Fiber grating laser annealing system and method

Abstract

The application provides a fiber grating laser annealing system and a method thereof. The system comprises a laser annealing device, wherein the laser annealing device comprises a reference platform, a laser, a laser divergence focusing unit and a grating clamping unit; the reference platform is used for fixing the laser, the laser divergence focusing unit and the grating clamping unit; the laser is used for outputting laser to the laser divergence focusing unit; the laser divergence focusing unit is used for first diverging the laser and then focusing the laser to a grating along the longitudinal direction of a fiber to be processed; and the grating clamping unit is used for fixing the grating of the fiber to be processed. The fiber grating laser annealing system and the method thereof effectively solve the problem of uneven heating of one-side laser annealing, and integrate a real-time monitoring module of spectral parameters in the annealing process, and annealing parameters can be accurately controlled and optimized according to real-time test spectral information.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical fiber, in particular, to an optical fiber grating laser annealing system and method thereof. BACKGROUND

[0002] With the development of fiber lasers, the requirements for the core device of fiber lasers, fiber gratings, in terms of power tolerance and reliability are becoming higher and higher. The preparation process of fiber gratings generally includes fiber hydrogenation, grating writing, grating annealing, recoating and packaging. The traditional grating annealing process is to remove residual hydrogen atoms in the fiber. The commonly used method is to put the whole grating into an incubator, and the annealing temperature is generally not more than 120℃, otherwise the coating layer will be aged. However, the fiber grating produced by this process has low power tolerance, which is difficult to meet the increasing demand for high-power applications of fiber lasers. In order to improve the power tolerance of fiber gratings, local high-temperature annealing needs to be performed on the grating writing area to remove the defects caused by writing, and the temperature is generally between 300-800℃. This kind of local high-temperature annealing method usually uses external heat radiation such as resistance wire or graphite high-temperature furnace, flame, etc. However, there are many shortcomings in using this kind of heating method for local annealing, such as easy pollution and damage, and the heating area cannot be flexibly adjusted, which cannot meet the stable production in batches. In patent CN114518620A, the present inventors proposed a laser annealing system to solve the defects of external heat radiation annealing method, but there are still the following shortcomings:

[0003] (1) The fiber grating is a cylindrical structure, and the annealing method in patent CN114518620A is that the laser annealing light source is incident from a single side of the fiber grating, the annealing temperature is not uniform, and thermal stress is easy to produce, and the annealing time is long and the efficiency is low.

[0004] (2) Higher power level fiber grating requires higher annealing temperature, and the annealing time is also longer. Since the annealing method in patent CN114518620A is that the laser annealing light source is incident from a single side of the fiber grating, in order to make the fiber grating core area reach the required annealing temperature, the temperature of the incident surface will be higher, and the heat accumulation produced by long-time annealing is easy to cause damage to the cladding material of the fiber grating, and the higher power annealing parameters cannot be further optimized.

[0005] High-power fiber gratings have strict requirements on spectral parameters such as center wavelength, bandwidth and reflectivity. The control of high-temperature annealing process will directly affect the spectral parameters of fiber gratings such as center wavelength, bandwidth and reflectivity. Excessive annealing temperature or time may even cause the erasure of the grating area. The annealing system in patent CN114518620A lacks the function of real-time monitoring of the spectral parameters of fiber gratings such as center wavelength, bandwidth and reflectivity during the annealing process, and the annealing parameters are difficult to accurately control and optimize. SUMMARY

[0006] The application provides a fiber grating laser annealing system and a method thereof to solve the problems of uneven heating of unilateral laser annealing and inability to further optimize higher power annealing parameters in the process of local high-temperature annealing of high-power fiber gratings, and the application further provides the functions of real-time monitoring of spectral parameters in the annealing process, accurate control and optimization of annealing parameters.

[0007] In a first aspect, the application provides a fiber grating laser annealing system, characterized in that the system comprises a laser annealing device.

[0008] The laser annealing device comprises a reference platform, a laser, a laser divergence and focusing unit, and a grating clamping unit, wherein

[0009] The reference platform is used to fix the laser, the laser divergence and focusing unit, and the grating clamping unit.

[0010] The laser is used to output laser to the laser divergence and focusing unit.

[0011] The laser divergence and focusing unit is used to first diverge the laser and then focus the laser to a grating along the longitudinal direction of a fiber to be processed.

[0012] The grating clamping unit is used to fix the grating of the fiber to be processed.

[0013] In a second aspect, the application further provides a fiber grating laser annealing method, characterized in that the method comprises:

[0014] Shaping laser from a laser into divergent laser;

[0015] Focusing the divergent laser to a grating along the longitudinal direction of a fiber to be processed.

[0016] Performing annealing operation on the grating.

