Fiber Bragg grating stress-free packaging device and method

Abstract

The present invention discloses a stress-free packaging device and method for fiber grating, including a copper heat sink plate, a glue dispensing groove, a TEC semiconductor refrigerator, a thermistor, an invar shell, a polyimide cover plate, a thermal conductive silicone grease, and a thermal insulation and vibration isolation cotton. The present invention combines the traditional packaging technology of fiber grating and the prestressed tuning grating center wavelength technology, selects room temperature curing packaging glue to eliminate the packaging stress introduced by temperature in the traditional thermal curing process, and at the same time, by accurately applying prestress to the grating, real-time monitoring of the center wavelength and precise control of the glue dispensing amount, the stress introduced by the shrinkage of ultraviolet glue curing is offset, and the stress-free packaging of the fiber grating is realized, and the grating wavelength is consistent before and after packaging; then the grating is actively temperature-controlled and thermally and vibration-insulated, and the influence of self-heating of the grating during operation and external environmental disturbance on the grating wavelength is further eliminated.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber grating packaging, and in particular to a fiber grating stress-free packaging device and method. Background Art

[0002] In recent years, single-frequency fiber laser technology has developed rapidly and has been widely used in the fields of fiber-optic hydrophones, coherent optical communications, gravitational wave detection, etc. These application fields have very high requirements for the reliability, wavelength stability, and noise characteristics of fiber lasers. The laser resonant cavity grating in general fiber lasers is very sensitive to environmental disturbances, especially temperature and stress. The tiny stress introduced by temperature changes or packaging acts on the resonant cavity grating, and its central wavelength will change significantly, and the output power fluctuates significantly. When the disturbance is large, the laser will jump mode. Obviously, this is difficult to meet the actual application needs, especially in some applications that require working under complex environmental conditions. The output characteristics of the laser will be greatly affected. Therefore, it is necessary to adopt stress-free, active temperature control, and heat-insulated and vibration-insulated high-reliability packaging for the laser resonant cavity grating.

[0003] Regarding the packaging technology of the fiber laser resonant cavity grating, the conventional packaging method is to use packaging glue to directly fix the two ends of the fiber grating on the plate-type or tube-type packaging component (see the prior art [1]: invention patent CN201420155267.3: Environmentally resistant phase-shift grating packaging structure for fiber laser). The basic principle is that the optical fiber passes through a glass tube with two sealing points in the glass tube. The phase-shift grating area is sealed and fixed to the glass tube, and then the glass tube is covered with a metal tube, and the space between them is filled with silicone grease and sealed at both ends. However, when the external ambient temperature changes, due to the large difference in thermal expansion coefficients of glass and metal packaging materials, and the continued existence of stress introduced by the sealant, the central wavelength of the phase-shift grating area will be affected, which will ultimately significantly affect the long-term stability of the wavelength of the fiber laser.

[0004] In order to achieve the effect of grating temperature compensation from the packaging material and structure, Jian Wei et al. proposed a method for packaging fiber Bragg grating using a negative temperature coefficient material sleeve (see prior art [2]: invention patent CN200610169809.2: A method for packaging fiber Bragg grating temperature compensation). The basic principle is to use a material that does not have a negative temperature coefficient, and after special processing, to make a packaging sleeve with a weak negative thermal expansion coefficient, which can just compensate for the wavelength drift caused by the temperature change of the fiber Bragg grating. The fiber Bragg grating is quickly packaged at high temperature using the prepared packaging sleeve to produce a fiber Bragg grating that is insensitive to temperature and has high thermal stability, and is subjected to multiple high and low temperature cycle aging. However, when this packaging technology is applied to the fiber Bragg grating used to package fiber lasers, it can only offset part of the impact of the ambient temperature, and cannot eliminate the wavelength drift caused by the heating of the fiber Bragg grating itself, and cannot meet the increasingly high wavelength stability requirements for fiber lasers in practical applications. Summary of the invention

