Femtosecond laser inscribed fiber bragg grating positioning method, positioning device and application

Abstract

The invention discloses a femtosecond laser inscribed fiber bragg grating positioning method, which comprises the following steps: for a femtosecond laser inscribed fiber, probe light is injected into one end of the fiber, so that the probe light is spread in a fiber core and generates Mie scattering on a femtosecond laser inscribed gate region, and scattered light leaks from the side direction of a fiber cladding; and positioning of a femtosecond laser inscribed gate region is realized by identifying the position of laterally leaked scattered light. The Mie scattering is generated on the gate region and the scattered light is leaked out, the positioning and identification precision of the gate region is very high, and the higher the density of the gate region on the optical fiber is, the sensing capability of the sensor formed by the fiber bragg grating to the outside is greatly improved, and the fiber bragg grating is particularly suitable for application occasions requiring the high density of the gate region.

Description

Technical Field

[0001] The present invention belongs to the field of fiber grating, and more specifically, relates to a fiber grating positioning method, a positioning device and an application thereof for femtosecond laser inscription. Background Art

[0002] Fiber Bragg grating is a structure with periodic refractive index changes made inside the optical fiber. This structure can be used as an optical filter to reflect or transmit light of a specific wavelength. Under the action of external force or temperature, the central wavelength of the reflected light will change accordingly. Therefore, fiber Bragg grating can be packaged into a sensor for sensing stress or temperature, or a fiber Bragg grating array can be formed on the entire section of optical fiber. Both fiber Bragg grating devices and fiber Bragg grating arrays have a wide range of applications.

[0003] Fiber Bragg grating devices or the grating area of ​​fiber grating arrays are made by periodically modulating the axial refractive index of the fiber core using ultraviolet or femtosecond lasers. The ultraviolet laser interacts with the photosensitive material in the fiber core, causing the chemical bonds of the core material to change, thereby changing the refractive index of the core material. In contrast, femtosecond lasers mainly change the refractive index of the core through nonlinear absorption processes, including nonlinear field ionization and avalanche ionization, which can achieve permanent changes in the refractive index inside the material. The method of using femtosecond lasers to write fiber Bragg gratings does not require the optical fiber to be photosensitivity, nor does it require the removal of the optical fiber's coating, and has broad application prospects.

[0004] In many applications, the position of each grating area on the optical fiber needs to be accurately marked, because only the area engraved with the grating area has sensing capability, and the area outside the grating area has no sensing capability. However, the grating area of ​​the fiber Bragg grating is difficult to observe with the naked eye, which may cause the consistency of the fiber Bragg grating packaging device to be low, or the position accuracy of the fiber Bragg grating array to be low.

[0005] Especially for fiber grating array, it is necessary to write grating areas at intervals on the core of the optical fiber to form a fiber grating array on the entire section of optical fiber. The typical length of a single grating area is less than 10mm, and the interval between grating areas ranges from tens of millimeters to several meters. However, the appearance of the optical fiber engraved with the fiber grating array is the same as that of ordinary optical fiber, which cannot be distinguished by the naked eye, and the grating area used for sensing is also colorless and transparent, which greatly limits the accuracy of the fiber grating during manufacturing and installation.

[0006] In addition, during manufacturing, when continuously writing on the fiber grating array, the spacing accuracy is completely dependent on the mechanical precision control of the pay-off device, and the positioning accuracy is about ±5mm or worse, which is difficult to improve further; in actual application, the manufacturer needs to mark each grating area with a marker pen so that the user can accurately stick each grating area where sensing is required. When the density of grating areas on an optical fiber is very high, the spacing between grating areas becomes smaller and smaller, and it becomes increasingly difficult to accurately mark each grating area. Summary of the invention

[0007] In view of the above defects or improvement needs of the prior art, the present invention provides a fiber Bragg grating positioning method, positioning device and application for femtosecond laser inscription, which causes the grating area to emit light by Mie scattering, thereby accurately positioning the grating area so as to mark and / or inscribe the grating area.

[0008] To achieve the above object, according to one aspect of the present invention, a positioning method for a fiber grating written by a femtosecond laser is provided, characterized in that, for an optical fiber written by a femtosecond laser, a probe light is injected into one end of the optical fiber, the probe light is propagated in the fiber core and Mie scattering occurs on the grating region written by the femtosecond laser, and the scattered light leaks from the side of the optical fiber cladding;

[0009] The positioning of the gate area written by the femtosecond laser is achieved by identifying the position of the scattered light leaked laterally.

