Optical singular point enhanced strain sensing network architecture and implementation method thereof

Abstract

The application belongs to the technical field of strain measurement, and particularly relates to an optical singular point enhanced strain sensing network architecture and an implementation method thereof. In view of the problem of the strain sensitivity of the existing strain sensing measurement technology, the application writes an adjacent interval fiber grating in series in a fiber core, the adjacent two fiber gratings and the cavity therebetween form an F-P cavity, the three fiber gratings and the two F-P cavities are fixed with four supports, and the specific part of the support is fixed in the strain measurement area to respond to the strain change of the external environment. In combination with the advantages of the fiber, the singular point and the networking, the loss gamma of the second F-P cavity and the coupling kappa loss of the two F-P cavities are adjusted, the singular point appears when a certain relationship is met, the strain of the measured area is measured, the strain is measured through the singular point, and the measurement accuracy is improved and the test sensitivity is enhanced.

Description

Technical Field

[0001] This invention relates to the field of optical strain sensing technology, specifically to an optical singularity-enhanced strain sensing network architecture and its implementation method. Background Technology

[0002] Strain measurement is a key testing method in many engineering fields, widely used in structural health monitoring, mechanical performance evaluation of engineering structures, and early warning of geological disasters such as earthquakes. The resolution and response speed of strain measurement have become core requirements for the technological development of related industries.

[0003] In existing technologies, traditional strain measurement methods based on strain gauges are widely used, but they suffer from drawbacks such as insufficient sensitivity, limited response speed, and susceptibility to electromagnetic interference, making it difficult to meet the high-precision measurement requirements under complex working conditions. In recent years, although piezoelectric, capacitive, resonant, and fiber optic strain measurement technologies have made some progress, there is still room for improvement in terms of anti-interference capability, long-term stability, and system integration. There is an urgent need to develop strain sensing technologies with better overall performance.

[0004] As a low-loss, electromagnetically interference-resistant optical signal transmission medium, optical fiber has not only supported communication transmission but has also formed an important application branch in the field of sensing. Compared with traditional electronic measurement methods, optical fiber has significant advantages in high-reliability long-distance signal transmission due to its low transmission loss, wide operating bandwidth, and electromagnetic interference resistance. Its small diameter and flexible bending properties make it suitable for harsh environments with high temperature and high corrosion, and facilitate sensing deployment in space-constrained or complex working conditions. In addition, through processes such as ultraviolet irradiation or femtosecond laser direct writing, the dispersion characteristics of the optical field can be precisely controlled, achieving a high degree of integration between transmission and sensing functions, which aligns with the development trend of miniaturization and integration of modern sensing systems.

[0005] Exceptional points (EPs), as special spectral singularities in non-Hermitian physics systems, have yielded systematic research results in fields such as artificial optical micro / nanostructures, non-reciprocal optical transmission, nonlinear optics, and quantum physics. Among these, the sensing mechanism based on EPs is particularly crucial: by precisely controlling the matching of parameters such as the coupling coefficient and mode loss intensity of the non-Hermitian system, the eigenvalues ​​and eigenvectors of the non-Hermitian system simultaneously become degenerate, achieving a singularly degenerate state. In this state, the response of the system's resonant frequency to perturbations transforms from a traditional linear relationship to an nth-root relationship (e.g., the square root relationship appearing in a typical dual-cavity coupled structure, n=2), thereby significantly improving the system's sensitivity to weak signals. This sensing mechanism based on the degeneracy characteristics of non-Hermitian systems breaks through the sensitivity limit of traditional sensing, providing a novel principle for applications such as nanoscale displacement sensing. In recent years, the parameter control and gain principles based on non-equilibrium systems have broken through the bottlenecks of traditional sensing technologies, demonstrating enormous potential and representing one of the important development directions for the next generation of high-sensitivity sensing technologies. Summary of the Invention

