Absorption management active optical fiber and preparation method thereof

Abstract

The present invention discloses an absorption management active optical fiber and a preparation method thereof. The absorption management active optical fiber provided by the present invention realizes the adjustment of cladding absorption by combining the imperfectly symmetrical light energy distribution in the cross section and the change of the pitch in the length direction. The optical fiber structure can be flexibly designed according to the specific application, and the cladding absorption can be conveniently adjusted by changing the pitch. Without changing the rare earth ion doping and the size of the optical fiber structure, a controllable absorption distribution curve in the length direction can be achieved. The use of the above-mentioned optical fiber can effectively improve the thermal distribution of the optical fiber and reduce the peak thermal load, thereby not only greatly improving the transverse mode instability threshold of the rare earth-doped optical fiber, but also being able to control the power distribution curve of the optical fiber, thereby improving the nonlinear effect of the optical fiber. The preparation method of the absorption management active optical fiber provided by the present invention is simple and flexible, and the preform is similar to the ordinary absorption management active optical fiber, and the rotation of the preform can accurately adjust its pitch according to the preset pitch.

Description

Technical Field

[0001] The present invention belongs to the field of active optical fibers, and more specifically, relates to an absorption management active optical fiber and a preparation method thereof. Background Art

[0002] Active fiber is mainly used in high-power fiber lasers and fiber amplifiers. Its main feature is its large pump cladding, which allows the use of lower-cost pump sources (such as laser diodes) to effectively pump the fiber. The pump light enters the fiber through the outer cladding, while the doped core is responsible for the transmission and amplification of the signal.

[0003] The pump light injected into the active optical fiber enters the optical fiber through the outer cladding, undergoes multiple total reflections in the outer cladding, and the pump light passing through the core is absorbed. Cladding absorption is used to evaluate how fast the pump light is absorbed when it is transmitted in the cladding.

[0004] At present, most active optical fibers have a uniform structure in the length direction, and the structure of the optical fiber remains unchanged in the length direction, so the cladding absorption of this active optical fiber remains unchanged along the length of the optical fiber. Tapered fiber is a specially designed optical fiber whose cross-sectional area gradually changes along the length direction of the optical fiber to form a cone. A major feature of tapered fiber is that it can change the mode distribution of the optical fiber and the interaction between light and optical fiber materials, thereby affecting its cladding absorption and achieving a length-direction distribution of cladding absorption. However, when preparing this type of optical fiber, a preform rod with a corresponding tapered structure is required, which is difficult to process industrially. At the same time, it is difficult to flexibly control the cladding absorption and achieve a more complex length-direction distribution of cladding absorption. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides an absorption-managed active optical fiber and a preparation method thereof, the purpose of which is to combine the pump cladding with imperfectly symmetrical light energy distribution and the pitch varying in the length direction to regulate the absorption performance of the active optical fiber in the length direction, thereby optimizing the overall thermal load of the optical fiber in the length direction and reducing the peak thermal load of the optical fiber, thereby solving the technical problems of concentrated thermal load and excessively high peak value of the existing active optical fiber, and the inflexible control of the cladding absorption in the length direction of the tapered optical fiber and the difficulty in preparation.

[0006] To achieve the above object, according to one aspect of the present invention, there is provided an absorption-managed active optical fiber, wherein the optical fiber glass portion comprises a rare-earth-doped core and a pump cladding;

[0007] The fiber core is cylindrical, and its axis coincides with the geometric center axis of the absorption management active optical fiber;

[0008] On any cross section, when an angular coordinate system is established with the geometric center of the rare-earth-doped core as the origin, the polar diameter of any point (r, θ) on the cross section is r and the polar angle is θ. For any point (r, θ) on the pump cladding, f(r, θ) is the optical energy density of the point.

[0009] The pump cladding has an imperfectly symmetrical light energy distribution relative to the geometric center of the rare-earth-doped core, that is, on any cross section, when an angular coordinate system is established with the geometric center of the rare-earth-doped core as the origin, the polar diameter of any point of the pump cladding is r, the polar angle is θ, f(r,θ) is the light energy density of the point (r,θ), and for positions with the same distance r0 from the geometric center, there are two points (r0,θ1) and (r0,θ2), satisfying: f(r0,θ1)≠f(r0,θ2), where θ1≠θ2;

[0010] The optical fiber structure rotates in the length direction and the pitch changes along the length direction, so that the light energy distribution changes relative to the fiber core along the length direction.

