Optical amplifier apparatus, and related system and method

Abstract

Disclosed in the embodiments of the present application are an optical amplifier apparatus, and a related system and method. The optical amplifier apparatus comprises an optical-fiber isolator, a pump light source, a beam combiner, and an EYDF. A large amount of pump light in the EYDF cannot be completely absorbed by ytterbium ions, and ytterbium waveband ASE light generated by the ytterbium ions is further amplified by the pump light, resulting in the ytterbium waveband ASE light limiting the effective amplification of the pump light on signal light. In the embodiments of the present application, an optical-fiber isolator in an optical amplifier apparatus is modified, so that the optical-fiber isolator can reflect ytterbium waveband ASE light as an auxiliary signal back to an EYDF, and stimulated amplification of the auxiliary signal and the absorption thereof by the EYDF again can effectively suppress the generation of the ytterbium waveband ASE light by the EYDF, thus avoiding self-excited oscillation and self-pulsation of the ytterbium waveband ASE light, thereby improving the pump conversion efficiency and the stability of output power. Moreover, the optical amplification apparatus provided in the embodiments of the present application can effectively suppress the generation of ytterbium waveband ASE light by the EYDF without needing to add additional devices, thus being conducive to reducing costs and power consumption.

Description

Optical amplification device and related system and method

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on November 15, 2023, with application number 202311525223.5 and invention name “A light amplifying device and related systems and methods”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of optical transmission, and in particular to an optical amplification device and related systems and methods. Background Art

[0003] With the rapid development of application scenarios such as optical communications, high-power industrial lasers, and lidar, high-power amplification of 1.5um band lasers has attracted great attention from the industry. Erbium-doped fiber amplifiers (EDFAs) are the main gain medium for achieving 1.5um input light power amplification. However, due to the low absorption cross-section and low doping concentration of erbium ions, EDFAs are difficult to achieve high-power amplification of input light. To solve the above problems, the current method is to dope a certain concentration of ytterbium ions in the core of the erbium-doped fiber and adopt a double-clad fiber structure, so that a low-cost high-power multi-mode pump can be used as the excitation source of the gain fiber. Combined with the large absorption cross-section and population inversion rate of ytterbium ions for pump light, high-efficiency amplification of erbium ions can be achieved. In addition, thanks to ytterbium ion doping, the ytterbium ions surrounding the erbium ions can effectively avoid erbium ion clusters, thereby further increasing the erbium ion doping concentration and obtaining high-power and high-efficiency amplification of the input signal light.

[0004] However, when the pump power is further increased to achieve higher amplification power, a large amount of pump light in the erbium-ytterbium co-doped fiber (EYDF) cannot be fully absorbed by the ytterbium ions. The amplified spontaneous emission (ASE) generated by the ytterbium ions is further amplified by the gain fiber. As a result, the ASE in the 1µm band limits the effective amplification of the pump light on the 1.5µm band signal light. Since high-power ASE in the 1µm band is prone to self-pulsation and self-oscillation, it is very likely to damage the optical components in the optical amplifier link. Therefore, to achieve high-power signal light amplification in the 1.5µm band, it is urgent to adopt appropriate technologies to suppress the ASE generated by ytterbium ions in the 1µm band.

[0005] Summary of the Invention

[0006] The embodiments of the present application provide an optical amplification device and related systems and methods, which can effectively suppress the generation of ytterbium-band ASE light by EYDF, avoid the self-oscillation and self-pulsation of ytterbium-band ASE light, thereby improving the pump conversion efficiency and output power stability.

[0007] In a first aspect, an embodiment of the present application provides an optical amplifier device. The optical amplifier device includes: a first optical fiber isolator, a first pump light source, a first combiner, and a first erbium-ytterbium co-doped fiber (EYDF). The first optical fiber isolator is used to transmit the signal light from the signal light source to the first EYDF. The first pump light source is used to output the first pump light. The first combiner is used to couple the first pump light to the first EYDF. A large amount of the first pump light in the first EYDF cannot be completely absorbed by the ytterbium ions, and the first ytterbium-band amplified spontaneous emission (ASE) light generated by the ytterbium ions will be further amplified by the first pump light, resulting in the first ytterbium-band ASE light limiting the effective amplification of the signal light by the first pump light. The first ytterbium-band ASE light can also be referred to as 1um-band ASE light, and the first ytterbium-band ASE light will be transmitted in the same direction and opposite direction as the signal light transmission direction. In the embodiment of the present application, the first optical fiber isolator is modified so that the first optical fiber isolator can reflect the first ytterbium band ASE light as an auxiliary signal back to the first EYDF.

