Online power restoration method and device for fiber laser

Abstract

The method comprises the following steps: determining a to-be-repaired fiber laser, and selecting a bleaching light input arm according to the type of the to-be-repaired fiber laser; welding an output optical fiber of the blue light source with a bleaching light input arm of the to-be-repaired optical fiber laser; turning on the to-be-repaired fiber laser, synchronously turning on a blue light source, measuring the output power of the fiber laser in real time through time domain information, and monitoring the quality of a light beam at the same time; after bleaching light is input, when the output power of the optical fiber laser is increased to the initial power of the optical fiber laser and the mode instability threshold value is recovered to the initial level of the optical fiber laser, the blue light source can be turned off, and online power restoration of the optical fiber laser is completed. The optical fiber laser does not need to be disassembled or the gain optical fiber does not need to be separated, bleaching light is injected after the blue light source is connected to any input end of the pumping signal beam combiner, blue light laser is synchronously turned on in the working state of the optical fiber laser, and repairing can be completed.

Description

Technical Field

[0001] The present invention mainly relates to the field of fiber laser technology, and in particular to an on-line power repair method and device for a fiber laser. Background Art

[0002] In a fiber laser, a gain fiber doped with rare earth ions is a core component. During long-term use, the laser transmitted inside it will cause the gain and transmission ability of the fiber to degenerate, resulting in an increase in the internal transmission loss of the fiber laser, a decrease in the output power, an aggravation of the thermal effect, a reduction in the beam quality, and a decrease in the mode instability threshold. In recent years, the extensive application of fiber lasers has drawn the attention of researchers to the ability degradation of fiber lasers and the photon darkening effect has been proposed. The photon darkening effect refers to the fact that in a rare earth ion-doped fiber with a high doping concentration, such as a ytterbium-doped fiber, the doped ions are irradiated by laser to generate color center defects, resulting in a permanent degradation of the fiber gain ability. Since the matrix of the doped fiber is glass, a similar photon darkening effect may also exist. Existing research has proven that the photon darkening effect leads to a phenomenon that the power conversion efficiency of a fiber with a high concentration of rare earth ions decreases with the increase of the pump light action time. It causes additional loss of the fiber to the laser, and this loss increases with the increase of the pump action time. Its formation process is monotonous and irreversible. At the same time, the absorption spectrum change, refractive index change, mode instability threshold reduction, and temperature rise phenomenon caused by the photon darkening effect have also been confirmed by research.

[0003] To suppress the photon darkening effect, obtain a more stable laser output, and extend the service life of a rare earth-doped fiber laser, many units internationally have conducted extensive and in-depth research on the suppression methods of the photon darkening effect. According to the mechanism and form of photon darkening, existing research has proposed to design a new fiber laser system by means of fiber composition and process design, fiber carrier gas, and fiber bleaching to reduce the influence of the photon darkening effect. The research results up to now include the development of a new type of anti-photon darkening fiber laser and the repair of the gain fiber. Among them, in the patent application with the publication number CN104993369A, by adding darkening light sources of 793 nm and 808 nm in the laser structure design, but the additional loss recovery is relatively limited. In the patent application with the publication number CN115057631A, the photon darkening bleaching of the gain fiber is achieved by using a carrier gas and multi-segment optical bleaching, and the process is relatively complex. In the patent application with the publication number CN110247292A, a 500 nm - 550 nm green light source is applied to suppress the photon darkening effect. The existing invention results mainly focus on bleaching the fiber itself, and the bleaching effects in the near-infrared and green light bands of the whole machine bleaching are relatively effective. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention proposes an on-line power repair method and device for a fiber laser.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides an on-line power repair method for a fiber laser, including the following steps: Determine the fiber laser to be repaired; Select the bleaching light input arm according to the type of the fiber laser to be repaired; Fuse the output fiber of the blue light source and the bleaching light input arm of the fiber laser to be repaired; Turn on the fiber laser to be repaired, synchronously turn on the blue light source, and measure the output power of the fiber laser in real time through time-domain information, while monitoring the beam quality; After the bleaching light is input, when the output power of the fiber laser will increase to the initial power of the fiber laser, and at the same time the mode instability threshold returns to the initial level of the fiber laser, the blue light source can be turned off to complete the on-line power repair of the fiber laser.