[0017] The fiber grating laser annealing system and the method thereof provided by the application have the following advantages: first, the fiber grating uniform laser annealing system adopts a ring-shaped light spot to uniformly heat the outer periphery of a fiber grating grating area, so that the fiber grating is uniformly heated and has a high annealing temperature, and the fiber grating can greatly improve the power resistance; second, the fiber grating uniform laser annealing system integrates a real-time monitoring module of spectral parameters in the annealing process, and the annealing parameters can be accurately controlled and optimized according to the real-time test spectral information. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0019] Figure 1 is a schematic diagram of a fiber grating laser annealing system provided by Embodiment 1 of the present application;

[0020] Figure 2 is a ring-shaped divergent light beam and a circular divergent light beam formed by a beam shaper provided by the present application;

[0021] Figure 3 is a schematic diagram of a fiber grating laser annealing system provided by Embodiment 2 of the present application;

[0022] Figure 4 is a schematic diagram of a fiber grating laser annealing system provided by Embodiment 3 of the present application;

[0023] Figure 5 is a schematic diagram of a fiber grating laser annealing system provided by Embodiment 4 of the present application;

[0024] Figure 6 is a schematic diagram of a fiber grating laser annealing system provided by Embodiment 5 of the present application;

[0025] Figure 7 is a schematic diagram of a fiber grating laser annealing system provided by Embodiment 6 of the present application;

[0026] Figure 8 is a schematic diagram of a fiber grating laser annealing system provided by Embodiment 7 of the present application;

[0027] Figure 9 is a schematic diagram of a fiber grating laser annealing system provided by Embodiment 8 of the present application;

[0028] Figure 10 is a transmittance spectrum curve of a grating before and after annealing detected by a spectrum analyzer and an original transmittance spectrum without the grating;

[0029] Figure 11 is a convergent light beam incident angle θ focused to a grating provided by the present application;

[0030] Figure 12 is a reflectivity variation curve with incident angle. DETAILED DESCRIPTION

[0031] The technical solutions of the present application are described in further detail below with reference to the accompanying drawings and examples. SUMMARY

[0033] As described above, the present application provides a fiber grating laser annealing system and method thereof, which uses a ring-shaped light spot to heat the fiber grating grating area by laser, so that the outer surface of the grating is uniformly heated, the annealing temperature is high, and the power resistance of the fiber grating can be greatly improved. Moreover, the real-time monitoring module of the spectrum parameter during the annealing process is integrated, and the annealing parameters can be accurately controlled and optimized according to the real-time test spectrum information.

[0034] Figure 1 and Figures 3-9 is a schematic diagram of a fiber grating laser annealing system 100 provided by an embodiment of the present application, wherein the dashed line represents a light beam, and the solid line represents an optical fiber. The system 100 comprises: a laser annealing device; the laser annealing device comprises: a reference platform 111, a laser 112, a laser divergence focusing unit 113, and a grating clamping unit 114.

[0035] The reference platform 111 is used to fix the laser 112, the laser divergence focusing unit 113, and the grating clamping unit 114. The material of the reference platform 111 is generally aluminum, stainless steel, marble, etc., which is not limited here.

[0036] The laser 112 is used to output laser to the laser divergence focusing unit 113. The wavelength of the laser is generally selected in a wavelength band with a high absorption coefficient of the optical fiber 200, for example, a mid-infrared or far-infrared laser with a wavelength ≥4 μm. The laser power is continuously adjustable, and the power is selected according to the requirements, which is generally in the order of tens of watts.

[0037] The laser divergence focusing unit 113 is used to first diverge the laser and then focus it to the grating 201 along the longitudinal direction of the optical fiber 200 to be processed. Preferably, the length of the grating 201 is 0.5 cm to 10 cm.

[0038] The laser divergence focusing unit 113 comprises a beam shaper 1131 and a focuser 1132.

[0039] The beam shaper 1131 is used to change the laser into a divergent light beam.

[0040] The beam shaper 1131 adopts a convex lens, a concave lens, a convex mirror, or a concave mirror.

[0041] The convex lens or concave lens adopted by the beam shaper 1131 can be a conical lens with an outer convex or an inner concave.

[0042] The convex mirror or concave mirror adopted by the beam shaper 1131 can be a conical mirror with an outer convex or an inner concave.

[0043] The beam shaper 1131 is located in front of the laser 112 and is used to shape the laser beam from the laser 112 into a diverging beam. When the beam shaper 1131 uses a conical lens or a conical mirror, the laser beam shaped by it is a ring-shaped diverging beam, such as... Figure 2 The left side shows a circular diverging beam. A pyramidal lens can also be used to shape the beam into a ring-shaped polygonal diverging beam. When the beam shaper 1131 uses a general spherical lens or spherical mirror, such as a convex spherical lens, a concave spherical lens, a convex spherical mirror, or a concave spherical mirror, the laser beam after shaping is a circular diverging beam or spot (e.g., a Gaussian spot). Figure 2 As shown on the right. Compared to a circular diverging beam, the energy of a ring-shaped diverging beam is concentrated on the ring. When focused onto the fiber, it has a smaller angle of incidence, reducing reflections and resulting in higher effective energy for heating and annealing the grating. Furthermore, the ring-shaped diverging beam illuminates less of the fiber portion that does not require annealing, extending from the through-hole in the focuser 1132 or plane mirror 1134, thus avoiding burning the fiber cladding. Therefore, preferably, the beam shaper 1131 is a conical lens or a conical mirror.

[0044] like Figure 6 As shown, the beam shaper 1131 can be a conical mirror, which reflects the ring beam of the laser to a direction perpendicular to the optical fiber 200, thereby making the optical path more compact. The beam shaper 1131, using a mirror, can reflect the horizontal optical path into a vertical optical path, allowing the laser 112 to be positioned horizontally, without requiring... Figure 7 As shown, it extends vertically above the beam shaper 1131, which employs a lens, thereby making the optical path and the entire system more compact.

