Multi-parameter sensing optical cable based on ultra-weak fiber grating array

Abstract

The invention relates to a multi-parameter sensing optical cable based on an ultra-weak fiber grating array. The multi-parameter sensing optical cable comprises a strain reinforcing rib S-FRP, wherein the center of the strain reinforcing rib S-FRP is compounded with the ultra-weak fiber grating array; the vibration type ultra-weak fiber grating array is embedded in the PBT sleeve, and the PBT sleeve is filled with ointment; the fiber reinforced resin reinforcing rib FRP is symmetrically arranged relative to the strain reinforcing rib S-FRP and the PBT sleeve; and the strain reinforcing rib S-FRP, the PBT sleeve and the reinforcing rib FRP are subjected to hot extrusion molding through a mold to form a flat sheath. According to the ultra-weak fiber bragg grating multi-parameter sensing optical cable provided by the invention, the fiber reinforced resin strain sensing optical fibers and the fiber reinforced resin reinforcing ribs are compounded on the two sides, and the high-density polyethylene flat sheath is wrapped outside, so that the ultra-weak fiber bragg grating multi-parameter sensing optical cable has good mechanical tensile property and flattening resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of fiber grating strain sensing, and in particular relates to a multi-parameter sensing optical cable based on an ultra-weak fiber grating array. Background Art

[0002] In the field of structural health monitoring, although traditional monitoring methods can meet most of the monitoring needs, they also expose corresponding problems. Some technologies can only perform point measurements on structures, and the measurement data density is low; some technologies are easily affected by environmental factors; some technologies cannot be integrated with automation to meet the needs of digital monitoring. In recent years, fiber optic sensing technology has developed rapidly. Fiber grating sensors have begun to be widely used in perimeter security, aerospace, rail transportation, large-scale structural health monitoring and other fields due to their advantages such as distribution, high precision, resistance to environmental interference, and low cost. However, engineering accidents in such large-scale engineering applications are often accompanied by changes in physical quantities such as vibration, strain, and temperature. The credibility of the information change of a single physical quantity is insufficient, so obtaining multiple parameter indicators such as strain, temperature, and vibration of the measured structure can comprehensively evaluate its structural safety status.

[0003] Traditional fiber Bragg grating sensors can usually only demodulate one of the parameters such as strain, temperature, and strain, which is difficult to meet the monitoring needs of modern engineering structures for multiple parameters of their own structures, and cannot make a comprehensive evaluation of the health of the structure. Multi-parameter fiber Bragg grating sensor cable is the development direction of modern sensor cables. It can not only easily integrate FBG and distributed sensing optical fiber to realize functions such as state information extraction and damage identification, but also has the advantages of many sensing parameters, small sensor head size, easy telemetry, low cost, and high system integration. In 2017, Jiang Youhua et al. proposed and produced a lateral pressure and temperature dual-parameter optical fiber sensor, but the structural design was too simple, and the performance was only tested in the laboratory. The actual engineering application still needs further improvement. In 2021, Ye Shaomin et al. established a multi-parameter optical fiber sensing system in the Beijing-Xiong intercity tunnel to monitor physical quantities such as tunnel temperature, deformation, and vibration. It can reflect the safety status of the tunnel in real time and issue real-time warnings. However, the layout of the optical fiber sensors is numerous and complex, and single-fiber multi-parameter sensing has not been formed, which increases the construction difficulties and economic burden. In 2022, Feng Qian and others installed a multi-core fiber optic security project at the protective fence of the Wuhan Institute of Earthquake Engineering, realizing distributed multi-parameter sensing such as strain, temperature, and frequency. However, it was only used for monitoring small-scale fence projects. Due to its limited multiplexing capability, the monitoring capability of traditional FBG in large-scale structures needs to be improved. Summary of the invention

[0004] In view of the shortcomings of the prior art, specifically, the problems that the existing array-type fiber grating sensors cannot monitor multiple parameters at the same time, the existing multi-core multi-parameter sensing optical cables are difficult to adapt to harsh working conditions, and the monitoring capacity of large structures is limited. The present invention proposes a flat multi-parameter sensing optical cable based on an ultra-weak fiber grating array, which can demodulate vibration signals while demodulating strain signals; the built-in FRP strain sensing optical fiber and FRP reinforcement ribs greatly improve the mechanical tensile and compressive properties of the optical cable; the external flat sheath is hot-extruded by a mold, and the special shape structure can better combine with the object to be measured and sense vibration signals compared with traditional vibration optical fibers; the embedded strain-type and vibration-type ultra-weak fiber grating arrays can monitor the object to be measured over a long distance, and are more suitable for health monitoring of large structures such as rail transit.

