Raman grating variable-temperature annealing device and annealing method
By adopting the variable temperature annealing method in the Raman grating annealing device, using the heating section to form a temperature gradient zone, the Raman grating is gradient annealed, which solves the problems of unstable optical properties and potential safety hazards caused by traditional constant high temperature annealing, and achieves A more efficient and safe annealing effect.
Patent Information
- Application Number
- CN202411463176.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-21
- Publication Date
- 2025-01-21
AI Technical Summary
The traditional constant high temperature annealing process is unstable to the optical properties of the Raman grating, and there are safety hazards and problems such as excessive annealing leading to material embrittlement.
Using a variable temperature annealing device, through multiple heating sections arranged side by side on the heating block, the temperature changes from low to high, forming multiple temperature zones with a temperature gradient to achieve gradient annealing of the Raman grating.
It improves the stability of the optical properties of Raman gratings, reduces the temperature rise coefficient, improves mechanical properties, improves safety performance, and avoids material embrittlement.
Smart Images
Figure CN119330578A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of grating annealing, and more specifically, relates to a Raman grating variable temperature annealing device and annealing method. Background Art
[0002] In the field of high-power fiber lasers, due to the increase in laser output power, the extremely high power density in the fiber core will stimulate the fiber core to produce Raman scattering effect, which in turn affects the increase in laser power and the quality of the laser beam. In order to suppress the Raman scattering effect, ultraviolet writing method is often used to make Raman gratings. This method requires sensitization treatment such as hydrogen loading on the optical fiber.
[0003] After the Raman grating is written with hydrogen, the optical properties of the grating are unstable due to the presence of residual hydrogen molecules. Constant high-temperature annealing is often used to remove the incompletely reacted hydrogen molecules. In addition, annealing can also eliminate the internal stress on the grating, improve the mechanical properties of the grating and increase the service life of the grating. For some high-power fiber gratings, such as Bragg gratings, annealing treatment is required. If annealing is not performed, the working temperature will rise and it is easy to heat up.
[0004] The traditional annealing process places the fiber grating in a closed furnace for constant high-temperature annealing. The process takes a long time and the furnace must be cooled to a suitable temperature before the fiber can be taken out. The work efficiency is low. In addition, external thermal radiation is also used for annealing, such as resistance wire, flame, etc., but there are safety hazards, which can easily burn the staff, and excessive annealing can easily make the material of the Raman grating brittle, thereby reducing the mechanical properties and quality of the Raman grating. Summary of the invention
[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a Raman grating variable temperature annealing device and annealing method, in which the temperature of the heating section on the heating block is variable, and the annealing area is changed from low to high, so that the temperature of the space between the heating block and the insulation plate is also zoned and regulated and changed. The annealing heat treatment of the Raman grating is achieved by gradually changing the temperature from low to high, without damaging the performance of the cladding of the Raman grating.
[0006] To achieve the above object, according to one aspect of the present invention, a Raman grating variable temperature annealing device is provided, characterized in that it includes a base, an optical fiber clamp and a heating unit, wherein:
[0007] The optical fiber clamp is slidably mounted on the base to clamp the optical fiber and move with the optical fiber, wherein the Raman grating on the optical fiber clamped by the optical fiber clamp is exposed from the optical fiber clamp;
[0008] The heating unit comprises a heat preservation plate and a heating block which are fixedly connected together, the heat preservation plate is located above the heating block to maintain the temperature of the space between the heat preservation plate and the heating block, the space between the heat preservation plate and the heating block serves as a moving channel for the Raman grating, so that when the optical fiber clamp moves with the optical fiber, the heating block heats and anneals the Raman grating in the moving channel, and the entrance and exit of the moving channel are arranged at one end of the heating unit so that the Raman grating can enter and exit the heating unit;
[0009] The heating block has a plurality of heating sections arranged side by side, and the temperature of these heating sections gradually increases in the direction away from the entrance and exit of the moving channel, thereby forming a plurality of temperature zones arranged in sequence from low to high temperature in the moving channel.
[0010] Preferably, some of the heating sections near the entrance and exit of the moving channel have fin-shaped grooves.