[0045] The focuser 1132 is used to convert the diverging beam into a converging beam focused onto the grating 201, preferably, as follows: Figure 11 As shown, the incident angle θ of the converging beam focused onto the grating 201 is in the range of 10 degrees to 70 degrees. Figure 12 The reflectivity R shown n The curve showing the variation of reflectivity with incident angle, specifically from curve 401 in the figure for light incident from a less dense medium to a denser medium, shows that when the incident angle θ is in the range of 10 degrees to 70 degrees, the reflectivity R... n The increase in reflectivity is relatively slow; when the incident angle θ is greater than 70 degrees, the reflectivity R... n The reflectivity R rises rapidly, and when the incident angle θ rises to 90 degrees, the reflectivity R... nThe value is 1, meaning there is no incident light. To obtain a converged beam with high heating efficiency, the incident angle θ of the converged beam needs to be as small as possible. However, to obtain a converged beam capable of heating the outer peripheral surface of the grating 201, the laser must first diverge and then converge. It is difficult to achieve an infinitely small beam angle after divergence and convergence. This invention, through extensive experimental verification, shows that the incident angle θ of the converged beam is relatively easy to adjust within the range of 10 degrees to 70 degrees, and the reflectivity R within this range is... n The rise of the beam is relatively slow; therefore, this invention preferably uses a convergent beam incident angle θ within this range. Since the energy of the annular diverging beam is concentrated on the ring, it has a smaller incident angle when focused onto the fiber, reducing reflections and resulting in higher effective energy for heating and annealing the grating. Therefore, a tapered beam shaper 1131 is preferably used to shape the laser into an annular beam.

[0046] The focuser 1132 may be a convex lens, a concave mirror that makes the optical path more compact, or other optical elements with converging function, which are not limited here.

[0047] like Figure 1 As shown, the concave mirror used in the focuser 1132 can be a parabolic mirror, and more specifically, it can be an off-axis parabolic mirror.

[0048] When the focuser 1132 is located at the position of the optical fiber 200, it includes a through-hole for passing through the optical fiber 200, such as Figure 4 As shown.

[0049] like Figure 3 As shown, the focuser 1132 can be an ellipsoidal mirror located in front of the beam shaper 1131, which is used to converge and reflect the annular beam from the beam shaper 1131 to a direction perpendicular to the optical fiber 200, and then reflect and focus it onto the grating 201 by a plane mirror 1134 located at the position of the optical fiber 200. The plane mirror 1134 has a through hole for passing through the optical fiber 200.

[0050] like Figure 4 Or as shown in Figure 8, the focuser 1132 is an ellipsoidal mirror located at the optical fiber 200, which is used to converge and reflect the annular beam from the beam shaper 1131 onto the grating 201; or

[0051] like Figure 5 , 6As shown in Figure 7, the focuser 1132 can be a convex lens located on the optical path perpendicular to the optical fiber 200. It is used to converge the annular beam from the beam shaper 1131 onto the optical fiber 200, and then reflect and focus it onto the grating 201 by a plane mirror 1134 located on the optical fiber 200. This includes a linear scanner 1141 for adjusting the position of the focuser 1132 vertically, such that the focal point of the focuser 1132, reflected by the plane mirror 1134 located at the position on the optical fiber 200, scans the grating 201 along the longitudinal direction of the optical fiber 200.

[0052] like Figure 1 As shown, the laser divergence focusing unit 113 may further include a collimator 1133, which is used to convert the diverging beam into a collimated beam. When the laser divergence focusing unit 113 includes a collimator 1133, the focuser 1132 is used to focus the collimated beam onto the grating 201. The collimator 1133 may be a convex lens or a concave mirror to make the optical path more compact.

[0053] exist Figure 1 In the collimator 1133, the concave mirror used is a parabolic mirror, and more specifically, it can be an off-axis parabolic mirror.

[0054] The collimator 1133 is located between the beam shaper 1131 and the focuser 1132 in the optical path of the laser. It is used to transform the ring beam from the beam shaper 1131 into a collimated ring beam and illuminate the focuser 1132.

[0055] like Figures 3-7 As shown, the laser divergence and focusing unit 113 may further include a plane mirror 1134, which is used to reflect the light beam in a direction perpendicular to the optical fiber 200 or along the longitudinal direction of the optical fiber 200, that is, to change the direction of the optical path.

[0056] When the plane mirror 1134 is located at the position of the optical fiber 200, it includes a through hole for passing through the optical fiber 200.

[0057] like Figure 4 As shown in Figure 5, the plane mirror 1134 may be located between the beam shaper 1131 and the focuser 1132 in the optical path of the laser, and it is used to reflect the ring beam from the beam shaper 1131 onto the focuser 1132.

[0058] The grating clamping unit 114 is used to fix the grating 201 of the optical fiber 200 to be processed.

[0059] like Figure 1 , 3As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4 or FIG. 8, the grating holding unit 114 can include a linear scanner 1141 for controlling the grating holding unit 114 to adjust the longitudinal direction of the optical fiber 200 so that the focal point of the focuser 1132 scans on the grating 201.

