CN111175872B - Preparation method and device of long-period fiber grating with graphene coating - Google Patents

Abstract

A preparation method and device for a long-period fiber grating with a graphene coating, comprising the following steps: fixing a polyimide fiber on an optical fiber holder; setting motion parameters of the polyimide fiber and setting an ultraviolet laser Working path and moving speed; setting the first processing parameters of the ultraviolet laser; positioning the laser focus of the ultraviolet laser on the axis of the polyimide fiber; the laser emitted by the ultraviolet laser processes the core of the polyimide fiber; The second processing parameter of the ultraviolet laser is set; the laser focus is moved upward to above the upper surface of the polyimide fiber; the laser light emitted by the ultraviolet laser is dispersed to process the polyimide coating of the polyimide fiber. A preparation device for a long-period fiber grating with a graphene coating includes an ultraviolet laser, and the ultraviolet laser processes the same polyimide fiber step by step, thereby reducing the delicate and complicated operation of transferring graphene to a quartz fiber.

Description

A kind of preparation method and device of long-period fiber grating with graphene coating

technical field

The invention relates to the technical field of optical fiber communication and sensing, in particular to a preparation method and device of a long-period optical fiber grating with a graphene coating.

Background technique

Fiber Bragg grating is the most representative and promising optical fiber passive device, and it is the most widely used in the field of optical communication and optical sensing. In recent years, long-period fiber grating (LPFG), as a transmissive band-stop filter with a period generally greater than 100 μm, has the advantages of wide bandwidth, no retroreflection, sensitivity to external changes, low cost, and simple fabrication. extensive research in academia and industry. The characteristic of LPFG is that the energy of the core fundamental mode that meets the phase matching conditions is coupled into the high-order cladding mode transmitted in the same direction, and quickly leaks out of the cladding to interact with the external environment, thereby realizing sensing detection. The transmission spectrum appears as a loss peak at the corresponding resonant wavelength.

As a two-dimensional single-atom-layer nanomaterial, graphene has received more and more attention and research on its unique properties in the electrical and optical fields. Sensors produced by processing and transforming graphene are used as basic materials. , modulators and other new devices have been reported by various top journals and magazines. Due to the advantages of graphene's soft structure and ultra-thinness, the combination of graphite and other types of optical fiber devices, optical fiber microwave guides and other structures to make sensors by coating or cladding methods has also attracted much attention from researchers from all walks of life. Different characteristics are used in sensing areas with different needs. Since the diameter of the fiber is 125 microns, and the graphene flakes are generally nano-scale, the transfer of graphene to the surface of the fiber requires very delicate and tedious operations.

In the existing preparation methods, long-period fiber gratings are basically prepared on bare silica fibers by means of ultraviolet laser processing or arc discharge, and the graphene coating needs additional transfer coating. Similarly, the existing method can only prepare a graphene thin layer on a polyimide film by means of ultraviolet laser processing or infrared laser processing alone, but cannot prepare a long-period fiber grating at the same time. This greatly increases the difficulty of fabricating graphene-coated fiber gratings, and makes it impossible to achieve large-scale manufacturing and commercial applications.

In the existing literature, the article "Characteristics of long-period fiber grating sensors written by high-frequency CO ₂ laser pulses" in the journal "Acta Physica Sinica", Vol. 52, No. 6, June 2003, proposed a high-frequency CO ₂ laser Novel long-period fiber grating (LPFG) method for pulse writing. High-frequency CO ₂ laser pulses can write high-quality LPFG in ordinary single-mode fibers, with good thermal stability, no annealing treatment, and low cost. In addition, the scanning period of the CO ₂ laser can be arbitrarily changed to write different transmissions. Features LPFG. However, this method can only scan the fiber radially, and cannot process the upper and lower parts of the fiber, and the shape and pattern of the grating are relatively simple, which may not satisfy the preparation of gratings with special patterns, such as helical gratings, and laser writing LPFG. It has the disadvantage of excessive insertion loss.

The article "Femtosecond Laser Direct Writing Long Period Fiber Grating and Its Spectral Characteristics" in "Acta Photonica Sinica", Vol. 47, No. 11, November 2018, designed and built a long-period fiber grating preparation system, using 800nm femtosecond laser pulse point by point Etching long-period fiber gratings, improving the accuracy and efficiency of laser and fiber alignment, and improving the grating writing efficiency and spectral characteristics. However, when using this method to make a grating, the grating coating needs to be removed, and the use of point-by-point etching requires higher positioning accuracy, and the etching pattern is relatively simple.

Chinese patent CN201710444901.3 Graphene complex refractive index measurement method based on long-period fiber spectrum, in this patent, graphene sheets are first made and then transferred to long-period fiber gratings. This method is complicated to operate and has a low success rate. The graphene quality is easily affected during the transfer process. Due to the diverse requirements for the shape of the grating, the complexity of the graphene preparation process and the operational requirements for graphene transfer, a new technology is urgently needed to simplify the preparation process and improve the quality of graphene-coated long-period fiber gratings.

SUMMARY OF THE INVENTION

In view of the above-mentioned defects, the purpose of the present invention is to propose a preparation method and device of a long-period fiber grating with a graphene coating, to solve the tediousness of graphene preparation and the fine operation requirements of graphene coating on the surface of the optical fiber, and to optimize the processing process, improve processing efficiency, and improve the performance of fiber grating, which is conducive to its commercial large-scale manufacturing.