[0005] The present invention aims to provide a stress-free packaging device for fiber grating (FBG), which comprises an Invar shell, a copper heat sink plate and a TEC semiconductor refrigerator are arranged in the Invar shell, a thermistor placement groove, a thermistor reserved hole and a TEC wire reserved hole are provided on the Invar shell, a U-shaped groove and a glue dispensing groove are provided on the copper heat sink plate, a polyimide cover plate is provided above the Invar shell, and a three-position adjustment frame, a fiber grating, a pigtail clamp module, a UV curing light source, a spectrometer and a light source are also provided. The copper heat sink plate is fixed on the middle three-position adjustment frame, the fiber grating is arranged in the center of the U-shaped groove of the copper heat sink plate, the pigtails at both ends of the copper heat sink plate are respectively connected to the light source and the spectrometer through the pigtail clamp module, the fiber grating is used for constant prestress reading monitoring and control, the UV curing light source cures the UV curing glue at both ends to achieve a firm connection between the harmonic fiber grating and the copper heat sink plate, and the outer surface of the Invar shell is covered with heat insulation and vibration isolation cotton.

[0006] Preferably, the Invar shell is an open box structure with U-shaped holes on both end faces, and the fiber grating pigtail passes through the U-shaped hole of the Invar shell so that the grating area is placed in the U-shaped groove of the copper heat sink plate in the Invar shell, and the width of the U-shaped groove corresponds to the thickness of the optical fiber.

[0007] Preferably, a TEC semiconductor cooler and a thermistor are pre-installed at the lower end of the side surface of the copper heat sink plate of the Invar housing, and the TEC semiconductor cooler is in good contact with the copper heat sink plate and the housing through thermal conductive silicone grease.

[0008] Preferably, the optical fiber tensile gauge uses a digital dynamometer with a resolution of 0.001N / 0.1g, the UV curing adhesive can use EPO-TEK OG116-31 model adhesive, and the UV curing light source uses a 365nm 200mW / cm² UV air-cooled LED curing lamp.

[0009] Preferably, the thermistor is fixed in the copper heat sink plate and the Invar housing placement groove by means of a solidifiable thermally conductive adhesive, and the thermistor reserved hole is used for the thermistor wire to pass through.

[0010] Preferably, the TEC semiconductor cooler is fixed in the Invar housing by means of a solidifiable thermally conductive adhesive, and the TEC wire passes through a TEC wire reserved hole of the Invar housing.

[0011] Preferably, the copper heat sink plate and the polyimide cover plate are fixed to the Invar housing by screws.

[0012] Preferably, the U-shaped groove of the copper heat sink plate is filled with non-solidifiable thermal grease to fully contact the copper heat sink plate, the copper heat sink plate is aligned with the reserved hole of the Invar shell, the copper heat sink plate is placed on the TEC semiconductor cooler, and the gap between the two is filled with thermal grease.

[0013] A packaging method comprises the following steps: Step 1: Fasten the grating package module on the three-dimensional adjustment frame between the pigtail clamps by means of a pressing block or screws; Step 2: Pass the fiber grating pigtail through the reserved hole on the side of the invar shell of the grating package module, so that the grating area is placed in the U-shaped groove of the copper heat sink plate in the invar shell, and the pigtails at both ends of the resonant cavity fiber grating are respectively embedded in the U-shaped grooves of the pigtail fixture module; Step 3: Finely adjust the knob of the three-dimensional adjustment frame, install the fiber Bragg grating and the fiber pigtail fixture in the cavity, and apply axial prestress to the fiber Bragg grating by adjusting the fiber axial direction knob of the adjustment frame far away from the end of the fiber dynamometer. The magnitude of the applied constant prestress is monitored and controlled by the reading of the fiber tension. The tail end of the fiber Bragg grating is connected to the light source and spectrum respectively, and the fiber Bragg grating spectrum and central wavelength are monitored in real time.

