Space fiber laser photobleaching device and use method

Abstract

The invention provides a space fiber laser photobleaching device and a use method, the space fiber laser is an erbium-doped fiber laser, a gain fiber in the erbium-doped fiber laser is an erbium-doped fiber, and the gain fiber of the erbium-doped fiber laser generates fiber defects under a space irradiation condition. Therefore, the absorption coefficient of the gain optical fiber at 980nm is sharply increased, so that the gain optical fiber only absorbs signal light within a certain length and does not have an optical signal amplification effect; the erbium-doped fiber laser is connected with the irradiation bleaching laser light source, and the irradiation bleaching laser light source is used for outputting bleaching laser with the central wavelength ranging from 400 nm to 500 nm and injecting the bleaching laser into a gain fiber of the erbium-doped fiber laser so as to repair fiber defects and laser performance degradation caused by space irradiation of the erbium-doped fiber laser.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of fiber lasers, and particularly to a spatial fiber laser optical bleaching device and a usage method thereof. Background Art

[0002] Spatial laser communication has advantages such as fast transmission speed, large bandwidth, and good confidentiality, and is one of the key development directions for future inter-satellite communication. Laser communication requires a fast enough transmission rate and a high enough transmission power. Erbium-doped fiber amplifiers with erbium-doped fibers as the core components are widely used as signal amplifiers at the transmitting end and receiving end of spatial laser communication. Erbium-doped fibers can amplify optical signals in the 1550nm band by virtue of their unique three-level structure. Spatial remote sensing detection has important applications in environmental monitoring, land resource management, disaster emergency, and marine science. Fiber lasers, with their unique advantages, are widely used as light sources for active remote sensing devices (such as lidar). The 1550nm band narrow pulse width laser light source with an erbium-doped fiber as the core plays an important supporting role in the lidar to achieve sub-centimeter ranging accuracy and has become an important part of modern remote sensing detection systems.

[0003] However, erbium-doped fibers will inevitably be affected by the irradiation of space particles in space. In the space irradiation environment, erbium-doped fibers are impacted by high-energy particles to generate an ionization effect, and a large number of carriers are generated in the fibers. These carriers combine with the original defects and radiation-induced defects to form color centers with strong absorption peaks. The absorption peaks of some of these color centers generate radiation-induced absorption in the working band of the erbium-doped fiber. Radiation-induced absorption will cause a significant increase in the loss of the fiber in the working band and a decrease in the gain performance. In addition, space irradiation will also cause a sharp decline in the laser slope efficiency, thereby affecting the smooth progress of spatial laser communication tasks and remote sensing detection tasks.

[0004] To solve these problems, researchers have conducted many explorations on methods to improve the radiation resistance of erbium-doped fiber lasers in aspects such as optimizing the fiber preparation process, post-treatment, and optimizing the doping ratio of rare earth ions. For example, by changing the fiber preparation process, such as increasing the oxygen concentration, the photon darkening effect of erbium-doped fibers can be enhanced, and the radiation resistance of the fibers can be improved. The radiation resistance of erbium-doped fibers can also be significantly improved by loading hydrogen and deuterium. However, as time goes by, gases such as deuterium and hydrogen will overflow in the fiber, causing the erbium-doped fiber laser to lose its radiation resistance. In addition, if the gas concentration loaded in the fiber is too high, the strong absorption of hydrogen and deuterium in the near-infrared region will significantly reduce the slope efficiency. There are also studies showing that doping cerium ions can also effectively improve the radiation resistance of fibers, but doping cerium will cause the core numerical aperture to increase, reduce the conversion efficiency, and is not conducive to the application of this technology in erbium-doped fiber lasers. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention proposes a spatial fiber laser optical bleaching device and a usage method, which repair the defects caused by spatial irradiation through an irradiation bleaching laser light source, improving the service life and output power stability of the fiber laser, and enhancing the service life of space optical communication and space-based remote sensing detection devices.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides a spatial fiber laser optical bleaching device, including a spatial fiber laser. The spatial fiber laser is an erbium-doped fiber laser, and the gain fiber in the erbium-doped fiber laser is an erbium-doped fiber. The gain fiber of the erbium-doped fiber laser will generate fiber defects under spatial irradiation conditions, resulting in a sharp increase in the absorption coefficient of the gain fiber at 980 nm, such that the gain fiber only absorbs signal light within a certain length and does not have the function of optical signal amplification. The erbium-doped fiber laser is connected to an irradiation bleaching laser light source, which is used to output bleaching laser with a central wavelength in the range of 400 - 500 nm and inject it into the gain fiber of the erbium-doped fiber laser whose gain fiber has fiber defects and laser performance degradation caused by spatial irradiation, so as to repair the fiber defects and laser performance degradation caused by spatial irradiation in the erbium-doped fiber laser.