[0060] The system 100 can further include a process spectrum real-time monitoring device for detecting during the period when the laser 112 stops outputting pulsed laser light, when the laser 112 is a pulsed laser for outputting pulsed laser light to the laser divergence focusing unit 113.

[0061] The process spectrum real-time monitoring device includes a broadband light source 121 and a spectrum analyzer 122.

[0062] The broadband light source 121 is used to output broadband light through the grating 201 to the spectrum analyzer 122. The broadband light can be incoherent light covering the reflection band of the grating 201 of the optical fiber 200 to be processed, and the output power is generally in the order of milliwatts. The broadband light source can be an internal integrated back-reflection-proof isolator or an external isolator.

[0063] The spectrum analyzer 122 is used to detect the spectral information of the reflected light and / or transmitted light after passing through the grating 201.

[0064] The process spectrum real-time monitoring device can further include a first mode matcher 123 and a second mode matcher 124.

[0065] The first mode matcher 123 is used to convert the broadband light into light that can be transmitted in the optical fiber 200 to be processed.

[0066] The second mode matcher 124 is used to convert the light that can be transmitted in the optical fiber 200 to be processed into light that can be received by the spectrum analyzer 122.

[0067] The spectrum analyzer 122 can be used to detect whether the center wavelength, spectral width and depth of the transmission valley in the transmission spectrum after passing through the grating 201 reach a first predetermined threshold value to optimize the annealing time and annealing temperature of the local high-temperature annealing. Figure 10As shown in the figure, the abscissa is the wavelength value of the spectrum (unit: nm), the ordinate is the normalized intensity value (unit: dB), the horizontal line 301 of 0 dB represents the original transmission spectrum without access to the grating 201, the solid line 302 is the transmission spectrum before high-temperature annealing, the dashed line 303 is the transmission spectrum after high-temperature annealing, and the horizontal line 304 represents the first predetermined threshold. As can be seen from the transmission valleys before and after annealing in the comparison figure, annealing can enhance the transmission of the grating 201. In order to remove the residual hydrogen atoms in the optical fiber 200 without causing large-area erasure of the grating area, the present application optimizes the annealing time and annealing temperature of the local high-temperature annealing by detecting whether the center wavelength, spectral width and depth of the transmission valley detected by the spectrum analyzer 122 reach the acceptable first predetermined threshold.

[0068] The annealing temperature is between 300-800°C.

[0069] The spectrum analyzer 122 can also be used to detect whether the center wavelength, spectral width and height of the reflection peak in the reflection spectrum after the grating 201 reach the second predetermined threshold to optimize the annealing time and annealing temperature of the local high-temperature annealing.

[0070] The system 100 can also include a thermal imager 130 for detecting and monitoring the annealing temperature of the grating 201.

[0071] For the convenience of understanding, the following will be further explained by examples:

[0072] Example 1

[0073] As Figure 1 As shown in the figure, the system 100 includes the laser annealing device, which includes a reference platform 111, a laser 112, a laser divergence focusing unit 113 and a grating clamping unit 114.

[0074] The reference platform 111 fixes the laser 112, the laser divergence focusing unit 113 and the grating clamping unit 114.

[0075] The laser 112 outputs laser to the laser divergence focusing unit 113; the laser divergence focusing unit 113 first diverges the laser and then focuses it along the longitudinal direction of the optical fiber 200 to the grating 201, wherein the laser divergence focusing unit 113 comprises a beam shaper 1131, a collimator 1133 and a focusing device 1132; the beam shaper 1131 is a convex conical lens located in front of the laser 112, which shapes the laser from the laser 112 into a ring-shaped divergent beam; the collimator 1133 is a parabolic concave mirror located in front of the beam shaper 1131, which changes the divergent ring-shaped beam from the beam shaper 1131 into a collimated ring-shaped beam and reflects it to a direction perpendicular to the optical fiber 200; the collimated ring-shaped beam from the collimator 1133 is converged and reflected to the grating 201 by the focusing device 1132 located at the position of the optical fiber 200, wherein the focusing device 1132 is a parabolic concave mirror comprising a through hole for passing through the optical fiber 200.

[0076] The grating clamping unit 114 fixes the grating 201 of the optical fiber 200 to be processed, wherein the grating clamping unit 114 further comprises a linear scanner 1141, and turning on the linear scanner 1141 controls the grating clamping unit 114 to adjust the longitudinal direction of the optical fiber 200, as shown by the arrow below the linear scanner 1141 in the figure, so that the focal point of the focusing device 1132 scans on the grating 201, i.e. the grating 201 slowly passes through the focal point of the focusing device 1132 for high-temperature annealing. Figure 1

[0077] The broadband light source 121 outputs broadband light to the first mode matcher 123; the first mode matcher 123 converts the broadband light into light that can be transmitted in the optical fiber 200 to be processed; the second mode matcher 124 is used to convert the light that can be transmitted in the optical fiber 200 to be processed into light that can be received by the optical spectrum analyzer 122; the optical spectrum analyzer 122 detects the spectral information of the reflected light and the transmitted light after passing through the grating 201 (such as Figure 10 ​The right side spectrum analyzer 122 detects the center wavelength, spectral width and depth of the transmission valley in the transmission spectrum after the grating 201, and the left side spectrum analyzer 122 detects the center wavelength, spectral width and height of the reflection peak in the reflection spectrum after the grating 201, and the annealing time and temperature of the local high temperature annealing are optimized according to the spectrum information of the reflection light and the transmission light, and the annealing operation is stopped to avoid damage to the grating 201 when the first predetermined threshold or the second predetermined threshold is reached. The spectrum detection and the laser heating grating 201 operation are staggered to prevent the beams from interfering with each other.

