Optical fiber sensor and sensing device

Abstract

The utility model discloses an optical fiber sensor and a sensing device. The optical fiber sensor comprises a first single-mode optical fiber, a coreless optical fiber, a multi-core optical fiber and a second single-mode optical fiber which are connected in sequence; the multi-core optical fiber comprises a central fiber core and at least one peripheral fiber core; the joint of the multi-core optical fiber and the second single-mode optical fiber comprises a spherical structure, and the spherical structure forms a Mach-Zehnder interferometer; a fundamental-mode light beam is input from a fiber core of the first single-mode optical fiber and excited by the coreless optical fiber to generate a high-order-mode light beam, the fundamental-mode light beam and the high-order-mode light beam are coupled into a cladding and a fiber core of the multi-core optical fiber, and the light beams of the two modes are diverged and focused in the spherical structure and then are coupled into a fiber core of the second single-mode optical fiber to be output. According to the optical fiber sensor provided by the utility model, a single-mode fiber-coreless fiber-multi-core fiber (fused ball)-single-mode fiber structure is adopted, a high-order mode in the fiber is fully excited through the coreless fiber and the spherical structure, the mechanical strength of the sensing structure is increased, and the optical loss of a device is reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to sensing technology field especially relates to a kind of optical fiber sensor and sensing device. BACKGROUND

[0002] With the development of optical fiber technology, due to the excellent performance of optical fiber, for example: the performance of anti-electromagnetic and atomic radiation interference, the mechanical properties of thin diameter, soft quality and light weight; the electrical properties of insulation and non-inductive; the chemical properties of water resistance, high temperature resistance and corrosion resistance, etc., it has been widely used in the field of optical fiber sensing.

[0003] However, many current optical fiber sensors have low sensitivity, large preparation loss and other problems, which limit the application of optical fiber sensing. SUMMARY

[0004] The utility model embodiment provides a kind of optical fiber sensor and sensing device, which provides a kind of optical fiber sensor based on Mach-Zehnder interferometer (MZI) of ball type structure multicore optical fiber, adopts the structure of single-mode fiber-no-core optical fiber-multicore optical fiber (fusion ball)-single-mode fiber, excites high-order mode in optical fiber through no-core optical fiber and ball type structure, simultaneously increases the mechanical strength of sensing structure, reduces the optical loss of device. Experiments show that the highest curvature sensitivity is 55.42nm / m -1 At the same time, a new sensor packaging form is proposed to use the optical fiber sensor for air pressure measurement.

[0005] According to one aspect of the utility model, an optical fiber sensor is provided, comprising a first single-mode optical fiber, a no-core optical fiber, a multicore optical fiber and a second single-mode optical fiber connected in sequence, the multicore optical fiber includes a central core and at least one peripheral core;

[0006] The connection between the multicore optical fiber and the second single-mode optical fiber includes a ball type structure, and the ball type structure forms a Mach-Zehnder interferometer;

[0007] The fundamental mode light beam is input from the core of the first single-mode optical fiber, and high-order mode light beams are generated by excitation through the no-core optical fiber. The fundamental mode light beam and the high-order mode light beam are coupled into the cladding and core of the multicore optical fiber, and the two kinds of mode light beams are coupled into the core of the second single-mode optical fiber after divergence and focusing in the ball type structure and output from the second single-mode optical fiber.

[0008] Optionally, the length of the no-core optical fiber is greater than or equal to 0.5 cm and less than or equal to 1 cm.

[0009] Optionally, the length of the multicore optical fiber is greater than or equal to 1 cm and less than or equal to 3 cm.

[0010] Optionally, the diameter of the spherical structure is greater than or equal to 360 μm and less than or equal to 390 μm.

[0011] Optionally, the multi-core optical fiber includes a four-core optical fiber, a five-core optical fiber, a seven-core optical fiber, or a nine-core optical fiber.