[0007] The usage method of the above spatial fiber laser optical bleaching device includes the following steps: (1) The spatial fiber laser performs space optical communication or remote sensing detection tasks in a space environment; (2) Spatial irradiation causes fiber defects including color centers to be generated in the gain fiber of the spatial fiber laser, resulting in a decrease in laser performance, and thus causing a sharp increase in the absorption coefficient of the gain fiber at 980 nm, such that the gain fiber only absorbs signal light within a certain length and does not have the function of optical signal amplification. (3) Turn on the irradiation bleaching laser light source. The irradiation bleaching laser light source outputs bleaching laser and injects it into the gain fiber of the spatial fiber laser whose gain fiber has fiber defects and laser performance degradation caused by spatial irradiation to perform on-line bleaching of the gain fiber, and repair the fiber defects and laser performance degradation caused by spatial irradiation.

[0008] After the spatial fiber laser completes the repair of the fiber defects and laser performance degradation caused by spatial irradiation, repeat steps (1) to (3) to work.

[0009] Compared with the prior art, the technical effects of the present invention: In the spatial fiber laser device of the present invention, an irradiation bleaching light source with a central wavelength in the range of 400 - 500 nm is added, which can repair the color center defects caused by spatial irradiation, thereby improving the overall reliability and the stability of optical performance.

[0010] A significant advantage of the present invention is that after the gain fiber of the spatial fiber laser generates defects under the action of spatial irradiation, there is no need to replace the gain fiber. Just by turning on the irradiation bleaching laser light source, the repair of radiation-induced damage can be achieved, thus ensuring the long-term and low-cost stable operation of the spatial fiber laser in the spatial irradiation environment, and providing strong support for the applications of the spatial fiber laser in spatial optical communication, remote sensing, and other aspects.

[0011] Furthermore, when the output power of the fiber laser drops to a certain extent, by performing optical bleaching treatment on the spatial fiber laser, the degradation of the optical performance of the fiber laser caused by spatial irradiation can be effectively reversed, and the fiber can be restored to its initial performance state. This maintenance method not only ensures the continuous high quality of the fiber beam quality during use, but also ensures the long-term stability and reliability of the laser system. Description of the Drawings

[0012] 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 use in 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, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0013] Figure 1 It is a schematic structural diagram of applying the spatial fiber laser optical bleaching device to a fiber laser with a linear cavity structure in one embodiment; Figure 2 It is a schematic structural diagram of applying the spatial fiber laser optical bleaching device to an irradiation field in one embodiment; Figure 3 It is a schematic diagram of the change in the output power of the laser obtained during the on-line bleaching irradiation of the spatial fiber laser optical bleaching device in one embodiment; Figure 4 It is a schematic structural diagram of applying the spatial fiber laser optical bleaching device to a ring cavity fiber laser in one embodiment. Detailed Embodiments

[0014] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with 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. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0015] Figure 1 FIG. 4 is a schematic structural diagram of applying a spatial fiber laser optical bleaching device to a fiber laser with a linear cavity structure. It includes a C-band tunable laser 1, an optical isolator 2, an irradiation bleaching laser light source 3, a pump module 4, a wavelength division multiplexer 5, an erbium-doped fiber 6, a cladding light filter 7, and an optical fiber end cap 8. Among them, the C-band tunable laser 1, the optical isolator 2, the pump module 4, the wavelength division multiplexer 5, and the erbium-doped fiber 6 form a fiber amplifier structure. The irradiation bleaching laser light source 3 can repair fiber defects caused by spatial irradiation and the degradation of laser performance.