[0011] Preferably, the area where all heating divisions with a temperature less than T1 are located is a low-temperature area, the area where all heating divisions with a temperature greater than T1 and less than T2 are located is a medium-temperature area, and the area where all heating divisions with a temperature greater than T2 are located is a high-temperature area, where T1<T2; T1 and T2 are set thresholds.
[0012] The distribution density of the fin-shaped grooves on each heating subsection in the low temperature region is greater than the distribution density of the fin-shaped grooves on each heating subsection in the medium temperature region;
[0013] The groove width of the fin-shaped groove on each heating subsection in the low temperature region is smaller than the groove width of the fin-shaped groove on each heating subsection in the medium temperature region;
[0014] No fin-shaped grooves are provided on each heating section in the high temperature area.
[0015] Preferably, a spacing groove is provided between any two adjacent heating sections to reduce heat transfer between the two adjacent heating sections.
[0016] Preferably, each of the heating sections is connected to a thermocouple respectively.
[0017] Preferably, each of the heating sections is heated by a heating rod respectively;
[0018] The thermocouple sends the collected temperature of the heating section to the temperature transmitter module of the PLC, and the PLC adjusts the heating on and off time of the heating rod and the temperature of the heating section based on PID control.
[0019] Preferably, it further comprises an electric translation stage, wherein the electric translation stage is connected to the optical fiber clamp.
[0020] Preferably, the optical fiber clamp comprises an optical fiber support frame and an optical fiber clamping device, the optical fiber support frame is slidably mounted on the base, and the optical fiber clamping device is fixedly mounted on the optical fiber support frame for clamping the optical fiber.
[0021] Preferably, there are two optical fiber clamping devices for clamping two ends of the optical fiber, and the heating unit is located between the two optical fiber clamping devices.
[0022] According to another aspect of the present invention, there is also provided a Raman grating temperature-variable annealing method, characterized in that it comprises the following steps:
[0023] 1) Fixing the optical fiber on the optical fiber clamp, and making the Raman grating on the optical fiber exposed from the optical fiber clamp;
[0024] 2) The optical fiber fixture moves to allow the Raman grating to enter the moving channel from the entrance and exit of the moving channel;
[0025] 3) The Raman grating moves intermittently or continuously in a direction away from the entrance and exit of the moving channel until it moves above the heating section with the highest temperature, wherein the Raman grating has a corresponding annealing treatment time above each heating section;
[0026] 4) The optical fiber clamp moves the Raman grating with the Raman grating toward the entrance and exit of the moving channel, and finally allows the Raman grating to exit the heating unit from the entrance and exit of the moving channel, thereby completing the annealing of the Raman grating;
[0027] 5) Remove the optical fiber from the optical fiber holder.
[0028] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:
[0029] 1. In a Raman grating variable temperature annealing device of the present invention, the entrance and exit of the moving channel are arranged at one end of the heating unit, and the Raman grating can enter and exit the heating unit from this end. Therefore, after the optical fiber and the Raman grating completely exit the moving channel of the heating unit and the optical fiber clamp is at a certain distance from the heating unit, the optical fiber can be removed from the optical fiber clamp. Moreover, the temperature of the heating section close to the entrance and exit of the moving channel is the lowest among all the heating sections. Therefore, when removing the optical fiber, there is no need to worry about being burned by the high-temperature heating section, and the safety performance of the entire annealing device is relatively high.
[0030] 2. A Raman grating variable temperature annealing device of the present invention can realize the arrangement of different temperature zones in the space above the same heating block, and the temperature changes in steps; the Raman grating is annealed in the gradient-changing temperature range in the moving channel, so that the Raman grating can be gradually and adaptively annealed from low temperature to high temperature, and the optical properties are more stable. Compared with the conventional constant high temperature resistance wire or flame annealing method, this temperature gradient annealing method is more in line with the optical fiber photosensitivity characteristics, and the grating yield rate is higher.
[0031] 3. A Raman grating variable temperature annealing device of the present invention has a structure in which the heating block is divided into multiple heating sections, which can achieve a temperature range of 50°C-500°C, and can achieve consistent temperature in each heating section, while the temperature in the moving channel changes in a trapezoidal manner.
