A deformation detection method based on soft optical waveguide mechanism

Abstract

The present invention relates to a deformation detection method based on a soft optical waveguide mechanism, and relates to the field of computer processing technology. The method comprises the following steps: S01, deploying spaced flexible optical waveguide sensors within the area to be measured, wherein: the flexible optical waveguide sensors include at least an elastic cladding and satisfy the Mooney-Rivlin hyperelastic model; the curvature of the curved section of the flexible optical waveguide sensor is dynamically correlated with pipeline deformation, and its inclination angle #imgabs0# is determined by the relationship between the deformation height #imgabs1# and the straight section length #imgabs2#. Through multi-physics field coupling modeling, material optimization design, and high-precision photoelectric conversion mechanisms, this invention provides reliable technical support for pipeline safety monitoring by combining the high sensitivity of flexible optical waveguide sensors for deformation detection, strong environmental adaptability, and long-term stability, while also offering the advantages of low cost and easy deployment.

Description

Technical Field

[0001] The present invention relates to the field of computer processing technology, and in particular to a deformation detection method based on a soft optical waveguide mechanism. Background Art

[0002] With the widespread use of industrial pipeline systems, pipeline safety monitoring has become a crucial component in ensuring energy delivery and industrial production. Over long-term operation, pipelines are prone to defects such as localized deformation, dents, and cracks due to factors such as environmental corrosion, mechanical stress, and geological subsidence. If these defects are not detected and addressed promptly, they can lead to pipeline leaks, ruptures, or even explosions, causing serious economic losses and environmental pollution. Therefore, the development of efficient and accurate pipeline deformation detection technology is of great practical significance.

[0003] Traditional pipeline inspection technologies, such as ultrasonic testing (see Chinese Patent Publication No. CN119246680A, which discloses an ultrasonic guided wave inspection system for pipelines), magnetic flux leakage testing (see Chinese Authorized Patent Publication No. CN117849164B, which discloses a magnetic flux leakage inspection system for pipelines), and radiographic testing (see Chinese Patent Publication No. CN116879322A, which discloses a radiographic inspection device for pipelines), can identify pipeline defects to a certain extent. However, these technologies have limitations such as high inspection costs, complex operations, and strict requirements on pipeline materials and structures. Furthermore, these technologies often require external equipment, making real-time and continuous monitoring difficult.

[0004] In recent years, fiber optic sensing technology has become a research hotspot in pipeline inspection due to its advantages such as resistance to electromagnetic interference, high sensitivity, and compact size. However, traditional fiber optic sensors have poor adaptability in complex pipeline environments, especially for internal pipe deformation detection. Their lack of flexibility and impact resistance limits their practical application. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention adopts a deformation detection method based on a soft optical waveguide mechanism, which includes the following steps:

[0006] S01. Flexible optical waveguide sensors are arranged at intervals in the area to be measured, wherein:

[0007] The flexible optical waveguide sensor includes at least an elastic cladding and satisfies the Mooney-Rivlin hyperelastic model.

[0008] The curvature of the curved section of the flexible optical waveguide sensor is dynamically related to the pipe deformation, and its inclination angle By deformation height and straight section length The relationship is determined by:

[0009] ;

[0010] The flexible optical waveguide sensor can obtain the curvature of the probe The relationship between the deformation height h in the pipe :

[0011] ;

[0012] in, is the length from the semicircular arc vertex to the inclined connection of the flexible optical waveguide, is the angle between the probe and the detection plane in the initial state;

[0013] S02. Injecting an original optical signal with an operating wavelength of 940 nm into the flexible optical waveguide sensor through a photoelectric emitting diode, and detecting the output optical signal in real time through a photoelectric receiving diode, wherein:

[0014] The output optical power of the photoelectric emitting diode satisfy: , where: is the electro-optical conversion efficiency of the photo-emitting diode, is the driving current, (unit is C) is the electron charge, (Unit: m / s) is the speed of light in a vacuum, is the wavelength of the light source (unit: nm), (unit: J) is Planck's constant;

[0015] S03. Detecting the light intensity of the output optical signal in real time through a photoelectric receiving diode, and calculating the pipeline deformation parameter based on a light loss model, wherein the light loss model includes:

[0016] S31, macrobending loss:

[0017] ;

[0018] ;

[0019] Where, is the baseline light intensity when there is no deformation, is the material constant, L is the length of the bending section, is the curvature of the curved section of the flexible optical waveguide sensor, is the measured baseline light intensity, is the light intensity loss;

[0020] S32, radial squeeze loss: The relationship between normal stress and strain is described by the Neo-Hookean model:

[0021] ;

[0022] Where, is the radial stress, is the stretching ratio, is the material constant;

[0023] S33, Temperature-loss coupling effect: Eliminate the influence of ambient temperature on light intensity through the temperature compensation model, which includes the LED light power temperature drift and the dark current correction of the photodetector diode. :

[0024] ;

[0025] in, is the light responsivity of the photoreceiving diode, is the LED temperature coefficient, is the dark current, is the temperature change value (unit: K), For the temperature Optical output power under

[0026] S34, generating pipeline deformation detection results according to the deformation parameters, wherein the deformation parameters include bending radius, concave depth and local curvature, and the light intensity attenuation The mapping relationship is pre-established through experimental calibration or numerical simulation.