[0011] Preferably, in the absorption management active optical fiber, each cross section of the optical fiber has the same cross-sectional structure; and the cross-sectional structure of the optical fiber rotates along the length direction.

[0012] Preferably, the minimum pitch of the absorption management active optical fiber is between 0.01 meters and 30 meters.

[0013] Preferably, the pitch of the absorption management active optical fiber decreases monotonically along the light injection direction or decreases from both ends to the middle;

[0014] The pitch changes continuously, with a rate of change less than 1000, preferably greater than 0.1; or the pitch changes in steps.

[0015] Preferably, the pump cladding of the absorption-managed active optical fiber has a non-circular outer contour structure; the pump cladding is preferably a regular polygon, a D-shape, or a plum blossom shape; regular polygons are commonly regular pentagons, heptagons, octagons, or nonagons.

[0016] Preferably, the pump cladding of the absorption-managed active optical fiber has a non-uniform refractive index distribution, and preferably the pump cladding has a non-centrosymmetric refractive index distribution.

[0017] Preferably, the absorption management active optical fiber has a core-cladding ratio of 1.5 to 50.

[0018] Preferably, the absorption management active optical fiber has a rare earth element doping concentration of 0.005 mol% to 1 mol%, and a ratio of the core ratio to the rare earth element doping concentration is less than 500.

[0019] According to another aspect of the present invention, there is provided a method for preparing the absorption management active optical fiber, comprising the following steps:

[0020] (1) According to the design profile of the active optical fiber, an optical fiber preform having a circular core and a pump cladding with imperfectly symmetrical optical energy distribution is manufactured;

[0021] (2) Rotating and drawing the optical fiber preform produced in step (1) to rotate the optical fiber structure, and adjusting the drawing speed and the preform rotation speed to rotate the optical fiber structure in the length direction and change the pitch along the length direction.

[0022] Preferably, in the method for preparing the absorption management active optical fiber, the drawing speed in step (2) is 1-500 m / min, and the rotation speed is 0.5-500 rpm.

[0023] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0024] The absorption management active optical fiber provided by the present invention combines the imperfectly symmetrical light energy distribution in the cross section and the change of the pitch in the length direction to achieve the adjustment of the cladding absorption. The optical fiber structure can be flexibly designed according to the specific application, and the cladding absorption can be conveniently adjusted by changing the pitch. Without changing the rare earth ion doping and the size of the optical fiber structure, a controllable absorption distribution curve in the length direction can be achieved. The use of the above optical fiber can effectively improve the thermal distribution of the optical fiber and reduce the peak thermal load, thereby not only greatly improving the transverse mode instability threshold of the rare earth-doped optical fiber, but also being able to control the power distribution curve of the optical fiber, thereby improving the nonlinear effect of the optical fiber.

[0025] The preparation method of the absorption management active optical fiber provided by the present invention is simple and flexible, the preform is similar to the common absorption management active optical fiber, and the rotation of the preform can accurately adjust its pitch according to the preset pitch. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the absorption management active optical fiber structure of the octagonal pump cladding provided in Examples 1 and 2;

[0027] Figure 2 is a schematic diagram of the structure of an absorption-managed active optical fiber with an octagonal pump cladding provided in Example 3;

[0028] Figure 3 It is a schematic diagram of the structure of a circular active optical fiber with low-doping region absorption management provided in Example 4;

[0029] Figure 4 is a graph showing a pitch variation of an absorption-managed active optical fiber provided in Example 1;

[0030] Figure 5 is a graph showing a pitch variation of an absorption-managed active optical fiber provided in Example 2;

[0031] Figure 6 This is the absorption management active optical fiber pitch variation diagram provided in Example 3 Figure 7 This is a diagram of the pitch variation of the absorption-managed active optical fiber provided in Example 4.