[0014] Step 4: Accurately dispense glue on both ends of the fiber Bragg grating through the glue dispensing grooves on the copper heat sink plate; Step 5: According to the curing conditions of the UV glue, select appropriate UV curing light source curing process parameters, and firmly connect the fiber Bragg grating and the copper heat sink plate with glue; Step 6: Remove the grating package module and place it in a temperature cycle box for high temperature annealing to release the tiny structural deformation stress introduced during the package module assembly process; Step 7: Assemble the annealed copper heat sink plate and other components, and wrap the heat insulation and vibration isolation cotton outside the Invar shell, and the stress-free packaging of the fiber grating component is completed; Step 8: Connect the packaged fiber Bragg grating assembly to the laser system through fusion splicing for power-on performance testing. First, use a spectrometer to observe the consistency of the grating center wavelength before and after packaging, and test the effect of stress-free packaging. Then, power on the temperature-controlled TEC in the module, use a spectrometer to test the stability of the laser center wavelength, and verify the compensation effect of the resonant cavity fiber Bragg grating on the grating area's own temperature and ambient temperature disturbances.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention combines the traditional packaging technology of fiber Bragg gratings and the technology of prestressed tuning of the center wavelength of the grating, selects room temperature curing type packaging glue to eliminate the packaging stress introduced by temperature in the traditional thermal curing process, and at the same time, by accurately applying prestress to the grating, real-time monitoring of the center wavelength and precise control of the amount of glue dispensed, the stress introduced by the shrinkage of UV glue curing is offset, and the stress-free packaging of the fiber Bragg grating is achieved, and the grating wavelength is consistent before and after packaging; then the grating is actively temperature-controlled and heat-insulated and vibration-insulated, further eliminating the influence of self-heating of the grating during operation and external environmental disturbances on the grating wavelength. The present invention can well meet the application requirements of related scientific research fields and engineering applications that have high requirements for the long-term stability of the center wavelength of the fiber laser, and has the characteristics of high reliability and good process repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 It is a structural diagram of the fiber Bragg grating stress-free packaging device of the present invention.

[0017] Figure 2 yes Figure 1 A partial enlarged view of .

[0018] Figure 3 It is a structural block diagram of the fiber Bragg grating tension monitoring system of the present invention.

[0019] Figure 4 This is an example diagram of a fiber Bragg grating stress-free package provided by the present invention.

[0020] Figure 5 It is a stereoscopic diagram of a fiber Bragg grating stress-free package provided by the present invention.

[0021] In the figure: 1. Invar shell; 2. Copper heat sink plate; 3. Polyimide cover plate; 4. TEC semiconductor refrigerator; 5. U-shaped groove; 6. Glue dispensing groove; 7. Thermistor placement groove; 8. Thermistor placement groove; 9. Thermistor reserved hole; 10. TEC wire reserved hole; 201. Three-position adjustment frame; 202. Fiber dynamometer; 203. Pigtail clamp module; 204. UV curing light source; 205. Spectrometer; 206. Light source; 301. Solidifiable thermal adhesive; 302. Non-solidifiable thermal grease; 303. Thermistor wire; 304. TEC wire; 305. Thermal insulation and shock isolation cotton. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the embodiments.

[0023] Reference Figures 1 to 5 The present invention discloses a stress-free packaging device for optical fiber Bragg gratings, comprising an Invar steel shell 1, wherein a copper heat sink plate 2 and a TEC semiconductor refrigerator 4 are arranged in the Invar steel shell 1, a thermistor placement groove 7, a thermistor reserved hole 9 and a TEC wire reserved hole 10 are provided on the Invar steel shell 1, a U-shaped groove 5 and a glue dispensing groove 6 are provided on the copper heat sink plate 2, a polyimide cover plate 3 is arranged above the Invar steel shell 1, and further comprises a three-position adjustment frame 201, an optical fiber tensiometer 202, a pigtail clamp module 203, an ultraviolet curing light source 204, a spectrometer 205 and a light source 206, wherein the copper heat sink plate 2 is fixed on the middle three-position adjustment frame 201, the optical fiber Bragg grating is arranged in the center of the U-shaped groove of the copper heat sink plate 2, and the pigtails at both ends of the copper heat sink plate 2 are respectively connected by the pigtail clamp module. The light source and the spectrometer are connected, and the fiber optic tensiometer 202 is used for monitoring and controlling the reading of constant prestress. The ultraviolet solid-state light source cures the ultraviolet curing glue at both ends to achieve a firm connection between the harmonic fiber grating and the copper heat sink plate 2. The outer surface of the invar shell 1 is covered with thermal insulation and vibration isolation cotton. The present invention applies prestress to the fiber optic grating and monitors the reading of the fiber optic tensiometer to achieve precise application of prestress; real-time monitoring is performed through the central wavelength; the amount of ultraviolet curing glue at both ends of the grating area is precisely controlled through the glue dispensing groove 6 on the copper heat sink plate 2; the glue at both ends is cured by the ultraviolet solid-state light source to achieve fixation of the fiber optic grating and the copper heat sink plate 2; and the compensation of the grating area's own temperature and environmental disturbance is finally achieved through the temperature-controlled TEC in the grating package module and the thermal insulation and vibration isolation cotton packaging of the shell.