For this purpose, the present invention adopts the following technical solutions: a preparation method of a long-period fiber grating with graphene coating, comprising the following steps:

Step 1: fix the polyimide optical fiber on the optical fiber holder, and adjust the optical fiber holder so that the laser light emitted by the ultraviolet laser is directed to the polyimide optical fiber vertically;

Step 2: according to the shape and period of the target grating, set the motion parameters of the polyimide fiber and set the working path and moving speed of the ultraviolet laser;

Step 3: Set the first processing parameters of the ultraviolet laser, the first processing parameters include the first laser energy P1 of the laser emitted by the ultraviolet laser and the first cycle number K1 of the ultraviolet laser to cycle the working path ;

Step 4: positioning the laser focus of the ultraviolet laser on the axis of the polyimide fiber;

Step 5: The polyimide fiber moves according to the motion parameters, the ultraviolet laser operates according to the working path, the moving speed and the first processing parameter, and the laser emitted by the ultraviolet laser The core of the polyimide optical fiber is processed, and a refractive index modulation point is formed inside the polyimide optical fiber to make a long-period fiber grating;

Step 6: Set the second processing parameter of the ultraviolet laser, the second processing parameter includes the second laser energy P2 of the laser emitted by the ultraviolet laser and the second cycle number K2 of the ultraviolet laser to cycle the working path ;

Step 7: set the defocus amount Z2, move the laser focus according to the defocus amount Z2, so that the laser focus is moved upward to the upper surface of the polyimide fiber;

Step 8: The polyimide fiber moves according to the motion parameters, and the ultraviolet laser operates according to the working path, the moving speed, and the second processing parameter, so that the laser light emitted by the ultraviolet laser is dispersed. processing the polyimide coating of the polyimide optical fiber to form a graphene coating corresponding to the position of the grating;

Step 9: perform performance testing on the polyimide optical fiber.

Wherein: in the step 4, the process of positioning the laser focus of the ultraviolet laser on the axis of the polyimide fiber is:

positioning the laser focus on the upper surface of the polyimide fiber;

The radius value of the polyimide fiber is set as the downward movement amount Z1 of the laser focus, and the laser focus is moved downward according to the downward movement amount Z1 to make the laser focus move away from the polyimide The upper surface of the optical fiber moves down to the core axis of the polyimide optical fiber.

Wherein: in the second step, setting the working path of the ultraviolet laser includes the following steps:

Drawing the engraving path of the ultraviolet laser engraving the target grating;

According to the engraving path, draw the movement path of the ultraviolet laser to complete all the engraving paths;

Import the drawn engraving path and the motion path into the CNC laser processing system.

Wherein: when the target grating is an annular grating, the engraving path of a single period is a straight line running through the polyimide fiber, and the engraving path of a single period is perpendicular to the polyimide fiber the axis, the start and end of the engraved path of a single cycle are both arranged outside the polyimide fiber.

Wherein: when the target grating is a threaded grating, the engraving path of a single period is a straight line, and the engraving path of a single period is coincident with the axis of the polyimide fiber, wherein all the engraving paths of a single period are straight lines. The length of the engraving path is L, the moving speed of the ultraviolet laser is V, and the rotation speed of the polyimide fiber is w, and the relationship between the three satisfies 2πV=Lw.

A preparation device of a long-period fiber grating with a graphene coating, comprising a numerically controlled laser processing machine tool, which is applied to the preparation device of the above-mentioned preparation method of a long-period fiber grating with a graphene coating;

The numerical control laser processing machine tool is provided with a numerical control moving arm, an ultraviolet laser, an optical fiber fixed seat and a displacement platform, the ultraviolet laser is installed on the numerical control moving arm, the optical fiber fixed seat is arranged on the displacement platform, and the ultraviolet laser It is arranged above the optical fiber holder, and the laser light of the ultraviolet laser shoots vertically downward toward the optical fiber holder. The optical fiber holder is provided with an optical fiber rotation mechanism, and the polyimide optical fiber passes through the optical fiber. The rotation mechanism is rotatably mounted on the optical fiber holder so as to be rotatable around the axis.

Wherein: the optical fiber holder includes a base, a first installation side wall and a second installation side wall, the base is fixedly arranged on the displacement platform, and the first installation side wall and the second installation side wall are opposite to each other are arranged on both sides of the base, one end of the polyimide optical fiber is arranged on the first installation side wall, and the other end of the polyimide optical fiber is arranged on the second installation side wall;

The optical fiber rotation mechanism includes an optical fiber clamp and a motor, the optical fiber clamp is rotatably arranged on the first installation side wall, and the motor is used to drive the optical fiber clamp to rotate;

The second installation side wall is provided with a through hole for the polyimide optical fiber to pass through, the through hole is in clearance fit with the polyimide optical fiber, and the optical fiber clamp is used for clamping the polyimide optical fiber. One end of the imide fiber is the free end, and the other end of the polyimide fiber is the free end.

Wherein: the optical fiber holder is further provided with a coating stripping mechanism, and the coating stripping mechanism is arranged on the inner wall surface of the second installation side wall;

The coating stripping mechanism includes a first tool holder, a second tool holder and a blade, the first tool holder and the second tool holder are oppositely arranged on the inner wall surface of the second installation side wall, the The first tool holder is fixedly arranged on the second installation side wall, and the second tool holder is movably connected with the first tool holder;

Both the first tool rest and the second tool rest are provided with semi-circular knife grooves, the blades are in a semi-circular ring shape, the two blades are respectively arranged in the two semi-circular knife grooves, and a space is formed between the two blades. A clamping cavity, when the second blade holder and the first blade holder are closed, the clamping cavity and the polyimide optical fiber are in an interference fit.

Wherein: a tightening mechanism is provided between the first tool rest and the second tool rest, the tightening mechanism includes a connecting stud, a tightening nut and a return spring, and the two connecting studs are respectively fixed on the Both ends of the first tool rest, the second tool rest is sleeved on the connecting stud, the return spring is arranged between the second tool rest and the first tool rest, the A tightening nut is threadedly matched with the connecting stud, and the tightening nut is used to press the second tool rest toward the first tool rest.

Wherein: the optical fiber holder is further provided with a cutting mechanism, the cutting mechanism is arranged on the outer wall surface of the second installation side wall, the cutting mechanism comprises a sliding rail, a sliding block and a cutter, and the sliding rail is arranged on the outer wall surface of the second installation side wall. In the second installation side wall, the sliding block is slidably embedded in the sliding rail, and the cutting knife is fixedly arranged on the outer end surface of the sliding block.