[0032] 4. In a Raman grating variable temperature annealing device of the present invention, as the optical fiber enters and exits the annealing device, the temperature change intensity of the heating process and the cooling process is basically the same, the annealing effect is good, the optical fiber maintains good mechanical properties after annealing, and the grating has a low temperature rise coefficient.
[0033] 5. A Raman grating variable temperature annealing method of the present invention adopts a variable temperature annealing method, in which the Raman grating is gradually moved from a low temperature area to a high temperature area, and has a corresponding process residence time in each area, so that sufficient annealing can be performed. BRIEF DESCRIPTION OF THE DRAWINGS
[0034] Figure 1 It is a three-dimensional schematic diagram of the Raman grating variable temperature annealing device of the present invention;
[0035] Figure 2 is a schematic diagram of a heating block in the present invention;
[0036] Figure 3 is a schematic diagram of a heating unit in the present invention;
[0037] Figure 4 It is a schematic diagram of the electric translation stage, the optical fiber clamp and the heating unit in the present invention being installed on a base;
[0038] Figure 5 is a schematic diagram of one of the optical fiber clamping devices of the present invention;
[0039] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:
[0040] 1- annealing indicator light, 2- thermocouple, 3- heating section, 4- heating rod, 5- optical fiber clamping device, 6- emergency stop button, 7- touch screen, 8- heat sink fins, 9- thermocouple positioning hole, 10- heating rod hole, 11- spacing groove, 12- fin-type heat sink, 13- insulation board, 14- base, 15- electric translation stage, 16- U-shaped support plate, 17- optical fiber support frame, 18- heating section support frame, 19- slide rail, 20- stop screw, 21- optical fiber clamp, 22- micrometer head, 23- heating unit, 24- heating section, 25- moving channel. DETAILED DESCRIPTION
[0041] 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.
[0042] The fiber grating is annealed at a constant high temperature, especially for a special fiber grating such as a Raman grating. The heat accumulation caused by the long-term constant high-temperature annealing can easily cause damage to the cladding material of the Raman grating. The notches on the Raman grating are inclined relative to the optical fiber axis, and light of a specific wavelength can be coupled to the cladding for transmission to achieve broadband filtering. If the cladding is damaged, the transmission of light in the cladding and the filtering effect of the Raman grating will be affected. Therefore, the present invention adopts zoned temperature control for the Raman grating, and performs gradient temperature annealing from low to high temperature zones.
[0043] Reference Figure 1 to Figure 5 , a Raman grating variable temperature annealing device, comprising a base 14, an optical fiber clamp 21 and a heating unit 23, wherein:
[0044] The optical fiber clamp 21 is slidably mounted on the base 14 to clamp the optical fiber and move it, wherein the Raman grating on the optical fiber clamped by the optical fiber clamp 21 is exposed from the optical fiber clamp 21; the present invention preferably also includes an electric translation stage 15 mounted on the base 14, and the electric translation stage 15 is connected to the optical fiber clamp 21 to push the optical fiber clamp 21 to move.
[0045] The optical fiber clamp 21 preferably includes an optical fiber support frame 17 and an optical fiber clamping device 5. The optical fiber support frame 17 is preferably slidably mounted on the base 14 through a guide rail 19. The optical fiber clamping device 5 is fixedly mounted on the optical fiber support frame 17 to clamp the optical fiber. The optical fiber clamping device 5 is preferably two to clamp the two ends of the optical fiber. Each optical fiber clamping device 5 is respectively mounted on an optical fiber support frame 17. The optical fiber clamp 21 also includes a U-shaped support plate 16. Each optical fiber support frame 17 is respectively mounted on one end of the U-shaped support plate 16. The U-shaped support plate 16 is mounted on the guide rail 19. The U-shaped support plate 16 slides along the guide rail 19 and can move with the two optical fiber clamping devices 5 at the same time. The two optical fiber clamping devices 5 can move with the optical fiber and the Raman grating on the optical fiber. The electric translation stage 15 is connected to the U-shaped support plate 16 of the optical fiber clamp 21. The optical fiber clamping device 5 has a slide table, a stop screw 20 and a differential head 22 to facilitate the adjustment and fixing of the optical fiber position.