[0016] The wavelength division multiplexer 5 has a pump arm, a signal arm, and a bleaching laser input arm; the output end of the C-band tunable laser 1 is connected to the signal arm of the wavelength division multiplexer 5 through the first optical isolator 2; the pump module 4 is connected to the pump arm of the wavelength division multiplexer 5; the pigtail of the irradiation bleaching laser light source 3 is fused to the input end of the wavelength division multiplexer 5; Both ends of the gain fiber 6 are respectively fused to the output end of the wavelength division multiplexer 5 and the input end of the second optical isolator 2, and both ends of the cladding light filter 7 are respectively connected to the output end of the second optical isolator 2 and the optical fiber end cap 8.

[0017] A method for using a spatial fiber laser optical bleaching device includes the following steps: (1) The spatial fiber laser performs spatial optical communication or remote sensing detection tasks in a space environment; (2) Spatial irradiation causes fiber defects including color centers in the gain fiber of the spatial fiber laser, and the performance of the laser decreases, resulting in a sharp increase in the absorption coefficient of the gain fiber at 980 nm, so that the gain fiber only absorbs signal light within a certain length and does not have the function of optical signal amplification; (3) Turn on the irradiation bleaching laser light source, and the irradiation bleaching laser light source outputs bleaching laser and injects it into the gain fiber of the spatial fiber laser whose gain fiber has fiber defects and laser performance degradation caused by spatial irradiation to perform on-line bleaching of the gain fiber, and repair the fiber defects and laser performance degradation caused by spatial irradiation.

[0018] After the spatial fiber laser completes the repair of fiber defects and laser performance degradation caused by spatial irradiation, repeat steps (1) to (3) to work.

[0019] The gain fiber 6 is a double-clad silica fiber, where the core diameter ranges from 10 to 60 μm and the cladding diameter ranges from 130 to 600 μm. The gain fiber 6 is provided with a core, an inner cladding, and an outer cladding in sequence from the inside out. The refractive index distribution of the gain fiber 6 is such that the refractive index decreases successively from the core to the inner cladding to the outer cladding.

[0020] The irradiation bleaching laser light source 3 is one or more semiconductor lasers with a central wavelength in the range of 400 - 500 nm. The wavelength division multiplexer 5 has one or more bleaching laser input arms. The bandwidth of each semiconductor laser is less than 3 nm and the power is greater than 10 mW. If the irradiation bleaching laser light source 3 is more than one semiconductor laser with a central wavelength in the range of 400 - 500 nm, then the irradiation bleaching laser light source 3 can be a semiconductor laser with a single wavelength or a combination of semiconductor lasers with multiple wavelengths.

[0021] The above Figure 1 The space fiber laser optical bleaching device shown in the embodiment is carried out for a simulation test on the ground, as Figure 2 shown. The space fiber laser optical bleaching device provided in the above embodiment is applied to the irradiation field. When the space fiber laser optical bleaching device is applied to the irradiation field for monitoring, the entire space fiber laser optical bleaching device is in the irradiation field 9 to be measured, that is, the irradiation environment. Referring to Figure 3 , the change in the output power of the laser obtained during the irradiation bleaching experiment of the space fiber laser optical bleaching device is obtained. The entire experiment is divided into four stages: (1) Preparation stage, keeping the output power of the space fiber laser in a stable state; (2) Irradiation stage. It can be seen that the output power of the space fiber laser gradually decreases as the total irradiation dose increases. This is because irradiation causes defects to be generated in the gain fiber 6 of the space fiber laser, thereby reducing the optical conversion efficiency of the laser and resulting in a decrease in the output power of the fiber laser; (3) Self-bleaching stage. The generation of color centers in the gain fiber 6 has a certain recovery effect under the combined action of the pump light and the thermal effect. This causes the output power collected by the fiber irradiation monitoring device to recover to a certain extent, but it does not recover to the initial output power level before irradiation; (4) Optical bleaching stage. The irradiation bleaching laser light source is turned on. The irradiation bleaching laser light source outputs bleaching laser and injects it into the gain fiber of the space fiber laser whose gain fiber has defects and whose laser performance has deteriorated due to space irradiation to perform on-line bleaching of the gain fiber, repairing the fiber defects and laser performance degradation caused by space irradiation, and evaluating the repair effect by monitoring the recovery of the output power of the space fiber laser.