[0032] In all drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1 is a core, 2 is a pump cladding, 3 is an inner coating of an organic coating, 4 is an outer coating of an organic coating, and 5 is a low-doped region. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] The absorption management active optical fiber provided by the present invention, the optical fiber glass portion includes a rare earth doped core and a pump cladding;

[0035] On any cross section, when an angular coordinate system is established with the geometric center of the rare-earth-doped core as the origin, the polar diameter of any point (r, θ) on the cross section is r, and the polar angle is θ. For any point (r, θ) on the core cross section, c(r, θ) is the rare-earth ion doping concentration at the point, and for any point (r, θ) on the pump cladding, f(r, θ) is the light energy density at the point;

[0036] The fiber core is cylindrical, and its axis coincides with the geometric center axis of the absorption management active optical fiber. In a preferred embodiment, the fiber core has a rare earth ion doping concentration with circular distribution on the cross section, that is, for any two points (r1, θ1) and (r2, θ2) on the same cross section of the fiber core, if r1=r2, then c(r1, θ1)=c(r2, θ2);

[0037] The pump cladding has an imperfectly symmetrical light energy distribution relative to the geometric center of the rare-earth-doped core; perfectly symmetrical light energy distribution means that the light energy distribution of the optical fiber cross section remains unchanged after rotating at any angle. For the pump cladding with an imperfectly symmetrical light energy distribution, that is, for the position with the same distance r0 from the geometric center, there are two points (r0, θ1) and (r0, θ2), satisfying: f(r0, θ1) ≠ f(r0, θ2), where θ1 ≠ θ2;

[0038] The pitch of the fiber structure rotation represents the amplitude of the fiber structure rotation at a certain point in the fiber length direction. The larger the pitch, the smaller the rotation amplitude. The pitch at the length direction l is defined as follows:

[0039]

[0040] Wherein, l is the position in the length direction, that is, the distance from the light injection end, and α is the phase angle of the optical fiber structure.

[0041] The optical fiber structure rotates in the length direction and the pitch changes along the length direction, so that the light energy distribution changes relative to the core along the length direction. Combined with the rotation of the optical fiber structure in the length direction, for a unit length of optical fiber, the smaller the rotation pitch, the more uniform and sufficient the absorption of the core, so the cladding absorption is higher. Therefore, the present invention is based on pumping the cladding with imperfectly symmetrical light energy distribution, and adjusts the absorption of the active optical fiber cladding in combination with the pitch change of the optical fiber structure rotation, thereby achieving absorption management. The absorption management optical fiber can adjust the pump light absorption of the optical fiber in the length direction, optimize the peak thermal load of the active optical fiber, and improve the instability of the lateral mode. Typically, when single-end pumping is used, the absorption management optical fiber has a uniform heat load in the length direction, with the pitch reduced and the cladding absorption increased according to the light injection direction; when two-end pumping is used, the two ends decrease gradually toward the middle.

[0042] In order to facilitate the production of active optical fibers with absorption management characteristics, each cross-section of the optical fiber has the same cross-sectional structure; and the cross-sectional structure of the optical fiber is rotated along the length direction, so that the cross-section has an imperfectly symmetrical light energy distribution, and the rotation in the length direction can change the light energy distribution.

[0043] The preferred solution is to make the changes in cladding absorption stable and controllable. The rare earth element doping concentration in the fiber core is circularly distributed and circumferentially uniform. The pump cladding with imperfectly symmetrical light energy distribution is combined to reduce the parameters that affect the cladding absorption. By controlling the pitch of the fiber structure rotation, the changes in cladding absorption can be more stably controlled.

[0044] The minimum pitch value varies from 0.01m to 30m. The pitch variation range is limited by the manufacturing process on the one hand and the application of active optical fiber on the other hand. Too large or too small a pitch makes it difficult to obtain an effective pitch variation range within the suitable active optical fiber working length (about 40m), resulting in unclear cladding absorption distribution and inability to perform effective absorption management. In order to achieve effective cladding absorption distribution, the pitch variation range of the absorption management active optical fiber over the entire length is greater than 0, generally above 0.5m. The pitch variation range ΔL is defined as follows: ΔL = L max -L min , where L max is the maximum pitch, Lmin is the minimum pitch.

[0045] In a preferred embodiment, when applied to single-end pumping, the pitch variation of the absorption management active fiber decreases monotonically in the direction of optical injection, i.e.:

[0046] When there are two locations l1 and l2 on the absorption management active fiber with l1 < l2, the pitches at these two locations satisfy L1 ≥ L2, where L1 is the pitch at location l1 of the absorption management active fiber and L2 is the pitch at location l2 of the absorption management active fiber.