[0012] Optionally, a protective layer is further included, covering the coreless optical fiber, the multi-core optical fiber, the spherical structure, at least a partial region of the first single-mode optical fiber near the coreless optical fiber, and at least a partial region of the second single-mode optical fiber near the spherical structure.

[0013] Optionally, the protective layer includes ultraviolet curing glue.

[0014] According to another aspect of the present application, a sensing device is provided, including a light source, a spectrometer, a first displacement table, a second displacement table, and the above-mentioned optical fiber sensor, the output end of the light source is connected with the first single-mode optical fiber of the optical fiber sensor, the spectrometer is connected with the second single-mode optical fiber of the optical fiber sensor, the first single-mode optical fiber is fixed on the first displacement table, the second single-mode optical fiber is fixed on the second displacement table, and the optical fiber sensor is used for curvature sensing.

[0015] According to another aspect of the present application, a sensing device is provided, including a light source, a spectrometer, and the above-mentioned optical fiber sensor, the output end of the light source is connected with the first single-mode optical fiber of the optical fiber sensor, the spectrometer is connected with the second single-mode optical fiber of the optical fiber sensor, the optical fiber sensor further includes a packaging structure, the coreless optical fiber, the multi-core optical fiber, the spherical structure, at least a partial region of the first single-mode optical fiber near the coreless optical fiber, and at least a partial region of the second single-mode optical fiber near the spherical structure are packaged in the packaging structure, and the optical fiber sensor is used for air pressure detection.

[0016] Optionally, the packaging structure includes a sealed shell, the first single-mode optical fiber and the second single-mode optical fiber are fixed on the side wall of the sealed shell, one side of the sealed shell includes an elastic film, and a partial region of the optical fiber sensor is attached to the side surface of the elastic film inside the sealed shell.

[0017] The fiber optic sensor provided in this embodiment includes a first single-mode fiber, a coreless fiber, a multi-core fiber, and a second single-mode fiber connected in sequence. The multi-core fiber includes a central core and at least one peripheral core. A spherical structure is set at the connection between the multi-core fiber and the second single-mode fiber, forming a Mach-Zehnder interferometer to improve detection sensitivity. The fundamental mode beam is input from the core of the first single-mode fiber, excited by the coreless fiber to generate a higher-order mode beam. The fundamental mode beam and the higher-order mode beam are coupled into the cladding and core of the multi-core fiber. The two modes of beams diverge and focus in the spherical structure before coupling into the core of the second single-mode fiber and outputting from the second single-mode fiber. This structure, employing single-mode fiber-coreless fiber-multi-core fiber (fused sphere)-single-mode fiber, simultaneously increases the mechanical strength of the sensing structure and reduces optical loss. By fully exciting the higher-order modes in the coreless fiber and then transmitting them to the spherical structure for interference, changes in the emission of the physical quantity to be detected will cause spectral changes, achieving high-precision sensing measurement.

[0018] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this utility model, nor is it intended to limit the scope of this utility model. Other features of this utility model will become readily apparent from the following description. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of an optical fiber sensor provided in an embodiment of the present invention;

[0021] Figure 2 A transmission spectrum of an optical fiber sensor provided for an embodiment of this utility model;

[0022] Figure 3 for Figure 2 The curve obtained after processing with Fast Fourier Transform;

[0023] Figure 4 A schematic diagram of the structure of a sensing device provided in an embodiment of this utility model;

[0024] Figure 5 For application Figure 4 Transmission spectrum of the device shown;

[0025] Figure 6 for Figure 5In the fitting curve graph of the transmission spectrum wavelength and the curvature change;

[0026] Figure 7 The structure schematic diagram of the first step encapsulated optical fiber sensor is provided for the embodiment of the utility model,

[0027] Figure 8 The structure schematic diagram of the second step encapsulated optical fiber sensor is provided for the embodiment of the utility model. DETAILED DESCRIPTION

[0028] In order to make the personnel in the technical field better understand the utility model scheme, the technical scheme in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model, obviously, the described embodiment is only a part of the embodiment of the utility model, rather than all the embodiments. Based on the embodiment in the utility model, all other embodiments obtained by the person skilled in the art without making creative labor should belong to the protection scope of the utility model.

