embodiments only, and is not intended to limit the application. As used in this application and the appended claims, the singular forms "a", "the", and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It should also be understood that the term "and/or" as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

It should be understood that although the terms first, second, third, etc. may be used in this application to describe various information, the information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of the present application, first information may also be called second information, and similarly, second information may also be called first information. Depending on the context, the word "if" as used herein may be interpreted as "at" or "when" or "in response to a determination." In addition, belonging to "first" and "second" is only for descriptive purposes, and should not be understood as indicating or implying relative importance.

In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as there is no conflict with each other.

In the existing technology, the curvature sensor is often accompanied by temperature changes while measuring the curvature. The sensing signal collected by the sensor is the result of the joint action of the bending curvature and the temperature change, because FBG is sensitive to both temperature and strain, expressed as wavelength of the mobile. Existing demodulation schemes for curvature sensors cannot distinguish between curvature and temperature, so there are errors in curvature demodulation.

Referring to FIG. 1, FIG. 1 shows a temperature-insensitive curvature sensor based on strongly coupled multi-core optical fiber provided by an exemplary embodiment of the present invention, including:

Strongly-coupled multicore fiber 1 (Strongly-coupled multicore fiber, SCMCF), comprising a central core 101 and six peripheral cores 102 arranged in a regular hexagonal shape on the periphery of the central core 101, the central fiber The contours of the core 101 and the peripheral core 102 are regular hexagons;

Seven FBGs 103 with the same central wavelength are respectively written into the same positions of the central core 101 and six peripheral cores 102;

A first single-mode optical fiber 201 and a second single-mode optical fiber 202 (Single mode fiber, SMF) are respectively aligned and welded to two ends of the central fiber core 101 .

In this exemplary embodiment, the first single-mode optical fiber 201 and the second single-mode optical fiber 202 serve as the input end and the output end of the entire curvature sensor respectively. The following content is described with the first single-mode optical fiber 201 as the input end and the second single-mode optical fiber 202 as the output end, and the corresponding functions can also be realized by exchanging the two.

Specifically, the external light source enters the strong coupling multi-core fiber 1 through the first single-mode fiber 201 through the first fusion point (the fusion point between the first single-mode fiber 201 and the strong coupling multi-core fiber 1), due to the strong The seven cores of the coupled multi-core fiber 1 are all regular hexagons, so two kinds of supermodes are generated during the transmission of the strongly coupled multi-core fiber 1 . And when the two supermodes are transmitted to the FBG 103 position, the two reflected signals related to the two supermodes are passed through the second fusion point (the fusion point between the second single-mode fiber 202 and the strongly coupled multi-core fiber) Re-coupling into the second single-mode fiber 202 interferes due to the phase difference between the two reflected spectra. Therefore, in the spectrum formed by the reflection of the FBG 103 (as shown in Figure 2, the abscissa Wavelength in Figure 2 represents the wavelength, and the ordinate Amplitude represents the amplitude, that is, the depth of the notch), two resonance peaks (peak1 and peak2) and A gap depth (Notch) between them. At this time, when the sensor is affected jointly by bending and temperature, the depth of the notch only changes with bending, but hardly changes with temperature. Therefore, in this exemplary embodiment, the curvature is determined by demodulating the depth of the notch, thereby realizing a temperature-insensitive curvature sensor.

Therefore, when the ordinary single-mode fiber and the special fiber (strongly coupled multi-core fiber 1 ) of this exemplary embodiment are bent, the central core 101 of the strongly coupled multi-core fiber 1 has most of the light intensity due to excitation conditions. Therefore, the FBG 103 in this central core 101 contributes more to the reflection spectrum than the FBG 103 written in the peripheral core 102 . Therefore, when the strongly coupled multi-core optical fiber 1 is bent, its reflection spectrum has no obvious wavelength shift. In addition, as the fiber is bent, the mode distribution of the two supermodes will change, so their effective refractive index difference will also change. The size of the radius of curvature determines the amount of cumulative phase difference change between the two supermodes participating in the interference. Thus, the interference of the two supermodes causes the variation of the notch depth, while the temperature is hardly affected. Therefore, the bending radius (ie, curvature) can be determined by monitoring the notch depth of the reflectance spectrum.

Compared with the traditional wavelength reading method, the curvature sensor in this exemplary embodiment can effectively eliminate the cross-sensitivity problem caused by temperature, and at the same time reduce the requirement on the resolution of optical spectrum analyzers (OSA). At the same time, the sensor of the invention also has the advantages of compact structure, simple demodulation, low cross sensitivity and the like.