[0046] The heating unit 23 is located between the two optical fiber clamping devices 5 , so that the Raman grating between the two optical fiber clamping devices 5 enters the heating unit 23 for annealing treatment.
[0047] The heating unit 23 includes a heat preservation plate 13 and a heating block 3 fixedly connected together, and there is a space between the heat preservation plate 13 and the heating block 3. The heat preservation plate 13 is located above the heating block 3 to maintain the temperature of the space between the heat preservation plate 13 and the heating block 3. The space between the heat preservation plate 13 and the heating block 3 serves as a moving channel 25 for the Raman grating, so that when the optical fiber clamp 21 moves with the optical fiber, the heating block 3 heats and anneals the Raman grating in the moving channel 25. The entrance and exit of the moving channel 25 are arranged at one end of the heating unit 23 so that the Raman grating enters and exits the heating unit 23; the arrangement of the heat preservation plate 13 and the heating block 3 makes the heating unit 23 U-shaped, and one end of the heating unit 23 is open, so that the Raman grating can enter the moving channel 25 on the heating unit 23. The heating unit 23 is preferably installed on the base 14 through the heating unit support frame 18.
[0048] The heating block 3 has a plurality of heating subsections 24 arranged side by side, and the temperature of these heating subsections 24 gradually increases in the direction away from the entrance and exit of the moving channel 25, thereby forming a plurality of temperature zones arranged in order from low to high temperature in the moving channel 25. By heating the heating subsections 24, the temperature zone control and the temperature gradient change in the moving channel 25 can be realized.
[0049] Reference Figure 2 , Figure 3The heating block 3 has a total of 10 heating sections 24, which are 1# heating section to 10# heating section in sequence along the direction away from the entrance and exit of the moving channel 25; the area above each heating section 24 of the heating block 3 has different temperatures through program control, thereby forming different temperature zones, and the temperatures of the temperature zones change in a trapezoidal manner. For example, there are currently 10 heating sections 24, the temperature zone above the 1# heating section is 50°C, the temperature zone above the 2# heating section is 100°C, the temperature zone above the 3# heating section is 150°C…the temperature zone above the 10# heating section is 500°C, and the temperature of the temperature zone above each heating section 24 is uniform, that is, the moving channel 25 is divided into 10 temperature zones with temperature gradient changes, and along the direction away from the entrance and exit of the moving channel 25, the temperature of the temperature zone increases from 50°C to 500°C in sequence, driving the Raman grating to move in the moving channel 25, and the time for moving in each temperature zone can be customized according to process requirements. The whole process is to move gradually from the low temperature area to the high temperature area, maintain a process residence time after reaching the high temperature area, and then the Raman grating moves in the opposite direction and quickly exits the moving channel 25, thereby also exiting the heating unit 23.
[0050] This variable temperature annealing method solves the problem that the Raman grating is directly exposed to the high temperature region, causing the grating structure to be destroyed and the optical properties to be unstable.
[0051] Furthermore, some of the heating subsections 24 near the entrance and exit of the moving channel 25 have fin-shaped grooves 12 for heat dissipation. In order to reduce the device space, the temperature zoning control on the smaller size heating subsection 24 is realized. The structure of the heating block 3 is thermally designed, and the fin-shaped grooves 12 are used to increase the ventilation volume of the temperature zone and weaken the heat conduction effect between each temperature zone. A fin-shaped groove 12 is formed between two adjacent heat dissipation fins 8.
[0052] Furthermore, the area where all heating divisions 24 with a temperature less than T1 are located is a low temperature area, the area where all heating divisions 24 with a temperature greater than T1 and less than T2 are located is a medium temperature area, and the area where all heating divisions 24 with a temperature greater than T2 are located is a high temperature area, wherein T1<T2, T1 and T2 are set thresholds.
[0053] The distribution density of the fin-type grooves 12 on each heating section 24 in the low temperature area is greater than the distribution density of the fin-type grooves 12 on each heating section 24 in the medium temperature area, and the groove width of the fin-type grooves 12 on each heating section 24 in the low temperature area is smaller than the groove width of the fin-type grooves 12 on each heating section 24 in the medium temperature area.