[0029] It should be noted that the terms "first", "second" and the like in the specification and claims of the utility model and the above-mentioned drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the utility model described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to the clearly listed steps or units, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0030] Figure 1 The structure schematic diagram of the optical fiber sensor is provided for the embodiment of the utility model, refer to Figure 1 The optical fiber sensor includes first single-mode optical fiber 10, coreless optical fiber 20, multi-core optical fiber 30 and second single-mode optical fiber 40 connected in sequence, multi-core optical fiber 30 includes central core 31 and at least one peripheral core 32;The connection of multi-core optical fiber 30 and second single-mode optical fiber 40 includes spherical structure 50, and the spherical structure 50 forms a Mach-Zehnder interferometer;The fundamental mode light beam is input from the core of the first single-mode optical fiber 10, and the high-order mode light beam is excited to generate through the coreless optical fiber 20, the fundamental mode light beam and the high-order mode light beam are coupled into the cladding and the core of the multi-core optical fiber 30, and the two mode light beams are coupled into the core of the second single-mode optical fiber 40 after being diverged and focused in the spherical structure 50 and output from the second single-mode optical fiber 40.

[0031] The first single-mode optical fiber 10 and the second single-mode optical fiber 40 can be single-mode optical fibers with any dispersion value, and the specific type and model are not limited, for example, the first single-mode optical fiber 10 and the second single-mode optical fiber 40 can be the same type of optical fiber, for example, SMF-28 optical fiber. The hollow optical fiber 20 can also be called a hollow optical fiber, which has only a cladding layer and a coating layer structure, without a fiber core structure, is commonly used as a terminal optical fiber, can effectively reduce the light energy density of the end face, and can reduce back reflection. In the embodiment, the hollow optical fiber 20 is connected with the first single-mode optical fiber 10 and is used for exciting generation of a high-order mode light beam. The multi-core optical fiber 30 includes a central core 31 and at least one peripheral core 32, for example, the multi-core optical fiber 30 can be a seven-core optical fiber including one central core 31 and six peripheral cores 32, and the specific type and model of the multi-core optical fiber are not limited, and the number of peripheral cores 32 is not limited (for example, the seven-core optical fiber is taken as an example). Figure 1 The spherical structure 50 forms a Mach-Zehnder interferometer structure, is used for interference of the fundamental mode light beam and the high-order mode light beam transmitted by the multi-core optical fiber 30, improves sensing sensitivity, and outputs the light beams to the second single-mode optical fiber 40 after divergence and focusing. The second single-mode optical fiber 40 can be connected with a spectrometer, and the change of the to-be-measured physical quantity is analyzed through spectrum analysis.

[0032] The optical fiber sensor provided in the embodiment of the utility model, the fundamental mode light beam is input from the fiber core of the first single-mode optical fiber, the high-order mode light beam is excited and generated through the hollow optical fiber, the fundamental mode light beam and the high-order mode light beam are coupled into the cladding layer and the fiber core of the multi-core optical fiber, and the light beams of the two modes are coupled into the fiber core of the second single-mode optical fiber after divergence and focusing in the spherical structure and are output from the second single-mode optical fiber, the structure of single-mode optical fiber-hollow optical fiber-multi-core optical fiber (fused ball)-single-mode optical fiber is adopted, the mechanical strength of the sensing structure is increased, and the optical loss of the device is reduced. The high-order mode in the optical fiber is fully excited through the hollow optical fiber, then is transmitted to the spherical structure to interfere, the spectrum changes when the to-be-detected physical quantity emits changes, and high-precision sensing measurement is realized.