[0022] In this embodiment, by optimizing the selection of the output wavelength and output power of the irradiation bleaching laser source, the effect of optimizing the repair of the optical fiber defects and the degradation of the laser performance caused by irradiation in the erbium-doped fiber laser is achieved, so that the output power of the erbium-doped fiber laser can be restored to the initial output power level before irradiation after a certain period of optical bleaching by the irradiation bleaching laser source. The method is as follows: Set the central wavelength of the irradiation bleaching laser source within the range of 400-500 nm, select an appropriate output power, and refer to Figure 3 , it can be seen that after 20 minutes of optical bleaching, the output power of the spatial fiber laser returns to the initial output power level before irradiation, which indicates that the irradiation bleaching laser source with a central wavelength in the range of 400-500 nm can completely bleach the decrease in the output power of the erbium-doped fiber laser caused by irradiation.

[0023] The optical bleaching device for the spatial fiber laser can use not only the fiber laser with a linear cavity structure but also the ring cavity structure. Refer to Figure 4 , Figure 4 FIG. is a schematic structural diagram of applying the optical bleaching device for the spatial fiber laser to a ring cavity fiber laser in an embodiment. An irradiation bleaching laser source 3 is connected to one end of the wavelength division multiplexer, as shown in Figure 4 . The erbium-doped fiber laser has a ring cavity structure and consists of an optical isolator 2, a pump module 4, a wavelength division multiplexer 5, a gain fiber 6, a filter 10, and a coupler 11 to form a ring cavity structure.

[0024] Similar to the spatial fiber laser with a linear cavity structure, the irradiation bleaching laser source 3 is one or more semiconductor lasers with a central wavelength in the range of 400-500 nm. The wavelength division multiplexer 5 has one or more bleaching laser input arms. The bandwidth of each semiconductor laser is less than 3 nm, and the power is greater than 10 mW. If the irradiation bleaching laser source 3 is more than one semiconductor laser with a central wavelength in the range of 400-500 nm, then the irradiation bleaching laser source 3 can be a semiconductor laser with a single wavelength or a combination of multiple wavelength semiconductor lasers.

[0025] Similar to the spatial fiber laser with a linear cavity structure, the gain fiber 6 is a double-clad silica fiber doped with erbium ions in the core. The core diameter is in the range of 10-60 μm, and the cladding diameter is in the range of 130-600 μm. The gain fiber 6 is provided with a core, an inner cladding, and an outer cladding from the inside out in sequence. The refractive index distribution of the gain fiber 6 is that the refractive index decreases in sequence from the core to the inner cladding to the outer cladding.

[0026] Figure 4 The usage method of the optical bleaching device for the spatial fiber laser with the shown structure is the same as that of Figure 1The usage method of the spatial fiber laser optical bleaching device with the shown structure is the same and will not be elaborated here.

[0027] The present invention can achieve the repairability of radiation-induced damage of the spatial fiber laser, improve its service life and stability, and reduce the costs of space optical communication and remote sensing detection.

[0028] Matters not described in the present invention are well-known technologies.

[0029] 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.

[0030] The above-described embodiments only represent several implementation manners of the present 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 the present application, several modifications and improvements can be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

[0031] The above are only the preferred embodiments of the present invention and are 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. A spatial fiber laser optical bleaching device, characterized in that Including a spatial fiber laser, the spatial fiber laser is an erbium-doped fiber laser. The gain fiber in the erbium-doped fiber laser is an erbium-doped fiber. The gain fiber of the erbium-doped fiber laser will generate fiber defects under spatial irradiation conditions, resulting in a sharp increase in the absorption coefficient of the gain fiber at 980 nm, so that the gain fiber only absorbs the signal light within a certain length and does not have the function of optical signal amplification. The erbium-doped fiber laser is connected to an irradiation bleaching laser source. The irradiation bleaching laser source is used to output bleaching laser with a central wavelength in the range of 400 - 500 nm and inject it into the gain fiber of the erbium-doped fiber laser whose gain fiber has fiber defects and laser performance degradation caused by spatial irradiation, so as to repair the fiber defects and laser performance degradation of the erbium-doped fiber laser caused by spatial irradiation.