[0008] In this embodiment, the first fiber isolator can reflect the first ytterbium-band ASE light as an auxiliary signal back to the first EYDF. The stimulated amplification and subsequent absorption of the auxiliary signal by the first EYDF effectively suppresses the generation of ytterbium-band ASE light by the first EYDF, preventing self-oscillation and self-pulsation of the ytterbium-band ASE light, thereby improving pump conversion efficiency and output power stability. Furthermore, the optical amplifier device provided in this embodiment of the application effectively suppresses the generation of ytterbium-band ASE light by the first EYDF without the need for additional components, thereby reducing cost and power consumption.

[0009] In some possible embodiments, the first optical fiber isolator includes a first collimator, an isolator, a second collimator, and a reflective element. The first and second collimators are located at opposite ends of the first optical fiber isolator, with the first collimator positioned near the signal light source and the second collimator positioned near the first EYDF. The reflective element is positioned between the isolator and the second collimator. The reflective element is used to reflect the first ytterbium-band ASE light back to the first EYDF. This embodiment provides a specific implementation of an optical fiber isolator by adding a reflective element to the existing optical fiber isolator structure, resulting in simple implementation and low cost.

[0010] In some possible implementations, the reflective element is a reflective film located on the end face of the second collimator, or the reflective element is a reflective film located on the end face of the isolator. It should be understood that the use of a reflective film coating method introduces lower insertion loss and better practical effect.

[0011] In some possible implementations, the reflective element is a dielectric mirror located between the isolator and the second collimator, which expands the implementation method of the embodiment of the present application.

[0012] In some possible implementations, the reflective element is used to reflect light with a wavelength smaller than the signal light wavelength and transmit light with a wavelength greater than or equal to the signal light wavelength, thereby being adaptable to most signal light transmission scenarios.

[0013] In some possible implementations, the first combiner is located between the first fiber isolator and the first EYDF, and the first pump light and the signal light are transmitted in the same direction. In other words, the present embodiment can be adapted to the application scenario of forward pumping and has good practical effects.

[0014] In some possible implementations, a dielectric coating is used on a side of the first EYDF away from the first beam combiner to reflect the first pump light that is not fully absorbed by the first EYDF back to the first EYDF. In other words, the first pump light that is not fully absorbed by the first EYDF is reflected back by the dielectric coating, causing it to be reabsorbed, thereby improving pumping efficiency.

[0015] In some possible implementations, the first combiner is connected to a side of the first EYDF away from the first fiber isolator, and the first pump light and the signal light are transmitted in opposite directions. In other words, this embodiment of the present application can also be adapted to backward pumping applications, demonstrating good adaptability.

[0016] In some possible implementations, the first optical fiber isolator is further configured to suppress the first pump light from being transmitted toward the signal light source, thereby effectively protecting the signal light source.

[0017] In some possible embodiments, the optical amplification device further includes a second fiber isolator, a second pump light source, a second combiner, and a second EYDF. Signal light from the first EYDF is transmitted to the second EYDF via the second fiber isolator. The second pump light source is configured to output a second pump light. The second combiner is configured to couple the second pump light to the second EYDF. Secondary ase (ASE) light generated in the second EYDF is transmitted in the same direction as and opposite to the direction of transmission of the signal light. The second fiber isolator is configured to reflect the second ytterbium-band ASE light back to the second EYDF. In other words, embodiments of the present application can also achieve higher-power optical amplification through a cascaded design.

[0018] In some possible implementations, the first EYDF includes an outer cladding, an inner cladding, and a core, the outer cladding wraps the inner cladding, the inner cladding wraps the core, the signal light and the first ytterbium band ASE light are transmitted in the core, and the first pump light is transmitted in the inner cladding.

[0019] In some possible implementations, the wavelength of the signal light is greater than the wavelength of the first ytterbium band ASE light, and the wavelength of the first ytterbium band ASE light is greater than the wavelength of the first pump light.

[0020] In a second aspect, embodiments of the present application provide an optical amplification system comprising a signal light source, a first lens group, and an optical amplification device as described in any embodiment of the first aspect. Specifically, the signal light source is configured to output signal light. The optical amplification device is configured to amplify the signal light. The first lens group is configured to collimate the signal light from the EYDF in the optical amplification device.

[0021] In some possible implementations, the optical amplification system further includes a second lens group, which is configured to process the signal light passing through the first lens group, including but not limited to beam expansion, beam splitting, and / or beam combining.