[0027] Preferably, the curvature of the macrobending loss in the optical loss model in step S03 is The dynamic correction formula of the geometric parameters of the flexible optical waveguide sensor is as follows:

[0028] ;

[0029] Where R is the bending radius, is the central angle of the bending section of the flexible optical waveguide sensor, L is the length of the bending section, and the material constant Through experimental calibration, .

[0030] As a preference, the attenuation coefficient of the macrobending loss in 31 is Further satisfy:

[0031] ;

[0032] Where, is the refractive index of the waveguide core, is the cladding refractive index, is the core radius, is a constant related to the material, is the curvature of the curved section of the flexible optical waveguide sensor.

[0033] As a preference, in the Neo-Hookean model of radial squeeze loss described in 32, the material constant The value range is , and the stretch ratio and compressive strain coefficient The relationship is: ,in, .

[0034] Preferably, the radial compression loss includes the light intensity attenuation satisfy: ,in, (Unit: dB / ℃) is the bending sensitivity coefficient, is the temperature change value (unit: K).

[0035] Preferably, in the temperature compensation model:

[0036] The temperature correction formula for output power is: ,in, At the reference temperature That is, the optical output power under standard test conditions, (Unit: °C) is the LED temperature coefficient, is the temperature change value (unit: K), For the temperature Optical output power under

[0037] The temperature dependence of the dark current of the photoreceiving diode satisfies: , where is the band gap energy of the photoelectric receiving / emitting diode material, is the Boltzmann constant, is the temperature value (unit: K), is the initial value of dark current.

[0038] Preferably, the temperature-loss coupling effect in step S33 includes a temperature drift correction for the waveguide refractive index. : , where is the temperature change value (unit: K), (Unit: °C) is the temperature coefficient of the material's refractive index.

[0039] Preferably, in step S02:

[0040] The temperature drift of the light emitting wavelength of the photoelectric emitting diode satisfies: (Unit is nm / ℃), and the electro-optical conversion efficiency of the photoelectric emitting diode The value of , is the temperature drift value of the luminescence wavelength, is the temperature change value (unit: K);

[0041] The photoresponsivity of the photoreceiving diode satisfy: ,in, is the quantum efficiency of the photoreceiving diode (indicating the ratio of photons converted to effective carriers), is the light frequency, (Unit: J) is Planck's constant.

[0042] Preferably, the Mooney-Rivlin hyperelastic model parameters in step S01 are: (Unit is MPa), (Unit is MPa), the strain energy density expression is: ,in, is the strain invariant, is a material constant, the flexible optical waveguide sensor comprises a core layer, an elastic cladding layer and a filling layer;

[0043] The flexible optical waveguide sensor comprises a core layer, an elastic cladding layer and a filling layer.

[0044] Preferably, the optical loss model in step S03 further includes Rayleigh scattering loss:

[0045] ;

[0046] Where, ,in, is the refractive index of the waveguide core, represents the Boltzmann constant, is the temperature value (unit: K), is the coefficient of volume expansion, which indicates the volume change caused by temperature change.

[0047] The present invention has at least the following beneficial effects:

[0048] 1. By constructing a multi-physics optical loss model that includes macrobending loss, radial squeeze loss, and temperature-loss coupling effects, the impact of different deformation types on the optical signal can be accurately quantified, significantly improving the detection sensitivity of pipeline deformation.

[0049] 2. The flexible optical waveguide sensor adopts an integrated casting design of elastic cladding and filling layer, which has super elasticity and can closely fit the deformation of the pipeline to avoid performance degradation due to mechanical fatigue.

[0050] 3. The light emitting diode uses a 940nm wavelength light source, matching the high transmittance of the glycerol core layer, combined with the quantum efficiency of the photoelectric receiving diode Optimization: optical power output is increased to 50nW, reducing transmission loss.

[0051] 4. Rayleigh scattering loss modeling and microbend loss suppression design reduce total scattering loss to 0.04dB / m, enhancing long-distance transmission performance. Furthermore, dynamic correction of macrobend loss and the correlation model of radial extrusion strain can distinguish deformation types and reduce false positives.

[0052] 5. The flexible sensor based on flexible optical waveguide has a simple structure and does not require external complex circuits, reducing manufacturing costs by more than 40%. It can be directly embedded in the pipe cleaning probe for integrated installation, making it suitable for rapid deployment and large-scale application in various scenarios such as oil and gas pipelines and urban pipeline networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0054] Figure 1 A schematic diagram of macrobending loss provided in an embodiment of the present invention.

[0055] Figure 2 Schematic diagram of normal extrusion deformation loss provided by an embodiment of the present invention.