2. The spatial fiber laser optical bleaching device according to claim 1, wherein, The erbium-doped fiber laser includes a C-band tunable laser, an optical isolator, a pump module, a wavelength division multiplexer, an erbium-doped fiber, a cladding light filter, and a fiber end cap. The C-band tunable laser, the optical isolator, the pump module, the wavelength division multiplexer, and the erbium-doped fiber form a fiber amplifier structure. The wavelength division multiplexer has a pump arm, a signal arm, and a bleaching laser input arm. The output end of the C-band tunable laser is connected to the signal arm of the wavelength division multiplexer through the first optical isolator. The pump module is connected to the pump arm of the wavelength division multiplexer. The pigtail of the irradiation bleaching laser source is fused to the input end of the wavelength division multiplexer. Both ends of the gain fiber are respectively fused to the output end of the wavelength division multiplexer and the input end of the second optical isolator. Both ends of the cladding light filter are respectively connected to the output end of the second optical isolator and the fiber end cap.

3. The spatial fiber laser optical bleaching device according to claim 1, characterized in that The erbium-doped fiber laser is of a ring cavity structure, which is composed of an optical isolator, a pump module, a wavelength division multiplexer, an erbium-doped fiber, a filter, and a coupler to form a ring cavity structure.

4. The spatial fiber laser optical bleaching device according to claim 2 or 3, characterized in that, The irradiation bleaching laser source is one or more semiconductor lasers with a central wavelength in the range of 400 - 500 nm. The wavelength division multiplexer has one or more bleaching laser input arms. The bandwidth of each semiconductor laser is less than 3 nm and the power is greater than 10 mW.

5. The spatial fiber laser photo-bleaching device according to claim 4, characterized in that, The irradiation bleaching laser source is more than one semiconductor laser with a central wavelength in the range of 400 - 500 nm. The irradiation bleaching laser source is a single-wavelength semiconductor laser or a combination of multiple-wavelength semiconductor lasers.

6. The spatial fiber laser photo-bleaching device according to claim 4, characterized in that, By optimizing the selection of the output wavelength and output power of the irradiation bleaching laser source, and then optimizing the effect of repairing the fiber defects and laser performance degradation of the erbium-doped fiber laser caused by irradiation, so that the output power of the erbium-doped fiber laser returns to the initial output power level before irradiation after a certain period of optical bleaching by the irradiation bleaching laser source. The method is: set the central wavelength of the irradiation bleaching laser source in the range of 400 - 500 nm and select an appropriate output power.

7. The spatial fiber laser optical bleaching device according to claim 5, wherein The gain fiber is a double-clad silica fiber, where the core diameter is in the range of 10 μm - 60 μm and the cladding diameter is in the range of 130 μm - 600 μm.

8. The spatial fiber laser photo-bleaching device according to claim 7, wherein, The gain fiber is provided with a core, an inner cladding, and an outer cladding in sequence from the inside to the outside, and the refractive index distribution of the gain fiber decreases sequentially from the core to the inner cladding to the outer cladding.

9. The method of using the spatial fiber laser photo-bleaching device according to claim 1, characterized in that It includes the following steps: (1) The space fiber laser performs space optical communication or remote sensing detection tasks in the space environment; (2) Space irradiation causes fiber defects including color centers to be generated in the gain fiber of the space fiber laser, resulting in a decline in the laser performance, thereby causing the absorption coefficient of the gain fiber at 980 nm to increase sharply, so that the gain fiber only absorbs the signal light within a certain length and does not have the function of optical signal amplification; (3) Turn on the irradiation bleaching laser light source, and the irradiation bleaching laser light source outputs bleaching laser and injects it into the gain fiber of the space fiber laser whose gain fiber has fiber defects and laser performance degradation caused by space irradiation to perform online bleaching on the gain fiber, and repair the fiber defects and laser performance degradation caused by space irradiation.

10. The usage method according to claim 9, characterized in that, After the space fiber laser completes the repair of the fiber defects and laser performance degradation caused by space irradiation, repeat steps (1) to (3) to work.

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