[0006] Further, determining the fiber laser to be repaired includes: when the fiber laser is affected by the photon darkening effect, the mode instability threshold decreases. When the mode instability threshold decreases to the operating power of the fiber laser, the fiber laser shows the phenomena of a sudden drop in the output power in the time domain and a rapid switching of the output spot shape between the fundamental mode and the high-order mode. At this time, the fiber laser needs to be repaired.

[0007] Further, the present invention also includes verifying the fiber laser that has completed the on-line repair. By continuously operating the fiber laser at the initial power for one hour without a power drop and without a rapid switching of the output spot shape between the fundamental mode and the high-order mode, the repair effect of the blue light on-line bleaching is verified.

[0008] The fiber laser to be repaired can be a fiber laser oscillator, and the bleaching light input arm is any one of the pump fibers of the pump combiner in the fiber laser oscillator.

[0009] The fiber laser to be repaired can be a fiber laser amplifier, and the bleaching light input arm is the signal fiber or any one of the pump fibers of the pump signal combiner in the fiber laser amplifier.

[0010] On the other hand, the present invention provides an on-line power repair device for a fiber laser, and the fiber laser is a fiber laser oscillator or a fiber laser amplifier.

[0011] An on-line power repair device for a fiber laser, wherein the fiber laser is a fiber laser oscillator, and the bleaching light input arm is any unconnected pump module or any pump fiber disconnected from the pump module in the pump combiner of the fiber laser oscillator. The output fiber of the blue light source is fused with the bleaching light input arm of the fiber laser to be repaired.

[0012] An on-line power repair device for a fiber laser, wherein the fiber laser is a fiber laser amplifier. The signal fiber of the pump signal combiner in the fiber laser amplifier is cut off from the seed light output fiber and used as the bleaching light input arm, or the signal fiber of the pump signal combiner in the fiber laser amplifier couples the output fiber of the blue light source and the signal fiber of the signal pump combiner through a wavelength division multiplexer. The input fiber of the wavelength division multiplexer fused with the output fiber of the blue light source is used as the bleaching light input arm, or any unconnected pump module or any pump fiber disconnected from the pump module in the pump signal combiner of the fiber laser amplifier is used as the bleaching light input arm.

[0013] Compared with the prior art, the technical effects of the present invention are as follows: The present invention does not require disassembling the fiber laser or separating the gain fiber. After connecting the blue light source to any input end of the pump signal combiner and injecting bleaching light, when the fiber laser is in the working state, the blue laser is turned on synchronously to complete the repair. The method is simple and convenient, has strong adaptability, and low cost. The laser in the blue light band used in the present invention can efficiently repair the power drop and beam quality drop caused by photon darkening. Compared with the previous invention results, the repair efficiency of on-line bleaching has been greatly improved. Description of the Drawings

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the structures shown in these drawings without creative efforts.

[0015] Figure 1 It is a schematic structural diagram when repairing a fiber laser oscillator in an embodiment. Figure 2 It is a schematic structural diagram when repairing a fiber laser amplifier in an embodiment. Figure 3 It is a schematic diagram of a repair example of a fiber laser amplifier repaired by a laser bleaching light source provided by the present invention from the signal fiber. Figure 4 It is a repair effect diagram of injecting bleaching light from the signal arm. Figure 5The repair effect diagram of injecting bleaching light from the pump arm; Figure 6 It is a schematic structural diagram of an embodiment when repairing an optical fiber laser amplifier. Specific implementation mode

[0016] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0017] The present invention provides an on-line power repair method for an optical fiber laser, including the following steps: Determine the optical fiber laser to be repaired; Select the bleaching light input arm according to the type of the optical fiber laser to be repaired; Fuse the output optical fiber of the blue light source and the bleaching light input arm of the optical fiber laser to be repaired; Turn on the optical fiber laser to be repaired, synchronously turn on the blue light source, and measure the output power of the optical fiber laser in real time through time-domain information, while monitoring the beam quality; After injecting the bleaching light, when the output power of the optical fiber laser rises to the initial power of the optical fiber laser, and at the same time the mode instability threshold returns to the initial level of the optical fiber laser, the blue light source can be turned off to complete the on-line power repair of the optical fiber laser.