[0024] The Invar shell 1 is an open box structure with U-shaped holes on both end faces. The fiber grating pigtail passes through the U-shaped hole of the Invar shell 1, so that the grating area is placed in the U-shaped groove 5 of the copper heat sink plate 2 in the Invar shell 1, and the width of the U-shaped groove corresponds to the thickness of the optical fiber to ensure good thermal contact of the fiber grating area. At the same time, the two ends of the fiber grating area are respectively fixed to the copper heat sink plate 2 by ultraviolet curing glue; the copper heat sink plate 2 is fixed to the Invar shell 1 by screws, and a TEC semiconductor cooler 4 and a thermistor are pre-installed on the lower end of the side of the copper heat sink plate 2 of the Invar shell 1. The TEC semiconductor cooler 4 is in good contact with the copper heat sink plate 2 and the shell through thermal grease, and the thermistor is fixed to the copper heat sink plate 2 and the Invar shell placement groove by solidifiable thermal conductive glue, and the thermistor reserved hole 9 is for the thermistor wire to pass through.

[0025] The fiber Bragg grating stress-free packaging device of the present invention combines the traditional packaging technology of fiber Bragg grating and the technology of prestressed tuning of the center wavelength of the grating. It uses room temperature curing type packaging glue to eliminate the packaging stress introduced by temperature in the traditional thermal curing process. At the same time, by accurately applying prestress to the grating and accurately controlling the amount of glue dispensed, the wavelength drift caused by the stress introduced by the shrinkage of the UV glue curing is offset, and the stress-free packaging of the resonant cavity grating is realized, thereby significantly improving the wavelength stability of the light emitted by the fiber laser; at the same time, the grating area of ​​the resonant cavity grating of the present invention maintains good thermal contact with the heat sink plate with U-shaped groove 5 in the packaging module. When the fiber laser is powered on and in working state, the constant temperature of the grating copper heat sink plate 2 is achieved through the temperature-controlled TEC semiconductor refrigerator 4, and the active temperature control technology is used to eliminate the influence of self-heating of the grating during operation on the grating wavelength drift. At the same time, the packaging Invar steel shell 1 is heat-insulated and vibration-isolated, which can further reduce the influence of external environmental disturbance on the wavelength stability of the laser.

[0026] The optical fiber tensile gauge uses a digital display force gauge with a resolution of 0.001N / 0.1g, the UV curing adhesive can use EPO-TEK OG116-31 model adhesive, and the UV curing light source uses a 365nm 200mW / cm² UV air-cooled LED curing lamp.