[0022] In a third aspect, embodiments of the present application provide a radar system comprising a signal light source, a light receiving device, and an optical amplifier as described in any embodiment of the first aspect. Specifically, the signal light source is configured to output signal light. The optical amplifier is configured to amplify the signal light and transmit it toward a target. The light receiving device is configured to receive the signal light reflected by the target.

[0023] Fourthly, embodiments of the present application further provide an optical amplification method, which is applied to an optical amplification device comprising: a first optical fiber isolator, a first pump light source, a first beam combiner, and a first optical fiber optical fiber optic fiber (EYDF). The optical amplification method includes: transmitting signal light from the signal light source to the first EYDF via the first optical fiber isolator; outputting first pump light from the first pump light source; coupling the first pump light to the first EYDF via the first beam combiner; wherein first ytterbium-band amplified spontaneous emission (ASE) light generated in the first EYDF is transmitted in the same direction and opposite to the transmission direction of the signal light; and reflecting the first ytterbium-band ASE light back to the first EYDF via the first optical fiber isolator.

[0024] In this embodiment, the first fiber isolator can reflect the first ytterbium-band ASE light as an auxiliary signal back to the first EYDF. The stimulated amplification and subsequent absorption of the auxiliary signal by the first EYDF effectively suppresses the generation of ytterbium-band ASE light by the first EYDF, preventing self-oscillation and self-pulsation of the ytterbium-band ASE light, thereby improving pump conversion efficiency and output power stability. Furthermore, the optical amplifier device provided in this embodiment of the application effectively suppresses the generation of ytterbium-band ASE light by the first EYDF without the need for additional components, thereby reducing cost and power consumption.

[0025] In some possible embodiments, the first optical fiber isolator includes a first collimator, an isolator, a second collimator, and a reflective element. The first collimator and the second collimator are located at opposite ends of the first optical fiber isolator, respectively, with the first collimator being located near the signal light source and the second collimator being located near the first EYDF. The reflective element is located between the isolator and the second collimator. Reflecting the first ytterbium-band ASE light back to the first EYDF via the first optical fiber isolator includes reflecting the first ytterbium-band ASE light back to the first EYDF via the reflective element. This embodiment provides a specific implementation of an optical fiber isolator by adding a reflective element to the existing optical fiber isolator structure, resulting in simple implementation and low cost.

[0026] In some possible implementations, the reflective element is a reflective film located on the end face of the second collimator, or the reflective element is a reflective film located on the end face of the isolator. It should be understood that the use of a reflective film coating method introduces lower insertion loss and better practical effect.

[0027] In some possible implementations, the reflective element is a dielectric mirror located between the isolator and the second collimator, which expands the implementation method of the embodiment of the present application.

[0028] In some possible implementations, the reflective element is used to reflect light with a wavelength smaller than the signal light wavelength and transmit light with a wavelength greater than or equal to the signal light wavelength, thereby being adaptable to most signal light transmission scenarios.

[0029] In some possible implementations, the first combiner is located between the first fiber isolator and the first EYDF, and the first pump light and the signal light are transmitted in the same direction. In other words, the present embodiment can be adapted to the application scenario of forward pumping and has good practical effects.

[0030] The side of the first EYDF away from the first beam combiner reflects the first pump light that is not completely absorbed by the first EYDF back to the first EYDF through the dielectric coating. In other words, the first pump light that is not completely absorbed by the first EYDF is reflected back by the dielectric coating, causing the first pump light to be reabsorbed, thereby improving pumping efficiency.

[0031] In some possible implementations, the first combiner is connected to a side of the first EYDF away from the first fiber isolator, and the first pump light and the signal light are transmitted in opposite directions. In other words, this embodiment of the present application can also be adapted to backward pumping applications, demonstrating good adaptability.

[0032] In some possible implementations, the method further includes: suppressing the first pump light from being transmitted toward the signal light source through a first optical fiber isolator, thereby effectively protecting the signal light source.

[0033] In some possible embodiments, the optical amplification device further includes a second fiber isolator, a second pump light source, a second combiner, and a second optical fiber isolator. Signal light from the first EYDF is transmitted to the second EYDF via the second fiber isolator. The method further includes: outputting a second pump light via the second pump light source. Coupling the second pump light to the second EYDF via the second combiner, wherein second ASE light generated in the second EYDF is transmitted in the same direction as and opposite to the direction of transmission of the signal light. The second ytterbium-band ASE light is reflected back to the second EYDF via the second fiber isolator. In other words, embodiments of the present application can also achieve higher-power optical amplification through a cascade design.

