CN114923430B - Non-gel fiber grating strain sensor - Google Patents

Abstract

The invention discloses a glue-free optical fiber grating strain sensor, which relates to the technical field of optical fiber grating sensors. The sensor includes a base, a base guide rail, a bollard, an optical fiber, a fastening slot and a helical distance adjustment device. The bollards for encapsulating both ends of the optical fiber are fixed on the upper part of the base, and the two bases are connected by a base guide rail, and can slide relative to each other along the base guide rail. Both sides of the optical fiber with the Bragg grating are wound on the bollard from top to bottom, and the optical fiber led out from the lower end is fixed by the fastening slot. The friction between the optical fiber wound on the bollard with enough turns and the bollard can effectively fix the optical fiber, and the optical fiber can be pre-tensioned to a certain extent by fine-tuning the distance between the substrates to prevent the optical fiber from loosening. The sensor of the present invention is packaged without glue, has long service life, high durability, higher precision and good stability under long-term use. The optical fiber does not need to be welded, the installation process is simple, the cost is low, and it is easy to produce in batches.

Description

A non-adhesive fiber grating strain sensor

technical field

The invention discloses a non-glue optical fiber grating strain sensor and relates to the technical field of optical fiber grating sensors.

Background technique

Fiber Bragg grating is to use the photosensitivity of fiber material to form a spatial phase grating in the fiber core. This kind of grating is equivalent to a filter, which can periodically change the reflection or refractive index of the fiber. When the external environment changes, causing the center wavelength of Bragg to shift, measuring the wavelength shift can detect changes in external temperature, stress, etc. Therefore, grating fibers are widely used in the sensing field. As a kind of fiber grating sensor, the fiber Bragg grating sensor is also the most widely used fiber grating sensor at present. It is small, can realize multi-point multiplexing, multi-parameter simultaneous measurement, and can realize distributed sensing and other advantages. At present, the research on the grating sensor has been in the stage of rapid development, and a large number of research results have been applied in practical places. From 2012 to 2017, the average annual growth rate of the consumption value of global fiber optic sensors (including point-separated and distributed) is as high as 20.3%. The United States occupies the vast majority of the global fiber optic sensor market share. From 2015 to 2020, the Asia-Pacific region will become the fastest growing market with a compound annual growth rate of 12.7%.

Although fiber gratings have many advantages as sensors, it is inevitable that due to the fragile characteristics of fiber optic materials, as sensors that are actually used in practical engineering, certain protection measures must be applied to the fiber grating itself, that is, the packaging of the fiber grating sensor. The encapsulated sensor can not only effectively protect the FBG components, but also design FBG sensors with different functions according to different packaging forms. Known optical fiber grating sensors can detect physical parameters such as temperature, strain, stress, displacement, vibration, and flow. And its installation methods also have embedded type, paste type, welding type and so on. However, most of the existing fiber grating sensors use glue to fix the fiber grating components during packaging, and the selected adhesives often use glue such as epoxy resin, ultraviolet glue, and 353ND. However, the packaging structure using these glues will have problems such as aging and failure under long-term use, which will reduce the measurement accuracy, durability and service life of the fiber grating sensor.

Aiming at the durability of fiber grating sensors, some related research has made great progress, and some related technologies have also been put into actual production and use. Patent CN210774420U discloses a grating fiber optic temperature sensor without glue packaging, and patent CN105583484A discloses a glueless packaging device and method for an optical fiber sensor. Research. The method is to use specific glass solder to realize the welding between the fiber grating and stainless steel, so as to realize the packaging of the fiber grating sensor. Among the fiber grating sensors that have been put into production, a fiber grating temperature sensor developed by Wuhan Institute of Technology Optical Technology Co., Ltd. combines material science methods to realize the glue-free packaging of the sensor structure.