[0033] The optical fiber sensor provided in the embodiment of the utility model is mainly divided into two points during preparation, one is to fuse the left (corresponding to the left) hollow optical fiber 20 and the multi-core optical fiber 30, and the other is to fuse the right end face of the multi-core optical fiber 30 into the spherical structure 50 and fuse the spherical structure 50 with the second single-mode optical fiber 40. Figure 1

[0034] ​First, the end of the multi-core optical fiber 30 is cut flat with an optical fiber cutter, and is placed stably in an optical fiber fusion splicer. The position of the multi-core optical fiber 30 is adjusted by a step displacement table inside the fusion splicer. The fusion splicer selects a manual fusion mode, and the hollow-core optical fiber 20 and the multi-core optical fiber 30 are fused. Then, the right end face of the multi-core optical fiber 30 is fused into a spherical structure 50 by repeated discharging. The number of discharges and the size of the discharge amount are determined by the size of the required spherical structure 50. Finally, the fused end face spherical structure 50 is fused with the second single-mode optical fiber 40. Since there is a difference in structure and size between the spherical structure 50 and the second single-mode optical fiber 40, manual fusion is also required. Figure 2 A transmission spectrum diagram of the optical fiber sensor is provided for the embodiment of the utility model, Figure 3 A transmission spectrum diagram of the optical fiber sensor is provided for the embodiment of the utility model, Figure 2 A curve diagram obtained after fast Fourier transform processing.

[0035] On the basis of the above-mentioned embodiments, the length of the hollow-core optical fiber 20, the length and the number of cores of the multi-core optical fiber 30, and the diameter of the spherical structure 50 can be designed according to actual conditions to obtain optical fiber sensors with different sensitivities, and the embodiments of the utility model do not limit this. Optionally, the length of the hollow-core optical fiber 20 is greater than or equal to 0.5 cm and less than or equal to 1 cm, the length of the multi-core optical fiber 30 is greater than or equal to 1 cm and less than or equal to 3 cm, the diameter of the spherical structure 50 is greater than or equal to 360 μm and less than or equal to 390 μm, and the multi-core optical fiber 30 includes a four-core optical fiber, a five-core optical fiber, a seven-core optical fiber, or a nine-core optical fiber. In an exemplary embodiment, the length of the hollow-core optical fiber 20 is 1 cm, the multi-core optical fiber 30 is a seven-core optical fiber, the length is 2 cm, and the diameter of the spherical structure 50 is 385 μm.

[0036] In another embodiment, optionally, the optical fiber sensor provided by the embodiments of the utility model further includes a protective layer, which covers at least part of the area of the hollow-core optical fiber, the multi-core optical fiber, the spherical structure, the first single-mode optical fiber close to the hollow-core optical fiber, and the second single-mode optical fiber close to the spherical structure.

[0037] The protective layer can improve the toughness and mechanical strength of the optical fiber sensor, and optionally, the protective layer includes ultraviolet curing glue.

[0038] The optical fiber sensor provided by the embodiment of the utility model can be used for temperature sensing, when used for temperature sensing, the temperature sensing device can include a light source, a spectrometer and the optical fiber sensor provided by the above embodiment, specifically, the output end of the light source is connected with the first single-mode optical fiber of the optical fiber sensor, the spectrometer is connected with the second single-mode optical fiber of the optical fiber sensor, the light source includes but is not limited to a broadband light source, the light source, the spectrometer and the optical fiber sensor should be matched with each other, for example, the test range and the accuracy of the spectrometer are adapted to the output wavelength range of the light source and the sensing range and the accuracy of the optical fiber sensor, before temperature testing, the optical fiber sensor can be placed in a thermostat, one side of the sensor is connected with the broadband light source, and the other side records the transmission spectrum change of the sensor at different temperatures through the spectrometer to calibrate.