The invention discloses a preparation method and device for a long-period fiber grating with a graphene coating. The ultraviolet laser first locates the laser focus on the axis of the polyimide fiber, and the ultraviolet laser is based on The set first processing parameters, the working path and the moving speed are used to process the core of the polyimide optical fiber, so that the laser first passes through the coating to process the fiber of the polyimide optical fiber. The core of the polyimide fiber will form a color center and other structures where the core is irradiated by the laser, and at the same time, because the core of the polyimide fiber is expanded by the laser irradiation, the cladding will be squeezed and densified. , so that the refractive index of the cladding of the polyimide fiber is changed; then the laser focus of the ultraviolet laser is adjusted so that the laser focus is defocused from the surface of the polyimide fiber. The polyimide coating of the polyimide optical fiber is processed with the predetermined second processing parameters, the working path and the moving speed. After the polyimide coating is irradiated by the laser, due to the Photothermal action and photochemical action change the chemical structure of polyimide to form a photo-induced graphene coating, thereby making a graphene-coated long-period fiber grating.

The same polyimide fiber is processed by the ultraviolet laser step by step, thereby reducing the fine and complicated operation of transferring the graphene coating to the silica fiber, simplifying the production process of the fiber grating with the graphene coating, which is beneficial to commercial production;

During the laser processing, the motion parameters of the polyimide fiber, the working path and the moving speed of the UV laser remain unchanged, so the formation position of the graphene coating corresponds to the formation position of the grating, so as to avoid the dislocation of the two. , thereby improving the sensing performance of the optical fiber;

By changing any one of the motion parameters of the polyimide fiber, the working path and the moving speed of the ultraviolet laser, different shapes of gratings and graphene coatings can be processed on the polyimide fiber, To meet the needs of different industries.

Description of drawings

1 is a schematic diagram of the installation of a polyimide optical fiber in an embodiment of the present invention, wherein A is the laser focus positioned on the upper surface of the polyimide optical fiber, and B is the laser focus positioned on the axis of the polyimide optical fiber;

Fig. 2 is the installation schematic diagram that polyimide optical fiber can rotate around the axis in one embodiment of the present invention;

3 is a schematic structural diagram of a coating stripping mechanism in an embodiment of the present invention;

4 is a schematic structural diagram of a cutting mechanism in an embodiment of the present invention;

Fig. 5 is the schematic diagram of drawing the engraving path in one embodiment of the present invention;

6 is a schematic diagram of drawing a motion path in an embodiment of the present invention;

7 is a schematic structural diagram of a long-period fiber grating with a graphene coating of an annular grating in an embodiment of the present invention, wherein T is the grating period;

FIG. 8 is a schematic diagram of drawing a motion path in an embodiment of the present invention.

Among them: 1. Polyimide fiber; 2. CNC machining machine; 21. CNC moving arm; 22. Ultraviolet laser; 23. Optical fiber holder; 231. Base; Side wall; 2331, through hole; 24, displacement platform; 25, optical fiber rotating mechanism; 251, optical fiber clamp; 252, motor; 253, rotating chassis; 254, driven gear teeth; 255, driving gear; 26, coating stripping Mechanism; 261, the first tool holder; 262, the second tool holder; 263, the blade; 264, the semi-circular knife groove; 265, the clamping cavity; 2661, the connecting stud; 2662, the tightening nut; 2663, the return spring; 27, Cutting mechanism; 271, slide rail; 272, slider; 273, cutter; 3, engraving path; 4, motion path; 5, graphene coating; 6, refractive index change area; 7, quartz fiber; 8, Polyimide coating.

Detailed ways

The technical solutions of the present invention are further described below with reference to the accompanying drawings and through specific embodiments.

As shown in Figure 1 to Figure 8, a preparation method of a long period fiber grating with a graphene coating, comprising the following steps:

Step 1: Fix the polyimide optical fiber 1 on the optical fiber holder 23, and adjust the optical fiber holder 23 so that the laser light emitted by the ultraviolet laser 22 is directed to the polyimide optical fiber 1 vertically; The polyimide optical fiber 1 is a quartz optical fiber 7 with a polyimide coating 8, and the light source of the ultraviolet laser 22 can be any one of a femtosecond ultraviolet laser, a picosecond ultraviolet laser and an excimer ultraviolet laser. The method for engraving the optical fiber by the ultraviolet laser 22 includes galvanometer scanning and laser direct writing.

Step 2: According to the shape and period of the target grating, set the motion parameters of the polyimide fiber 1 and set the working path and moving speed of the ultraviolet laser 22; The motion parameters include the angular velocity w of the polyimide fiber 1 rotating around the axis and the motion parameters of the fiber holder 23 moving in the X-axis or the Y-axis, and the like.

Step 3: Set the first processing parameters of the ultraviolet laser 22, the first processing parameters include the first laser energy P1 of the laser emitted by the ultraviolet laser 22 and the first laser energy P1 of the ultraviolet laser 22 to cycle the working path. The number of cycles K1; specifically, the first laser energy P1 is 50-500 nJ, and the first number of cycles K1 is 6 times.

Step 4: positioning the laser focus of the ultraviolet laser 22 on the axis of the polyimide fiber 1;

Step 5: The polyimide fiber 1 moves according to the motion parameters, the ultraviolet laser 22 operates according to the working path, the moving speed and the first processing parameter, and the laser light emitted by the ultraviolet laser 22 The core of the polyimide fiber 1 is processed to form a refractive index modulation point inside the polyimide fiber 1 to make a long-period fiber grating; The core of the polyimide optical fiber 1 is processed through the coating, and structures such as color centers will be formed where the core of the polyimide optical fiber 1 is irradiated by the laser. The core of 1 is thermally expanded to produce a compacting effect on the cladding, so that the refractive index of the cladding of the polyimide fiber 1 is changed, thereby making a long-period fiber grating.

Step 6: Set the second processing parameters of the ultraviolet laser 22, the second processing parameters include the second laser energy P2 emitted by the ultraviolet laser 22 and the second cycle of the ultraviolet laser 22 circulating the working path The number of times K2; specifically, the second laser energy P2 is 3-8 mJ, and the second cycle number K2 is 1 time.

Step 7: Set the defocus amount Z2, move the laser focus according to the defocus amount Z2, and move the laser focus upward to the upper surface of the polyimide fiber 1, so that the laser focus The distance from the upper surface of the polyimide optical fiber 1 is the defocus amount Z2; specifically, the defocus amount Z2 is 3 mm.