To sum up, at present, most fiber grating sensors are packaged with adhesives. This kind of fiber grating sensors has poor durability and will face problems such as aging and colloid shedding under long-term use, which will shorten the life of the sensor. However, the existing glue-free packaging methods all have problems such as complex processing technology, high environmental requirements, and easy damage to fiber grating components.

Contents of the invention

The technical problem to be solved by the present invention is to provide a fiber grating strain sensor packaged without glue, which can solve the problem of inaccurate measurement data under long-term use of the sensor due to the aging and falling off of the glue of the fiber grating strain sensor packaged in the existing traditional adhesive package. The problem of reduced lifespan, and the existing non-glue-packaged fiber grating sensor packaging process is complex, sensitive to the environment, and easy to cause damage to the sensor and other problems.

Based on this purpose, technical scheme of the present invention:

A non-glue optical fiber grating strain sensor, comprising: a base 6, a base guide rail 5, a bollard 1, an optical fiber 2, a fastening slot 3 and a helical distance adjusting device.

There are two bases 6 , base guide rails 5 are arranged between the two bases 6 , and the two bases 6 can slide relative to each other along the base guide rails 5 .

Further, both sides of the base 6 have strip bolt holes 4, and the base 6 and the structure are connected and fixed by bolts.

The bollards 1 are fixed on the base 6, and the two bollards 1 are installed symmetrically and parallel to the sliding direction of the base guide rail 5.

Further, the bollard 1 is a cylinder, and the radius of the bollard 1 should not be less than 10 mm, or the minimum radius of the bollard 1 should not be less than 10 times the diameter of the optical fiber 2 .

The part of the optical fiber 2 is fixed in the middle of the two bollards 1 as a measuring element, and the part of the optical fiber 2 as the measuring element has a Bragg grating, and is parallel to the base 6 along the sliding direction of the base guide rail 5; the optical fibers 2 on both sides are tightly Wrapped around the bollard 1.

The fastening slot 3 is arranged on the outside of the bollard 1 for fixing the two ends of the optical fiber 2 .

Further, the fastening slot 3 includes a cover plate 7, a base plate 13 and a rotating shaft.

The cover plate 7 and the base plate 13 are rotatably connected by a rotating shaft. The cover plate 7 and the base plate 13 are respectively equipped with a cover plate magnet 8 and a base plate magnet 9. The inner surface of the cover plate 7 is provided with an elastic pad 11. A V-shaped groove 12 is provided on the top, corresponding to the position of the elastic pad 11 .

The optical fiber 2 is wound and pulled out from the bollard 1 and placed in the V-shaped groove 12 , the cover magnet 8 is attracted to the substrate magnet 9 , and the elastic pad 11 presses and fixes the optical fiber 2 .

Further, the base plate 13 is provided with buckles 10 for further locking the cover plate 7 and the base plate 13 after the fastening slot 3 is magnetically closed.

The said helical pitch adjusting device is arranged between the two bases 6, and is used to adjust the distance between the two bases 6, so that the bases 6 have a pre-tension, and prevent measurement errors caused by loosening of the optical fiber due to long-term use.

The screw distance adjustment device includes a metal claw 15 that can be opened and closed, a fine-tuning knob 14 and a scale, and the fine-tuning knob 14 includes a fine-tuning nut and a screw rod.

The optical fiber led by the optical fiber grating strain sensor is connected to the optical fiber demodulator to realize the temperature and strain monitoring of the structure.

Compared with the technology that has been applied at present, the beneficial effect of the present invention is: the optical fiber of the present invention is packaged and fixed through the bollard and the fastening slot, and there is enough friction between the optical fiber and the bollard around which the optical fiber is wound. Therefore, the packaging of the fiber grating sensor is completely glue-free, and has the advantages of good durability, high measurement accuracy for long-term use, and long life. At the same time, compared with other fiber grating sensors packaged without glue, the packaging process of the present invention is simple, the packaging cost is low, and it is easy to produce in batches.