[0006] This invention addresses the insufficient sensitivity of existing strain sensing methods by providing an optical singularity-enhanced strain sensing network architecture and its implementation method. This invention integrates the advantages of fiber optic transmission and singularity (EP) sensitivity enhancement, achieving high-sensitivity measurement. Its core principle lies in utilizing a cascaded Fabry-Perot resonator (FP) cavity composed of multiple gratings in the same fiber. By adjusting the wavelength dispersion of the third fiber grating to introduce a loss γ in the second FP cavity, and matching the coupling strength κ between the first and second FP cavities, the system reaches a second-order singularity (EP2) state when a specific relationship is satisfied, resulting in a sensitivity enhancement effect. In strain measurement, high-sensitivity strain measurement is achieved, where the strain response transforms from the traditional linear relationship Δλ∝ε to a square root relationship Δλ∝√ε, where Δλ is the wavelength shift before and after strain, ε is the strain of the object being measured, and 1 / 2 is the square root response exponent. Furthermore, by serially connecting multiple fiber-optic strain sensors, an optical singularity-enhanced strain sensing network architecture can be constructed, enabling simultaneous monitoring of multiple strain regions. Compared with traditional strain gauge measurement methods, the method of this invention has advantages such as resistance to electromagnetic interference and high sensitivity, and is suitable for high-precision detection in various environments.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides an optical fiber-based strain sensor, comprising a first fiber grating, a second fiber grating, and a third fiber grating arranged sequentially along the core of the same optical fiber, with a preset interval between adjacent fiber gratings, and ordinary optical fiber portions provided with gratings not written into them, referred to as the first bare optical fiber and the second bare optical fiber, respectively; the first fiber grating, the first bare optical fiber, and the second fiber grating constitute a first FP cavity, and the second fiber grating, the second bare optical fiber, and the third fiber grating constitute a second FP cavity; the grating region of the first fiber grating is completely encapsulated and fixed on a first support, and the grating region of the second fiber grating is completely encapsulated and fixed on a second support; the grating region of the third fiber grating is exposed between a third support and a fourth support, and the bare optical fibers on both sides of the third fiber grating are respectively fixed on the third support and the fourth support; a first piezoelectric ceramic is disposed between the second support and the third support; and a second piezoelectric ceramic is disposed between the third support and the fourth support.

[0009] Furthermore, the first fiber Bragg grating, the second fiber Bragg grating, and the third fiber Bragg grating are all fiber Bragg gratings.

[0010] Furthermore, the materials of the first support, the second support, the third support, and the fourth support are selected from any one of metal materials, ceramics, glass, or composite materials.

[0011] Secondly, the present invention provides an optical singularity-enhanced strain sensing network architecture, including a laser and the strain sensor described in the first aspect. The optical signal output by the laser is sequentially input to the strain sensor via an attenuator and an optical fiber circulator. The reflected light from the strain sensor is input to a photoelectric converter via the optical fiber circulator. The first and second supports in the strain sensor are fixed to the strain object to be measured. The first and second piezoelectric ceramics included in the strain sensor are respectively connected to a DC voltage source via coaxial cables. The photoelectric converter is connected to an oscilloscope via a coaxial cable.

[0012] Furthermore, the optical singularity-enhanced strain sensing network architecture includes multiple strain sensors, each strain sensor corresponding to a strain-to-be-measured object, and the multiple strain sensors are connected in series via optical fibers. The sensing direction of each strain sensor is consistent with the strain direction of its corresponding strain-to-be-measured object.

[0013] Thirdly, the present invention provides a method for implementing an optical singularity-enhanced strain sensing network architecture, comprising the following steps:

[0014] A swept-frequency laser signal is generated by a laser, and the swept-frequency laser signal is input to a strain sensor in sequence through an attenuator and an optical fiber circulator; the reflected light from the strain sensor is input to a photoelectric converter through the optical fiber circulator and detected by an oscilloscope.

[0015] By adjusting the DC voltage source connected to the first piezoelectric ceramic, the cavity length of the second FP cavity is changed, so that the wavelength of any first-order cavity mode of the second FP cavity is consistent with that of a certain first-order cavity mode of the first FP cavity, thus achieving cavity mode matching.

[0016] By adjusting the DC voltage source connected to the second piezoelectric ceramic, the reflection spectrum of the third fiber grating is caused to drift in wavelength. At the same time, a loss γ is introduced into the second FP cavity. When the coupling strength κ between the loss γ and the first FP cavity and the second FP cavity satisfies a preset relationship, the strain sensor enters the singularity working state. At this time, the spectrum displayed by the oscilloscope has a specific shape.

[0017] When the strain-bearing object undergoes strain, the cavity length of the first FP cavity changes accordingly, causing the singularity state of the strain sensor to be disrupted, and the wavelength response of the oscilloscope to change accordingly.