Step 8: The polyimide fiber 1 moves according to the motion parameters, and the ultraviolet laser 22 operates according to the working path, the moving speed and the second processing parameter, so that the ultraviolet laser 22 emits The polyimide coating 8 of the polyimide optical fiber 1 is processed by laser light emission to form the graphene coating 5 corresponding to the position of the grating. Wherein, after the polyimide coating 8 is irradiated by laser, due to photothermal action and photochemical action, the chemical structure of the polyimide is changed to form the photo-graphene coating 5 .

Step 9: Perform performance testing on the polyimide optical fiber 1 .

The working principle of the present invention: the ultraviolet laser 22 first locates the laser focus on the axis of the polyimide fiber 1, and the ultraviolet laser 22 works according to the set first processing parameters, the The path and the moving speed are used to process the core of the polyimide optical fiber 1, so that the laser first passes through the coating to process the core of the polyimide optical fiber 1. The place where the fiber core is irradiated by the laser will form structures such as color centers, and at the same time, because the core of the polyimide fiber 1 is expanded by the laser irradiation, the cladding will be squeezed and densified, so that the polyimide fiber 1 will be compressed. The refractive index of the cladding of the fiber 1 changes; then adjust the laser focus of the ultraviolet laser 22 to make the laser focus defocus from the surface of the polyimide fiber 1. The ultraviolet laser 22 is set according to the set Two processing parameters, the working path and the moving speed are used to process the polyimide coating 8. After the polyimide coating 8 is irradiated by the laser, due to the photothermal action and photochemical action, the polymer The chemical structure of the imide changes to form a photo-induced graphene coating 5 , thereby making a long-period fiber grating with the graphene coating 5 .

The same polyimide fiber 1 is processed in steps by the ultraviolet laser 22, thereby reducing the fine and complicated operation of transferring the graphene coating 5 to the silica fiber 7, and simplifying the processing of the fiber grating with the graphene coating. The production process is conducive to commercial production;

In the laser processing, the motion parameters of the polyimide fiber 1, the working path and the moving speed of the ultraviolet laser 22 are unchanged, so the formation position of the graphene coating 5 corresponds to the formation position of the grating, avoiding The two are dislocated, thereby improving the sensing performance of the optical fiber;

By changing any one of the motion parameters of the polyimide fiber 1, the working path and the moving speed of the ultraviolet laser 22, gratings and graphenes of different shapes can be processed on the polyimide fiber 1 Coating 5 to meet different industry needs.

Further, in the step 4, the process of positioning the laser focus of the ultraviolet laser 22 on the axis of the polyimide fiber 1 is as follows:

As shown in Figure 1, firstly, the laser focus is positioned on the upper surface of the polyimide fiber 1;

Then, the radius value of the polyimide fiber 1 is set as the downward movement amount Z1 of the laser focus, and the laser focus is moved downward according to the downward movement amount Z1, so that the laser focus The upper surface of the imide fiber 1 moves down to the core axis of the polyimide fiber 1 .

By first positioning the laser focus on the upper surface of the polyimide fiber 1, and then taking the radius value of the polyimide fiber 1 as the downward movement amount Z1 of the laser focus, the laser is moved downward. The focus of the laser is precisely moved down from the upper surface of the polyimide fiber 1 to the core axis of the polyimide fiber 1, thereby improving the preparation accuracy, reducing the defective product rate, and being beneficial to commercial production, and the operating principle is simple.

Further, in the second step, setting the working path of the ultraviolet laser 22 includes the following steps:

Drawing the engraving path 3 for engraving the target grating by the ultraviolet laser 22;

According to the engraving path 3, draw the movement path 4 of the ultraviolet laser 22 to complete all the engraving paths 4;

Import the drawn engraving path 3 and the motion path 4 into the CNC laser processing system.

Specifically, the working path includes an engraving path 3 and a moving path 4. The engraving path 3 refers to the path through which the ultraviolet laser 22 emits laser to engrave the grating, and the moving path 4 refers to the ultraviolet laser 22. full movement path. As shown in FIG. 5, the engraving path 3 is drawn according to the grating of the target shape and period, the ultraviolet laser 22 emits laser light when passing through the engraving path 3, and then the motion path 4 is determined, and one of the The ultraviolet laser 22 can quickly pass through all the moving paths of the engraving path 3, thereby increasing the processing and production speed and facilitating mass production.

Further, when the target grating is a ring-shaped grating, as shown in FIG. 5 , the engraving path 3 of a single period is a straight line running through the polyimide fiber 1, and the engraving path of a single period is a straight line. 3 is perpendicular to the axis of the polyimide optical fiber 1 , and the beginning and the end of the engraving path 3 of a single cycle are set outside the polyimide optical fiber 1 . Wherein, in order to ensure that the ultraviolet laser 22 can completely process the upper surface of the polyimide fiber 1 , the length of the engraving path 3 in a single cycle is longer than the diameter of the polyimide fiber 1 . long, so that the start and end of the engraving path 3 of a single cycle are set outside the polyimide fiber 1, so as to avoid the jump delay or switching delay of the ultraviolet laser 22 at the beginning and end of a single cycle. Sometimes the illumination time at the inflection point is prolonged, so as to ensure that the illumination time of the core of the polyimide optical fiber 1 is consistent, so that the refractive index of the cladding of the polyimide optical fiber 1 changes uniformly, and the performance of the optical fiber is improved. Reduce defective product rate.

When the target grating is a threaded grating, as shown in FIG. 8 , the engraving path 3 of a single period is a straight line, and the engraving path 3 of a single period and the axis of the polyimide fiber 1 Coincidence, wherein, the length of the engraving path 3 in a single cycle is L, the moving speed of the ultraviolet laser 22 is V, the rotation speed of the polyimide fiber 1 is w, and the relationship between the three satisfies 2πV=Lw. When the ultraviolet laser 22 is linearly engraved along the central axis of the polyimide optical fiber 1, the polyimide optical fiber 1 rotates around the central axis, thereby processing a thread-like grating.