[0005] The technical purpose of the present invention is achieved through the following technical solutions: providing a multi-parameter sensing optical cable based on an ultra-weak fiber grating array, comprising a strain reinforcement rib S-FRP with an ultra-weak fiber grating array composited in the center; a PBT sleeve with a vibration-type ultra-weak fiber grating array embedded, the PBT sleeve also being filled with grease; a fiber-reinforced resin reinforcement rib FRP symmetrically arranged with respect to the strain reinforcement rib S-FRP and the PBT sleeve; the strain reinforcement rib S-FRP, the PBT sleeve and the reinforcement rib FRP are formed into a flat sheath by hot extrusion of a mold.

[0006] It should be noted that in the description of the present invention, S-FRP stands for Strain-Fiber Reinforced Polymer, i.e., strain-type fiber reinforced composite material; PBT stands for Polybutylene Terephthalate, i.e., polybutylene terephthalate; and FRP stands for Fiber Reinforced Polymer, i.e., fiber reinforced composite material.

[0007] Preferably, the strain reinforcement rib S-FRP is formed by hot pultrusion of high-strength glass fiber, polymer matrix and the ultra-weak fiber grating array, and is used to couple the strain transmitted on the flat sheath.

[0008] Preferably, the vibration-type ultra-weak fiber grating array is used to couple the micro-vibration transmitted on the flat sheath through the grease and the PBT sleeve.

[0009] Preferably, the fiber reinforced resin reinforcement FRP is formed by hot pultrusion of glass fiber and polymer matrix, and is used to improve mechanical tensile and compressive properties.

[0010] Preferably, the flat sheath is trapezoidal.

[0011] Preferably, the strain reinforcement rib S-FRP and the sheath are bonded with glue.

[0012] Compared with the existing method, the present invention has the following beneficial effects: 1. The present invention provides a multi-parameter sensing optical cable based on an ultra-weak fiber grating array. The ultra-weak fiber grating multi-parameter sensing optical cable has composite fiber-reinforced resin strain sensing optical fibers and fiber-reinforced resin reinforcement ribs on both sides, and is wrapped with a high-density polyethylene flat sheath on the outside, and has excellent mechanical tensile and compressive resistance.

[0013] 2. The ultra-weak fiber Bragg grating multi-parameter sensing cable provided by the present invention can monitor strain and vibration signals simultaneously, meeting the multi-parameter monitoring needs of large structures.

[0014] 3. The ultra-weak fiber Bragg grating multi-parameter sensing optical cable provided by the present invention can be better integrated with the ground due to its special shape and structure, and can better sense vibration signals compared with traditional vibration optical cables.

[0015] 4. The ultra-weak fiber Bragg grating multi-parameter sensing optical cable provided by the present invention has a fiber-reinforced resin strain sensing optical fiber portion and a sheath bonded with glue, thereby enhancing the sensor's ability to sense strain signal transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the present invention.

[0017] Figure 2 This is a strain-wavelength curve diagram of the multi-parameter sensing optical cable provided by the present invention.

[0018] Figure 3 This is a temperature-wavelength curve diagram of the multi-parameter sensing optical cable provided by the present invention.

[0019] Figure 4 The frequency-phase curve of the multi-parameter sensing optical cable provided by the present invention is compared with that of a bare optical fiber and a circular vibration optical cable under the action of a vibration table.

[0020] In the above figures: 1. Ultra-weak fiber Bragg grating array; 2. Strain reinforcement rib S-FRP; 3. Vibration type ultra-weak fiber Bragg grating array; 4. PBT sleeve; 5. Reinforcement rib FRP; 6. Flat sheath. DETAILED DESCRIPTION

[0021] The present invention is described in detail below in conjunction with specific implementation modes.

[0022] This embodiment provides a multi-parameter sensing optical cable based on ultra-weak fiber grating array, such as Figure 1As shown, it includes: a strain stiffener S-FRP2 with an ultra-weak fiber grating array 1 composited in the center; a PBT sleeve 4 with a vibration-type ultra-weak fiber grating array 3 embedded therein, the PBT sleeve 4 is also filled with grease; a fiber-reinforced resin stiffener FRP5 symmetrically arranged with respect to the strain stiffener S-FRP2 and the PBT sleeve 4; the strain stiffener S-FRP2, the PBT sleeve 4 and the stiffener FRP5 are formed into a flat sheath 6 by hot extrusion of a mold.

[0023] In the above embodiment, the strain reinforcement rib S-FRP2 is formed by hot pultrusion of high-strength glass fiber, polymer matrix and the ultra-weak fiber grating array 1, and is used to couple the strain transmitted on the flat sheath 6.

[0024] The vibration-type ultra-weak fiber grating array 3 is used to couple the micro-vibration transmitted on the flat sheath 6 through the grease and the PBT sleeve 4 .

[0025] In some embodiments, the fiber reinforced resin reinforcement FRP5 is formed by hot pultrusion of glass fiber and polymer matrix to improve mechanical tensile and compressive properties.

[0026] In some preferred embodiments, the flat sheath 6 is trapezoidal. The special shape structure of the flat sheath in this embodiment can be better integrated with the ground, so that the vibration-type ultra-weak fiber grating array in the PBT sheath can sense vibration more sensitively.