[0034] In some possible implementations, the first EYDF includes an outer cladding, an inner cladding, and a core, the outer cladding wraps the inner cladding, the inner cladding wraps the core, the signal light and the first ytterbium band ASE light are transmitted in the core, and the first pump light is transmitted in the inner cladding.

[0035] In some possible implementations, the wavelength of the signal light is greater than the wavelength of the first ytterbium band ASE light, and the wavelength of the first ytterbium band ASE light is greater than the wavelength of the first pump light.

[0036] In an embodiment of the present application, a beam combiner couples signal light and pump light to the EYDF, and the ytterbium-band ASE light generated in the EYDF is transmitted in the same and opposite directions as the signal light transmission direction. In an embodiment of the present application, the optical fiber isolator in the optical amplifier device is modified. The optical fiber isolator can reflect the ytterbium-band ASE light back to the EYDF as an auxiliary signal. The stimulated amplification of the auxiliary signal and its subsequent absorption by the EYDF can effectively suppress the generation of ytterbium-band ASE light by the EYDF, avoiding the self-oscillation and self-pulsation of the ytterbium-band ASE light, thereby improving the pump conversion efficiency and the stability of the output power. At the same time, the optical amplifier device provided in the embodiment of the present application can effectively suppress the generation of ytterbium-band ASE light by the EYDF without adding additional devices, which is beneficial to reducing costs and power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG1 is a schematic diagram of a first structural example of an optical amplifying device according to an embodiment of the present application;

[0038] FIG2 is a schematic diagram of a first structure of an optical fiber isolator according to an embodiment of the present application;

[0039] FIG3 is a schematic diagram of a second structure of an optical fiber isolator according to an embodiment of the present application;

[0040] FIG4 is a schematic diagram of a third structure of the optical fiber isolator according to an embodiment of the present application;

[0041] FIG5 is a schematic diagram of the structure of an EYDF in an embodiment of the present application;

[0042] FIG6 is a schematic diagram of a second structure of an optical amplifying device according to an embodiment of the present application;

[0043] FIG7 is a schematic diagram of a third structure of an optical amplifying device according to an embodiment of the present application;

[0044] FIG8 is a schematic diagram of an embodiment of a light amplification method according to an embodiment of the present application;

[0045] FIG9 is a schematic diagram of an optical amplification system according to an embodiment of the present application;

[0046] FIG10 is a schematic diagram of a radar system according to an embodiment of the present application. DETAILED DESCRIPTION

[0047] The embodiments of the present application provide an optical amplifier device and related systems and methods, which can effectively suppress the generation of ytterbium-ytterbium co-doped fiber (EYDF)-generated amplified spontaneous emission (ASE) light in the ytterbium band, avoid the self-oscillation and self-pulsation of the ytterbium-band ASE light, and thus improve the pump conversion efficiency and the stability of the output power. It should be understood that the optical amplifier device provided in the embodiments of the present application can also be referred to as an erbium-ytterbium co-doped fiber amplifier (EYDFA). For example, EYDFA can be used in scenarios such as space optical communications and optical fiber communication links; for another example, EYDFA can be used in vehicle-mounted laser radars to achieve high-efficiency amplification of pulsed light; for another example, EYDFA can be used as an optical amplifier for industrial laser processing to significantly increase the output power of the input laser.

[0048] It should be noted that the terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar objects, rather than to limit a specific order or precedence. It should be understood that the above terms can be interchangeable where appropriate so that the embodiments described in this application can be implemented in a sequence other than that described in this application. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0049] FIG1 is a schematic diagram of the first structure of the optical amplifier device in an embodiment of the present application. As shown in FIG1 , a signal light source 10 is used to output signal light. The optical amplifier device includes: an optical fiber isolator 20, a pump light source 30, a combiner 40, and an EYDF 50. The signal light is transmitted to the combiner 40 through the optical fiber isolator 20. The optical fiber isolator 20 is used to isolate the echo reflected light generated by the signal light transmission, thereby ensuring that the signal light has a single transmission direction. The pump light source 30 is used to output the pump light to the combiner 40. The combiner 40 is used to couple the signal light and the pump light to the EYDF 50. The signal light and the pump light in the EYDF 50 are transmitted in the same direction, and the signal light is amplified by the EYDF 50. It should be understood that in actual applications, the signal light source 10 refers to a signal light emitting device, such as an optical module, etc. The optical amplifier device may include the signal light source 10 or may not include the signal light source 10, and the specific details are not limited here.