[0078] The advantages of the embodiment are as follows: first, the beam shaper 1131 adopts a conical lens, which not only makes the laser from the laser 112 into a ring-shaped divergent beam to be focused to the outer peripheral surface of the grating 201 at a small incident angle instead of heating only one side, so that the grating 201 is uniformly annealed, and compared with a general spherical lens or spherical mirror, the laser shaped by the conical lens is a ring-shaped divergent beam, which has a smaller incident angle when focused to the optical fiber, can reduce reflection, and makes the effective energy for heating and annealing the grating higher; second, the collimator 1133 converges the divergent ring-shaped beam from the beam shaper 1131 into a collimated ring-shaped beam, which facilitates adjusting the positions of the laser 112, the beam shaper 1131 and the collimator 1133 before annealing so that the beam passing through the collimator 1133 is accurately irradiated on the focuser 1132, and the collimated ring-shaped beam can reduce the incident angle of the beam finally focused on the grating 201, so that the grating 201 obtains higher annealing temperature and energy utilization rate, and in addition, the collimator 1133 adopts a mirror with reflection function instead of a lens, which can reflect the horizontal light path to the vertical light path, so that the laser 112 and the beam shaper 1131 are arranged in the horizontal direction, without the need to extend the beam shaper 1131 above in the vertical direction, thereby making the light path and the whole system more compact and saving space; third, the focuser 1132 converges and reflects the collimated ring-shaped beam from the collimator 1133 to the grating 201, further reducing the incident angle of the beam irradiated on the grating 201 and improving the incident beam energy; fourth, the grating clamping unit 114 fixes the grating 201 of the optical fiber 200 to be processed, so that the position of the grating 201 is stable, and the linear scanner 1141 in the grating clamping unit 114 is used to control the slow movement of the grating 201 in the longitudinal direction of the optical fiber 200, so that the grating 201 is uniformly annealed at high temperature in the longitudinal direction of the optical fiber 200; fifth, the spectrum information of the reflection light and the transmission light obtained by the spectrum detection is used to accurately control and optimize the annealing temperature and time of the local high temperature annealing in real time.

[0079] Examples 2 and 3

[0080] As Figure 3 shown, the system 100 of embodiment 2 compared with embodiment 1, the laser divergence focusing unit 113 omits the collimating mirror 1133, increases the plane mirror 1134, sets the focuser 1132 at the original collimating mirror 1133 position, sets the plane mirror 1134 at the original focuser 1132 position, that is, the plane mirror 1134 is located at the position of the optical fiber 200, and other parts are consistent with embodiment 1.

[0081] The focuser 1132 is an ellipsoidal concave mirror located in front of the beam shaper 1131, which changes the divergent annular beam from the beam shaper 1131 into a convergent but not collimated annular beam and reflects it in a direction perpendicular to the optical fiber 200; reflected and focused by the plane mirror 1134 located at the position of the optical fiber 200 to the grating 201, wherein the plane mirror 1134 includes a through hole for passing through the optical fiber 200.

[0082] Embodiment 2 omits the high-cost collimating mirror 1133 and increases the low-cost plane mirror 1134, and uses the ellipsoidal focuser 1132 to perform one large-angle convergence on the divergent annular beam from the beam shaper 1131, which can greatly save costs. In addition, the plane mirror 1134 and the focuser 1132 can be interchanged in position, as Figure 4 shown in embodiment 3, compared with the above two embodiments, embodiment 3 has a smaller incident angle of the final convergent beam and a higher energy utilization rate because the focuser 1132 is closer to the focal point.

[0083] Example 4

[0084] As Figure 5 shown, the system 100 of embodiment 4 compared with embodiment 3, the laser divergence focusing unit 113 increases another plane mirror 1134 located at the position of the optical fiber 200, replaces the ellipsoidal concave mirror focuser 1132 with a convex lens and sets it between the two plane mirrors 1134 on the optical path perpendicular to the optical fiber 200, which includes a linear scanner 1141 for adjusting the position of the focuser 1132 up and down, and the grating holding unit 114 omits the linear scanner 1141, and other parts are consistent with embodiment 3.

[0085] A plane mirror 1134 is located in front of the beam shaper 1131 to reflect the divergent annular beam from the beam shaper 1131 to a direction perpendicular to the optical fiber 200; a focusing lens 1132 is a convex lens located in the optical path perpendicular to the optical fiber 200 to converge the annular divergent beam reflected from the plane mirror 1134 to the optical fiber 200, which includes a linear scanner 1141 for adjusting the position of the focusing lens 1132 up and down, so that the focal point of the focusing lens 1132, after being reflected by the plane mirror 1134 located at the position of the optical fiber 200, scans the grating 201 along the longitudinal direction of the optical fiber 200, and the plane mirror 1134 located at the position of the optical fiber 200 includes a through hole for passing through the optical fiber 200.