A preparation device of a long-period fiber grating with a graphene coating, comprising a numerically controlled laser processing machine tool 2, which is applied to the preparation device of the above-mentioned preparation method of a long-period fiber grating with a graphene coating; the numerical control laser processing The machine tool 2 is provided with a numerically controlled moving arm 21, an ultraviolet laser 22, an optical fiber holder 23 and a displacement platform 24, the ultraviolet laser 22 is installed on the numerically controlled moving arm 21, and the optical fiber holder 23 is arranged on the displacement platform 24, The ultraviolet laser 22 is arranged above the optical fiber holder 23, and the laser light of the ultraviolet laser 22 is directed vertically downward toward the optical fiber holder 23. The optical fiber holder 23 is provided with an optical fiber rotation mechanism 25, so The polyimide optical fiber 1 is rotatably mounted on the optical fiber holder 23 through the optical fiber rotating mechanism 25 , so as to be rotatable around the axis.

Specifically, the numerically controlled laser processing machine tool 2 further includes a numerically controlled laser processing system, which controls the numerically controlled moving arm 21 to move along the moving path 4 , and the numerically controlled laser processing system controls the ultraviolet laser 22 The laser is emitted from the engraving path 3 , and the numerical control laser processing system can also control the movement of the displacement platform 24 .

As shown in FIG. 1 , the ultraviolet laser 22 is installed on the numerical control moving arm 21 , so that the ultraviolet laser 22 moves with the numerical control moving arm 21 . The optical fiber holder 23 is set on the displacement platform 24 , so that the optical fiber holder 23 moves with the displacement platform 24 . Both the ultraviolet laser 22 and the optical fiber holder 23 can move, and the two are dynamically matched to facilitate the processing of gratings and graphene coatings 5 of different shapes to meet the needs of different industries.

The polyimide optical fiber 1 is rotatably arranged on the optical fiber holding base 23 by providing the optical fiber rotating mechanism 25 on the optical fiber holding base 23 . During the processing, the optical fiber rotating mechanism 25 rotates the polyimide optical fiber 1, which is convenient to process the long-period fiber grating and the graphene coating 5 in the shape of a thread or a ring, and is convenient for manufacturing different shapes of gratings and The graphene coating 5 realizes the diversification of grating shapes to meet the needs of different industries and is conducive to commercial production.

Further, as shown in FIG. 2 , the optical fiber holder 23 includes a base 231 , a first installation side wall 232 and a second installation side wall 233 , the base 231 is fixedly arranged on the displacement platform 24 , and the first installation The side wall 232 and the second installation side wall 233 are oppositely arranged on both sides of the base 231, one end of the polyimide optical fiber 1 is arranged on the first installation side wall 232, and the polyimide fiber 1 is arranged on the first installation side wall 232. The other end of the amine optical fiber 1 is disposed on the second installation side wall 233; the optical fiber rotation mechanism 25 includes an optical fiber clamp 251 and a motor 252, and the optical fiber clamp 251 is rotatably disposed on the first installation side wall 232, The motor 252 is used to drive the optical fiber clamp 251 to rotate; the second installation side wall 233 is provided with a through hole 2331 for the polyimide optical fiber 1 to pass through, and the through hole 2331 is connected to the polyimide fiber 1. The imide fiber 1 is gap-fitted, the fiber clamp 251 is used to clamp one end of the polyimide fiber 1, and the other end of the polyimide fiber 1 is a free end.

One end of the polyimide optical fiber 1 penetrates into the optical fiber holder 23 from the through hole 2331 , and is clamped and fixed by the optical fiber clamp 251 . The first installation side wall 232 is provided with a rotating chassis 253, and the optical fiber clamp 251 is installed on the rotating chassis 253. The drive shaft of the motor 252 drives the rotating chassis 253 to rotate, so that the polyamide The imide fiber 1 realizes rotation.

Specifically, as shown in FIG. 2 , the rotating chassis 253 is provided with driven gear teeth 254 , the drive shaft of the motor 252 is provided with a driving gear 255 , and the driving gear 255 is meshed with the driven gear teeth 254 . The motor 252 rotates the driving gear 255 , and the driving gear 255 drives the rotating chassis 253 through the driven gear teeth 254 to rotate the fiber holder 251 , thereby rotating the polyimide fiber 1 . Further, the motor 252 is a servo motor, which is convenient to control the rotation speed and direction of the polyimide optical fiber 1 .

Further, the optical fiber holder 23 is further provided with a coating stripping mechanism 26, the coating stripping mechanism 26 is disposed on the inner wall surface of the second installation side wall 233, and the coating stripping mechanism 26 includes a first A tool holder 261 , a second tool holder 262 and a blade 263 are arranged oppositely on the inner wall surface of the second installation side wall 233 , and the first tool holder 261 and the second tool holder 262 The frame 261 is fixedly arranged on the second installation side wall 233 , and the second tool holder 262 is movably connected with the first tool holder 261 ; the first tool holder 261 and the second tool holder 262 are both provided with The semicircular knife groove 264, the blade 263 is in the shape of a semicircle, the two blades 263 are respectively arranged in the two semicircular knife grooves 264, and a clamping cavity 265 is formed between the two blades 263, when the second knife holder After 262 and the first blade holder 261 are closed, the clamping cavity 265 and the polyimide optical fiber 1 are in an interference fit.

As shown in FIG. 3 , the coating stripping mechanism 26 is divided into upper and lower parts, wherein the clamping cavity 265 communicates with the through hole 2331 . After the graphene-coated fiber grating is prepared, it needs to be detected. Therefore, the coating stripping mechanism 26 is used to strip off both ends of the graphene-coated fiber grating so as to be compatible with the optical fiber. Check device connection. The second blade holder 262 is moved toward the first blade holder 261, and the clamping cavity 265 is closed, so that the blade 263 is in close contact with the coating of the polyimide fiber 1, and the polyimide fiber 1 is closed. The imide fiber 1 is drawn out from the through hole 2331 , so that the blade 263 scrapes off the coating of the polyimide fiber 1 . In non-working conditions, the clamping cavity 265 is in clearance fit with the polyimide fiber 1 .

Further, as shown in FIG. 3 , a tightening mechanism 266 is provided between the first tool rest 261 and the second tool rest 262 , and the tightening mechanism 266 includes a connecting stud 2661 , a tightening nut 2662 and a reset A spring 2663, the two connecting studs 2661 are respectively fixed on both ends of the first tool holder 261, the second tool holder 262 is sleeved on the connecting stud 2661, and the return spring 2663 is arranged on the Between the second tool rest 262 and the first tool rest 261 , the tightening nut 2662 is threadedly engaged with the connecting stud 2661 , and the tightening nut 2662 is used to attach the second tool rest 262 Press toward the first tool holder 261 .