[0050] The EYDF 50 adopts a double-cladding structure, that is, the EYDF 50 includes an outer cladding, an inner cladding, and a core. The outer cladding wraps around the inner cladding, which in turn wraps around the core. The signal light is transmitted in the core. The pump light is injected into the inner cladding. The refractive index of the inner cladding is greater than that of the outer cladding. The outer cladding creates a total reflection condition for the pump light, and the pump light is transmitted by reflection in the inner cladding. As an example, the signal light source 10 can be connected to the optical fiber isolator 20 and the optical fiber isolator can be connected to the combiner 40 using a single-mode optical fiber. The pump light source 30 can be connected to the combiner 40 using a multimode optical fiber. The core of the single-mode optical fiber can be connected to the core of the EYDF 50, and the signal light is transmitted to the core of the EYDF 50 through the core of the single-mode optical fiber.

[0051] It should be understood that a large amount of pump light in the EYDF 50 cannot be completely absorbed by the ytterbium ions. The ytterbium-band ASE light generated by the ytterbium ions will be further amplified by the pump light, resulting in the ytterbium-band ASE light limiting the effective amplification of the pump light on the signal light. Among them, the ytterbium-band ASE light can also be referred to as 1um-band ASE light. The ytterbium-band ASE light will be transmitted in the same direction and opposite to the transmission direction of the signal light. The embodiment of the present application has modified the optical fiber isolator 20 in the optical amplification device. The optical fiber isolator 20 can reflect the ytterbium-band ASE light back to the EYDF 50 as an auxiliary signal. The stimulated amplification of the auxiliary signal and its further absorption by the EYDF can effectively suppress the generation of ytterbium-band ASE light by the EYDF, avoiding the self-oscillation and self-pulsation of the ytterbium-band ASE light, thereby improving the pump conversion efficiency and the stability of the output power. Several possible structures of the optical fiber isolator 20 are introduced below.

[0052] FIG2 is a schematic diagram of the first structure of the optical fiber isolator in an embodiment of the present application. As shown in FIG2 , the optical fiber isolator 20 includes a first collimator 201, an isolator 202, a second collimator 203, and a dielectric mirror 204. The first collimator 201 and the second collimator 203 are respectively located at the two ends of the optical fiber isolator 20, and the isolator 202 is located between the first collimator 201 and the second collimator 203. The first collimator 201 is used to collimate the signal light diverging from the optical fiber to obtain signal light transmitted parallel in space, and the second collimator 203 is used to couple the signal light passing through the isolator 202 into the optical fiber. Among them, the dielectric mirror 204 is located between the isolator 202 and the second collimator 203. The dielectric mirror 204 is used to transmit the signal light and reflect the ytterbium band ASE light back to the EYDF 50.

[0053] Figure 3 is a schematic diagram of a second embodiment of the optical fiber isolator structure. Unlike the structure shown in Figure 2, Figure 3 shows a reflective coating 205 on the end face of the second collimator 203 near the isolator 202. Reflective coating 205 performs the same function as dielectric mirror 204: transmitting signal light and reflecting ytterbium-band ASE light back to the EYDF 50.

[0054] Figure 4 is a schematic diagram of a third embodiment of the optical fiber isolator structure. Unlike the structures shown in Figures 2 and 3 , Figure 4 shows a reflective coating 206 on the end face of isolator 202 near second collimator 203. Reflective coating 206 performs the same function as dielectric mirror 204: it transmits signal light and reflects ytterbium-band ASE light back to EYDF 50.

[0055] It should be understood that in the optical fiber isolator shown in Figures 3 and 4 above, the insertion loss introduced by coating a reflective film is lower than that introduced by adding a dielectric reflector. It should be noted that, under normal circumstances, the wavelength of the signal light is greater than the wavelength of the ytterbium band ASE light, and the wavelength of the ytterbium band ASE light is greater than the wavelength of the pump light. For example, the signal light is in the 1.5um band, the ytterbium band ASE light is in the 1um band, and the wavelength of the pump light is ≤980nm, with typical values ​​including 915nm, 940nm, and 976nm. In the embodiment of the present application, the dielectric reflector 204, the reflective film 205, and the reflective film 206 can be designed according to the wavelength of the signal light and the wavelength of the ytterbium band ASE light in actual applications, which is not limited here. For example, the dielectric reflector 204, the reflective film 205, and the reflective film 206 reflect light with a wavelength less than 1.2um, and the reflectivity ranges from 10% to 99.9%.