[0086] The focusing lens 1132 including the linear scanner 1141 in embodiment 4 adopts a convex lens and is located in the optical path perpendicular to the optical fiber 200 between the two plane mirrors 1134, and the position of the focusing lens 1132 can be adjusted up and down, and by controlling the slow movement of the focal point of the beam finally focused on the grating 201 in the longitudinal direction of the optical fiber 200, the grating 201 is uniformly high-temperature annealed in the longitudinal direction of the optical fiber 200. Compared with the first three embodiments, the adjustment of the position of the grating 201 to achieve the uniform high-temperature annealing of the grating 201 in the longitudinal direction of the optical fiber 200, the operation structure of adjusting the focusing lens 1132 to control the focal point of the beam in embodiment 4 is simpler and easier to implement.

[0087] Examples 5 and 6

[0088] As shown in Figure 6 , the system 100 shown in embodiment 5 is compared with embodiment 4, the plane mirror 1134 located in front of the beam shaper 1131 in the laser divergence focusing unit 113 is omitted, and the position thereof is set to the beam shaper 1131, and the other parts are consistent with embodiment 4.

[0089] The beam shaper 1131 is an outward convex conical mirror located in front of the laser 112 to shape the laser from the laser 112 into an annular divergent beam and reflect it to the focusing lens 1132 in the direction perpendicular to the optical fiber 200.

[0090] The plane mirror 1134 located in front of the beam shaper 1131 in the laser divergence focusing unit 113 in embodiment 5 is omitted to save cost; and the beam shaper 1131 adopts a mirror instead of a lens (as shown in Figure 7 , which can also reflect the horizontal direction optical path to the vertical direction optical path, so that the laser 112 can be arranged in the horizontal direction, compared with embodiment 6 shown in Figure 7 , it is not necessary to extend in the vertical direction and be arranged above the focusing lens 1132, so that the optical path and the whole system are more compact and save space.

[0091] Example 7

[0092] As Figure 8 shown in the system 100 of embodiment 7, compared with embodiment 1, the collimating lens 1133 in the laser divergence focusing unit 113 is omitted, and the position of the beam shaper 1131 is set, and the other parts are consistent with embodiment 1.

[0093] The beam shaper 1131 is a convex conical mirror located in front of the laser 112, which shapes the laser from the laser 112 into a ring-shaped divergent beam and reflects it in a direction perpendicular to the optical fiber 200; the ring-shaped divergent beam from the beam shaper 1131 is converged and reflected to the grating 201 by the ellipsoidal focusing lens 1132 located at the position of the optical fiber 200.

[0094] In embodiment 7, the laser divergence focusing unit 113 omits the collimating lens 1133, saving cost, and reducing laser energy loss due to the reduction of one lens.

[0095] Example 8

[0096] As Figure 9 shown in the system 100 of embodiment 8, compared with embodiment 7, the laser divergence focusing unit 113 is added with the focusing lens 1132 and is arranged on the optical path perpendicular to the optical fiber 200 between the original beam shaper 1131 and the original focusing lens 1132 located at the position of the optical fiber 200, which includes a linear scanner 1141 for adjusting the position of the focusing lens 1132 up and down, and the linear scanner 1141 in the grating clamping unit 114 is omitted, and the other parts are consistent with embodiment 7.

[0097] The newly added focusing lens 1132 is a convex lens located on the optical path perpendicular to the optical fiber 200, which converges the ring-shaped divergent beam from the beam shaper 1131 onto the optical fiber 200 once, and includes a linear scanner 1141 for adjusting the position of the focusing lens 1132 up and down, so that the focal point of the focusing lens 1132 is twice converged by the original focusing lens 1132 located at the position of the optical fiber 200 and reflects the grating 201 along the longitudinal direction of the optical fiber 200, and the original focusing lens 1132 located at the position of the optical fiber 200 includes a through hole for passing through the optical fiber 200.

[0098] The focusing device 1132 added in Embodiment 8 adopts a convex lens and is arranged on the optical path perpendicular to the optical fiber 200, and its position can be adjusted up and down. By controlling the slow movement of the light beam focus point on the grating 201 in the longitudinal direction of the optical fiber 200, the grating 201 can be uniformly high-temperature annealed in the longitudinal direction of the optical fiber 200. Compared with adjusting the position of the grating 201 to realize the uniform high-temperature annealing of the grating 201 in the longitudinal direction of the optical fiber 200, the operation of adjusting the focusing device 1132 to control the light beam focus point is simpler and easier to realize.

[0099] It should be noted that although several means, units, or modules of the fiber grating laser annealing system are mentioned in the foregoing detailed description, such division is merely exemplary and not mandatory. In fact, according to the embodiments of the present application, the features and functions of two or more modules described above can be embodied in one module. Conversely, the features and functions of one module described above can be further divided into modules for embodiment.

[0100] In addition, although the operations of the fiber grating laser annealing method of the present application are described in a specific order in the accompanying drawings, this does not require or imply that the operations must be performed in this specific order, or that all of the shown operations must be performed to achieve the desired result. Additionally or alternatively, certain steps can be omitted, a plurality of steps can be combined into one step, and / or one step can be divided into a plurality of steps.