When the tightening nut 2662 is tightened, the second tool holder 262 moves toward the first tool holder 261 due to the movement of the tightening nut 2662, and the clamping cavity 265 is closed, thereby allowing the blade 263 is in close contact with the coating of the polyimide fiber 1, and the polyimide fiber 1 is pulled out from the through hole 2331, so that the blade 263 scrapes the polyimide fiber 1 coating; when the tightening nut 2662 is loosened, the second tool holder 262 is reset due to the action of the return spring 2663, so the clamping cavity 265 is opened, so that the blade 263 leaves the The coating of the polyimide fiber 1 is described.

Further, as shown in FIG. 4 , the optical fiber holder 23 is further provided with a cutting mechanism 27 , the cutting mechanism 27 is arranged on the outer wall surface of the second installation side wall 233 , and the cutting mechanism 27 includes a slide rail 271 , A sliding block 272 and a cutting knife 273, the sliding rail 271 is arranged in the second installation side wall 233, the body of the sliding block 272 is slidably embedded in the sliding rail 271, and the cutting knife 273 is fixed It is provided on the outer end surface of the slider 272 . The cutter 273 is disposed on the outer end face of the sliding block 272 , and the sliding block 272 slides in the sliding rail 271 , so that the cutter 273 can quickly translate, thereby cutting the optical fiber neatly. By improving the uniformity of the cut of the optical fiber, the polyimide optical fiber 1 can be spliced with the transmission optical fiber in the detection device during detection, thereby reducing the reprocessing process.

According to the above-mentioned preparation method and device of a graphene-coated long-period fiber grating, the completed embodiment is completed.

Embodiment 1: A long-period fiber grating with graphene coating, wherein the shape of the grating is annular, and the period of the grating is 420 μm.

Step S11 : preparing an optical fiber with a diameter of 150 μm coated with polyimide, wherein the coating thickness of the polyimide optical fiber 1 is 15 μm and the length is 20 cm. The polyimide optical fiber 1 is horizontally installed on the optical fiber holder 23 , and the optical fiber holder 23 is moved directly below the ultraviolet laser 22 by the displacement platform 24 . Wherein, as shown in FIG. 2 , one end of the polyimide optical fiber 1 is set on the optical fiber holder 251 , and the other end of the polyimide optical fiber 1 is a free end.

Step S12: setting the rotational speed w of the polyimide fiber 1 to 0 rad/s, and the fiber holder 23 not moving; setting the moving speed V of the ultraviolet laser 22 to 300 mm/s;

Set the working path of the ultraviolet laser 22; specifically, as shown in FIG. 5, first draw the engraving path 3 according to the target grating, and the engraving path 3 in a single period is to run through the polyimide fiber 1, the spacing between adjacent engraving paths 3 is 420 μm, the engraving path 3 in a single cycle is perpendicular to the axis of the polyimide fiber 1, and the engraving path 3 in a single cycle The beginning and end of the fiber optic cable are both arranged outside the polyimide fiber 1 . Then, the moving path 4 of the ultraviolet laser 22 is drawn. Specifically, the moving path 4 is a Z-shaped path as shown in FIG. 6 . Finally, the drawn engraving path 3 and motion path 4 are imported into the CNC laser processing system.

Step S13 : setting the first processing parameters of the ultraviolet laser 22 . Specifically, the first laser energy P1 is 300 nJ, and the first cycle number K1 is 8 times.

Step S14 : adjusting the position of the laser focus, and moving the laser focus to the axis of the polyimide fiber 1 . Specifically, firstly, the laser focus is positioned on the upper surface of the polyimide fiber 1; the radius value of the polyimide fiber 1 is set as the downward movement Z1 of the laser focus, namely Z1 is 75 μm, the laser focus is moved down by 75 μm, and the laser focus is moved down from the upper surface of the polyimide fiber 1 to the axis of the polyimide fiber 1 .

Step S15: the polyimide fiber 1 moves according to the motion parameters, the ultraviolet laser 22 operates according to the working path, the moving speed and the first processing parameter, and the laser light emitted by the ultraviolet laser 22 The core of the polyimide fiber 1 is processed to form a refractive index modulation point inside the polyimide fiber 1 to make a long-period fiber grating; The core of the polyimide optical fiber 1 is processed through the coating, and structures such as color centers will be formed where the core of the polyimide optical fiber 1 is irradiated by the laser. The core of 1 is thermally expanded to produce a compacting effect on the cladding, so that the refractive index of the cladding of the polyimide fiber 1 is changed, thereby making a long-period fiber grating.

Step S16 : setting the second processing parameters of the ultraviolet laser 22 . Specifically, the second laser energy P2 is 6 mJ, and the second cycle number K2 is 1 time.

Step S17: Set the defocus amount Z2, move the laser focus according to the defocus amount Z2, and move the laser focus upward to the upper surface of the polyimide fiber 1, so that the laser focus is defocused. The distance between the upper surfaces of the polyimide fiber 1 is 3 mm.

Step S18: The polyimide fiber 1 moves according to the motion parameters, the ultraviolet laser 22 operates according to the working path, the moving speed and the second processing parameter, so that the ultraviolet laser 22 emits The polyimide coating 8 is processed by laser light emission to form the graphene coating 5 corresponding to the position of the grating. Wherein, after the polyimide coating 8 is irradiated by laser, due to photothermal action and photochemical action, the chemical structure of the polyimide is changed to form the photo-graphene coating 5 .

Rotate the polyimide fiber 1 by 180°, and repeat the above steps S1-S18 once. Specifically, the optical fiber holder 251 is rotated by the motor 252 to rotate the polyimide optical fiber 1 by 180°, and laser processing is performed on the lower half of the polyimide optical fiber 1, as shown in FIG. 7 . Graphene-coated annular grating shown. The reference numeral 5 is the graphene coating, the reference numeral 6 is the refractive index change region of the cladding, the reference numeral 7 is the silica fiber, and the reference numeral 8 is the polyimide coating.

Step S19 : performing performance detection on the polyimide optical fiber 1 .

Embodiment 2: A long-period fiber grating with a graphene coating, wherein the grating is in the shape of a thread.