For the description of the resonant peaks (peak1 and peak2) in Figure 2, the two peaks with the largest amplitudes (ie notch depth) in the spectrum are the resonant peaks (peak1 and peak2) here.

It should be noted that the first single-mode fiber 201 and the second single-mode fiber 202, that is, SMF, are standard single-mode fibers with a circular core; the seven cores of the strongly coupled multi-core fiber 1, that is, SCMCF, are The hexagon is a necessary feature, so that the optical signal generates two specific supermodes during transmission; and the distance between each core of the strongly coupled multi-core fiber 1 must be close enough to be strongly coupled. Although the shapes of the single-mode fiber (the first single-mode fiber 201 and the second single-mode fiber 202) and the strongly coupled multi-core fiber 1 are different, the two kinds of optical fibers can be welded; and in a preferred exemplary embodiment, the two The center of the fiber is aligned. The two supermodes produced by the strong coupling multi-core fiber 1 are different, so that when the fiber is bent, two reflection peaks are equivalently formed without overlapping, and interference occurs, forming a deep gap.

In addition, the length between the position where the FBG 103 is written in the strong coupling multi-core fiber 1 and the fusion point of the single-mode fiber (the first single-mode fiber 201 and the first single-mode fiber 20) and the strong coupling multi-core fiber 1 should be To meet the sensing requirements, ensure that the two reflection peaks equivalently formed by the two supermodes can interfere to produce a deep enough gap. On this basis, the length of the single-mode fiber should be as short as possible to ensure the same curvature at the two fusion points.

At the same time, the numerical apertures of the strongly coupled multi-core fiber 1 and the single-mode fiber match, so that when the strongly-coupled multi-core fiber 1 is spliced with the single-mode fiber, the coupling loss is minimized.

In a specific exemplary embodiment, the diameters of the first single-mode fiber 201 and the first single-mode fiber 202 are both 8.5um, and the cladding diameter is 125um; the core diameter of the selected strong coupling multi-core fiber 1 is 9.2um, the distance between the fiber core and the fiber core is 11um, the numerical aperture is 1.4, the length of the strongly coupled multi-core fiber section is 13mm (the length of the first single-mode fiber 201 and the first single-mode fiber 202 is selected according to actual needs ); and the length of the FBG 103 written in each core of the strongly coupled multi-core optical fiber 1 is 2 mm, and the length between the FBG and the fusion splicing point is 6.5 mm, which is located in the middle of the strongly coupled multi-core optical fiber 1.

More preferably, in an exemplary embodiment, as shown in FIG. 1 , six sides of the central core 101 are aligned with one side of the six peripheral cores 102 . (similar to a honeycomb structure)

More preferably, in an exemplary embodiment, the writing method of the FBG 103 includes a phase mask method, a femtosecond laser direct writing method or an arc discharge preparation method. Among them, the phase mask method is preferable.

More preferably, in an exemplary embodiment, the FBG 103 is located in the middle of the central core 101 and the six peripheral cores 102 .

In addition, another exemplary embodiment provides a method for preparing a temperature-insensitive curvature sensor based on a strongly coupled multi-core optical fiber, comprising the following steps:

The first single-mode optical fiber 201 and the second single-mode optical fiber 202 are respectively aligned and welded at both ends of the strongly coupled multi-core optical fiber 1 with the central core 101; The peripheral core 102 arranged in a regular hexagonal shape, the outlines of the central core 101 and the peripheral core 102 are regular hexagonal;

Seven FBGs 103 with the same central wavelength are respectively written in the same positions of the central core 101 and the six peripheral cores 102 .

Wherein, since this method has the same inventive concept as that of the curvature sensor in the above-mentioned exemplary embodiment, the content of advantages and principles will not be repeated here.

In addition, it should be noted that the order of the two steps can be changed and arranged according to actual needs and the order of the production line.

More preferably, in an exemplary embodiment, as shown in FIG. 1 , six sides of the central core 101 are aligned with one side of the six peripheral cores 102 . (similar to a honeycomb structure)

More preferably, in an exemplary embodiment, the writing method of the FBG 103 includes a phase mask method, a femtosecond laser direct writing method or an arc discharge preparation method. Among them, the phase mask method is preferable.

More preferably, in an exemplary embodiment, the FBG 103 is located in the middle of the central core 101 and the six peripheral cores 102 .

Referring to Fig. 3, Fig. 3 shows that another exemplary embodiment of the present invention provides a curvature measurement device based on a temperature-insensitive curvature sensor, the device comprising:

The curvature sensor described in any of the above exemplary embodiments;

A light source connected to the input end of the curvature sensor;

The spectrum analyzer is connected to the output terminal of the curvature sensor, and is used to calculate the spectrum according to the output of the curvature sensor;

The curvature calculating device is connected with the spectrum analyzer, and is used to calculate and obtain the curvature value according to the gap depth between the two resonance peaks in the spectrum.