[0101] Although the spirit and principles of the present application have been described with reference to several specific embodiments, it should be understood that the present application is not limited to the disclosed specific embodiments, and the division of aspects does not mean that the features in these aspects cannot be combined to benefit. Such division is only for the convenience of expression. The present application is intended to cover various modifications and equivalent arrangements included in the spirit and scope of the appended claims.

Claims

1. A fiber grating laser annealing system, characterized in that, The system includes a laser annealing device; The laser annealing apparatus includes: a reference platform, a laser, a laser divergence and focusing unit, and a grating clamping unit; wherein... The reference platform is used to fix the laser, the laser divergence and focusing unit, and the grating clamping unit; The laser is used to output laser light to the laser divergence and focusing unit; The laser divergence and focusing unit includes a beam shaper and a focuser. The beam shaper is used to convert the laser into a ring-shaped diverging beam, and the focuser is used to focus the ring-shaped diverging beam onto the grating along the longitudinal direction of the optical fiber to be processed, so as to achieve uniform heating of the outer periphery of the grating. The grating clamping unit is used to fix the grating of the optical fiber to be processed. The system also includes a real-time process spectral monitoring device; The process spectral real-time monitoring device includes: a broadband light source and a spectral analyzer; wherein... The broadband light source is used to output broadband light through the grating to the spectrum analyzer; The spectrometer is used to detect the spectral information of reflected and / or transmitted light after passing through the grating.

2. The laser annealing system according to claim 1, characterized in that, The process spectral real-time monitoring device further includes a first mode matcher and a second mode matcher; wherein The first mode matcher is used to convert the broadband light into light that is transmitted in the optical fiber to be processed; The second mode matcher is used to convert the light transmitted in the optical fiber to be processed into light received by the spectrometer.

3. The laser annealing system according to claim 1, characterized in that, The laser divergence and focusing unit also includes a collimator, which is used to convert the annular diverging beam into a collimated beam; The focuser is used to focus the collimated beam onto the grating.

4. The laser annealing system according to claim 1, characterized in that, The laser divergence and focusing unit also includes a plane mirror, which is used to reflect the light beam in a direction perpendicular to the optical fiber or along the longitudinal direction of the optical fiber.

5. The laser annealing system according to claim 3, characterized in that, The beam shaper uses a convex lens, a concave lens, a convex mirror, or a concave mirror; The focusing device and the collimator are either convex lenses or concave mirrors.

6. The laser annealing system according to claim 5, characterized in that, The beam shaper uses either a convex conical lens (convex outwards) or a concave conical lens (concave inwards).

7. The laser annealing system according to claim 5, characterized in that, The beam shaper uses either a convex conical mirror that is convex outwards, or a concave conical mirror that is concave inwards.

8. The laser annealing system according to claim 5, characterized in that, The concave mirrors used in the focusing and collimating are parabolic mirrors.

9. The laser annealing system according to claim 1, characterized in that, The focuser is located at the position of the optical fiber, including a through-hole for passing through the optical fiber.

10. The laser annealing system according to claim 1, characterized in that, The laser divergence and focusing unit further includes a plane mirror for reflecting the light beam in a longitudinal direction along the optical fiber, the plane mirror being located at the position of the optical fiber and including a through-hole for passing through the optical fiber.

11. The laser annealing system according to claim 1, characterized in that, The beam shaper is located in front of the laser.

12. The laser annealing system according to claim 11, characterized in that, The beam shaper is a conical mirror used to reflect the ring beam of the laser in a direction perpendicular to the optical fiber.

13. The laser annealing system according to claim 1, characterized in that, The focuser is an ellipsoidal mirror located in front of the beam shaper, used to converge and reflect the annular diverging beam from the beam shaper to a direction perpendicular to the optical fiber, and then reflect and focus it onto the grating by a plane mirror located at the position of the optical fiber; or The focuser is an ellipsoidal mirror located at the optical fiber, used to converge and reflect the annular diverging beam from the beam shaper onto the grating; or The focuser is a convex lens located on the optical path perpendicular to the optical fiber. It is used to converge the annular diverging beam from the beam shaper onto the optical fiber, and then reflect and focus it onto the grating by a plane mirror located on the optical fiber.

14. The laser annealing system according to claim 3, characterized in that, The collimator is located between the beam shaper and the focuser in the optical path of the laser. It is used to transform the annular diverging beam from the beam shaper into a collimated annular beam and illuminate the focuser.

15. The laser annealing system according to claim 4, characterized in that, The plane mirror is located between the beam shaper and the focuser in the optical path of the laser, and is used to reflect the annular diverging beam from the beam shaper onto the focuser.

16. The laser annealing system according to claim 11 or 12, characterized in that, The focuser is a convex lens located on an optical path perpendicular to the optical fiber. It includes a linear scanner for adjusting the position of the focuser up and down, such that the focal point of the focuser is reflected by a plane mirror located at the position of the optical fiber and scans the grating along the longitudinal direction of the optical fiber.

17. The laser annealing system according to any one of claims 1-12, characterized in that, The grating clamping unit includes a linear scanner, which controls the grating clamping unit to adjust the longitudinal direction of the optical fiber so that the focus of the focuser scans on the grating.