[0056] Figure 3 Schematic diagram of the geometric structure of the flexible optical waveguide sensor provided by an embodiment of the present invention.

[0057] Figure 4 The embodiment of the present invention provides Figure 3 Schematic diagram of the implementation structure of the flexible optical waveguide sensor under force and deformation. DETAILED DESCRIPTION

[0058] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0059] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way are interchangeable where appropriate so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or server that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0060] This embodiment provides a deformation detection method based on a soft optical waveguide mechanism, the method comprising the following steps: Figure 1-4 As shown:

[0061] S01. Flexible optical waveguide sensors are arranged at intervals in the area to be measured, wherein:

[0062] The flexible optical waveguide sensor comprises at least a core layer, an elastic cladding layer and a filling layer (and the flexible optical waveguide sensor satisfies the Mooney-Rivlin hyperelastic model).

[0063] The curvature of the curved section of the flexible optical waveguide sensor is dynamically related to the pipe deformation, and its tilt angle By deformation height and straight section length The relationship is determined by:

[0064] ;

[0065] The curvature of the curved section of the flexible optical waveguide sensor is dynamically correlated with the pipe deformation, and the probe curvature can be obtained. The relationship between the deformation height h in the pipe (Combined with Figure 4 Known):

[0066] ;

[0067] in, is the length from the semicircular arc vertex to the inclined connection of the flexible optical waveguide, is the angle between the probe and the detection plane in the initial state.

[0068] The parameters of the Mooney-Rivlin hyperelastic model in the above S01 are (Unit is MPa), (Unit is MPa), the strain energy density expression is: ,in, is the strain invariant, is the material constant.

[0069] The above Figure 4 The figure shows the deformation of a flexible optical waveguide sensor upon encountering a bump on a light surface. Initially, the sensor is in its normal form. Upon encountering the bump, it bends as indicated by the deformation. This bending of the sensor alters the conduction of the optical path, thereby acquiring deformation detection parameters. Due to the unique characteristics of flexible optical waveguide sensors, the aforementioned test areas can be rigid pipes, flexible pipes, and confined areas, including boxes, tanks, and walls, as well as collapse detection, including seawall subsidence, riverbank collapse, and landslide detection.

[0070] When testing sealed areas such as pipes or boxes, the flexible optical waveguide sensor needs to be bent into a U-shape, with both ends of the U-shaped sensor pressed against the sidewalls, and then moved for testing. Preferably, the present application employs a spaced arrangement, where the flexible optical waveguide sensor is bent into a U-shape and then deformed during use. For collapse testing, bending into a U-shape is not necessary.

[0071] The flexible optical waveguide sensor includes a core layer, an elastic cladding layer and a filling layer, wherein:

[0072] The aforementioned filling layer can be any filling material known to those skilled in the art, such as glycerin, an optical path filling layer, or a flexible colloid. However, in actual applications, when the filling layer is glycerin or an optical path filling layer, volatility needs to be calculated to obtain light loss. The calculation formula is as follows: The vapor pressure of the filling layer is calculated using the Antoine equation:

[0073] ,

[0074] And in When the vapor pressure (The unit is pa).

[0075] In this technology, the core layer uses high-refractive-index glycerol, which also boasts high transparency and low volatility. The cladding layer is made of rubber tubing, a flexible material with a low modulus (Young's modulus approximately 1 MPa), allowing for large curvatures. The optoelectronic system utilizes a 940nm photodiode as the LED light source.

[0076] When the filling layer is a flexible colloid, there is no need to worry about the light loss caused by volatility.

[0077] Furthermore, in the non-deformed state, the light loss of the optical waveguide is mainly due to material absorption, Rayleigh scattering, mode decoupling, and port coupling. The optical signal will experience constant attenuation, and the attenuation formula is as follows:

[0078] ;

[0079] in, The material absorbs the loss. is the Rayleigh scattering loss (as decline), is the energy loss caused by mode decoupling, is the port coupling loss (depending on the waveguide end face quality, incident angle, etc.).

[0080] In the deformed state, due to the deformation of the optical waveguide, the equivalent refractive index of the higher-order mode decreases, and the equivalent refractive index of the m-th order mode is: ;

[0081] in, For the The equivalent refractive index of the order mode (dimensionless), For the Propagation constant of the order mode (unit: ), is the free space wave vector, and the calculation formula is .when When the high-order mode leaks into the cladding, the mode leakage loss is formed, and its loss coefficient The calculation is as follows:

[0082] ;

[0083] in, is the operating wavelength (unit: nm), a Core radius, R bending radius, is the refractive index of the waveguide core, is the cladding refractive index. When the deformation radius of curvature, R, decreases, mode leakage increases significantly, exacerbating optical signal attenuation. This indicates that when the flexible optical waveguide is not deformed, higher-order mode loss is constrained by total internal reflection, resulting in low light loss. However, when deformation occurs, higher-order mode leakage reduces light loss.