[0010] Preferably, the position of the scattered light is photographed and identified by an industrial camera.

[0011] Preferably, the writing points of the gate region written by the femtosecond laser are nearly spherical, and the equivalent diameter of the nearly spherical writing points is between 550 nanometers and 800 nanometers.

[0012] Preferably, the wavelength of the detection light is between 577 nanometers and 760 nanometers.

[0013] Preferably, one or more gate regions are used to locate near one end where the probe light is injected;

[0014] When a plurality of gate regions are positioned close to one end where the detection light is injected, the number of the positioned gate regions is 5 or more.

[0015] According to another aspect of the present invention, there is also provided a fiber Bragg grating positioning device for femtosecond laser inscription, characterized in that it comprises a laser light source;

[0016] The laser light source is optically coupled to a pigtail of an optical fiber having a grating region inscribed by a femtosecond laser;

[0017] The laser light source is a monochromatic laser, which is used to emit detection light, and its wavelength range falls within the visible light wavelength range.

[0018] Preferably, the laser light source is a wavelength-tunable laser light source, and its power is between 10 mW and 30 mW.

[0019] Preferably, it also includes an industrial camera, which is used to image the grating area that emits scattered light.

[0020] According to another aspect of the present invention, an application of the fiber grating positioning device for femtosecond laser inscription is also provided, characterized in that it is applied to position the grating area when the optical fiber needs to be installed at a set position, so as to facilitate the accurate installation of the grating area, thereby improving the installation accuracy of the grating area;

[0021] or,

[0022] It is used to position the grating area when femtosecond laser writes optical fiber, so as to write and mark the grating area, thereby improving the writing and marking accuracy of the grating area.

[0023] Preferably, it is applied to position the grating area when the femtosecond laser is writing the optical fiber, so as to write and mark the grating area, thereby improving the writing accuracy of the grating area, as follows:

[0024] The laser light source is connected to one end of the optical fiber on the fiber-releasing device where the grating area is not written through the optical fiber rotary connector and emits a detection light. The optical fiber released by the fiber-releasing device is written with a grating area by the femtosecond laser, and the grating area that has been written and is adjacent to the femtosecond laser undergoes Mie scattering, and after the scattered light leaked laterally from the cladding is identified, the marking device marks the portion of the outer surface of the optical fiber corresponding to the luminous grating area being photographed by the industrial camera, and the optical fiber that has been written with a grating area and marked is wound on the fiber-receiving device;

[0025] In addition, when the industrial camera recognizes that the grid area adjacent to the femtosecond laser has reached the set position and has been written, the controller controls the femtosecond laser to write on the fiber core so that the positioning accuracy of each grid area meets the set requirements.

[0026] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0027] 1) The fiber grating positioning method for femtosecond laser writing of the present invention injects detection light into one end of the optical fiber, utilizes the Mie scattering effect generated by the grating area, and allows the scattered light to leak out and be identified, thereby achieving high-precision positioning and marking of the grating area.

[0028] 2) The fiber Bragg grating positioning method for femtosecond laser inscription of the present invention uses an industrial camera to identify the position of the visible luminous area, that is, the luminous grating area, and then can perform high-precision mark position adjustment and high-precision inscription.

[0029] 3) The fiber Bragg grating positioning method for femtosecond laser writing of the present invention can be applied to fiber writing and installation. The higher the density of the fiber Bragg grating array, the greater the perception ability of the fiber Bragg grating sensor composed of the fiber Bragg grating array to the outside world. The positioning accuracy of the grating area writing of the present invention is very high, and the positioning accuracy can reach ≤±1mm level, which is particularly suitable for applications requiring high density of fiber Bragg grating arrays.

[0030] 4) The fiber grating positioning device for femtosecond laser inscription of the present invention emits detection light through a laser light source, and its wavelength range falls within the visible light wavelength range, so that the position of the grating area can be quickly and conveniently identified.

[0031] 5) The application of the fiber Bragg grating positioning device for femtosecond laser writing of the present invention can accurately install, manufacture and mark the grating area by positioning the grating area. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the principle of the positioning method of fiber Bragg grating written by femtosecond laser.