[0027] In the present invention, the copper heat sink plate 2 is placed in a high-temperature annealing furnace for high-temperature annealing before packaging to eliminate the bending of the copper heat sink plate 2 caused by process problems; The thermistor is fixed in the copper heat sink plate 2 and the Invar housing placement groove 7 and the Invar housing placement groove 8 by means of a solidifiable thermal conductive adhesive 301; The TEC semiconductor cooler 4 is fixed in the Invar housing 1 by a solidifiable heat-conductive adhesive, and the TEC wire 304 passes through a reserved hole in the Invar housing 1; The treated copper heat sink plate 2 is placed on the three-position adjustment frame 201. After being fixed, the position of the optical fiber is adjusted so that the optical fiber grating falls in the center of the U-shaped groove 5 of the copper heat sink plate 2 and is close to the bottom of the copper heat sink plate 2. The pigtails at both ends of the FBG are precisely applied with constant prestress and monitored and controlled by the reading of the fiber optic tension meter 202; One end of the fiber Bragg grating pigtail is connected to the light source 206, and another end of the pigtail is connected to the spectrometer 205 to monitor the fiber Bragg grating spectrum and central wavelength in real time; The glue dispensing groove 6 on the copper heat sink plate 2 dispenses glue on both ends of the fiber grating; The UV light source 204 cures the UV glue at both ends to achieve a firm connection between the harmonic fiber grating and the copper heat sink plate 2; After the fiber Bragg grating is fixed on the copper heat sink plate 2, the copper heat sink plate 2 with the fiber Bragg grating fixed is placed in a temperature cycle box for high temperature annealing and aging; After annealing is completed, the U-shaped groove of the copper heat sink plate 2 is filled with non-solidifiable thermal conductive silicone grease 302 to fully contact the copper heat sink plate 2, the copper heat sink plate 2 is aligned with the reserved hole of the Invar shell 1, the copper heat sink plate 2 is placed on the TEC semiconductor cooler, and the gap between the two is filled with thermal conductive silicone grease 302, the copper heat sink plate 2 is fixed in the Invar shell 1 by screws, and the thermistors of the Invar shell 1 and the copper heat sink plate 2 are placed in the reserved positions to avoid being crushed; The polyimide cover plate 3 is covered, and the outer surface of the Invar shell 1 is coated with heat-insulating and vibration-isolating cotton 305 .

[0028] By controlling the temperature-controlled TEC semiconductor cooler 4 in the packaging module, the resonant cavity fiber grating can finally compensate for the temperature disturbance of the grating area itself and the ambient temperature, thereby ensuring the long-term stability of the central wavelength of the fiber laser.

[0029] It should be noted that due to the elastic-optical effect and thermo-optical effect of the optical fiber, when the stress or temperature changes, the reflection center wavelength of the optical fiber grating will change in theory. The room temperature curing glue is used in this implementation case, which can eliminate the wavelength change introduced by the temperature change during the curing process. The magnitude of the prestress applied in this implementation case is mainly determined by the stress introduced by the shrinkage of the UV glue during curing. Under the same experimental conditions, we have conducted experiments on the same type of grating to monitor the change in the central wavelength before and after the packaging and curing by a spectrometer, and obtained the parameters of the pre-stress applied during packaging. In addition, we can accurately control the amount of room temperature UV curing glue at both ends of the grating area through the glue dispensing groove 6 on the copper heat sink plate 2, that is, the stress introduced by the curing of glue with different amounts of glue is very small, and the process repeatability is good, and the prestress applied to the grating can offset this part of the glue shrinkage stress. After packaging, the high temperature annealing and aging process of the resonant cavity grating package module can also eliminate the tiny structural deformation stress during assembly, and finally achieve stress-free packaging of the resonant cavity grating.

[0030] The embodiment of the present invention further provides a stress-free packaging method for a fiber Bragg grating, which is used to prepare any fiber Bragg grating packaging structure provided in the above embodiment. The explanation of the structures and terms that are the same or corresponding to the above embodiment will not be repeated here. The method comprises the following steps: Step 1: Fasten the grating package module on the three-dimensional adjustment frame between the pigtail clamps by means of a pressing block or screws; Step 2: Pass the fiber grating pigtail through the reserved hole on the side of the invar shell 1 of the grating package module, so that the grating area is placed in the U-shaped groove of the copper heat sink plate 2 in the invar shell 1, and the pigtails at both ends of the resonant cavity fiber grating are respectively embedded in the U-shaped grooves of the pigtail clamp module, and are fastened and installed by the upper cover plate with elastic pads to achieve stable clamping of the pigtail; Step 3: Finely adjust the knob of the three-position adjustment stand 201, install the fiber Bragg grating on the fiber pigtail fixture, and realize the center coaxial installation of the fiber optic tension gauge. Apply axial prestress to the fiber Bragg grating by adjusting the fiber axial direction knob of the adjustment stand away from one end of the fiber optic tension gauge. The magnitude of the applied constant prestress is monitored and controlled by the reading of the fiber tension. The tail end of the fiber Bragg grating is connected to the light source and spectrum respectively, and the fiber Bragg grating spectrum and central wavelength are monitored in real time.