[0018] By comparing the wavelengths corresponding to the valley values ​​in the spectrum before and after strain occurs, the wavelength shift is calculated to obtain strain information.

[0019] Furthermore, multiple strain sensors can be connected in any multiplexing manner to achieve simultaneous measurement of multiple strain regions.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention integrates the advantages of fiber optic transmission and singularity (EP) sensitivity enhancement. It utilizes a Fabry-Perot resonator (FP cavity) within a fiber optic grating as the optical resonator. By controlling the loss γ of the second FP cavity with the coupling strength κ between the first and second FP cavities through a DC voltage source, a degenerate state of the second-order singularity (EP2) is achieved when a specific relationship is satisfied. In strain measurement, when the object under strain undergoes strain, the cavity length of the first FP cavity of the sensor changes, disrupting the established degeneracy state and causing a change in the wavelength response. By comparing the wavelengths corresponding to the valley values ​​in the spectrum before and after strain, the wavelength shift can be calculated, thus obtaining the strain information. The sensitivity enhancement mechanism of the second-order singularity (EP2) significantly improves the sensitivity of strain measurement. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the fiber-optic strain sensor of the present invention.

[0023] Figure 2 This is a schematic diagram of the optical singularity-enhanced strain sensing network architecture of the present invention.

[0024] Figure 3 This is a schematic diagram showing the changes in the oscilloscope curves before and after strain occurs.

[0025] Figure 4 This is a comparison diagram of the square root response relationship after strain occurs and the traditional linear response relationship. Detailed Implementation

[0026] To further understand the technical solution of the present invention, the present invention will be further described below through embodiments.

[0027] Example 1

[0028] like Figure 1 As shown, this embodiment provides a fiber-optic strain sensor. Fiber Bragg gratings (FBGs) are sequentially written along the fiber core in the same fiber using methods such as hydrogen-loaded ultraviolet irradiation or femtosecond laser direct writing. These FBGs are arranged sequentially along the fiber length and are referred to as the first FBG 601, the second FBG 602, and the third FBG 603. Intervals of unwritten ordinary fiber are provided between the three FBGs, referred to as the first bare fiber and the second bare fiber, respectively. Each pair of FBGs constitutes a Fabry-Perot resonant cavity (FP cavity) in the fiber. The first FBG 601, together with the first bare fiber and the second FBG 602, constitutes the first FP cavity 604, while the second FBG 602, together with the second bare fiber and the third FBG 603, constitutes the second FP cavity 605.

[0029] The fiber optic segments are fixed to the four-segment support using epoxy adhesive, welding, and other methods. Specific areas of the support are fixed to the surface of the strained object to sense strain changes in the environment. The supports are sequentially named Support 1 (606), Support 2 (607), Support 3 (608), and Support 4 (609). The specific fixing methods for each support are as follows:

[0030] The entire grating region of the first fiber Bragg grating 601 is encapsulated and fixed on the first bracket 606; the entire grating region of the second fiber Bragg grating 602 is encapsulated and fixed on the second bracket 607; the grating region of the third fiber Bragg grating 603 is exposed between the third bracket 608 and the fourth bracket 609, and the third fiber Bragg grating 603 is fixed on both the third bracket 608 and the fourth bracket 609; a portion of the second bare fiber is fixed on the third bracket 608. The aforementioned fixed installation areas are marked with gray boxes. A first piezoelectric ceramic 610 (connected by epoxy adhesive or screws, etc.) is disposed between the second bracket 607 and the third bracket 608; a second piezoelectric ceramic 611 is disposed between the third bracket 608 and the fourth bracket 609.

[0031] Among them, the first fiber grating 601, the second fiber grating 602 and the third fiber grating 603 are all fiber Bragg gratings.

[0032] The materials of the first support 606, the second support 607, the third support 608, and the fourth support 609 are selected from any one of the following: metal, ceramic, glass, or composite materials, such as aluminum alloy and stainless steel.