[0056] FIG5 is a schematic diagram of the structure of an EYDF in an embodiment of the present application. Taking the optical fiber isolator shown in FIG1 as an example, a dielectric film can be plated on the end face of the EYDF 50 away from the combiner 40. The dielectric film is used to transmit the signal light and reflect the pump light. For example, the dielectric film can be a dichroic mirror. In other words, the pump light that is not completely absorbed by the EYDF 50 will be reflected back by the dielectric film so that the pump light is reabsorbed, thereby improving the pumping efficiency. For example, the dielectric film can reflect the pump light in the wavelength range of 915nm to 980nm. It should be understood that in some possible scenarios, the end of the EYDF 50 away from the combiner 40 is used to connect to the passive optical fiber, and a dielectric film can also be plated on the end face of the connected passive optical fiber to achieve a similar effect. Alternatively, other reflective elements with similar functions can be set on the side of the EYDF 50 away from the combiner 40.

[0057] It should be understood that Figure 1 employs a forward pumping implementation, i.e., both the signal light source 10 and the pump light source 30 are located at the front end of the EYDF 50, and the signal light and the pump light are transmitted in the same direction. Alternatively, the present embodiment may employ a backward pumping implementation, as described below.

[0058] Figure 6 is a schematic diagram of a second structural embodiment of the optical amplifier device in the present application. As shown in Figure 6, the combiner 40 is connected to the side of the EYDF 50 away from the fiber isolator 20, and the pump light and signal light are transmitted in opposite directions. In this scenario, the fiber isolator 20 can also transmit the signal light and divert the Ytterbium-band ASE light. In addition, the fiber isolator 20 can also inhibit the pump light from being transmitted toward the signal light source 10. In the optical amplifier device shown in Figure 6, the fiber isolator 20 can also adopt any of the implementations described in Figures 2 to 4 above, which will not be repeated here.

[0059] FIG7 is a schematic diagram of the third structure of the optical amplifier device in the embodiment of the present application. As shown in FIG7, based on the optical amplifier device shown in FIG1 above, higher power optical amplification can also be achieved through a cascade design. As an example, the optical amplifier device also includes a fiber isolator 60, a pump light source 70, a combiner 80, and an EYDF 90. The rear end of the EYDF 50 is connected to the fiber isolator 60, and the fiber isolator 60 is connected to the EYDF 90 through the combiner 80. The combiner 80 is used to couple the pump light output by the pump light source 70 to the EYDF 90. Among them, the fiber isolator 60 adopts a design similar to the fiber isolator 20. The fiber isolator 60 can reflect the ytterbium band ASE light from the EYDF 90 back to the EYDF 90. The end face of the EYDF 90, facing away from the combiner 80, can also be coated with a dielectric film. This dielectric film transmits the signal light and reflects the pump light. Pump light not fully absorbed by the EYDF 90 is reflected back by the dielectric film, allowing the pump light to be reabsorbed, thereby improving pumping efficiency. For details, see the design shown in Figure 5. It should be understood that a cascade design similar to that shown in Figure 7 can also be adopted based on the optical amplifier device shown in Figure 6, which will not be described in detail here.

[0060] As can be seen from the above description, the embodiments of the present application modify the fiber isolator in the optical amplifier device. The fiber isolator can reflect ytterbium-band ASE light back to the EYDF as an auxiliary signal. The stimulated amplification of the auxiliary signal and its subsequent absorption by the EYDF effectively suppresses the generation of ytterbium-band ASE light by the EYDF, thus avoiding self-oscillation and self-pulsation of ytterbium-band ASE light, thereby improving pump conversion efficiency and output power stability. Furthermore, the optical amplifier device provided by the embodiments of the present application effectively suppresses the generation of ytterbium-band ASE light by the EYDF without the addition of additional components, which helps reduce costs and power consumption.

[0061] The optical amplification method provided in the embodiments of the present application is introduced below.

[0062] Figure 8 is a schematic diagram of an embodiment of an optical amplification method according to an embodiment of the present application. It should be noted that this optical amplification method is implemented based on the optical amplification device described above. For an introduction to the optical amplification device, please refer to the relevant descriptions of the above embodiments and will not be repeated here. In this example, the optical amplification method includes the following steps.

[0063] 11. Transmit the signal light from the signal light source to the EYDF through the optical fiber isolator.