[0084] (2) Reversibility of light intensity response

[0085] The reversibility of the light intensity response is mainly determined by the elastic recovery mechanism of the rubber material and the long-term stability of glycerol. The rubber coating has superelastic properties (Mooney-Rivlin hyperelastic model):

[0086] ;

[0087] Where W is the strain energy density of the rubber material, that is, the elastic energy stored in the material per unit volume, (Unit is MPa), (unit is MPa) is the material constant, is the strain invariant, is the material constant.

[0088] The vapor equation for glycerol, according to the Antoine equation:

[0089] ;

[0090] P is the equilibrium vapor pressure of the liquid (unit: Pa), T is the temperature (unit: K), A and B are empirical constants of a specific substance. For glycerol, experimental data has given the corresponding constants A=18.3 (dimensionless) and B=5200 (unit: K), so: ;

[0091] Therefore, the evaporation of glycerol meets the light intensity reversibility requirement.

[0092] S02. Injecting an original optical signal with an operating wavelength of 940 nm into the flexible optical waveguide sensor through a photoelectric emitting diode, and detecting the output optical signal in real time through a photoelectric receiving diode, wherein:

[0093] Output optical power of the photo-emitting diode satisfy: , where: is the electro-optical conversion efficiency of the photo-emitting diode, is the driving current, (unit is C) is the electron charge, (Unit: m / s) is the speed of light in a vacuum, is the wavelength of the light source (unit: nm), (Unit: J) is Planck's constant.

[0094] In the aforementioned technology, the photoelectric receiving / transmitting diode is the core component of the optical waveguide sensor system, responsible for converting optical signals into electrical signals. This application uses a 940nm emission as the light source for the photoelectric emitting diode and a photoelectric receiving diode for photocurrent detection. A stable constant current source is used for power supply at the transmitting end, and a stable voltage is used at the receiving end to reverse-bias the photoelectric receiving diode to ensure the stability and high sensitivity of the sensing system.

[0095] Furthermore, a photoluminescent diode (PLD) is a light source based on the electroluminescent effect. When the LED is forward biased, electrons in the N region and holes in the P region recombine in the depletion layer, releasing energy and generating photons. The LED light emission mechanism can be described by the following equation:

[0096] ;

[0097] in, is the energy of the photon (unit: ), (Unit: J), (Unit: m / s) is the speed of light in a vacuum. is the wavelength of the light source (unit: nm). =940nm, as the emission wavelength of the photoelectric emitting diode, can effectively improve the transmittance of the glycerol core layer and reduce the light consumption during the transmission process. The light wave with a wavelength of 940nm can improve the quantum efficiency of the photoelectric receiving diode. , improve signal conversion efficiency, in addition, it improves environmental interference resistance, avoids visible light interference, and reduces the impact of ambient light on the sensing system.

[0098] Among them, the light output power of the LED depends on its injection current and photoelectric conversion efficiency, which can be derived through the carrier recombination process:

[0099]

[0100] in, (unit is C) is the electron charge. The expression of light power is as follows:

[0101] ;

[0102] in, is the electro-optical conversion efficiency of the photo-emitting diode (typical value 15%), (unit is C) is the electron charge, is the driving current of the LED (unit: A), is the wavelength of the light source (unit: ), (unit: J) is Planck's constant, (Unit: m / s) is the speed of light in a vacuum. Increase the LED drive current , can improve the optical power output. Optimize the electro-optical conversion efficiency of the photoelectric diode , which can improve the luminous intensity of the system.

[0103] Furthermore, the above-mentioned photoreceiving diode is operated in the photocurrent mode with a 3.3V reverse bias. In the reverse bias state: the incident photons excite electron-hole pairs, forming a photocurrent under the action of the electric field. The calculation of the photocurrent involves the photon flux, quantum efficiency and photoelectric conversion efficiency. The incident light power The corresponding photon rate:

[0104] ;

[0105] in, is the photon flux per unit time, (unit: J) is Planck's constant, Indicates the frequency of light.

[0106] Quantum efficiency of photoreceiving diode is the ratio of photons converted to effective carriers (typical value 80%), effective carrier rate:

[0107] ;

[0108] in, is the quantum efficiency of the photodiode, dimensionless, The photon flux per unit time, is the incident light power, (unit: J) is Planck's constant, Indicates the frequency of light.

[0109] Photocurrent expression: The amount of charge passing through the device per unit time is the current:

[0110] ;

[0111] in, is the effective carrier efficiency, (unit is C) is the electron charge, (unit: J) is Planck's constant, Indicates the frequency of light.

[0112] Further defining photoresponsivity:

[0113] ;

[0114] in, (unit is C) is the electron charge, (unit: J) is Planck's constant, Indicates the frequency of light.

[0115] The final photocurrent model is obtained:

[0116] ;

[0117] because is a constant that is only related to device parameters (such as quantum efficiency, electron charge, photon energy), so Linear with incident light power Sex is related, that is, it is in direct proportion.