Description of drawings

Fig. 1 is the structural representation of fiber grating strain sensor of the present invention;

Fig. 2 is a structural schematic diagram of the fastening slot of the present invention;

Fig. 3 is a schematic diagram of the screw distance adjusting device of the present invention;

In the attached drawings: 1. bollard; 2. optical fiber; 3. fastening slot; 4. strip bolt hole; 5. base guide rail; 6. base; 7. cover plate; 8. cover plate magnet; 9. Substrate magnet; 10, buckle; 11, elastic pad; 12, V-shaped groove; 13, substrate; 14, fine-tuning knob; 15, metal claw.

Detailed ways

The technical solutions of the present invention will be described in detail below in conjunction with the accompanying drawings. Apparently, the described examples are only some examples of the application, not all examples. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Hereinafter, an embodiment will be described with reference to the drawings. In addition, the examples shown below do not limit the content of the application described in the claims in any way.

Referring to the accompanying drawing 1, the fiber grating strain sensor described in the example of the present invention is composed of a base 6, a base guide rail 5, a bollard 1, an optical fiber 2, and a fastening slot 3. The base 6 is a cuboid connected by the base guide rail 5 and can slide relatively along the base guide rail 5 .

The base 6 has strip bolt holes 4, and is fixed with the structure through bolt connection.

When the base 6 is installed, the bolts fix the base 6 on the structure, but the bolts are not tightened, so that the base 6 can still be adjusted within the length of the strip bolt hole 4 . After the optical fiber 2 is tensioned and a pre-tension force is applied, the bolts are tightened to ensure tight fixation between the substrate 6 and the structure.

Both ends of the optical fiber 2 are tightly wound on the two bollards 1, and the number of winding turns should not be less than three, so as to ensure sufficient friction to fix the optical fiber 2. The optical fiber 2 is tensioned with a certain pretension to ensure that the measuring element of the optical fiber 2 can accurately reflect the strain change of the structure.

The requirements for the radius of the bollard 1 are as follows: according to different types of optical fibers, the specified minimum bending radius is also different. In this example, G.657 optical fiber is used, which has better bending resistance, and its minimum bending radius is 10mm, that is, The minimum radius of bollard 1 should not be less than 10mm. If other types of optical fibers are selected, the minimum radius of the bollard 1 should not be less than 10 times the diameter of the optical fiber. Due to the fragile nature of the optical fiber, excessive bending of the optical fiber will greatly increase the optical loss and even destroy the optical fiber. Therefore, specifying the minimum radius of the bollard 1 can prevent the measurement error of the FBG strain sensor from increasing.

The optical fiber is wound and led out from the bollard 1 and then fixed through the fastening slot 3, so that the fiber grating components are completely packaged and fixed.

Referring to accompanying drawing 2 , the fastening slot 3 is composed of a cover plate 7 , a cover plate magnet 8 , a substrate magnet 9 , buckles 10 , an elastic pad 11 , a V-shaped groove 12 , and a substrate 13 . The extracted optical fiber is placed in the V-shaped groove 12, the cover plate magnet 8 and the substrate magnet 9 are magnetically attracted to close the cover plate 7 and the substrate, and the upper elastic pad 11 fixes the optical fiber in the V-shaped groove 12. After closing the cover plate 7, the The buckle 10 is fixed to finally realize the fixing of the outgoing optical fiber.

Referring to FIG. 3 , during the installation process of the fiber grating strain sensor, the relative distance between the two substrates 6 needs to be fine-tuned to ensure that the fiber grating is tensioned and has a certain pre-tension. In the fine-tuning process, the distance adjustment device needs to have high precision, so as to prevent the optical fiber from being broken due to excessive tension on the fiber grating. The helical distance adjusting device proposed in Fig. 3 has a high-precision fine-tuning function, and can realize the pre-tension adjustment of the fiber grating of the present invention.