[0018] When the optical fiber laser is affected by the photon darkening effect, the mode instability threshold decreases. When the mode instability threshold decreases to the operating power of the optical fiber laser, the output of the laser will show a mode instability phenomenon. The mode instability phenomenon is manifested as: the power of the optical fiber laser drops suddenly in the time domain (the evaluation method of the sudden drop is that the drop speed exceeds the set threshold) and the output spot shape quickly switches between the fundamental mode and the high-order mode (that is, the output spot shape switches between the fundamental mode and the high-order mode and the switching speed exceeds the set threshold). The photon darkening effect will also cause the output power of the laser to decrease slowly. When the photon darkening effect accumulates with the working time of the optical fiber laser, the output power will have an obvious permanent decrease.

[0019] When a fiber laser is affected by the photon darkening effect, the mode instability threshold decreases. When the threshold drops to the operating power of the laser, mode instability may occur in the laser output, manifested as a sudden drop in power in the time domain and a rapid switching of the output spot shape between the fundamental mode and the high-order mode. The photon darkening effect also causes a slow decrease in the laser output power. When the photon darkening effect accumulates with the working time of the laser, the output power will show a significant permanent decrease. The present invention proposes that blue-light bleaching can completely repair the damage caused by the photon darkening effect to the fiber laser. By blue-light bleaching, the output power of the fiber laser damaged by the photon darkening effect will quickly recover to the initial power before the fiber laser is damaged by the photon darkening effect, and the mode instability threshold of the fiber laser damaged by the photon darkening effect will recover to the initial level before the fiber laser is damaged by the photon darkening effect.

[0020] For fiber lasers with different initial powers and usage times, the degree of influence by the photon darkening effect is different. By adjusting the bleaching light power, the repair can be completed within a few minutes. When the output power of the fiber laser recovers to the initial power, the mode instability threshold will simultaneously recover to the initial level before the fiber laser is damaged by the photon darkening effect. When the laser operates at the initial power without mode instability, the blue-light source can be turned off to complete the on-line repair. Further, the repair effect can be verified. By continuously operating the repaired fiber laser at the initial power for one hour without power drop and without mode instability, the repair effect of blue-light on-line bleaching can be verified. The laser center wavelength of the blue-light source output is 400 - 460 nm, and the output power is greater than 3 mW.

[0021] The fiber laser to be repaired can be a fiber laser oscillator, and the bleaching light input arm is any one of the pump fibers of the pump combiner in the fiber laser oscillator. Take any pump fiber that is not connected to the pump module at the input end of the pump combiner as the bleaching light input arm, or cut off the connection between any pump fiber and the pump module and use it as the bleaching light input arm, and use a fusion splicer to fuse the output fiber of the blue-light source and the bleaching light input arm.

[0022] The fiber laser to be repaired can be a fiber laser amplifier, and the bleaching light input arm is the signal fiber or any one of the pump fibers of the pump signal combiner in the fiber laser amplifier. Cut off the signal fiber of the pump signal combiner from the seed light output fiber and use it as the bleaching light input arm, and fuse it with the output fiber of the blue-light source; or use a wavelength division multiplexer to couple the output fiber of the blue-light source and the signal fiber of the signal pump combiner.

[0023] Figure 1FIG. 0 is a schematic structural diagram of an embodiment during the repair of a fiber laser oscillator. The online power repair of the fiber laser is realized by using the fiber laser online power repair method provided in the above embodiment. The fiber laser oscillator is used as the fiber laser to be repaired. The pumping method of the fiber laser oscillator is not limited, and it can be a forward pumping structure, a backward pumping structure or a bidirectional pumping structure. The fiber laser oscillator to be repaired includes a pumping module 11, a pumping combiner 12, a high-reflection fiber grating 13, a low-reflection fiber grating 14, a gain fiber 15, a cladding light filter 16 and an output end cap 17. The repair device includes a blue light source 21 and a regulating power supply 22. A cladding light filter 16 is connected to the output optical fiber of the fiber laser oscillator to realize the filtering of the cladding light.

[0024] Select a pumping optical fiber at the input end of the pumping combiner of the fiber laser oscillator to be repaired that is not connected to the pumping module as the bleaching light input arm and fuse it with the output optical fiber of the blue light source. Alternatively, disconnect any pumping optical fiber connected to the pumping module from the original pumping module and fuse the output optical fiber of the blue light source with this pumping optical fiber.