[0047] When applied to double-end pumping, the pitch variation of the absorption management active fiber decreases from both ends towards the middle.

[0048] The pitch variation of the absorption management active fiber can be a continuous variation or a step variation. When it is a continuous variation, the preferred pitch variation rate is less than 1000, and more preferably greater than 0.1.

[0049] In this case, along the direction of optical injection, the pump light energy decays while the cladding absorption increases, enabling the energy absorption of the core to be balanced in the length direction, thereby optimizing the overall working performance of the active fiber.

[0050] The variation characteristics of the pitch can be a stepwise variation or a continuous variation. A continuous variation is relatively easier to achieve. According to the design requirements and fiber manufacturing equipment, the continuously varying pitch can be continuously and smoothly varying (as shown in Figure 5 , 6 ) or have intervals where the pitch remains unchanged (as shown in Figure 4 , 7 ).

[0051] More conveniently, an asymmetric pump cladding geometry can be used to achieve an imperfectly symmetric optical energy distribution. Typically, the pump cladding has a non-circular outer contour structure; the pump cladding is preferably a regular polygon, D-shaped, or plum blossom-shaped; among them, the regular polygon commonly includes regular quadrilateral, pentagon, hexagon, heptagon, octagon, and nonagon. This non-circular outer contour of the pump cladding is commonly used in double-clad active fibers, and its function is to disrupt the helical light, enabling the fiber to pass through the core more, thereby increasing the cladding absorption. To achieve effective absorption management, the preferred asymmetry of the pump cladding is relatively obvious, such as D-shaped, plum blossom-shaped, regular quadrilateral, pentagon, hexagon, and heptagon.

[0052] In addition, in order to control the distribution of pump cladding light energy and achieve more obvious absorption management in a shorter optical fiber, a non-uniform refractive index distribution design of the pump cladding cross section can be adopted, that is, the different material compositions can achieve an imperfectly symmetrical light energy distribution, and a non-centrosymmetric refractive index distribution is preferred. From the perspective of ease of implementation, a doped region can be added to the pump cladding to destroy the symmetry of the light energy distribution. It is preferred to use a low-doped region to reduce the core distribution of the pump light, manage the cladding absorption, and improve the energy utilization. Typically, a pure quartz pump cladding structure with a fluorine-doped region can be used.

[0053] The cladding ratio of the active optical fiber and the rare earth element doping concentration of the core are also factors that affect the thermal load distribution of the absorption management optical fiber. The cladding ratio is the ratio of the cross section of the pump cladding to the core. When the cladding ratio is too small, the pump light is absorbed over a smaller length, and the thermal load distribution is not obvious when heat conduction plays a dominant role; when the cladding ratio is relatively large, the imperfectly symmetrical light energy distribution of the cladding has little effect on the core, and the pitch change of the optical fiber structure rotation has no obvious effect on the absorption of the active optical fiber cladding; and when the rare earth element doping concentration of the core is too large or too small, the pitch change of the optical fiber structure rotation will have no obvious effect on the absorption of the active optical fiber cladding. When the rare earth element doping concentration of the core is too large, the absorption of the core cladding is high, so the effect of the pitch change of the optical fiber structure rotation is relatively small. When the rare earth element doping concentration of the core is too small, the core is close to the saturated absorption at all places in the length direction. Even if the pitch of the optical fiber structure rotation is small, it is difficult to further increase the absorption of the core. Specifically, the preferred core ratio of the absorption management active optical fiber of the present invention is between 1.5 and 50, and the rare earth element doping concentration is 0.005 mol% to 1 mol%. In addition, the core ratio and the rare earth element doping concentration jointly affect the absorption of pump light of the rare earth doped element concentration in the core. When the rare earth element doping concentration and the core ratio are matched to make the ratio of the actual absorption energy of the rare earth element to the theoretical saturation absorption energy of the rare earth element within a suitable range, the core cladding absorption is adjusted in combination with the pitch change of the optical fiber structure rotation, and the ratio of the core ratio to the rare earth element doping concentration is preferably less than 500.