18. The laser annealing system according to any one of claims 1-12, characterized in that, The spectrometer is used to detect whether the center wavelength, spectral width, and depth of the transmission valley in the transmission spectrum after passing through the grating reach a first predetermined threshold in order to optimize the annealing time and annealing temperature of local high-temperature annealing.

19. The laser annealing system according to any one of claims 1-12, characterized in that, The spectrometer is used to detect whether the center wavelength, spectral width, and height of the reflection peak in the reflection spectrum after passing through the grating reach a second predetermined threshold in order to optimize the annealing time and annealing temperature of local high-temperature annealing.

20. The laser annealing system according to any one of claims 1-12, characterized in that, The system also includes a thermal imager for detecting and monitoring the annealing temperature of the grating.

21. The laser annealing system according to any one of claims 1-12, characterized in that, The laser is a pulsed laser, which is used to output pulsed laser light to the laser divergence and focusing unit; The process spectrum real-time monitoring device is used to perform detection during the period when the pulsed laser stops outputting pulsed laser light.

22. The laser annealing system according to any one of claims 2-12, characterized in that, The incident angle of the annular diverging beam focused onto the grating is in the range of 10 degrees to 70 degrees.

23. The laser annealing system according to any one of claims 1-12, characterized in that, The length of the grating is 0.5cm to 10cm.

24. The laser annealing system according to claim 18, characterized in that, The annealing temperature is between 300 and 800°C.

25. A method for laser annealing of fiber optic gratings, characterized in that, The fiber grating laser annealing system according to claim 1, the method comprising: The laser beam from the laser is shaped into a ring-shaped diverging beam; The annular diverging beam is focused onto the grating along the longitudinal direction of the optical fiber to be processed, so as to achieve uniform heating of the outer periphery of the grating. The grating is annealed.

26. The laser annealing method according to claim 25, characterized in that, The method further includes: During the annealing process, the spectral information of the reflected and / or transmitted light after the broadband light passes through the grating is detected.

27. The laser annealing method according to claim 26, characterized in that, These include: The broadband light is converted into light that is transmitted in the optical fiber to be processed; The light transmitted in the optical fiber to be processed is converted into light received by the spectrometer.

28. The laser annealing method according to claim 25, characterized in that, The method further includes: The annular diverging beam is transformed into a collimated beam; The collimated beam is focused onto the grating.

29. The laser annealing method according to claim 27 or 28, characterized in that, The method further includes: reflecting the light beam in a direction perpendicular to the optical fiber or along the longitudinal direction of the optical fiber using a plane mirror.

30. The laser annealing method according to claim 25, characterized in that, The method further includes reflecting the annular diverging beam of the laser in a direction perpendicular to the optical fiber.

31. The laser annealing method according to claim 25, characterized in that, The method further includes: The annular diverging beam is converged and reflected in a direction perpendicular to the optical fiber, and then reflected and focused onto the grating by a plane mirror located at the position of the optical fiber.

32. The laser annealing method according to claim 25, characterized in that, The method further includes: The annular diverging beam is converged and reflected onto the grating by a parabolic or ellipsoidal mirror located on the optical fiber; or The annular diverging beam is focused onto the optical fiber and then reflected and focused onto the grating by a plane mirror located on the optical fiber.

33. The laser annealing method according to claim 25, characterized in that, The method further includes: converting the annular diverging beam into a collimated annular beam.

34. The laser annealing method according to claim 25, characterized in that, The method further includes: adjusting the position of a convex lens on an optical path perpendicular to the optical fiber, such that the focal point of the convex lens is reflected by a plane mirror located at the position of the optical fiber and scans the grating along the longitudinal direction of the optical fiber.

35. The laser annealing method according to claim 25, characterized in that, The method further includes: controlling the grating to adjust the longitudinal direction of the optical fiber, so that the focal point focused on the grating scans on the grating.

36. The laser annealing method according to any one of claims 26-28, characterized in that, The method further includes: detecting whether the center wavelength, spectral width, and depth of the transmission valley in the transmission spectrum after passing through the grating reach a first predetermined threshold to optimize the annealing time and annealing temperature of local high-temperature annealing.

37. The laser annealing method according to any one of claims 26-28, characterized in that, The method further includes: detecting whether the center wavelength, spectral width, and height of the reflection peak in the reflection spectrum after passing through the grating reach a second predetermined threshold to optimize the annealing time and annealing temperature of local high-temperature annealing.

38. The laser annealing method according to any one of claims 25-28, characterized in that, The method further includes using a thermal imager to detect and monitor the annealing temperature of the grating.

39. The laser annealing method according to any one of claims 26-28, characterized in that, The method further includes: The laser is a pulsed laser; During the period when the pulsed laser output stops, the spectral information of the reflected and / or transmitted light after the broadband light passes through the grating is detected.

40. The laser annealing method according to any one of claims 25-28, characterized in that, The incident angle of the converging beam focused onto the grating is in the range of 10 degrees to 70 degrees.

41. The laser annealing method according to any one of claims 25-28, characterized in that, The length of the grating is 0.5cm to 10cm.

42. The laser annealing method according to claim 36, characterized in that, The annealing temperature is between 300 and 800°C.

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