[0033] Figure 2 It is a schematic diagram of a conventional device for online preparation of a fiber grating array;

[0034] Figure 3 It is a schematic diagram of the partial composition structure of the production line for online writing and marking grid areas of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0036] Reference Figure 1 The fiber grating positioning method for femtosecond laser inscription provided by the present invention utilizes the Mie scattering phenomenon to allow scattered light to be identified after leaking from the side of the optical fiber.

[0037] When a light beam passes through a medium with uneven optical properties, the phenomenon that the light propagates in all directions is called scattering. There are many types of light scattering, such as Rayleigh scattering and Mie scattering. Rayleigh scattering occurs when the size of the particles encountered on the propagation path of light is much smaller than the wavelength. The main feature of Rayleigh scattering is that the scattering intensity is inversely proportional to the fourth power of the wavelength. The shorter the wavelength, the greater the scattering intensity. Rayleigh scattering occurs when sunlight encounters air molecules in the atmosphere. The blue-violet light in visible light has the strongest scattering, so the sky is blue. When the size of the particles encountered on the propagation path of light is close to the wavelength, Mie scattering occurs. The scattering intensity of Mie scattering is inversely proportional to the square of the wavelength, and the scattering is stronger in the forward direction of the light than in the backward direction, and the directionality is more obvious. Therefore, when light propagation encounters nearly spherical particles whose size is close to the wavelength of light, Mie scattering occurs.

[0038] The present invention utilizes the principle of femtosecond laser writing. The writing points formed by the femtosecond laser are nearly spherical and can produce relatively obvious Mie scattering. The gate area formed by femtosecond laser writing can be identified by marking the position of scattered light emitted by Mie scattering.

[0039] More conveniently, the intensity of Mie scattering of the writing point formed by femtosecond laser is more obvious for the detection light in the visible light band. Using the laser in the visible light band as the detection light can be easily observed by naked eyes, which is especially convenient for the installation of fiber grating or fiber grating array.

[0040] According to one aspect of the present invention, a positioning method for a fiber grating written by a femtosecond laser is provided. For an optical fiber 2 written by a femtosecond laser, a detection light 12 is injected into one end of the optical fiber 2, and the detection light 12 is propagated in the fiber core and Mie scattered on the grating area 3 written by the femtosecond laser, and the scattered light 4 leaks laterally from the cladding of the optical fiber 2; the grating area 3 written by the femtosecond laser is positioned by identifying the position of the laterally leaked scattered light 4. The present invention preferably connects a laser light source 10 to one end of the optical fiber 2 and emits the detection light 12 into the optical fiber 2. The detection light 12 is preferably a monochromatic visible light with a wavelength close to the equivalent diameter size of the writing point 13 of the grating area 3.

[0041] Furthermore, the wavelength of the detection light 12 is between 577 nanometers and 760 nanometers, and the wavelength of the detection light 12 covers yellow light to red light. The reasons for the wavelength selection of the present invention are as follows: the closer the wavelength of visible light is to red light, the longer the wavelength is, the higher the scattering intensity is, and the number of illuminated grid areas 3 will be reduced; the closer to purple light, the smaller the wavelength is, the Mie scattering tends to geometric scattering, the forward effect is not obvious, and the number of illuminated grid areas 3 is also reduced; the wavelength of the detection light is more preferably close to the yellow light band, the forward effect is good, the number of grid areas 3 that produce Mie scattering is also relatively large, and the number of identified grid areas 3 can also be more.

[0042] Further, it is used to locate one or more gate regions 3 close to one end where the detection light 12 is injected;

[0043] When positioning multiple gate regions 3 close to one end where the detection light 12 is injected, the number of the positioned gate regions 3 is more than 5. A relatively large number of positioned gate regions 3 is helpful to improve the recognition efficiency.

[0044] Reference Figure 1 The process of directly writing the gate area 3 by the femtosecond laser of the present invention is to focus the energy of the femtosecond laser on the 9μm fiber core, and form a large number of writing points 13 with an axial length of 1μm in the axial direction of the fiber core. A plurality of writing points 13 are written along the axis of the fiber core to form a gate area 3. Each writing point 13 is spherical, and the equivalent diameter of the writing point 13 is close to the wavelength of the detection light 12 emitted by the laser light source 10. The detection light 12 emitted by the laser light source 10 is preferably visible light. When the light 12 emitted by the laser light source 10 propagates along the fiber core, the detection light 12 encounters the writing point string of the gate area 3 and generates Mie scattering (the writing points 13 of the gate area 3 are spherical, similar to smaller scattering particles, and can generate stronger Mie scattering), and the scattered light 4 will leak out from the cladding of the optical fiber 2. If the detection light 12 is visible light, the scattered light 4 emitted by the gate area 3 can be made visible, and then the Mie scattering effect can be used to make the gate area 3 invisible to the naked eye visible.