[0064] The fiber isolator isolates the echo reflections generated by signal light transmission, ensuring that the signal light has a single transmission direction. In the forward pumping scenario shown in Figure 1, the signal light passing through the fiber isolator is further transmitted through the combiner to the EYDF core. In the backward pumping scenario shown in Figure 6, the signal light passing through the fiber isolator is transmitted directly to the EYDF core.

[0065] 12. Output pump light through a pump light source.

[0066] 13. Couple the pump light into the EYDF through a beam combiner.

[0067] Specifically, the EYDF adopts a double-cladding structure, and the combiner can couple the pump light into the inner cladding of the EYDF, and the pump light is transmitted in the inner cladding by reflection.

[0068] 14. The Ytterbium band ASE light is reflected back to the EYDF through the fiber isolator.

[0069] A large amount of pump light in the EYDF cannot be fully absorbed by the ytterbium ions. The ytterbium-band ASE light generated by the ytterbium ions is further amplified by the pump light, resulting in the ytterbium-band ASE light limiting the effective amplification of the pump light by the signal light. The ytterbium-band ASE light can propagate in both the same and opposite directions as the signal light. A fiber isolator can reflect the ytterbium-band ASE light back to the EYDF as an auxiliary signal. This stimulated amplification of the auxiliary signal and its subsequent absorption by the EYDF effectively suppresses the generation of ytterbium-band ASE light in the EYDF, preventing self-oscillation and self-pulsation of the ytterbium-band ASE light, thereby improving pump conversion efficiency and output power stability.

[0070] The following introduces possible application scenarios of the above optical amplification device.

[0071] FIG9 is a schematic diagram of an optical amplification system in an embodiment of the present application. As shown in FIG9 , the optical amplification system includes a signal light source 21, an optical amplification device 22, and a first lens group 23. The optical amplification device 22 may be an optical amplification device as described in any of the above embodiments. Specifically, the optical amplification device 22 amplifies the signal light output by the signal light source 21, and the amplified signal light is transmitted to the first lens group 23 through the EYDF in the optical amplification device 22. The first lens group 23 collimates the signal light diverging from the EYDF to obtain signal light transmitted in parallel in space. Optionally, the optical amplification system further includes a second lens group 24, which may process the signal light transmitted in parallel in space according to actual needs, including but not limited to beam expansion, beam splitting, and beam combining.

[0072] Figure 10 is a schematic diagram of a radar system in an embodiment of the present application. As shown in Figure 10, the radar system includes a signal light source 31, an optical amplifier 32, and a light receiving device 33. Among them, the optical amplifier 32 can be an optical amplifier as described in any of the above embodiments. Specifically, the optical amplifier 32 amplifies the signal light output by the signal light source 31 and transmits the amplified signal light to the target object. The light receiving device 33 receives the light beam reflected by the target object. The light beam receiving device can process the received light beam to calculate the flight time of the light beam, thereby realizing the radar ranging function. It should be understood that the signal light source 31 can specifically be a pulse signal source. In a possible scenario, the signal light source 31 and the optical amplifier 32 can also be integrated together.

[0073] It should be noted that the above embodiments are intended only to illustrate the technical solutions of the present application and are not intended to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents; and such modifications or replacements do not deviate from the spirit and scope of the technical solutions of the various embodiments of the present application.

Claims

1. An optical amplification device, characterized in that: include: A first optical fiber isolator, a first pump light source, a first beam combiner and a first erbium-ytterbium co-doped optical fiber EYDF; The first optical fiber isolator is used to transmit the signal light from the signal light source to the first EYDF; The first pump light source is used to output a first pump light; The first beam combiner is used to couple the first pump light to the first EYDF, wherein the first ytterbium-band amplified spontaneous emission (ASE) light generated in the first EYDF is transmitted in the same direction as and in the opposite direction to the transmission direction of the signal light; The first optical fiber isolator is used to reflect the first ytterbium-band ASE light back to the first EYDF.

2. The optical amplifier device according to claim 1, characterized in that: The first optical fiber isolator includes a first collimator, an isolator, a second collimator and a reflective element. The first collimator and the second collimator are respectively located at two ends of the first optical fiber isolator. The first collimator is close to the signal light source, and the second collimator is close to the first EYDF. The reflective element is located between the isolator and the second collimator, and the reflective element is used to reflect the first ytterbium band ASE light back to the first EYDF.

3. The optical amplification device according to claim 2, characterized in that: The reflective element is a reflective film located on an end surface of the second collimator, or the reflective element is a reflective film located on an end surface of the isolator.