[0118] The wavelength and output power of the above-mentioned LED are affected by temperature. When the temperature rises, the band gap energy of the LED Reduced, resulting in the temperature drift of the light emitting diode's wavelength satisfying: (Unit is nm / ℃), and the electro-optical conversion efficiency of its photoelectric diode The value of , is the temperature drift value of the luminescence wavelength, is the temperature change value (unit: K).

[0119] Temperature increase will affect the transmission efficiency of the optical waveguide and the output power of the LED will decrease. Therefore, the temperature correction formula for the LED output power is: ,in, At the reference temperature That is, the optical output power under standard test conditions, (Unit: °C) is the LED temperature coefficient, is the temperature change value (unit: K), For the temperature Optical output power under

[0120] The temperature dependence of the dark current of the photoreceiving diode satisfies: , where is the band gap energy of the photoelectric receiving / emitting diode material, is the Boltzmann constant, is the temperature value (unit: K), is the initial value of dark current.

[0121] The temperature drift formula of photocurrent is: ,in, For the temperature The photocurrent under is the reference temperature The photocurrent under is the sensitivity coefficient of photocurrent to temperature change, is the temperature change value (unit: K).

[0122] S03. Detect the light intensity of the output optical signal in real time through a photoelectric receiving diode, and calculate the pipeline deformation parameters based on the optical loss model.

[0123] The curvature of the macrobending loss in the optical loss model in the above steps is The dynamic correction formula of the geometric parameters of the flexible optical waveguide sensor is as follows:

[0124] ;

[0125] Where R is the bending radius, is the central angle of the bending section of the flexible optical waveguide sensor, L is the length of the bending section, and the material constant Through experimental calibration, .

[0126] The above optical loss model also includes Rayleigh scattering loss:

[0127] ;

[0128] Where, ,in, is the refractive index of the waveguide core, represents the Boltzmann constant, is the temperature value (unit: K), is the coefficient of volume expansion, which indicates the volume change caused by temperature change.

[0129] Rayleigh scattering loss is caused by microscopic defects, impurities, or inhomogeneities within the optical waveguide. Rayleigh scattering is more pronounced on short-wavelength optical signals, causing energy loss by altering the propagation direction of light. Rayleigh scattering has less of an impact on long-wavelength light.

[0130] The above optical loss model includes:

[0131] S31, macrobending loss:

[0132] ;

[0133] ;

[0134] Where, is the baseline light intensity when there is no deformation, is the material constant, L is the length of the bending section, is the curvature of the curved section of the flexible optical waveguide sensor, is the measured baseline light intensity, is the light intensity loss;

[0135] The attenuation coefficient of the above macrobending loss is Further satisfy:

[0136] ;

[0137] Where, is the refractive index of the waveguide core, is the cladding refractive index, is the core radius, is a constant related to the material, is the curvature of the curved section of the flexible optical waveguide sensor.

[0138] S32, radial squeeze loss: The relationship between normal stress and strain is described by the Neo-Hookean model:

[0139] ;

[0140] Where, is the radial stress, is the stretching ratio, is a material constant, and combined with Figure 2 As shown, is the circumferential diameter of the original core layer, and is the circumferential diameter of the core layer under bending deformation, and the stretching ratio is the ratio of the two, that is, .

[0141] In the Neo-Hookean model of radial squeeze loss mentioned above, the material constant The value range is , and the stretch ratio and compressive strain coefficient The relationship is: ,in, .

[0142] And the light intensity attenuation of radial compression loss satisfy: ,in, (Unit: dB / ℃) is the bending sensitivity coefficient, is the temperature change value (unit: K).

[0143] S33, Temperature-loss coupling effect: Eliminate the influence of ambient temperature on light intensity through the temperature compensation model, which includes the LED light power temperature drift and the dark current correction of the photodetector diode. :

[0144] ;

[0145] in, is the light responsivity of the photoreceiving diode, (Unit: °C) is the LED temperature coefficient, is the dark current, is the temperature change value (unit: K), For the temperature Optical output power under

[0146] In the above temperature compensation model:

[0147] In the temperature compensation model:

[0148] The temperature correction formula for LED output power is: ,in, At the reference temperature That is, the optical output power under standard test conditions, (Unit: °C) is the LED temperature coefficient, is the temperature change value (unit: K), For the temperature Optical output power under

[0149] The temperature dependence of the dark current of the photoreceiving diode satisfies: , where is the band gap energy of the photoelectric receiving / emitting diode material, is the Boltzmann constant, is the temperature value (unit: K), is the initial value of dark current.

[0150] Furthermore, the temperature-loss coupling effect includes the temperature drift correction of the waveguide refractive index. : , where is the temperature change value (unit: K), (Unit: °C) is the temperature coefficient of the material's refractive index.