[0045] Furthermore, the industrial camera 5 captures and identifies the position of the grating area 3 corresponding to the scattered light 4, thereby realizing the positioning of each grating area 3 on the optical fiber 2. The industrial camera 5 can detect and identify the luminous grating area 3, and perform positioning and measurement, such as measuring the size and position of the grating area 3.

[0046] Furthermore, the marking device 8 marks the portion of the outer surface of the optical fiber 2 corresponding to the luminous grid area 3 being photographed by the industrial camera 5 to form a marking portion 7. After marking, the industrial camera 5 can accurately identify whether the position and length of the marking portion 7 are consistent with the length and position of the grid area 3 that generates scattered light. In particular, the high-resolution industrial camera 5 can accurately identify which luminous position is not marked. The marking device 8 cooperates with the industrial camera 5 to keep the marking portion 7 consistent with the position of the grid area 3, avoiding that some writing points 13 on the grid area 3 are not covered by the mark. Therefore, the industrial camera 5 shoots the luminous grid area 3 that needs to be marked, so that it can identify whether the marking is accurate and the accuracy of the marking. After recognition by the industrial camera, the positioning accuracy of the marked grid area 3 is ≤±1mm.

[0047] Furthermore, the marking device 8 marks the outer surface of the optical fiber 2 by spraying a coating, for example, by inkjet or paint spraying, to form a marking portion 7 on the outer surface of the optical fiber 2 .

[0048] Furthermore, an industrial camera 14 is arranged at a position corresponding to the femtosecond laser 9 so that the femtosecond laser 9 is aligned with the core of the optical fiber 2. Since the accuracy of an industrial camera or an industrial camera when shooting a large field of view may not meet the requirements, the requirements of the present invention for high-precision writing and marking of the grid area cannot be met. Therefore, an industrial camera 5 and an industrial camera 14 are arranged at positions corresponding to the marking device 8 and the femtosecond laser 9, respectively, to meet the requirements of high-precision marking and writing.

[0049] According to another aspect of the present invention, a fiber grating positioning device for femtosecond laser inscription is also provided, comprising a laser light source 10, the laser light source 10 is optically coupled to the pigtail of the optical fiber 2 having the grating area 3 inscribed by the femtosecond laser, the laser light source 10 is a monochromatic laser, and is used to emit a detection light, and its wavelength range falls within the visible light wavelength range. The laser light source 10 is preferably a wavelength-tunable laser light source, and its power is between 10 milliwatts and 30 milliwatts, so that the wavelength of the detection light can be adjusted within a large range, so that it is convenient to adjust the wavelength to cause Mie scattering on the grating area 3 to position the grating area 3.

[0050] Furthermore, the laser light source 10 is connected to one end of the optical fiber 2 through the optical fiber rotary connector 11 to adapt to the rotation of the optical fiber 2. When the optical fiber 2 is to be rotated, the optical fiber rotary connector 11 is required to ensure that the transmission of the optical signal is not interrupted due to the rotation of the optical fiber 2.

[0051] Furthermore, it is applied to position the grid area 3 when the optical fiber 2 needs to be installed at a set position, so as to facilitate accurate installation of the grid area 3, thereby improving the installation accuracy of the grid area 3;

[0052] or,

[0053] It is used to position the grating area 3 when the femtosecond laser is writing the optical fiber 2, so as to write and mark the grating area 3, thereby improving the writing and marking accuracy of the grating area 3.

[0054] The positioning method of the present invention can be applied to improving the writing accuracy of a fiber grating array.