[0054] The method for preparing the absorption management active optical fiber provided by the present invention comprises the following steps:

[0055] (1) According to the design profile of the active optical fiber, an optical fiber preform having a circular core and a pump cladding with an imperfectly symmetrical optical energy distribution is manufactured;

[0056] (2) Rotating and drawing the optical fiber preform produced in step (1) to rotate the optical fiber structure, and adjusting the drawing speed and the preform rotation speed to rotate the optical fiber structure in the length direction and change the pitch along the length direction.

[0057] The drawing speed is 1-500 m / min, preferably 10 m / min, and the rotation speed is 0.5-500 / min.

[0058] The following are examples:

[0059] The absorption management active optical fiber provided in the embodiment is preferably applied to single-end pumping, and the cross-sectional structure is as follows: Figures 1 to 3 As shown, the stripped portion of the optical fiber includes a rare earth doped core and a pump cladding. Due to the shape and / or refractive index distribution of the pump cladding, the energy distribution of light transmitted therein is not perfectly symmetrical. The cross section of the core is circular. The cross-sectional structure of the absorption management active optical fiber of the octagonal pump cladding of Examples 1 and 2 and the double cladding active optical fiber of the comparative example is as follows: Figure 1 The cross-sectional structure of the absorption management active optical fiber of the octagonal pump cladding of Example 3 is shown as follows: Figure 2 As shown; the cross-sectional structure of the circular active optical fiber with low-doping region absorption management of Example 4 is as shown Figure 3 As shown, the doped region is a circle with a diameter of 100 microns, the center of the circle is 100 microns away from the center of the fiber core, and the refractive index is 1.448.

[0060] The optical fiber provided in the embodiment is prepared by drawing a preform rod, and the drawing ratio is between 5 and 1000.

[0061] In this embodiment, the pitch L (meter) is calculated according to the following method:

[0062] L=V l / V r

[0063] Among them, V l is the drawing speed, V r is the preform rotation speed.

[0064] The absorption management active optical fiber parameters provided in the embodiment are shown in Table 1.

[0065]

[0066]

[0067] The variation rule of the pitch along the light injection direction in the embodiment is as follows:

[0068] The absorption management optical fiber provided in Example 1 has a step change in pitch as follows: Figure 4 As shown, the preparation process is as follows:

[0069] For a single optical fiber in application, the first section along the light injection direction is 10m long, the pitch is infinite, the drawing speed is 10m / min, the preform rotation speed is 0, and the cladding absorption @915nm is 0.4dB / m; the second section is 10m long, the pitch is 0.33 meters, the drawing speed is 10m / min, the preform rotation speed is 30rpm, and the cladding absorption @915nm is 0.5dB / m. In actual production, the first and second sections can be prepared continuously, and a 20m long optical fiber including the first and second sections is cut for application. The transition between the first and second sections generally has a transition area of ​​about 0.5m, and the preform rotation speed is adjusted between 0rpm and 30rpm.

[0070] The absorption management optical fiber provided in Example 2 has a continuously varying pitch such as Figure 5 As shown, the preparation process is as follows:

[0071] The length of a single optical fiber in application is 20m, and the pitch decreases linearly along the light injection direction from 3.3m to 1m, the pitch change rate is 0.115, the drawing speed is 10m / min, the preform rotation speed gradually increases from 3rpm to 10rpm, and the cladding absorption @915nm increases from 0.6dB / m to 0.8dB / m. In actual production, it can be carried out continuously, with a transition area of ​​about 5m between the optical fibers at both ends, and the preform rotation speed is adjusted to 3rpm.

[0072] The absorption management optical fiber provided in Example 3 has a continuously varying pitch such as Figure 6 As shown, the preparation process is as follows:

[0073] The single optical fiber used as the gain medium is 8m long, and the pitch along the light injection direction decreases linearly from infinite to 0.4m, the drawing speed is 8m / min, the preform rotation speed gradually increases from 0rpm to 20rpm, and the cladding absorption @915nm increases from 2dB / m to 3dB / m. In actual production, it can be carried out continuously, with a transition area of ​​about 2m between the optical fibers of the application length at both ends, and the preform rotation speed is adjusted to 0rpm.