[0054] The above arrangement enables the heating subsection 24 in the low temperature area to dissipate heat relatively quickly, and the temperature is not easily affected by the adjacent heating subsection 24 with a higher temperature and thus rises, and the temperature can always be maintained at a set lower temperature.
[0055] No fin-shaped groove 12 is provided on each heating subsection 24 in the high temperature area, so that the heat of the heating subsection 24 in the high temperature area is dissipated slowly and can be kept at a high temperature all the time.
[0056] Therefore, in terms of the structure of the heating block 3, each heating section 24 in the low temperature area adopts a high-density, small-sized fin-shaped groove 12; each heating section 24 in the medium temperature area adopts a low-density, large-sized fin-shaped groove 12; and each heating section 24 in the high temperature area does not have a fin-shaped groove 12. There are three types of structures.
[0057] Furthermore, a spacing groove 11 and / or a heat insulating pad are provided between any two adjacent heating subsections 24 to reduce the heat transfer between the two adjacent heating subsections 24. The heat insulating pad can be installed in the spacing groove 11.
[0058] Furthermore, each of the heating subdivisions 24 is connected to a thermocouple 2, which is mounted on the thermocouple positioning hole 9 of the heating subdivision 24 to measure the temperature of the heating subdivision 24, thereby adjusting the temperature zone above the heating subdivision 24. In addition, each of the heating subdivisions 24 is heated by a heating rod 4, which is mounted in the electric heating rod mounting hole 10. The thermocouple 2 sends the collected temperature of the heating subdivision 24 to the temperature transmitter of the PLC, and the PLC adjusts the heating on-off time of the heating rod 4 and the temperature of the heating subdivision 24 based on PID control, thereby achieving precise control of multiple temperature zones of the heating subdivision 24. PID is achieved by PLC calculation, and then a pulse signal is sent to the SSR solid-state relay, so that the heating rod heats up.
[0059] According to another aspect of the present invention, there is also provided a Raman grating temperature-variable annealing method, comprising the following steps:
[0060] 1) Fix the optical fiber on the optical fiber clamp 21 and expose the Raman grating on the optical fiber from the optical fiber clamp 21 to facilitate the subsequent heating unit 23 to perform annealing treatment on the Raman grating.
[0061] 2) The optical fiber clamp 21 moves, allowing the Raman grating to enter the moving channel 25 (and also enter the heating unit 23) from the entrance and exit of the moving channel 25. The optical fiber clamp 21 can be moved manually or electrically. The present invention preferably uses an electrically driven method to drive the optical fiber clamp 21 to move via the electric translation stage 15.
[0062] 3) The Raman grating moves intermittently or continuously in a direction away from the entrance and exit of the moving channel 25 until it moves to above the heating section 24 with the highest temperature, wherein the Raman grating has a corresponding annealing treatment time above each heating section 24, and intermittent movement means that the optical fiber pauses to stay in the temperature zone for a set time, and then moves to the temperature zone above the next heating section 24 for annealing.
[0063] 4) The optical fiber clamp 21 moves with the Raman grating toward the entrance and exit of the moving channel 25, and finally allows the Raman grating to exit the heating unit from the entrance and exit of the moving channel 25, thereby completing the annealing of the Raman grating. The annealing method is variable temperature gradient annealing, which will not damage the cladding and make the material of the Raman grating brittle.
[0064] 5) Remove the optical fiber from the optical fiber clamp 21. Since the optical fiber is removed in an exposed atmospheric environment, away from the heating section 24 and the temperature zone with the highest temperature, it is safer when removing the optical fiber and is not easy to burn the operator.
[0065] The annealing device of the present invention has a touch screen 7, an annealing indicator light 1 and an emergency stop button 6. When the operation button is pressed on the touch screen 7, the annealing indicator light 1 will light up, and the optical fiber is transported to the heating unit 23 through the electric translation stage 15. According to the process requirements, the moving speed and process residence time of the optical fiber in each temperature zone are set, and the optical fiber is gradually moved in the direction of the temperature zone from low to high temperature. After reaching the high temperature area, it is kept for a period of time required by the process, and then the optical fiber is quickly returned to the starting point through the electric translation stage 15.