[0151] Furthermore, the optical loss model in step S03 also includes Rayleigh scattering loss:

[0152] ;

[0153] Where, ,in, is the refractive index of the waveguide core, represents the Boltzmann constant, is the temperature value (unit: K), is the volume expansion coefficient, which represents the volume change caused by temperature change. In the above technology, macrobending loss refers to the reduction in transmitted light power due to the leakage of light modes when the optical waveguide is bent on a large scale. When the optical waveguide is bent at a large angle, the propagation path of light changes with the curvature, and some light may not be able to maintain total internal reflection, thereby penetrating the cladding and leaking into the external environment. This loss mainly occurs in high-order modes, because these modes have a larger propagation angle and are more susceptible to bending and refraction leakage. As the bending radius decreases, the mode leakage effect increases, which increases the overall loss of the optical waveguide. The magnitude of the macrobending loss is affected by factors such as the structure of the waveguide, the refractive index distribution, and the operating wavelength.

[0154] When only the macrobending effect is considered, the light intensity loss (by is defined as:

[0155] ;

[0156] is the measured baseline light intensity, is the baseline strength without deformation.

[0157] When the cross-sectional area of ​​the optical waveguide is considered as a circle, the curvature is In a curved fiber, the attenuation coefficient per unit length is can be written as:

[0158] ;

[0159] Where, is the refractive index of the waveguide core, is the cladding refractive index, is the core radius, is a constant related to the material, is the curvature of the curved section of the flexible optical waveguide sensor.

[0160] Using Beer's law, the total power around a bend of length L can be found to be:

[0161] .

[0162] Combining the above three equations, we can derive the relationship between the measured strength of a flexible optical waveguide with a bending curvature k and the initial strength without deformation:

[0163] ;

[0164] L is the length of the bending section, is the curvature of the curved section of the flexible optical waveguide sensor, is the measured baseline light intensity, is the light intensity loss. Figure 3 It can be seen that the so-called bending section length refers to the tilt angle of the flexible optical waveguide sensor. The length of the part, i.e. .

[0165] It can be seen that when other variables are constant, the ratio of the measured strength to the initial strength has an exponential relationship with the bending radius.

[0166] (like Figure 2 Normal compression loss (as shown) refers to the radial compression of a flexible optical waveguide sensor caused by external forces, which in turn affects the light propagation characteristics within the waveguide. Normal compression is typically caused by external physical forces acting on the waveguide cladding, resulting in deformation of the waveguide core and cladding. This deformation not only affects the waveguide geometry but can also induce small local bends, leading to light loss.

[0167] When modeling the loss of radial extrusion deformation, the Neo-Hookean material model is used. This material model is widely used to describe soft materials such as rubber that are subject to large deformation. The stress-strain relationship of this model can be expressed as follows:

[0168] ;

[0169] in, is the radial stress, is the stretching ratio. This model is suitable for describing compression behavior under large deformation and can reasonably reflect the effect of deformation caused by normal extrusion on optical waveguide transmission.

[0170] Under normal compression conditions, the optical signal in the waveguide will undergo two major changes: first, the size of the waveguide changes, especially the local bending between the core and the cladding; second, slight deformations may be caused on both sides of the indenter, which will further affect the transmission characteristics of the optical waveguide. According to existing research and experimental data, the small bending caused by normal compression is the main source of light intensity loss, while the leakage of high-order modes is not the main loss mechanism in such large-sized optical waveguides. The optical loss caused by squeezing can be estimated by the local bending caused by the indenter. Due to the large size of the waveguide (for example, the core diameter of the waveguide is 3mm), at this size, the light mode in the waveguide will not be significantly decoupled, and the loss is mainly caused by slight bending. Based on this, the relationship between loss and radial compressive strain can be approximately expressed by the following formula:

[0171] ;

[0172] in, is the light intensity loss (light intensity attenuation) caused by compression, is the sensitivity coefficient related to bending, is the temperature change caused by the normal compressive strain (or the direct compressive strain change), that is, the temperature change value (unit: K).

[0173] Normal squeeze deformation loss is primarily due to the geometric deformation of the waveguide caused by external pressure, particularly the compression of the waveguide cladding and core. Although mode decoupling has a minor impact on the loss, the optical signal will be attenuated due to local bending effects, especially when the indenter applies pressure.

[0174] Under the influence of temperature changes, optical waveguide transmission loss manifests itself through two main mechanisms: optical loss due to geometric deformation, and light intensity attenuation due to changes in the material's refractive index. Temperature changes cause changes in the waveguide length, which in turn affects the light propagation path and mode matching. By comprehensively analyzing geometric deformation and material property changes, a temperature-loss coupling model can be constructed. Temperature changes lead to changes in waveguide length, and the specific temperature effect can be expressed as:

[0175] ;

[0176] in, is the original length, is the linear expansion coefficient of the material, is the temperature change value (unit: K).

[0177] Temperature changes also cause changes in the refractive index of the waveguide material, so the temperature-loss coupling effect mentioned above includes the temperature drift correction of the waveguide refractive index. : , where is the temperature change value (unit: K), (Unit: °C) is the temperature coefficient of the refractive index of the core material.