[0033] Example 2

[0034] like Figure 2 As shown, this embodiment provides an optical singularity-enhanced strain sensing network architecture, including a laser 1 and the strain sensor 6 described in Embodiment 1. The optical signal output from the laser 1 is sequentially input to the strain sensor 6 via an attenuator 2 and an optical fiber circulator 7; the reflected light from the strain sensor 6 is input to the photoelectric converter 5 via the optical fiber circulator 7. A strain-to-be-measured object 8 is disposed above the first support 606 and the second support 607 in the strain sensor 6. The first piezoelectric ceramic 610 and the second piezoelectric ceramic 611 included in the strain sensor 6 are respectively connected to a DC voltage source 9 via a coaxial cable 4. The photoelectric converter 5 is connected to an oscilloscope 3 via a coaxial cable 4.

[0035] Among them, the fiber optic circulator 7 and the photoelectric converter 5 are connected to the strain sensor 6 via optical fiber; the attenuator 2 is connected to the laser 1 via optical fiber.

[0036] Laser 1 provides an optical signal within the operating wavelength range for strain sensor 6. Attenuator 2 adjusts the optical signal power. Fiber optic circulator 7 guides the optical signal output from the laser into strain sensor 6 and outputs the reflection spectrum signal of the fiber optic grating to photoelectric converter 5. Photoelectric converter 5 converts the optical signal into an electrical signal. Oscilloscope 3 reads the converted electrical signal from photoelectric converter 5. When the strain-bearing object 8 undergoes strain, the spectral lines detected by oscilloscope 3 will change accordingly. By comparing the changes in the wavelength of the spectral lines, strain information can be obtained.

[0037] The optical singularity sensing network architecture of this embodiment may include multiple strain sensors 6 (e.g., ... Figure 2 (60, 61 and 62 in the figure), each strain sensor 6 is matched with a strain object 8 to be measured. Each strain sensor 6 is connected in series through optical fiber, and the DC voltage source 9 is connected to the corresponding strain sensor 6.

[0038] Example 3

[0039] like Figure 3 As shown, this embodiment provides a method for implementing an optical singularity-enhanced strain sensing network architecture, including the following steps:

[0040] A swept-frequency laser signal is generated by laser 1, and the swept-frequency laser signal enters strain sensor 6 through attenuator 2 and fiber optic circulator 7 in sequence; the reflected light from strain sensor 6 enters photoelectric converter 5 through fiber optic circulator 7 and is detected by oscilloscope 3.

[0041] By adjusting the DC voltage source 9 connected to the first piezoelectric ceramic 610, the cavity length of the second FP cavity 605 is changed, so that the wavelength of any first-order cavity mode of this cavity is consistent with that of a certain first-order cavity mode of the first FP cavity 604, thus achieving cavity mode matching (see [link]). Figure 3 (a) Then, by adjusting the DC voltage source 9 connected to the second piezoelectric ceramic 611, the reflection spectrum of the third fiber grating 603 is caused to drift in wavelength, while a loss γ is introduced into the second FP cavity 605. When the coupling strength κ between the loss γ and the first FP cavity 604 and the second FP cavity 605 satisfies a preset relationship, the spectrum displayed by the oscilloscope 3 exhibits a specific shape (see [reference]). Figure 3 In (b), strain sensor 6 is now operating in a singularity state. When strain occurs in the object 8 to be measured, the cavity length of the first FP cavity 604 changes accordingly, the singularity state of strain sensor 6 is disrupted, and the wavelength response of oscilloscope 3 changes accordingly (see [reference]). Figure 3 (c) By comparing the wavelengths corresponding to the valley values ​​in the spectrum before and after strain occurrence, the wavelength shift can be calculated to obtain strain information. By connecting multiple strain sensors 6 in series, simultaneous measurement of multiple strain regions can be achieved, thus overcoming the limitations of single-point measurement.

[0042] Example 4

[0043] like Figure 4 As shown in the figure, this embodiment presents a comparison between the square root response relationship Δλ∝√ε after strain occurs and the traditional linear response relationship Δλ∝ε. The dashed line in the figure represents the square root response relationship, and the solid line represents the traditional linear relationship. Figure 4 The comparison of the two curves shows that the wavelength response sensitivity of the sensing mechanism based on the square root response is significantly improved compared with the traditional linear measurement sensitivity.