[0066] 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 Raman grating variable temperature annealing device, characterized in that: It includes a base, an optical fiber clamp and a heating unit, wherein: The optical fiber clamp is slidably mounted on the base to clamp the optical fiber and move with the optical fiber, wherein the Raman grating on the optical fiber clamped by the optical fiber clamp is exposed from the optical fiber clamp; The heating unit comprises a heat preservation plate and a heating block which are fixedly connected together, the heat preservation plate is located above the heating block to maintain the temperature of the space between the heat preservation plate and the heating block, the space between the heat preservation plate and the heating block serves as a moving channel for the Raman grating, so that when the optical fiber clamp moves with the optical fiber, the heating block heats and anneals the Raman grating in the moving channel, and the entrance and exit of the moving channel are arranged at one end of the heating unit so that the Raman grating can enter and exit the heating unit; The heating block has a plurality of heating sections arranged side by side, and the temperature of these heating sections gradually increases in the direction away from the entrance and exit of the moving channel, thereby forming a plurality of temperature zones arranged in sequence from low to high temperature in the moving channel.
2. A Raman grating variable temperature annealing device according to claim 1, characterized in that: Some of the heating sections near the entrance and exit of the moving channel have fin-shaped grooves.
3. A Raman grating variable temperature annealing device according to claim 2, characterized in that: The area where all heating divisions with a temperature less than T1 are located is a low temperature area, the area where all heating divisions with a temperature greater than T1 and less than T2 are located is a medium temperature area, and the area where all heating divisions with a temperature greater than T2 are located is a high temperature area, where T1<T2; T1 and T2 are set thresholds. The distribution density of the fin-shaped grooves on each heating subsection in the low temperature region is greater than the distribution density of the fin-shaped grooves on each heating subsection in the medium temperature region; The groove width of the fin-shaped groove on each heating subsection in the low temperature region is smaller than the groove width of the fin-shaped groove on each heating subsection in the medium temperature region; No fin-shaped grooves are provided on each heating section in the high temperature area.
4. The Raman grating variable temperature annealing device according to claim 1, characterized in that: A spacing groove is provided between any two adjacent heating sections to reduce the transfer of heat between the two adjacent heating sections.
5. The Raman grating variable temperature annealing device according to claim 1, characterized in that: Each of the heating sections is respectively connected with a thermocouple.
6. A Raman grating variable temperature annealing device according to claim 5, characterized in that: Each of the heating sections is heated by a heating rod respectively; The thermocouple sends the collected temperature of the heating section to the temperature transmitter module of the PLC, and the PLC adjusts the heating on and off time of the heating rod and the temperature of the heating section based on PID control.
7. The Raman grating variable temperature annealing device according to claim 1, characterized in that: It also includes an electric translation stage, which is connected to the optical fiber clamp.
8. The Raman grating variable temperature annealing device according to claim 1, characterized in that: The optical fiber clamp comprises an optical fiber support frame and an optical fiber clamping device. The optical fiber support frame is slidably mounted on the base, and the optical fiber clamping device is fixedly mounted on the optical fiber support frame for clamping the optical fiber.
9. A Raman grating variable temperature annealing device according to claim 8, characterized in that: There are two optical fiber clamping devices for clamping the two ends of the optical fiber, and the heating unit is located between the two optical fiber clamping devices.
10. A Raman grating temperature-variable annealing method according to any one of claims 1 to 9, characterized in that: The following steps are involved: 1) Fixing the optical fiber on the optical fiber clamp, and making the Raman grating on the optical fiber exposed from the optical fiber clamp; 2) The optical fiber fixture moves to allow the Raman grating to enter the moving channel from the entrance and exit of the moving channel; 3) The Raman grating moves intermittently or continuously in a direction away from the entrance and exit of the moving channel until it moves above the heating section with the highest temperature, wherein the Raman grating has a corresponding annealing treatment time above each heating section; 4) The optical fiber clamp moves the Raman grating with the Raman grating toward the entrance and exit of the moving channel, and finally allows the Raman grating to exit the heating unit from the entrance and exit of the moving channel, thereby completing the annealing of the Raman grating; 5) Remove the optical fiber from the optical fiber holder.