Step S21 : preparing an optical fiber with a diameter of 150 μm coated with polyimide, wherein the coating thickness of the polyimide optical fiber 1 is 15 μm and the length is 20 cm. The polyimide optical fiber 1 is horizontally installed on the optical fiber holder 23 , and the optical fiber holder 23 is moved directly below the ultraviolet laser 22 by the displacement platform 24 . Wherein, as shown in FIG. 2 , one end of the polyimide optical fiber 1 is set on the optical fiber holder 251 , and the other end of the polyimide optical fiber 1 is a free end.

Step S22: Setting the working path of the ultraviolet laser. First, draw the engraving path 3. Specifically, as shown in FIG. 8, the engraving path 3 is an intermittent straight line. The length L of the engraving path 3 in a single cycle is 5 mm. The manufacturing path 3 coincides with the axis of the polyimide fiber 1 . Then, the movement path 4 of the ultraviolet laser is drawn. Specifically, the movement path 4 is a continuous straight line. Finally, the drawn working path is imported into the CNC laser processing system.

Then set the rotation speed w of the polyimide fiber 1 to 250 rad/s, and the fiber holder 23 does not move; set the moving speed V of the ultraviolet laser 22 to 200 mm/s; The length L of the engraving path 3, the moving speed of the ultraviolet laser 22 is V, and the rotation speed of the polyimide fiber 1 is w, and the relationship between the three satisfies 2πV=Lw.

Step S23 : setting the first processing parameters of the ultraviolet laser 22 . Specifically, the first laser energy P1 is 300 nJ, and the first cycle number K1 is 8 times.

Step S24 : adjusting the position of the laser focus, and moving the laser focus to the axis of the polyimide fiber 1 . Specifically, firstly, the laser focus is positioned on the upper surface of the polyimide fiber 1; the radius value of the polyimide fiber 1 is set as the downward movement Z1 of the laser focus, namely Z1 is 75 μm, the laser focus is moved down by 75 μm, and the laser focus is moved down from the upper surface of the polyimide fiber 1 to the axis of the polyimide fiber 1 .

Step S25: The polyimide fiber 1 moves according to the motion parameters, the ultraviolet laser 22 operates according to the working path, the moving speed and the first processing parameter, and the laser light emitted by the ultraviolet laser 22 The core of the polyimide fiber 1 is processed to form a refractive index modulation point inside the polyimide fiber 1 to make a long-period fiber grating; The core of the polyimide optical fiber 1 is processed through the coating, and structures such as color centers will be formed where the core of the polyimide optical fiber 1 is irradiated by the laser. The core of 1 is thermally expanded to produce a compacting effect on the cladding, so that the refractive index of the cladding of the polyimide fiber 1 is changed, thereby making a long-period fiber grating.

Step S26 : setting the second processing parameters of the ultraviolet laser 22 . Specifically, the second laser energy P2 is 6 mJ, and the second cycle number K2 is 1 time.

Step S27: Set the defocus amount Z2, move the laser focus according to the defocus amount Z2, and move the laser focus upward to the upper surface of the polyimide fiber 1, so that the laser focus is defocused. The distance between the upper surfaces of the polyimide fiber 1 is 3 mm.

Step S28: The polyimide fiber 1 moves according to the motion parameters, and the ultraviolet laser 22 operates according to the working path, the moving speed and the second processing parameter, so that the ultraviolet laser 22 emits The polyimide coating 8 is processed by laser light emission to form the graphene coating 5 corresponding to the position of the grating. Wherein, after the polyimide coating 8 is irradiated by laser, due to photothermal action and photochemical action, the chemical structure of the polyimide is changed to form the photo-graphene coating 5 .

Step S29 : performing performance detection on the polyimide optical fiber 1 .

The technical principle of the present invention has been described above with reference to the specific embodiments. These descriptions are only for explaining the principle of the present invention, and should not be construed as limiting the protection scope of the present invention in any way. Based on the explanations herein, those skilled in the art can think of other specific embodiments of the present invention without creative efforts, and these methods will all fall within the protection scope of the present invention.

Claims (10)

1. A preparation method of a long-period fiber grating with a graphene coating is characterized by comprising the following steps:

the method comprises the following steps: fixing the polyimide optical fiber (1) on an optical fiber fixing seat (23), and adjusting the optical fiber fixing seat (23) to enable laser emitted by an ultraviolet laser (22) to vertically irradiate the polyimide optical fiber (1);

step two: setting the motion parameters of the polyimide optical fiber (1) and setting the working path and the moving speed of the ultraviolet laser (22) according to the shape and the period of a target grating;

step three: setting first processing parameters of the ultraviolet laser (22), the first processing parameters including a first laser energy P1 of the ultraviolet laser (22) emitting laser light and a first cycle number K1 of the ultraviolet laser (22) cycling the working path;

step four: positioning the laser focus of the ultraviolet laser (22) at the axis of the polyimide optical fiber (1);

step five: the polyimide optical fiber (1) moves according to the motion parameters, the ultraviolet laser (22) operates according to the working path, the moving speed and the first processing parameters, laser emitted by the ultraviolet laser (22) processes a fiber core of the polyimide optical fiber (1), and refractive index modulation points are formed in the polyimide optical fiber (1) to manufacture a long-period optical fiber grating;

step six: setting second processing parameters of the ultraviolet laser (22), the second processing parameters including a second laser energy P2 of the ultraviolet laser (22) emitting laser light and a second cycle number K2 of the ultraviolet laser (22) cycling the working path;

step seven: setting a defocus amount Z2, and moving the laser focus according to the defocus amount Z2 to move the laser focus upward above the upper surface of the polyimide optical fiber (1);

step eight: the polyimide optical fiber (1) moves according to the motion parameters, the ultraviolet laser (22) operates according to the working path, the moving speed and the second processing parameters, and laser emitted by the ultraviolet laser (22) is enabled to dispersedly process the polyimide coating (8) of the polyimide optical fiber (1) to form a graphene coating (5) corresponding to the grating position;

step nine: and carrying out performance detection on the polyimide optical fiber (1).