[0031] Step 4: Precisely glue the two ends of the fiber Bragg grating through the glue dispensing groove 6 on the copper heat sink plate 2; Step 5: According to the curing conditions of the ultraviolet glue, select appropriate ultraviolet light source curing process parameters, and firmly connect the fiber grating and the copper heat sink plate 2 through glue; Step 6: Remove the grating package module and place it in a temperature cycle box for high temperature annealing to release the tiny structural deformation stress introduced during the package module assembly process; Step 7: Assemble the annealed copper heat sink plate 2 and other components, and coat the heat insulation and vibration isolation cotton outside the Invar housing 1, and the stress-free packaging of the fiber Bragg grating component is completed; Step 8: Connect the packaged fiber Bragg grating assembly to the laser system by fusion splicing, and perform power-on performance testing. First, use a spectrometer to observe the consistency of the grating center wavelength before and after packaging, and test the effect of stress-free packaging. Then, power on the temperature-controlled TEC semiconductor cooler in the module, use a spectrometer to test the stability of the laser center wavelength, and verify the compensation effect of the resonant cavity fiber Bragg grating on the grating area's own temperature and ambient temperature disturbances.

[0032] The present invention combines the traditional packaging technology of fiber Bragg gratings and the technology of prestressed tuning of the center wavelength of the grating. It uses room temperature curing type packaging glue to eliminate the packaging stress introduced by temperature in the traditional thermal curing process. At the same time, the stress introduced by the shrinkage of UV glue curing is offset by accurately applying prestress to the grating and accurately controlling the amount of glue dispensed. After curing, the grating is annealed at high temperature to release the tiny structural deformation stress introduced by the assembly process, and finally the stress-free packaging of the resonant cavity grating is achieved, and the grating wavelength is consistent before and after packaging; in addition, the grating is actively temperature-controlled and heat-insulated and vibration-insulated, further eliminating the influence of self-heating and external environmental disturbances on the grating wavelength during the operation of the grating. The present invention can well meet the application requirements of related scientific research fields and engineering applications that have high requirements for the long-term stability of the center wavelength of the fiber laser, and has the characteristics of high reliability and good process repeatability.

[0033] As above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes may be made to it in form and detail without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A stress-free packaging device for optical fiber Bragg gratings, characterized in that: It includes an Invar shell, in which a copper heat sink plate and a TEC semiconductor refrigerator are arranged, the Invar shell is provided with a thermistor placement groove, a thermistor reserved hole and a TEC wire reserved hole, the copper heat sink plate is provided with a U-shaped groove and a glue dispensing groove, a polyimide cover plate is arranged on the top of the Invar shell, and also includes a three-position adjustment frame, an optical fiber tensiometer, a pigtail clamp module, an ultraviolet curing light source, a spectrometer and a light source, the copper heat sink plate is fixed on the middle three-position adjustment frame, the optical fiber grating is arranged in the center of the U-shaped groove of the copper heat sink plate, the pigtails at both ends of the copper heat sink plate are respectively connected to the light source and the spectrometer through the pigtail clamp module, the optical fiber tensiometer is used for constant prestress reading monitoring and control, the ultraviolet curing light source cures the ultraviolet curing glue at both ends to achieve a firm connection between the harmonic optical fiber grating and the copper heat sink plate, and the outer surface of the Invar shell is covered with heat insulation and vibration isolation cotton.

2. A fiber Bragg grating stress-free packaging device according to claim 1, characterized in that: The Invar shell is an open box structure with U-shaped holes on both end faces. The fiber grating pigtail passes through the U-shaped hole of the Invar shell so that the grating area is placed in the U-shaped groove of the copper heat sink plate in the Invar shell, and the width of the U-shaped groove corresponds to the thickness of the optical fiber.