4. The optical amplification device according to claim 2, characterized in that: The reflective element is a dielectric mirror located between the isolator and the second collimator.

5. The optical amplification device according to any one of claims 2 to 4, characterized in that: The reflective element is used to reflect light whose wavelength is smaller than the wavelength of the signal light.

6. The optical amplification device according to any one of claims 1 to 5, characterized in that: The first beam combiner is located between the first optical fiber isolator and the first EYDF, and the first pump light and the signal light have the same transmission direction.

7. The optical amplifier device according to claim 6, characterized in that: The first EYDF reflects the first pump light that is not completely absorbed by the first EYDF back to the first EYDF through coating on one side of the first EYDF away from the first beam combiner.

8. The optical amplification device according to any one of claims 1 to 5, characterized in that: The first beam combiner is connected to a side of the first EYDF away from the first optical fiber isolator, and the transmission directions of the first pump light and the signal light are opposite.

9. The optical amplifying device according to claim 8, characterized in that: The first optical fiber isolator is further used to suppress the first pump light from being transmitted to the signal light source.

10. The optical amplification device according to any one of claims 1 to 9, characterized in that: The optical amplification device further includes a second optical fiber isolator, a second pump light source, a second beam combiner and a second EYDF, and the signal light from the first EYDF is transmitted to the second EYDF through the second optical fiber isolator; The second pump light source is used to output a second pump light; The second combiner is used to couple the second pump light to the second EYDF, wherein the second ASE light generated in the second EYDF is transmitted in the same direction as and in the opposite direction to the transmission direction of the signal light; The second optical fiber isolator is used to reflect the second ytterbium band ASE light back to the second EYDF.

11. The optical amplification device according to any one of claims 1 to 10, characterized in that: The first EYDF includes an outer cladding, an inner cladding and a core, the outer cladding wraps the inner cladding, the inner cladding wraps the core, the signal light and the first ytterbium band ASE light are transmitted in the core, and the first pump light is transmitted in the inner cladding.

12. The optical amplification device according to any one of claims 1 to 11, characterized in that: The wavelength of the signal light is greater than the wavelength of the first ytterbium-band ASE light, and the wavelength of the first ytterbium-band ASE light is greater than the wavelength of the first pump light.

13. An optical amplification system, characterized in that: The optical amplifier comprises a light amplifying device, a signal light source and a first lens group as claimed in any one of claims 1 to 12; The signal light source is used to output signal light; The optical amplifying device is used to amplify the signal light; The first lens group is used to collimate the signal light from the erbium-ytterbium co-doped optical fiber EYDF in the optical amplification device.

14. The optical amplification system according to claim 13, characterized in that: The optical amplification system further includes a second lens group; The second lens group is used to expand, split and / or combine the signal light passing through the first lens group.

15. A radar system, characterized in that: The optical amplifier, signal light source and optical receiving device according to any one of claims 1 to 12; The signal light source is used to output signal light; The optical amplifying device is used to amplify the signal light and transmit it to a target object; The light receiving device is used to receive the signal light reflected by the target object.

16. A light amplification method, characterized in that: The optical amplification method is applied to an optical amplification device, which includes: a first optical fiber isolator, a first pump light source, a first beam combiner and a first erbium-ytterbium co-doped optical fiber EYDF; the optical amplification method includes: transmitting the signal light from the signal light source to the first EYDF through the first optical fiber isolator; outputting a first pump light through the first pump light source; coupling the first pump light to the first EYDF through the first beam combiner, wherein the first ytterbium-band amplified spontaneous emission (ASE) light generated in the first EYDF is transmitted in the same direction as and in the opposite direction to the transmission direction of the signal light; The first ytterbium-band ASE light is reflected back to the first EYDF through the first optical fiber isolator.

17. The method according to claim 16, characterized in that The first optical fiber isolator comprises a first collimator, an isolator, a second collimator and a reflective element, the first collimator and the second collimator are respectively located at two ends of the first optical fiber isolator, the first collimator is close to the signal light source, the second collimator is close to the first EYDF, and the reflective element is located between the isolator and the second collimator; Reflecting the first ytterbium band ASE light back to the first EYDF through the first optical fiber isolator comprises: The first ytterbium-band ASE light is reflected back to the first EYDF by the reflective element.

18. The method according to claim 17, characterized in that The first reflective element is a reflective film located on an end surface of the second collimator, or the first reflective element is a reflective film located on an end surface of the isolator.

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