[0044] The foregoing has shown and described the main features and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0045] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A fiber-optic-based strain sensor, characterized in that, The fiber includes a first fiber grating (601), a second fiber grating (602), and a third fiber grating (603) arranged sequentially along the same fiber core. Adjacent fiber gratings are spaced apart by a preset interval. The portions of ordinary fiber with gratings not written into them are referred to as the first bare fiber and the second bare fiber, respectively. The first fiber grating (601), the first bare fiber, and the second fiber grating (602) constitute a first FP cavity (604), and the second fiber grating (602), the second bare fiber, and the third fiber grating (603) constitute a second FP cavity (605). All grating regions of the first fiber grating (601) are encapsulated and fixed within... On the first support (606), the grating region of the second fiber grating (602) is completely encapsulated and fixed on the second support (607); the grating region of the third fiber grating (603) is exposed between the third support (608) and the fourth support (609), and the bare optical fibers on both sides of the third fiber grating (603) are respectively fixed on the third support (608) and the fourth support (609); a first piezoelectric ceramic (610) is disposed between the second support (607) and the third support (608); a second piezoelectric ceramic (611) is disposed between the third support (608) and the fourth support (609).

2. The fiber-optic strain sensor according to claim 1, characterized in that, The first fiber Bragg grating (601), the second fiber Bragg grating (602) and the third fiber Bragg grating (603) are all fiber Bragg gratings.

3. The fiber-optic strain sensor according to claim 1, characterized in that, The materials of the first support (606), the second support (607), the third support (608) and the fourth support (609) are selected from any one of metal materials, ceramics, glass or composite materials.

4. An optical singularity-enhanced strain sensing network architecture, characterized in that, The device includes a laser (1) and a strain sensor as described in any one of claims 1 to 3. The optical signal output by the laser (1) is sequentially input to the strain sensor (6) via an attenuator (2) and an optical fiber circulator (7). The reflected light from the strain sensor (6) is input to a photoelectric converter (5) via the optical fiber circulator (7). The first bracket (606) and the second bracket (607) in the strain sensor (6) are fixed on the strain object (8) to be measured. The first piezoelectric ceramic (610) and the second piezoelectric ceramic (611) in the strain sensor (6) are respectively connected to a DC voltage source (9) via a coaxial cable (4). The photoelectric converter (5) is connected to an oscilloscope (3) via a coaxial cable (4).

5. The optical singularity-enhanced strain sensing network architecture according to claim 4, characterized in that, The optical singularity-enhanced strain sensing network architecture includes multiple strain sensors (6), each strain sensor (6) is matched with a strain object (8) to be measured, and the multiple strain sensors (6) are connected in series through optical fibers. The sensing direction of each strain sensor (6) is consistent with the strain direction of its corresponding strain object (8).

6. A method for implementing an optical singularity-enhanced strain sensing network architecture, characterized in that, Includes the following steps: Step 1: A swept-frequency laser signal is generated by a laser (1), and the swept-frequency laser signal is input to the strain sensor (6) through an attenuator (2) and an optical fiber circulator (7) in sequence; the reflected light from the strain sensor (6) is input to the photoelectric converter (5) through the optical fiber circulator (7) and detected by an oscilloscope (3); Step 2: By adjusting the DC voltage source (9) connected to the first piezoelectric ceramic (610), the cavity length of the second FP cavity (605) is changed so that the wavelength of any first-order cavity mode of the cavity is consistent with that of a certain first-order cavity mode of the first FP cavity (604), thereby achieving cavity mode matching; Step 3: By adjusting the DC voltage source (9) connected to the second piezoelectric ceramic (611), the reflection spectrum of the third fiber grating (603) is shifted by wavelength, and loss γ is introduced into the second FP cavity (605). Step 4: When the loss γ of the second FP cavity (605) and the coupling strength κ between the first FP cavity (604) and the second FP cavity (605) satisfy a preset relationship, the strain sensor (6) enters the singularity working state. At this time, the spectrum displayed by the oscilloscope (3) has a specific shape. Step 5: When the strain object (8) to be measured is strained, the cavity length of the first FP cavity (604) changes accordingly, which causes the singularity working state of the strain sensor (6) to be destroyed, and the wavelength response of the oscilloscope (3) changes accordingly. Step 6: By comparing the wavelengths corresponding to the valley values ​​in the spectrum before and after strain occurs, calculate the wavelength shift to obtain strain information.

7. The method for implementing an optical singularity-enhanced strain sensing network architecture according to claim 6, characterized in that, Multiple strain sensors (6) can be connected in any multiplexing manner to achieve simultaneous measurement of multiple strain regions.

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