Specifically, in this exemplary embodiment, the light source passes through the first single-mode optical fiber 201 of the curvature sensor and passes through the first fusion splicing point (the fusion splicing between the first single-mode optical fiber 201 and the strong coupling multi-core optical fiber 1 Point) into the strong coupling multi-core fiber 1, because the seven cores of the strong coupling multi-core fiber 1 are all regular hexagons, so two kinds of supermodes are produced during the transmission of the strong coupling multi-core fiber 1. And when the two supermodes are transmitted to the FBG 103 position, the two reflected signals related to the two supermodes are passed through the second fusion point (the fusion point between the second single-mode fiber 202 and the strongly coupled multi-core fiber) Re-coupling into the second single-mode fiber 202 interferes due to the phase difference between the two reflected spectra. At this time, the spectrum analyzer receives the output of the curvature sensor and calculates the spectrum, so that the spectrum reflected by the FBG 103 (as shown in Figure 2, the abscissa Wavelength in Figure 2 represents the wavelength, and the ordinate Amplitude represents the amplitude (ie, the depth of the gap) ), two resonance peaks (peak1 and peak2) and a notch depth (Notch) between them can be observed. At this time, when the sensor is affected jointly by bending and temperature, the depth of the notch only changes with bending, but hardly changes with temperature. Since the notch depth has a certain relationship with the curvature, the curvature calculation device uses the spectrum output by the spectrum analyzer to calculate the curvature value according to the notch depth between two resonance peaks in the spectrum.

It should be noted that the curvature calculation device may be a PC or other computing equipment.

More preferably, in an exemplary embodiment, calculating the curvature value according to the gap depth between two resonance peaks in the spectrum includes: using the depth-curvature curve and the gap between the two resonance peaks in the spectrum The notch depth is calculated to obtain the actual curvature value.

Specifically, in this exemplary embodiment, since the depth of the notch has a certain relationship with the curvature, the relationship can be expressed in the form of a depth-curvature curve, so that the actual curvature value can be directly calculated when the depth of the notch is known.

More preferably, in an exemplary embodiment, the device further includes:

The experimental fixture is used to fix the curvature sensor in different experimental curvatures; the spectrum analyzer is also used to calculate the experimental spectra under different curvatures fixed by the experimental fixture;

The curvature calculation device is also used to obtain the experimental curvature value according to the experimental fixture, and to obtain the experimental notch depth by using the experimental spectrum; the curvature calculation device is also used to calculate the experimental notch depth under different experimental curvature values to obtain the depth- curvature curve.

In this exemplary embodiment, the depth-curvature curve is calculated from experimental data. Specifically, referring to Fig. 4, Fig. 4 shows the curvature sensor under the effect of the experimental fixture, and the experimental fixture includes: a curvature sensor input fixture 301, a curvature sensor output fixture 303 and a curvature adjustment table 302, the curvature The adjustment table 302 is located between the curvature sensor input end fixing device 301 and the curvature sensor output end fixing device 303 , and the curvature adjustment steel belt 304 is connected between the curvature adjustment table 302 and the curvature sensor input end fixing device 301 .

When needing to carry out experimental measurement, at first after adjusting the curvature of curvature adjustment steel band 304 self by curvature adjustment platform 302 (passing through), fix the position of curvature adjustment platform 302; On the curvature adjusting steel belt, the first single-mode optical fiber 201 is fixed by the fixing device 301 at the input end of the curvature sensor, and the second single-mode optical fiber 202 is fixed; after that, the measurement can be performed.

It should be noted that, in one of the exemplary embodiments, when the curvature adjustment table 302 moves to the curvature sensor input end fixing device 301 when it is in the initial position (that is, the curvature adjustment steel belt 304 is in a straight state), the curvature adjustment steel belt The strap 304 is curved upwards (from the center of the curvature adjustment steel strap 304).

Among them, the spectral data under different curvatures are shown in Fig. 5. Fig. 5 (the abscissa Wavelength represents the wavelength, and the ordinate Amplitude represents the magnitude (that is, the depth of the notch)) shows that a certain curvature sensor is at 0m ^-1 , 0.29m Spectral data under curvatures of ^-1 , 0.51m ^-1 , 0.70m ^-1 , 0.87m ^-1 , 1.02m ^-1 , 1.15m ^-1 .