[0178] Changes in the refractive index will directly affect the propagation mode of the optical waveguide, especially the propagation efficiency of the high-order mode. In the optical waveguide, the propagation of the high-order mode is greatly affected by the change in the refractive index of the material. Therefore, temperature changes will cause leakage or propagation loss of these modes, which in turn affects the light intensity. The change in light intensity caused by temperature changes can be calculated by the combined effect of temperature on the waveguide length and refractive index. Generally, the rate of change of light intensity is determined by multiple factors such as the change in the geometric shape of the optical waveguide (length change, bending, etc.), the mode loss caused by the change in the refractive index, and the propagation loss of the light mode in the optical waveguide. The final expression for the change in light intensity can be expressed as:

[0179] ;

[0180] in, and are the temperature sensitivity coefficients due to waveguide bending and normal compression, respectively.

[0181] In the absence of deformation, temperature changes mainly affect the refractive index of the material, resulting in generally gentle changes in light intensity, and the relationship between temperature change and light intensity change may show linear or weak nonlinear changes. When deformation occurs, especially when the optical waveguide is bent, the effect of temperature on light intensity shows more significant changes. This is because the propagation of high-order modes is restricted, and the leakage of high-order modes caused by bending significantly affects the propagation performance of the optical waveguide. Specifically, when the bending radius is small, the refractive index change caused by temperature may lead to a greater degree of leakage of high-order modes, resulting in changes in light intensity. The flexible optical waveguide sensor in this article is embedded in the probe of the pipe cleaner and is cast in one piece. When the external operating temperature is constant, the friction generated during operation has limited effect on the temperature of the internal flexible optical waveguide sensor.

[0182] S04. Generate pipeline deformation detection results based on deformation parameters, including bending radius, concave depth and local curvature, which are related to light intensity attenuation. The mapping relationship is pre-established through experimental calibration or numerical simulation.

[0183] As mentioned above, the geometric structure of the flexible optical waveguide sensor determines its optical transmission characteristics in practical applications. This embodiment designs a flexible optical waveguide sensor structure based on the general size of the pipe cleaner probe on the market. Figure 4 The figure shows the basic shape and related geometric parameters of the flexible optical waveguide sensor. The tilt angle of the flexible optical waveguide sensor is:

[0184] ;

[0185] in: is the height and length of the probe deformation The flexible optical waveguide sensor is bent into a U-shaped curved section with a radius of and curvature The relationship between defines the bending characteristics of the optical waveguide. This geometric feature affects the propagation path of light, especially in the curved section of the flexible optical waveguide sensor, where the propagation of light is greatly affected by the curvature.

[0186] Pipe deformation typically manifests as bending, concavity, and ovalization. Changes in the bend radius and angle are particularly significant in U-shaped waveguide structures. The light propagation path changes with curvature, particularly affecting higher-order modes. Consequently, increased light mode leakage leads to light intensity attenuation. In U-shaped waveguides, changes in waveguide curvature directly affect the propagation of light modes, making higher-order modes particularly susceptible to leakage. A reduction in the curvature radius leads to more severe leakage of higher-order modes, thereby increasing the overall loss of the waveguide.

[0187] In summary, by constructing a multi-physics field optical loss model that includes macro-bending loss, radial extrusion loss, and temperature-loss coupling effects, it is possible to accurately quantify the impact of different deformation types on optical signals and significantly improve the detection sensitivity of pipeline deformation. Furthermore, the flexible optical waveguide sensor adopts an integrated casting design of elastic cladding and filling layer, which has superelasticity and can fit closely to pipeline deformation to avoid performance degradation due to mechanical fatigue. Secondly, the electro-emitting diode uses a 940nm wavelength light source to match the high transmittance of the glycerol core layer, combined with the quantum efficiency of the photodetector diode. Optimization increases optical power output to 50wM, reducing transmission loss. Furthermore, Rayleigh scattering loss modeling and microbending loss suppression design reduce total scattering loss to 0.04dB / m, enhancing long-distance transmission performance. The dynamic correction of macrobending loss and the radial extrusion strain correlation model can distinguish deformation types and reduce misjudgment rates. Furthermore, the flexible sensor based on flexible optical waveguides has a simple structure, does not require external complex circuits, reduces manufacturing costs by more than 40%, and can be directly embedded in the pig probe for integrated installation, making it suitable for rapid deployment and large-scale application in various scenarios such as oil and gas pipelines and urban pipeline networks.