[0027] In some other preferred embodiments, the strain reinforcement ribs S-FRP2 are bonded to the sheath 4 with glue, thereby enhancing the ability of the sensor to sense strain signal transmission.

[0028] The ultra-weak fiber grating array multi-parameter sensing optical cable of the present invention is placed in a tensile machine to perform a strain calibration experiment. The strain-wavelength curve of the flat multi-parameter sensing optical cable is shown in FIG. Figure 2 As shown, the horizontal axis is the strain applied to the optical cable, and the vertical axis is the central wavelength of the grating. The test results show that the ultra-weak fiber grating array multi-parameter sensing optical cable provided by the present invention has a linear relationship between strain and wavelength, and the strain sensitivity is, the linearity is 0.9996, and the strain transmission efficiency is high.

[0029] The ultra-weak fiber grating array multi-parameter sensing optical cable of the present invention is placed in a high and low temperature circulation box and connected to an ultra-weak fiber grating demodulator to perform a temperature calibration experiment. The temperature-wavelength curve of the flat multi-parameter sensing optical cable is shown in FIG. Figure 3 As shown, the horizontal axis is temperature and the vertical axis is the central wavelength of the grating. The test results show that the ultra-weak fiber grating array multi-parameter sensing optical cable provided by the present invention has a linear relationship between temperature and wavelength, and the temperature sensitivity is, and the linearity reaches 0.9991.

[0030] The ultra-weak fiber grating array multi-parameter sensing optical cable of the present invention is fixed on a vibration table. Under the action of the vibration table 1A, 0.6V amplitude, the vibration table is given an excitation of 100HZ. The flat multi-parameter sensing optical cable is connected to the ultra-weak fiber grating DAS demodulator, and the bare vibration optical fiber and the circular vibration optical cable are subjected to the same operation for comparison. The time-phase curves of the three are shown as follows: Figure 4 As shown, the horizontal axis is time, and the vertical axis is the phase change of the optical fiber and the optical cable. The test results show that the phase change of the ultra-weak fiber grating array multi-parameter sensing optical cable provided by the present invention is close to that of the bare optical fiber, while the phase change of the round optical cable is weaker than the two, and the flat optical cable can better sense vibration.

[0031] In summary, the present invention proposes a multi-parameter sensing optical cable based on an ultra-weak fiber grating array. Its special flat shape structure effectively improves the ability of the optical cable to sense vibration signals. The optical cable is composited with a fiber-reinforced resin FRP strain sensing optical fiber and a PBT sleeve with an embedded vibration-type ultra-weak fiber grating array. It can monitor strain and vibration signals at the same time, meeting the monitoring needs of multiple parameters of large structures. The fiber-reinforced resin reinforcement ribs and fiber-reinforced resin FRP strain sensing optical fiber are symmetrically arranged on both sides of the sensing optical cable, and high-density polyethylene is wrapped on the outside, so that the optical cable also has good tensile and compression resistance, providing a very potential solution for large-scale structure monitoring.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A multi-parameter sensing optical cable based on ultra-weak fiber grating array, characterized in that: The invention comprises a strain reinforcing rib S-FRP (2) with an ultra-weak fiber grating array (1) composited at the center; a PBT sleeve (4) with a vibration-type ultra-weak fiber grating array (3) embedded therein, wherein the PBT sleeve (4) is also filled with grease; a fiber-reinforced resin reinforcing rib FRP (5) symmetrically arranged with respect to the strain reinforcing rib S-FRP (2) and the PBT sleeve (4); the strain reinforcing rib S-FRP (2), the PBT sleeve (4) and the reinforcing rib FRP (5) are formed into a flat sheath (6) by hot extrusion through a mold.

2. The multi-parameter sensing optical cable based on ultra-weak fiber grating array according to claim 1, characterized in that: The strain reinforcement rib S-FRP (2) is formed by hot pultrusion of high-strength glass fiber, a polymer matrix and the ultra-weak fiber grating array (1), and is used to couple the strain transmitted on the flat sheath (6).

3. The multi-parameter sensing optical cable based on ultra-weak fiber grating array according to claim 1, characterized in that: The vibration-type ultra-weak fiber grating array (3) is used to couple the micro-vibration transmitted on the flat sheath (6) through the grease and the PBT sleeve (4).

4. The multi-parameter sensing optical cable based on ultra-weak fiber grating array according to claim 1, characterized in that: The fiber reinforced resin reinforcement FRP (5) is formed by hot pultrusion of glass fiber and polymer matrix, and is used to improve mechanical tensile and compressive properties.

5. The multi-parameter sensing optical cable based on ultra-weak fiber grating array according to claim 1, characterized in that: The flat sheath (6) is trapezoidal in shape.

6. The multi-parameter sensing optical cable based on ultra-weak fiber grating array according to claim 1, characterized in that: The strain reinforcement rib S-FRP (2) and the sheath (4) are bonded together with glue.

Images