Wherein, the measurement of the curvature C can be calculated according to the formula sin(LC/2)=(1/2)*(L-dL)*C, and different curvature values C can be calculated. Wherein, L represents the straight-line distance between the curvature sensor input fixing device 301 and the curvature adjustment table 302 when the curvature adjustment steel belt 304 is in a straight line state, and dL indicates the shortened distance when the curvature adjustment steel belt 304 is in a curved state.

Referring to Fig. 6, Fig. 6 shows that the curvature calculation device is also used to calculate the experimental notch depth under different experimental curvature values to obtain the specific calculation process of the depth-curvature curve: first, the abscissa Curvature in Fig. 6 represents the curvature, and the left ordinate Amplitude represents the magnitude, and the square points represent the values of the magnitude (that is, the depth of the gap) under different curvatures obtained in Figure 5; then connect all the values with a curve (that is, the depth-curvature curve) and fit the corresponding depth - a curvature formula, thereby obtaining a depth-curvature curve represented by a depth-curvature formula. In the exemplary embodiment shown in FIG. 6 , the formula corresponding to the curve is A=-4.46*C ² +15.9*C-4.62 (A represents the depth of the notch, and C represents the curvature).

Among them, it needs to be additionally explained that the right ordinate wavelength variation in Fig. 6 represents the wavelength variation, as can be seen from the figure, the wavelength variation using this exemplary embodiment is very small, the largest is only 16pm; while using the traditional The temperature measuring sensor of the prior art can even reach more than 1000pm.

After obtaining the depth-curvature curve, when the curvature sensor is used for measurement, it is only necessary to obtain the spectral data through the spectrum analyzer, and then obtain the depth of the gap between the two resonance peaks in the spectrum, and fill the depth of the gap into "depth- The value of A in the "curvature formula" can be calculated to obtain the value of curvature C.

It should be noted that different curvature sensors have different characteristics, so different experiments/calibrations are required.

More preferably, as shown in Figure 4, the experimental fixture also includes a load 305, the load 305 is located between the curvature adjustment platform 302 and the curvature sensor output end fixture 303, the load 305 is used to further fix the curvature sensor It is closely attached to the curvature-adjusting steel belt 304, so as to ensure that the degree of curvature of the curvature sensor is the same as that of the curvature-adjusting steel belt 304, thereby improving the data accuracy of the overall experiment.

Wherein, the load 305 can be placed between the steps of "Using 301—curvature sensor input end fixing device to fix the first single-mode optical fiber 201" and "Using the second single-mode optical fiber 202 to fix". In one of the exemplary embodiments, the top of the load 305 has a hook, which can be hooked on the second single-mode optical fiber 202; and in order to avoid inaccurate experimental data caused by weight asymmetry, the load 305 needs to be kept Even shape and even weight.

This exemplary embodiment has the same inventive concept as the curvature measuring device, and provides a method for measuring curvature based on a temperature-insensitive curvature sensor, using the output data of the curvature sensor; the method includes the following steps:

Obtain the spectrum converted from the output data of the curvature sensor to be measured;

Curvature values are calculated from the depth of the gap between two resonance peaks in the spectrum.

It should be noted that the method of this exemplary embodiment is applied to the curvature calculation device, that is, to use the advantage of the temperature insensitivity of the curvature sensor in any of the aforementioned exemplary embodiments to perform curvature calculation: first obtain stable spectral data, and then according to the The curvature value was calculated from the depth of the gap between the two resonance peaks in the above spectrum.

More preferably, in an exemplary embodiment, the curvature value calculated according to the gap depth between two resonance peaks in the spectrum includes:

Using the depth-curvature curve and the gap depth between two resonance peaks in the spectrum, the actual curvature value is calculated.

More preferably, in an exemplary embodiment, the acquisition method of the depth-curvature curve includes:

Obtain the experimental spectrum when the curvature sensor is in different experimental curvatures;

Calculate the experimental notch depth for each experimental spectrum;

Calculate the experimental notch depth under different experimental curvature values to obtain the depth-curvature curve.

Based on the realization of the curvature measurement method described in any exemplary embodiment, this exemplary embodiment also provides a storage medium on which computer instructions are stored. Curvature measurement method for sensitive curvature sensors.

At the same time, based on the realization of the curvature measurement method described in any exemplary embodiment, this exemplary embodiment also provides a terminal (that is, a curvature calculation device), including a memory and a processor. computer instructions running on the processor, and the processor executes the curvature measurement method based on a temperature-insensitive curvature sensor when running the computer instructions.

Based on this understanding, the technical solution of this embodiment is essentially or the part that contributes to the prior art or the part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium. Several instructions are included to make a computer device (which may be a personal computer, a server, or a network device, etc.) execute all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-OnlyMemory, ROM), random access memory (RandomAccessMemory, RAM), magnetic disk or optical disk, and various media capable of storing program codes.