[0074] The absorption management optical fiber provided in Example 4 has a step change in pitch as follows: Figure 7 As shown, the preparation process is as follows:

[0075] When used as a gain medium, the first section of a single optical fiber is 7.5m long along the light injection direction, with a pitch of 5m, a drawing speed of 10m / min, a preform rotation speed of 2rpm, and a cladding absorption @915nm of 0.8dB / m; the second section is 10m long, with a pitch of 0.5m, a preform rotation speed of 20rpm, and a cladding absorption @915nm of 1.3dB / m. In actual production, the first and second sections can be prepared continuously, and a 20m long optical fiber including the first and second sections can be cut for application. The transition between the first and second sections generally has a transition area of ​​about 0.5m, and the preform rotation speed is adjusted between 2rpm and 20rpm.

[0076] In the comparative example, the optical fiber preform does not rotate. Cladding absorption @915nm is 0.35 dB / m.

[0077] The data in Table 1 show that the absorption regulation in the length direction can reduce the peak heat load of the optical fiber, thereby increasing the transverse mode instability threshold of the optical fiber.

[0078] The absorption management active optical fiber applied to two-end pumping is prepared accordingly by controlling the rotation speed of the optical fiber preform according to the design.

[0079] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An absorption-managed active optical fiber, characterized in that: The optical fiber glass portion includes a rare earth doped core and a pump cladding; The fiber core is cylindrical, and its axis coincides with the geometric center axis of the absorption management active optical fiber; On any cross section, when an angular coordinate system is established with the geometric center of the rare-earth-doped core as the origin, the polar diameter of any point (r, θ) on the cross section is r and the polar angle is θ. For any point (r, θ) on the pump cladding, f(r, θ) is the optical energy density of the point. The pump cladding has an imperfectly symmetrical light energy distribution relative to the geometric center of the rare-earth-doped core, that is, on any cross section, when an angular coordinate system is established with the geometric center of the rare-earth-doped core as the origin, the polar diameter of any point of the pump cladding is r, the polar angle is θ, f(r,θ) is the light energy density of the point (r,θ), and for positions with the same distance r0 from the geometric center, there are two points (r0,θ1) and (r0,θ2), satisfying: f(r0,θ1)≠f(r0,θ2), where θ1≠θ2; The optical fiber structure rotates in the length direction and the pitch changes along the length direction, so that the light energy distribution changes relative to the fiber core along the length direction.

2. The absorption management active optical fiber according to claim 1, characterized in that: Each cross section of the optical fiber has the same cross-sectional structure; and the cross-sectional structure of the optical fiber rotates along the length direction.

3. The absorption management active optical fiber according to claim 1, characterized in that: The minimum value of the pitch is between 0.01 meters and 30 meters.

4. The absorption managed active optical fiber according to claim 3, characterized in that: The pitch decreases monotonically along the light injection direction or the pitch decreases from both ends to the middle; The pitch changes continuously, with a rate of change less than 1000, preferably greater than 0.1; or the pitch changes in steps.

5. The absorption management active optical fiber according to claim 2, characterized in that: The pump cladding has a non-circular outer contour structure; the pump cladding is preferably a regular polygon, a D-shape, or a plum blossom shape; among which the regular polygons are commonly regular pentagons, hexagons, heptagons, octagons, and nonagons.

6. The absorption managed active optical fiber according to any one of claims 1 to 5, characterized in that: The pump cladding has a non-uniform refractive index distribution, and preferably the pump cladding has a non-centrosymmetric refractive index distribution.

7. The absorption-managed active optical fiber according to claim 6, characterized in that: The core-cladding ratio of the absorption management active optical fiber is between 1.5 and 50.

8. The absorption managed active optical fiber according to any one of claims 1 to 7, characterized in that: The rare earth element doping concentration is 0.005 mol% to 1 mol%, and the ratio of the core ratio to the rare earth element doping concentration is less than 500.

9. The method for preparing an absorption-managed active optical fiber according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) According to the design profile of the active optical fiber, an optical fiber preform having a circular core and a pump cladding with imperfectly symmetrical optical energy distribution is manufactured; (2) Rotating and drawing the optical fiber preform produced in step (1) to rotate the optical fiber structure, and adjusting the drawing speed and the preform rotation speed to rotate the optical fiber structure in the length direction and change the pitch along the length direction.

10. The method for preparing the absorption management active optical fiber according to claim 9, characterized in that: In step (2), the wire drawing speed is 1-500 m / min and the rotation speed is 0.5-500 rpm.

Images