[0025] Turn on the fiber laser oscillator to be repaired and simultaneously turn on the blue light source to inject blue light into the fiber laser oscillator to be repaired. Monitor the output power of the fiber laser oscillator to be repaired in real time, and determine the repair conditions of the mode instability threshold and the beam quality through the time-domain information and the spot morphology. For the fiber laser oscillator to be repaired that has undergone photon darkening, during a period of time under the action of the bleaching light source, it can be monitored that the output power of the fiber laser oscillator to be repaired increases significantly, reaches saturation in a short time, and does not exhibit mode instability, and the beam quality is stable and good. After reaching saturation, turn off the regulating power supply 22 of the blue light source 21 and disconnect the connection between the output optical fiber of the blue light source and the fiber laser oscillator. The fiber laser oscillator can return to its original state.

[0026] Figure 2 FIG. 10 is a schematic structural diagram of an embodiment during the repair of a fiber laser amplifier. The online power repair of the fiber laser is realized by using the fiber laser online power repair method provided in the above embodiment. The fiber laser amplifier is used as the fiber laser to be repaired. The fiber laser amplifier includes a seed light source 18, a pumping module 11, a pumping signal combiner 19, a gain fiber 15, a cladding light filter 16 and an output end cap 17. The repair device includes a blue light source 21 and a regulating power supply 22. Cladding light filters 16 are respectively connected to the output optical fibers of the fiber laser amplifier to realize the filtering of the cladding light.

[0027] Select the pump fiber of the pump module that is not connected to the forward or backward pump signal combiner of the fiber laser amplifier to be repaired as the bleaching light input arm and fuse it with the output fiber of the blue light source, or disconnect any pump fiber connected to the pump module from the original pump module and fuse the output fiber of the blue light source with this pump fiber.

[0028] Turn on the fiber laser amplifier to be repaired and turn on the blue light source at the same time to inject blue light into the fiber laser amplifier to be repaired. The other pump modules can remain in the working state, monitor the output power of the fiber laser amplifier in real time, and determine the repair status of the mode instability threshold and beam quality through time-domain information and spot morphology. For a fiber laser that has undergone photon darkening, during a period of time under the action of the bleaching light source, a significant increase in output power can be monitored, and it reaches saturation in a short time without mode instability. After reaching saturation, turn off the control power supply 22 of the blue light source 21 and the power supply of the fiber laser amplifier, and disconnect the connection between the output fiber of the blue light source and the fiber laser amplifier. The fiber laser amplifier can return to its original state.

[0029] Figure 3 It is a schematic structural diagram when implementing the repair of a fiber laser amplifier in an embodiment, and is different from Figure 2 the embodiment shown. In this embodiment, the signal fiber of the pump signal combiner 19 is cut off and used as the bleaching light input arm, and is fused with the output fiber of the blue light source.

[0030] Turn on the fiber laser amplifier to be repaired and turn on the blue light source at the same time to inject blue light into the fiber laser amplifier to be repaired. After injecting the bleaching light, the gain fiber in the amplifier structure can be repaired. Through experimental verification, injecting bleaching light through the signal fiber can achieve higher-efficiency bleaching. As Figure 4 and Figure 5 shown, taking the bleaching of a fiber laser with 450nm blue light as an example, for the same fiber laser, after bleaching for the same time in the damaged state, record the output power to represent the bleaching speed during the bleaching process, and record the laser output power after the output power no longer rises to represent the saturation effect of bleaching. Compared with injecting bleaching light from the pump arm, injecting bleaching light from the signal arm of the pump signal combiner can obtain a faster bleaching speed and a higher bleaching saturation effect. Injecting only 450nm blue light from the signal arm can completely restore the output power of the fiber laser.

[0031] Figure 6 It is a schematic structural diagram when implementing the repair of a fiber laser amplifier in an embodiment, and is different from Figure 3The difference of the illustrated embodiment lies in that a wavelength division multiplexer 23 is added, specifically including: The fiber laser amplifier includes a seed light source 18, a pump module 11, a pump signal combiner 19, a wavelength division multiplexer 23, a gain fiber 15, a cladding light filter 16, and an output end cap 17. The repair device includes a blue light source 21 and a regulation power supply 22. The first input optical fiber on the input side of the wavelength division multiplexer 23 is fused to the output optical fiber of the seed light source 18, and the second input optical fiber on the input side of the wavelength division multiplexer 23 serves as a bleaching light input arm and is fused to the output optical fiber of the blue light source 21. The output optical fiber of the blue light source 21 and the signal optical fiber of the signal pump combiner 19 are coupled through the wavelength division multiplexer 23. When repairing the fiber laser amplifier, the output optical fiber of the blue light source 21 is coupled into the signal optical fiber through the wavelength division multiplexer 23, and the gain fiber in the fiber laser amplifier is repaired by controlling the blue light source 21 to inject bleaching light through the regulation power supply 22, realizing efficient bleaching in the online state. Cladding light filters 16 are respectively connected to the output optical fiber of the seed light source 18 and the output optical fiber of the fiber laser amplifier to filter the cladding light.