In all the embodiments provided by the present invention, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are only illustrative. For example, the division of the units/modules is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or modules can be Incorporation may either be integrated into another system, or some features may be omitted, or not implemented. In another point, the mutual coupling or direct coupling or communication connection shown or discussed may be through some communication interfaces, and the indirect coupling or communication connection of devices or units may be in electrical, mechanical or other forms.

Apparently, the above-mentioned embodiment is only an example for clearly explaining, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above-mentioned description. . It is not necessary and impossible to exhaustively list all the implementation manners here. However, the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (10)

1. A temperature insensitive curvature sensor based on a strong coupling multi-core fiber is characterized in that: the method comprises the following steps:

the strong-coupling multi-core optical fiber comprises a central fiber core and six peripheral fiber cores which are positioned at the periphery of the central fiber core and arranged in a regular hexagon shape, wherein the outlines of the central fiber core and the peripheral fiber cores are regular hexagons;

seven FBGs with the same central wavelength are respectively written into the same positions of the central fiber core and the six peripheral fiber cores;

the first single-mode fiber and the second single-mode fiber are respectively aligned and welded with two ends of the central fiber core;

obtaining two resonance peaks and a gap depth between the two resonance peaks in a spectrum formed by the FBG; determining the curvature by demodulating the depth of the notch; wherein, the two wave peaks with the largest notch depth in the spectrum are resonance peaks.

2. The temperature-insensitive curvature sensor based on the strongly-coupled multi-core optical fiber as claimed in claim 1, wherein: six sides of the central core are aligned with one of the six peripheral cores.

3. The temperature-insensitive curvature sensor based on the strongly-coupled multi-core optical fiber as claimed in claim 1, wherein: the writing mode of the FBG comprises a phase mask method, a femtosecond laser direct writing method or an arc discharge preparation method.

4. The temperature-insensitive curvature sensor based on the strongly-coupled multi-core optical fiber as claimed in claim 1, wherein: the FBGs are located at the middle of the central core and the six peripheral cores.

5. A curvature measuring device based on a temperature insensitive curvature sensor is characterized in that: the device comprises:

the curvature sensor of any one of claims 1~4;

the light source is connected with the input end of the curvature sensor;

the spectrum analyzer is connected with the output end of the curvature sensor and used for calculating to obtain a spectrum according to the output of the curvature sensor;

and the curvature calculation device is connected with the spectrum analyzer and used for calculating a curvature value according to the depth of a gap between two resonance peaks in the spectrum.

6. A curvature measuring device based on a temperature insensitive curvature sensor as claimed in claim 5, characterized in that: the step of calculating a curvature value according to the depth of a gap between two resonance peaks in the spectrum comprises: and calculating to obtain an actual curvature value by using the depth-curvature curve and the depth of a gap between two resonance peaks in the spectrum.

7. A curvature measuring device based on a temperature insensitive curvature sensor as claimed in claim 6, characterized in that: further comprising:

the experiment fixing device is used for fixing the curvature sensor at different experiment curvatures; the spectrum analyzer is also used for calculating and obtaining experimental spectra under different curvatures fixed by the experimental fixing device;

the curvature calculating device is also used for obtaining an experiment curvature value according to the experiment fixing device and obtaining an experiment notch depth by using the experiment spectrum; the curvature calculating device is also used for calculating the experimental notch depth under different experimental curvature values to obtain a depth-curvature curve.

8. A curvature measuring method based on a temperature insensitive curvature sensor is characterized in that: using the output data of the curvature sensor of any of claims 1~4; the method comprises the following steps:

acquiring a spectrum converted from output data of a curvature sensor to be measured;

and calculating according to the depth of a gap between two resonance peaks in the spectrum to obtain a curvature value.

9. A curvature measurement method based on a temperature insensitive curvature sensor as claimed in claim 8, characterized in that: the calculating according to the notch depth between two resonance peaks in the spectrum to obtain the curvature value comprises the following steps:

and calculating to obtain an actual curvature value by using the depth-curvature curve and the depth of a gap between two resonance peaks in the spectrum.

10. A method of curvature measurement based on a temperature insensitive curvature sensor as claimed in claim 9, characterized in that: the acquisition mode of the depth-curvature curve comprises the following steps:

acquiring experimental spectra of the curvature sensor under different experimental curvatures;

calculating the depth of an experimental notch of each experimental spectrum;

and calculating the depth of the experimental notch under different experimental curvature values to obtain a depth-curvature curve.

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