The screw fine-tuning device has a fine-tuning knob 14, a metal claw 15 and a ruler. The fine-tuning knob 14 includes a fine-tuning nut and a screw rod. When the distance is adjusted, the metal claw 15 is stuck in the middle of the two bases 6, and the fine-tuning nut inside the fine-tuning knob 14 is adjusted to rotate and push the screw to advance to realize the distance-adjusting function.

After the grating optical fiber strain sensor is installed on the structure, the finally drawn optical fiber is connected to the demodulator, and the demodulator measures and collects the data transmitted by the fiber grating to realize the measurement of the structural strain.

Finally, it needs to be explained: the above examples are only used to illustrate the design ideas and characteristics of the present invention, rather than to limit them; its purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The present invention has been described in detail, and those of ordinary skill in the art should understand that it is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements, The essence of the corresponding technical solutions does not depart from the scope of the technical solutions of the various embodiments of the present invention.

Claims (8)

1. A glue-free fiber grating strain sensor, characterized in that it comprises: base (6), base guide rail (5), bollard (1), optical fiber (2), fastening slot (3) and screw Distance adjustment device; There are two bases (6), a base guide rail (5) is arranged between the two bases (6), and the two bases (6) can slide relatively along the base guide rail (5); The bollards (1) are fixed on the base (6), and the two bollards (1) are installed symmetrically and parallel to the sliding direction of the base guide rail (5); The optical fiber (2) part is fixed between two bollards (1) as a measuring element, and the optical fiber (2) as a measuring element has a Bragg grating, and is connected with the base (6) along the base guide rail (5) The sliding direction is parallel; the optical fibers (2) on both sides are tightly wound on the bollard (1); The fastening slot (3) is arranged on the outside of the bollard (1), and is used to fix the two ends of the optical fiber (2); The helical distance adjusting device is arranged between two bases (6), and is used for adjusting the distance between the two bases (6), so that the bases (6) have a pre-tension force, and prevent measurement errors caused by long-term use of optical fiber loosening. 2. A kind of glue-free fiber grating strain sensor according to claim 1, characterized in that, both sides of the base (6) have strip bolt holes (4), and the base (6) and the structure pass through Bolted and secured. 3. A kind of glue-free fiber grating strain sensor according to claim 1, characterized in that, the bollard (1) is a cylinder, and the radius of the bollard (1) should not be less than 10mm, or the bollard (1) should not be less than 10mm, or The minimum radius of the bollard (1) should not be less than 10 times the diameter of the optical fiber (2). 4. A kind of glue-free fiber grating strain sensor according to claim 1, characterized in that, the fastening slot (3) includes a cover plate (7), a base plate (13) and a rotating shaft; The cover plate (7) and the base plate (13) are rotatably connected by a rotating shaft, and the cover plate (7) and the base plate (13) are respectively equipped with a cover plate magnet (8) and a base plate magnet (9). An elastic pad (11) is arranged on the surface, and a V-shaped groove (12) is provided on the inner surface of the base plate (13) corresponding to the position of the elastic pad (11). 5. A kind of glue-free fiber grating strain sensor according to claim 4, characterized in that, said optical fiber (2) is wound and drawn out from the bollard (1) and then placed in the V-shaped groove (12) , the cover magnet (8) is attracted to the substrate magnet (9), and the elastic pad (11) compresses and fixes the optical fiber (2). 6. A non-adhesive fiber grating strain sensor according to claim 4 or 5, characterized in that a clasp (10) is provided on the substrate (13) for fastening the clamping groove (3) After the magnetic attraction is closed, the cover plate (7) and the base plate (13) are further locked. 7. A kind of glue-free fiber grating strain sensor according to claim 1, characterized in that, said helical distance adjusting device comprises a metal claw (15) that can be stretched and closed, a fine-tuning knob (14) and a scale, and the fine-tuning Knob (14) comprises trimming nut and screw rod. 8 . The non-adhesive fiber grating strain sensor according to claim 1 , characterized in that the optical fiber leading out from the fiber grating strain sensor is connected to a fiber optic demodulator to monitor the temperature and strain of the structure.

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