[0032] Matters not described in this invention are well-known techniques.

[0033] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0034] The above-described embodiments only represent several implementation manners of this application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can still be made, and these all belong to the protection scope of this application. Therefore, the protection scope of this application should be subject to the appended claims.

[0035] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An online power repair method for a fiber laser, characterized in that, It includes the following steps: Determine the fiber laser to be repaired; Select the bleaching light input arm according to the type of the fiber laser to be repaired; Fuse the output fiber of the blue light source and the bleaching light input arm of the fiber laser to be repaired; Turn on the fiber laser to be repaired, synchronously turn on the blue light source, measure the output power of the fiber laser in real time through time-domain information, and monitor the beam quality at the same time; After the bleaching light is input, when the output power of the fiber laser will increase to the initial power of the fiber laser, and the mode instability threshold returns to the initial level of the fiber laser, the blue light source can be turned off to complete the online power repair of the fiber laser.

2. The online power repair method of the fiber laser according to claim 1, characterized in that The fiber laser to be repaired is a fiber laser oscillator, and the bleaching light input arm is any one of the pump fibers of the pump combiner in the fiber laser oscillator.

3. The online power repair method of the fiber laser according to claim 1, characterized in that The fiber laser to be repaired is a fiber laser amplifier, and the bleaching light input arm is the signal fiber of the pump signal combiner in the fiber laser amplifier or any one of the pump fibers.

4. The online power repair method of the fiber laser according to claim 1, characterized in that The laser output by the blue light source has a central wavelength of 400 - 460 nm and an output power greater than 3 mW.

5. The online power repair method of an optical fiber laser according to any one of claims 1 to 4, characterized in that, Determining the fiber laser to be repaired includes: when the fiber laser is affected by the photon darkening effect, the mode instability threshold decreases. When the mode instability threshold decreases to the operating power of the fiber laser, the fiber laser shows the phenomena of a sudden drop in output power in the time domain and a rapid switching of the output spot shape between the fundamental mode and the high-order mode. At this time, the fiber laser needs to be repaired.

6. The on-line power restoration method of an optical fiber laser according to claim 5, characterized in that It also includes verifying the fiber laser that has completed the online repair. By ensuring that the fiber laser operates at the initial power for one hour without a power drop and without a rapid switching of the output spot shape between the fundamental mode and the high-order mode, the repair effect of blue light online bleaching is verified.

7. An on-line power repair device for a fiber laser implementing the on-line power repair method of the fiber laser as described in claim 1, characterized in that, The fiber laser is a fiber laser oscillator, the bleaching light input arm is any unconnected pump module or any pump fiber disconnected from the pump module in the pump combiner of the fiber laser oscillator, and the output fiber of the blue light source is fused with the bleaching light input arm of the fiber laser to be repaired.

8. The on-line power restoration device for an optical fiber laser according to claim 7, wherein, The laser output by the blue light source has a central wavelength of 400 - 460 nm and an output power greater than 3 mW.

9. An online power repair device for a fiber laser implementing the online power repair method of the fiber laser as described in claim 1, characterized in that, The fiber laser is a fiber laser amplifier. After the signal fiber of the pump signal combiner in the fiber laser amplifier is cut off from the seed light output fiber, it is used as the bleaching light input arm. Or the signal fiber of the pump signal combiner in the fiber laser amplifier couples the output fiber of the blue light source and the signal fiber of the signal pump combiner through a wavelength division multiplexer. The input fiber of the wavelength division multiplexer fused with the output fiber of the blue light source is used as the bleaching light input arm. Or any unconnected pump module or any pump fiber disconnected from the pump module in the pump signal combiner of the fiber laser amplifier is used as the bleaching light input arm.

10. The on-line power repair device for an optical fiber laser according to claim 9, characterized in that, The laser output by the blue light source has a central wavelength of 400 - 460 nm and an output power greater than 3 mW.

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