[0188] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A deformation detection method based on a soft optical waveguide mechanism, characterized in that: The method comprises the following steps: S01. Flexible optical waveguide sensors are arranged at intervals in the area to be measured, wherein: The flexible optical waveguide sensor includes at least an elastic cladding and satisfies the Mooney-Rivlin hyperelastic model; The curvature of the curved section of the flexible optical waveguide sensor is dynamically related to the pipe deformation, and its inclination angle By deformation height and straight section length The relationship is determined by: ； The flexible optical waveguide sensor can obtain the curvature of the probe The relationship between the deformation height h in the pipe : ； in, is the length from the semicircular arc vertex to the inclined connection of the flexible optical waveguide, is the angle between the probe and the detection plane in the initial state; S02. Injecting an original optical signal with an operating wavelength of 940 nm into the flexible optical waveguide sensor through a photoelectric emitting diode, and detecting the output optical signal in real time through a photoelectric receiving diode, wherein: The output optical power of the photoelectric emitting diode satisfy: , where: is the electro-optical conversion efficiency of the photo-emitting diode, is the driving current, is the electron charge, is the speed of light in vacuum, is the wavelength of the light source, is Planck's constant; S03. Detecting the light intensity of the output optical signal in real time through a photoelectric receiving diode, and calculating the pipeline deformation parameter based on a light loss model, wherein the light loss model includes: S31, macrobending loss: ； ； Where, is the baseline light intensity when there is no deformation, is the material constant, L is the length of the bending section, is the curvature of the curved section of the flexible optical waveguide sensor, is the measured baseline light intensity, is the light intensity loss; S32, radial squeeze loss: The relationship between normal stress and strain is described by the Neo-Hookean model: ； Where, is the radial stress, is the stretching ratio, is the material constant; S33, Temperature-loss coupling effect: Eliminate the influence of ambient temperature on light intensity through the temperature compensation model, which includes the LED light power temperature drift and the dark current correction of the photodetector diode. : ； in, is the light responsivity of the photoreceiving diode, is the LED temperature coefficient, is the dark current, is the temperature change value, For the temperature The optical output power; S34, generating pipeline deformation detection results according to the deformation parameters, wherein the deformation parameters include bending radius, concave depth and local curvature, and the light intensity attenuation The mapping relationship is pre-established through experimental calibration or numerical simulation.

2. The deformation detection method based on the soft optical waveguide mechanism according to claim 1, characterized in that: The curvature of the macrobending loss in the optical loss model in step S03 The dynamic correction formula of the geometric parameters of the flexible optical waveguide sensor is as follows: ； Where R is the bending radius, is the central angle of the bending section of the flexible optical waveguide sensor, L is the length of the bending section, and the material constant Through experimental calibration, .

3. The deformation detection method based on the soft optical waveguide mechanism according to claim 1, characterized in that: The attenuation coefficient of the macrobending loss in S31 Further satisfy: ； Where, is the refractive index of the waveguide core, is the cladding refractive index, is the core radius, is a constant related to the material, is the curvature of the curved section of the flexible optical waveguide sensor.

4. The deformation detection method based on the soft optical waveguide mechanism according to claim 1, characterized in that: In the Neo-Hookean model of radial squeeze loss in step S32, the material constant The value range is , and the stretch ratio and compressive strain coefficient The relationship is: ,in, .

5. The deformation detection method based on the soft optical waveguide mechanism according to claim 4 is characterized in that: The radial compression loss includes the light intensity attenuation satisfy: ,in, is the bending sensitivity coefficient, is the temperature change value.

6. The deformation detection method based on the soft optical waveguide mechanism according to claim 1, characterized in that: In the temperature compensation model in step S33: The temperature correction formula for output power is: ,in, At the reference temperature That is, the optical output power under standard test conditions, is the LED temperature coefficient, is the temperature change value, For the temperature Optical output power under The temperature dependence of the dark current of the photoreceiving diode satisfies: , where is the band gap energy of the photoelectric receiving / emitting diode material, is the Boltzmann constant, is the temperature value, is the initial value of dark current.

7. The deformation detection method based on the soft optical waveguide mechanism according to claim 1, characterized in that: The temperature-loss coupling effect in step S33 includes a temperature drift correction of the waveguide refractive index. : , where is the temperature change value, is the temperature coefficient of the material's refractive index.

8. The deformation detection method based on the soft optical waveguide mechanism according to claim 1 is characterized in that: In the step S02: The temperature drift of the light emitting wavelength of the photoelectric emitting diode satisfies: , and the electro-optical conversion efficiency of the photo-emitting diode The value of , is the temperature drift value of the luminescence wavelength, is the temperature change value; The photoresponsivity of the photoreceiving diode satisfy: ,in, is the quantum efficiency of the photoreceiving diode, is the light frequency, is Planck's constant.

9. The deformation detection method based on the soft optical waveguide mechanism according to claim 1, characterized in that: The Mooney-Rivlin hyperelastic model parameters in step S01 are: , , the strain energy density expression is: ,in, is the strain invariant, is a material constant. The flexible optical waveguide sensor includes a core layer, an elastic cladding layer and a filling layer.

10. The deformation detection method based on the soft optical waveguide mechanism according to claim 1, characterized in that: The optical loss model in step S03 also includes Rayleigh scattering loss: ； Where, ,in, is the refractive index of the waveguide core, represents the Boltzmann constant, is the temperature value, is the volume expansion coefficient.

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