[0039] In another embodiment, the optical fiber sensor provided by the embodiment of the utility model can also be used for curvature sensing. Figure 4 The structure diagram of the sensing device provided by the embodiment of the utility model is shown in Figure 4 The sensing device includes a light source 1, a spectrometer 2, a first displacement table 4, a second displacement table 5 and the optical fiber sensor 3 provided by the above embodiment, the output end of the light source 1 is connected with the first single-mode optical fiber of the optical fiber sensor 3, the spectrometer 2 is connected with the second single-mode optical fiber of the optical fiber sensor 3, the first single-mode optical fiber is fixed on the first displacement table 4, the second single-mode optical fiber is fixed on the second displacement table 5, and the optical fiber sensor 3 is used for curvature sensing.

[0040] It can be understood that the curvature sensing test of the sensor is to fix the optical fiber sensor between the two displacement tables, the curvature radius of the optical fiber is changed by adjusting the position of the first displacement table 4 in the x direction, and the curvature is calculated through a formula. One side of the sensor is connected with the broadband light source, and the other side records the transmission spectrum change of the sensor at different curvatures through the spectrometer. The curvature calculation formula is as follows:

[0041]

[0042] Wherein, L is the distance between the two displacement tables, R is the curvature radius, x is the displacement of the left first displacement table 4, and C is the curvature.

[0043] Exemplarily, Figure 5 For the application Figure 4 The transmission spectrum diagram of the device is shown, Figure 6 For Figure 5 The fitting curve diagram of the transmission spectrum wavelength and the curvature change in the figure is shown, Figure 5 And Figure 6 The maximum curvature sensitivity of the sensor can reach 55.42nm / m -1 .

[0044] The utility model embodiment provides a kind of sensing device of optical fiber sensor in curvature sensing, output light line enters optical fiber sensor by light source, light line is in turn through first single mode optical fiber, coreless optical fiber, multicore optical fiber, spherical structure and second single mode optical fiber, according to the spectrum change of spectrometer acquisition, the test of curvature change is realized.

[0045] Using curvature sensing principle, the utility model embodiment further provides a sensing device for air pressure detection, the sensing device includes light source, spectrometer and the above-mentioned optical fiber sensor, the output end of light source is connected with the first single mode optical fiber of optical fiber sensor, spectrometer is connected with the second single mode optical fiber of optical fiber sensor, optical fiber sensor further includes packaging structure, coreless optical fiber, multicore optical fiber, spherical structure, at least part of the area of first single mode optical fiber close to the side of coreless optical fiber and at least part of the area of second single mode optical fiber close to the side of spherical structure are packaged in packaging structure, and optical fiber sensor is used for air pressure detection.

[0046] In the embodiment, optical fiber sensor packaging can be used for air pressure detection, to improve the mechanical properties of optical fiber sensor, in specific implementation, optical fiber sensor can adopt two-step packaging, Figure 7 The structure diagram of the first step of the packaging optical fiber sensor provided by the utility model embodiment is referred to Figure 7 First, optical fiber sensor 100 is placed in circular capillary quartz groove 200, then ultraviolet curing soft glue (UV glue) 300 is slowly injected into quartz groove 200, the glue is transparent jelly after ultraviolet curing, which increases the mechanical strength of optical fiber sensor 100 while isolating the damage that external environment can cause to optical fiber sensor 100. It should be noted that the inner wall of quartz groove 200 is coated with anti-adhesive agent in advance to prevent ultraviolet curing glue 300 from adhering to the inner wall of quartz groove 200 during ultraviolet curing, so that optical fiber sensor 100 cannot be taken out from quartz groove 200.

[0047] Figure 8 The structure diagram of the second step of the packaging optical fiber sensor provided by the utility model embodiment is referred to Figure 8 Optionally, the packaging structure includes airtight shell 400, first single mode optical fiber 10 and second single mode optical fiber 40 are fixed to the side wall of airtight shell 400, one side of airtight shell 400 includes elastic film 410, and part of the area of optical fiber sensor 100 is attached to the side surface of elastic film 410 inside airtight shell 400.