[0055] Conventional online fiber grating array equipment such as Figure 2As shown, on the left is a fiber-releasing device 1' that intermittently rotates clockwise to release the fiber, on the right is a fiber-collecting device 6' that collects the fiber, in the middle is a femtosecond laser 9' that writes the grating area, the femtosecond laser 9' uses a point-by-point method to write a grating area 3' on the optical fiber 2', the length of each grating area is <10mm, after completing the writing of a grating area 3', the fiber-releasing device 1' and the fiber-collecting device 6' cooperate to move the optical fiber, and move the grating area 3' to the corresponding position of the marking device 8' of the marking station, because the rotation accuracy of the fiber-collecting device 6' and the fiber-releasing device 1' is limited, the positioning accuracy of the grating area 3' is about ±5mm or worse; in addition, the grating area 3' on the core of the optical fiber 2' is transparent and invisible, and it is very difficult to achieve accurate preparation, positioning and marking of the grating area 3' at the level of ±1mm or higher on an optical fiber 2' on the equipment for online preparation of fiber grating arrays, Figure 2 For the marking area 7' on the outer surface of the optical fiber 2' corresponding to the position of the grid area 3', a general marking method is to use a marking device 8' to spray ink on the outer surface of the optical fiber 2'. However, since the rotation accuracy of the fiber collecting device 6' and the fiber releasing device 1' is not high, the mark of the inkjet mark may be misaligned with the actual grid area 3', and there may be a misalignment or error of the order of ±5mm or worse.

[0056] Reference Figure 3 , the partial composition structure of the production line for online writing and marking the grating area of ​​the present invention (the complete production line is not shown), the production line for online preparation of fiber grating arrays provided by the present invention comprises a laser light source 10, a fiber rotary connector 11, a fiber release device 1, a fiber collection device 6, a femtosecond laser 9, an industrial camera 5 and a marking device 8, the fiber release device 1 is used to release the optical fiber 2 without writing the grating area 3, the laser light source 10 is connected to one end of the optical fiber 2 on the fiber release device 1 through the fiber rotary connector 11 and emits a detection light 12 into the optical fiber 2, The grid area 3 on the core of the optical fiber 2 is caused to undergo Mie scattering and emit scattered light 4. The femtosecond laser 9 is used to write the grid area 3 on the core of the optical fiber 2 released by the fiber release device 1. The industrial camera 5 is used to capture the scattered light 4 emitted by the grid area 3 that has been written and is adjacent to the femtosecond laser 9, so as to obtain the position of the grid area 3. The marking device 8 is used to mark the part of the outer surface of the optical fiber 2 corresponding to the luminous grid area 3 being photographed by the industrial camera 5. The fiber collection device 6 is used to collect the optical fiber 2 with the grid area 3 written and marked. The fiber collection disk of the fiber collection device 6 is driven to rotate by a power mechanism, is an active component, and rotates intermittently, so that the femtosecond laser 9 can write and mark on the optical fiber 2.

[0057] In addition, when the industrial camera 5 captures the grid area 3 that has been written and is adjacent to the femtosecond laser 9 and reaches the set position, the femtosecond laser 9 writes on the core of the optical fiber 2 so that the positioning accuracy of each grid area 3 meets the set requirements, and the positioning accuracy of each grid area 3 can be guaranteed when writing the grid area 3 on the optical fiber 2. The position of each grid area 3 is controllable, and the positioning accuracy of each grid area 3 can be maintained at ±1mm or higher accuracy. Therefore, with the accurate recognition of the industrial camera 5, the time slot of the laser emitted by the femtosecond laser 9 is controlled by the controller, so that the accurate writing of the grid area 3 can be achieved, and the positioning accuracy of each grid area 3 can be guaranteed. Especially when the distribution density of the grid area 3 is very high, it is more important that each grid area 3 reaches the set positioning accuracy.

[0058] An optical fiber rotary connector 11 is arranged on the axis of the fiber-releasing disk of the fiber-releasing device 1. The optical fiber rotary connector 11 can connect the stationary laser light source 10 and the rotating optical fiber 2 together. The detection light 12 is introduced into the optical fiber 2 through the optical fiber rotary connector 11. When the detection light 12 reaches the grid area 3, due to the Mie scattering effect, the scattered light 4 leaks out from the grid area 3 through the cladding, so that the grid area 3 emits scattered light 4, and the grid area 3 can be identified. The industrial camera 5 is used to shoot and identify the luminous area and feed back to the controller. The machine vision automatic recognition technology is used to identify the precise position of the grid area 3. According to the feedback information of the industrial camera 5, the marking device 8 marks the specified position of the optical fiber 2 to form a marking part 7, so as to achieve precise positioning and marking of the grid area 3.