2. The method for preparing the long-period fiber grating with the graphene coating according to claim 1, wherein the method comprises the following steps: in the fourth step, the process of positioning the laser focus of the ultraviolet laser (22) at the axis of the polyimide optical fiber (1) is as follows:

positioning the laser focus on the upper surface of the polyimide optical fiber (1);

the radius value of the polyimide optical fiber (1) is set as the downward shift Z1 of the laser focus, and the laser focus is moved downward according to the downward shift Z1 so that the laser focus is moved downward from the upper surface of the polyimide optical fiber (1) to the core axis of the polyimide optical fiber (1).

3. The method for preparing the long-period fiber grating with the graphene coating according to claim 1, wherein the method comprises the following steps: in the second step, setting the working path of the ultraviolet laser (22) comprises the following steps,

drawing an engraving path (3) for engraving the target grating by the ultraviolet laser (22);

drawing a motion path (4) of the ultraviolet laser (22) for completing all the engraving paths (4) according to the engraving paths (3);

and guiding the drawn engraving path (3) and the drawn motion path (4) into a numerical control laser processing system.

4. The method for preparing the long-period fiber grating with the graphene coating according to claim 3, wherein the method comprises the following steps: when the target grating is a circular ring grating, the single-period engraving path (3) is a straight line penetrating through the polyimide optical fiber (1), the single-period engraving path (3) is perpendicular to the axis of the polyimide optical fiber (1), and the starting end and the terminal end of the single-period engraving path (3) are both arranged outside the polyimide optical fiber (1).

5. The method for preparing the long-period fiber grating with the graphene coating according to claim 3, wherein the method comprises the following steps: when the target grating is a thread grating, the single-period scribing path (3) is a straight line, the single-period scribing path (3) is overlapped with the axis of the polyimide optical fiber (1), wherein the length of the single-period scribing path (3) is L, the moving speed of the ultraviolet laser (22) is V, the rotating speed of the polyimide optical fiber (1) is w, and the relationship between the three satisfies 2 pi V Lw.

6. The utility model provides a take preparation facilities of long period fiber grating of graphite alkene coating, includes numerical control laser beam machining machine tool (2), its characterized in that: a manufacturing apparatus applied to the method for manufacturing a long-period fiber grating with a graphene coating according to any one of claims 1 to 5;

the numerical control laser processing machine tool (2) is provided with a numerical control moving arm (21), an ultraviolet laser (22), an optical fiber fixing seat (23) and a displacement platform (24), the ultraviolet laser (22) is installed on the numerical control moving arm (21), the optical fiber fixing seat (23) is arranged on the displacement platform (24), the ultraviolet laser (22) is arranged above the optical fiber fixing seat (23), laser of the ultraviolet laser (22) vertically and downwards irradiates towards the optical fiber fixing seat (23), the optical fiber fixing seat (23) is provided with an optical fiber rotating mechanism (25), and the polyimide optical fiber (1) can be rotatably installed on the optical fiber fixing seat (23) around the axial center through the optical fiber rotating mechanism (25).

7. The apparatus for preparing a long-period fiber grating with a graphene coating according to claim 6, wherein: the optical fiber fixing seat (23) comprises a base (231), a first mounting side wall (232) and a second mounting side wall (233), the base (231) is fixedly arranged on the displacement platform (24), the first mounting side wall (232) and the second mounting side wall (233) are oppositely arranged on two sides of the base (231), one end of the polyimide optical fiber (1) is arranged on the first mounting side wall (232), and the other end of the polyimide optical fiber (1) is arranged on the second mounting side wall (233);

the optical fiber rotating mechanism (25) comprises an optical fiber clamp (251) and a motor (252), wherein the optical fiber clamp (251) is rotatably arranged on the first mounting side wall (232), and the motor (252) is used for driving the optical fiber clamp (251) to rotate;

the second installation side wall (233) is provided with a through hole (2331) for the polyimide optical fiber (1) to pass through, the through hole (2331) is in clearance fit with the polyimide optical fiber (1), the optical fiber clamp (251) is used for clamping one end of the polyimide optical fiber (1), and the other end of the polyimide optical fiber (1) is a free end.

8. The apparatus for preparing a long-period fiber grating with a graphene coating according to claim 7, wherein: the optical fiber fixing seat (23) is also provided with a coating stripping mechanism (26), and the coating stripping mechanism (26) is arranged on the inner wall surface of the second mounting side wall (233);

the coating stripping mechanism (26) comprises a first tool rest (261), a second tool rest (262) and a blade (263), wherein the first tool rest (261) and the second tool rest (262) are oppositely arranged on the inner wall surface of the second installation side wall (233), the first tool rest (261) is fixedly arranged on the second installation side wall (233), and the second tool rest (262) is movably connected with the first tool rest (261);

the first tool rest (261) and the second tool rest (262) are respectively provided with a semicircular tool groove (264), the blades (263) are in a semicircular shape, the two blades (263) are respectively arranged in the two semicircular tool grooves (264), a clamping cavity (265) is formed between the two blades (263), and when the second tool rest (262) and the first tool rest (261) are closed, the clamping cavity (265) is in interference fit with the polyimide optical fiber (1).

9. The apparatus for preparing a long-period fiber grating with a graphene coating according to claim 8, wherein: first knife rest (261) with be equipped with between second knife rest (262) and screw mechanism (266), screw mechanism (266) including connecting stud (2661), nut (2662) and reset spring (2663) screw, two connecting stud (2661) is fixed the setting respectively in the both ends of first knife rest (261), second knife rest (262) cover is established on connecting stud (2661), reset spring (2663) set up second knife rest (262) with between first knife rest (261), screw nut (2662) with connecting stud (2661) screw-thread fit, screw nut (2662) are used for with second knife rest (262) press to first knife rest (261).

10. The apparatus for preparing a long-period fiber grating with a graphene coating according to claim 7, wherein: the optical fiber fixing seat (23) is further provided with a cutting mechanism (27), the cutting mechanism (27) is arranged on the outer wall surface of the second mounting side wall (233), the cutting mechanism (27) comprises a sliding rail (271), a sliding block (272) and a cutter (273), the sliding rail (271) is arranged in the second mounting side wall (233), the sliding block (272) is slidably embedded in the sliding rail (271), and the cutter (273) is fixedly arranged on the outer end surface of the sliding block (272).

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