[0048] After the softening and wrapping, the optical fiber sensor 100 is taken out from the capillary quartz groove and placed in the square tube shell (closed shell 400). The square tube shell has an elastic film 410 on the upper surface, and the film has good elasticity. The bottom of the film is attached to the surface of the UV softening glue of the optical fiber sensor 100. The optical fiber sensor 100 is placed in the square tube shell through the round holes reserved on both sides of the square tube shell. After being placed, the round holes on both sides are sealed. After sealing, a closed space is formed in the square tube shell, and the internal pressure is one standard atmosphere. When the external pressure changes, the film will extrude the optical fiber sensor 100 inward, so that the optical fiber sensor 100 deforms and changes the curvature. By calibrating the curvature through the shift of the spectrum, the size of the change of the external pressure can be judged.

[0049] The above specific embodiments do not constitute a limitation on the protection scope of the present application. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An optical fiber sensor, characterized in that, It includes a first single-mode fiber, a coreless fiber, a multi-core fiber, and a second single-mode fiber connected in sequence, wherein the multi-core fiber includes a central core and at least one peripheral core. The connection between the multi-core optical fiber and the second single-mode optical fiber includes a spherical structure, which forms a Mach-Zehnder interferometer. The fundamental mode beam is input from the core of the first single-mode fiber, and is excited by the coreless fiber to generate a higher-order mode beam. The fundamental mode beam and the higher-order mode beam are coupled into the cladding and core of the multi-core fiber. The two modes of beams diverge and focus in the spherical structure and then couple into the core of the second single-mode fiber and are output from the second single-mode fiber.

2. The fiber optic sensor according to claim 1, characterized in that, The length of the coreless optical fiber is greater than or equal to 0.5 cm and less than or equal to 1 cm.

3. The fiber optic sensor according to claim 1, characterized in that, The length of the multi-core optical fiber is greater than or equal to 1 cm and less than or equal to 3 cm.

4. The fiber optic sensor according to claim 1, characterized in that, The diameter of the spherical structure is greater than or equal to 360 μm and less than or equal to 390 μm.

5. The fiber optic sensor according to claim 1, characterized in that, The multi-core optical fiber includes four-core, five-core, seven-core, or nine-core optical fibers.

6. The fiber optic sensor according to claim 1, characterized in that, It also includes a protective layer that covers at least a portion of the coreless optical fiber, the multi-core optical fiber, the spherical structure, at least a portion of the first single-mode optical fiber near the coreless optical fiber, and at least a portion of the second single-mode optical fiber near the spherical structure.

7. The fiber optic sensor according to claim 6, characterized in that, The protective layer includes a UV-curable adhesive.

8. A sensing device, characterized in that, The device includes a light source, a spectrometer, a first displacement stage, a second displacement stage, and an optical fiber sensor as described in any one of claims 1 to 7. The output end of the light source is connected to a first single-mode optical fiber of the optical fiber sensor, the spectrometer is connected to a second single-mode optical fiber of the optical fiber sensor, the first single-mode optical fiber is fixed on the first displacement stage, the second single-mode optical fiber is fixed on the second displacement stage, and the optical fiber sensor is used for curvature sensing.

9. A sensing device, characterized in that, The optical fiber sensor includes a light source, a spectrometer, and an optical fiber sensor as described in any one of claims 1 to 7. The output end of the light source is connected to a first single-mode optical fiber of the optical fiber sensor, and the spectrometer is connected to a second single-mode optical fiber of the optical fiber sensor. The optical fiber sensor further includes an encapsulation structure in which the coreless optical fiber, the multi-core optical fiber, the spherical structure, at least a portion of the first single-mode optical fiber near the coreless optical fiber, and at least a portion of the second single-mode optical fiber near the spherical structure are encapsulated. The optical fiber sensor is used for air pressure detection.

10. The sensing device according to claim 9, characterized in that, The encapsulation structure includes a sealed housing, the first single-mode optical fiber and the second single-mode optical fiber are fixed to the side wall of the sealed housing, one side of the sealed housing includes an elastic film, and a portion of the optical fiber sensor is attached to the surface of the elastic film located inside the sealed housing.

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