[0059] The positioning method of the present invention can be applied to positioning the grid area 3 when the optical fiber 2 needs to be installed at the set position. The luminous grid area 3 can be observed by the naked eye, so as to facilitate the accurate installation of the grid area 3, thereby improving the installation accuracy of the grid area 3. Due to the conventional marking method, the positioning error of the grid area 3 of the optical fiber 2 after marking is a bit large. Therefore, if more accurate installation and alignment are to be achieved, the positioning method of the present invention needs to be adopted, and the laser light source 10 is used to make the grid area 3 illuminate to achieve accurate positioning during installation. The position of the grid area 3 can be identified by the naked eye during installation. In addition, the positioning method of the present invention can also be used for quality inspection of the optical fiber 2 on which all the grid areas 3 have been written, the number of grid areas 3, etc.

[0060] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A positioning method for fiber Bragg gratings written by femtosecond laser, characterized in that: For an optical fiber written by a femtosecond laser, a probe light is injected into one end of the optical fiber, the probe light is propagated in the fiber core and Mie scattered on the grating region written by the femtosecond laser, and the scattered light leaks laterally from the optical fiber cladding; The positioning of the gate area written by the femtosecond laser is achieved by identifying the position of the scattered light leaked laterally.

2. The positioning method of fiber Bragg grating written by femtosecond laser according to claim 1, characterized in that: The position of scattered light is captured and identified by an industrial camera.

3. The positioning method of fiber Bragg grating written by femtosecond laser according to claim 1, characterized in that: The writing points of the gate area written by the femtosecond laser are nearly spherical, and the equivalent diameter of the nearly spherical writing points is between 550 nanometers and 800 nanometers.

4. The positioning method of fiber Bragg grating written by femtosecond laser according to claim 1, characterized in that: The wavelength of the detection light is between 577 nanometers and 760 nanometers.

5. The positioning method of fiber Bragg grating written by femtosecond laser according to claim 1, characterized in that: One or more gate regions for positioning near an end where the probe light is injected; When a plurality of gate regions are positioned close to one end where the detection light is injected, the number of the positioned gate regions is 5 or more.

6. A fiber Bragg grating positioning device for femtosecond laser inscription, characterized in that: including a laser light source; The laser light source is optically coupled to a pigtail of an optical fiber having a grating region inscribed by a femtosecond laser; The laser light source is a monochromatic laser, which is used to emit detection light, and its wavelength range falls within the visible light wavelength range.

7. The fiber Bragg grating positioning device for femtosecond laser writing as claimed in claim 6, characterized in that: The laser light source is a wavelength-adjustable laser light source, and its power is between 10 milliwatts and 30 milliwatts.

8. The fiber Bragg grating positioning device for femtosecond laser inscription according to claim 6, characterized in that: An industrial camera is also included, which is used to image the grid area that emits scattered light.

9. Application of the fiber Bragg grating positioning device for femtosecond laser writing according to any one of claims 1 to 8, characterized in that: It is used to locate the grid area when the optical fiber needs to be installed at the set position, so as to facilitate the accurate installation of the grid area, thereby improving the accuracy of grid area installation; or, It is used to position the grating area when femtosecond laser writes optical fiber, so as to write and mark the grating area, thereby improving the writing and marking accuracy of the grating area.

10. The use according to claim 9, characterized in that: It is used to position the grating area when femtosecond laser writes optical fiber, so as to write and mark the grating area, thereby improving the writing accuracy of the grating area, as follows: The laser light source is connected to one end of the optical fiber on the fiber-releasing device where the grating area is not written through the optical fiber rotary connector and emits a detection light. The optical fiber released by the fiber-releasing device is written with a grating area by the femtosecond laser, and the grating area that has been written and is adjacent to the femtosecond laser undergoes Mie scattering, and after the scattered light leaked laterally from the cladding is identified, the marking device marks the portion of the outer surface of the optical fiber corresponding to the luminous grating area being photographed by the industrial camera, and the optical fiber that has been written with a grating area and marked is wound on the fiber-receiving device; In addition, when the industrial camera recognizes that the grid area adjacent to the femtosecond laser has reached the set position and has been written, the controller controls the femtosecond laser to write on the fiber core so that the positioning accuracy of each grid area meets the set requirements.

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