3. A fiber Bragg grating stress-free packaging device according to claim 2, characterized in that: A TEC semiconductor cooler and a thermistor are pre-installed on the lower end of the side of the copper heat sink plate of the Invar steel shell. The TEC semiconductor cooler is in good contact with the copper heat sink plate and the shell through thermal grease.

4. A stress-free packaging device for optical fiber Bragg gratings according to claim 3, characterized in that: The optical fiber tensile gauge uses a digital display force gauge with a resolution of 0.001N / 0.1g, the UV curing adhesive can use EPO-TEK OG116-31 model adhesive, and the UV curing light source uses a 365nm 200mW / cm² UV air-cooled LED curing lamp.

5. A stress-free packaging device for optical fiber Bragg gratings according to claim 4, characterized in that: The thermistor is fixed in the copper heat sink plate and the placement groove of the invar shell by means of a solidifiable thermal conductive adhesive, and the thermistor reserved hole is used for the thermistor wire to pass through.

6. A fiber Bragg grating stress-free packaging device according to claim 5, characterized in that: The TEC semiconductor cooler is fixed in the Invar housing by means of a solidifiable thermally conductive adhesive, and the TEC wire passes through a TEC wire reserved hole in the Invar housing.

7. A fiber Bragg grating stress-free packaging device according to claim 6, characterized in that: The copper heat sink plate and the polyimide cover plate are fixed to the Invar housing by screws.

8. A fiber Bragg grating stress-free packaging device according to claim 7, characterized in that: The U-shaped groove of the copper heat sink plate is filled with non-solidifiable thermal grease to fully contact the copper heat sink plate. The copper heat sink plate is aligned with the reserved hole of the Invar shell. The copper heat sink plate is placed on the TEC semiconductor cooler, and the gap between the two is filled with thermal grease.

9. A packaging method, comprising the fiber Bragg grating stress-free packaging device according to any one of claims 1 to 8, characterized in that: The steps include: Step 1: Fasten the grating package module on the three-dimensional adjustment frame between the pigtail clamps by means of a pressing block or screws; Step 2: Pass the fiber grating pigtail through the reserved hole on the side of the invar shell of the grating package module, so that the grating area is placed in the U-shaped groove of the copper heat sink plate in the invar shell, and the pigtails at both ends of the resonant cavity fiber grating are respectively embedded in the U-shaped grooves of the pigtail fixture module; Step 3: Finely adjust the knob of the three-dimensional adjustment frame, install the fiber Bragg grating and the fiber pigtail fixture in the cavity, and apply axial prestress to the fiber Bragg grating by adjusting the fiber axial direction knob of the adjustment frame far away from the end of the fiber tensiometer. The magnitude of the constant prestress is monitored and controlled by the reading of the fiber tension. The tail end of the fiber Bragg grating is connected to the light source and the spectrum, respectively, to monitor the fiber Bragg grating spectrum and central wavelength in real time; Step 4: Accurately dispense glue on both ends of the fiber Bragg grating through the glue dispensing grooves on the copper heat sink plate; Step 5: According to the curing conditions of the UV glue, select appropriate UV curing light source curing process parameters, and firmly connect the fiber Bragg grating and the copper heat sink plate with glue; Step 6: Remove the grating package module and place it in a temperature cycle box for high temperature annealing to release the tiny structural deformation stress introduced during the package module assembly process; Step 7: Assemble the annealed copper heat sink plate and other components, and wrap the heat insulation and vibration isolation cotton outside the Invar shell, and the stress-free packaging of the fiber grating component is completed; Step 8: Connect the packaged fiber Bragg grating assembly to the laser system through fusion splicing for power-on performance testing. First, use a spectrometer to observe the consistency of the grating center wavelength before and after packaging to test the effect of stress-free packaging. Then, power on the temperature-controlled TEC in the module and use a spectrometer to detect the stability of the laser center wavelength to verify the compensation effect of the resonant cavity fiber Bragg grating on the grating area's own temperature and ambient temperature disturbances.

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