Side pumping coupler and preparation method thereof, and multi-core amplifier and preparation method thereof

Abstract

The invention belongs to the technical field of optical fiber communication, and discloses a side pumping coupler and a preparation method thereof, and a multi-core amplifier and a preparation method thereof. The side pumping coupler provided by the invention comprises a plurality of double-cladding single-mode passive optical fibers and a pumping optical fiber, the pumping optical fiber is a multimode optical fiber, a coating layer is stripped from a part of the section of the pumping optical fiber, and the pumping optical fiber is tapered into a cone shape and then is spirally wound on the sections of the double-cladding single-mode passive optical fibers without the coating layer to form a coupling area; and the coupling region is tapered and fused into a whole. The multi-core amplifier provided by the invention comprises a multi-core active optical fiber, a fan-out device and a side pumping coupler, one end of the multi-core active optical fiber is connected with the side pumping coupler, and the other end of the multi-core active optical fiber is connected with the fan-out device; the side pumping coupler is used for inputting the pumping light and the signal light to the multi-core active optical fiber at the same time, and the fan-out device is used for outputting multiple paths of amplified signal light. According to the invention, the process can be simplified, the cost is reduced, and gain performance is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fiber communication, and more specifically, relates to a side pump coupler and a preparation method thereof, a multi-core amplifier and a preparation method thereof. Background Art

[0002] The development of optical fiber communication has brought great convenience to information exchange. However, with the increase of data transmission capacity in recent years, the traditional single-mode optical fiber transmission network system has reached its limit. How to achieve capacity expansion has become an urgent problem. Space division multiplexing uses mode division multiplexing and multi-core multiplexing schemes to differentiate a single optical fiber into multiple transmission channels, and transmit multiple signals simultaneously. It is a very potential solution to break through capacity limitations in the future. Among them, multi-core multiplexing uses multi-core optical fiber with multiple cores as the backbone network, loads multi-channel signals and transmits them simultaneously. It has the characteristics of good stability and low crosstalk, and has attracted much attention in recent years. However, its long-distance transmission still causes loss, and the attenuated optical signal needs to be regenerated and relayed at a certain distance. Traditional repeaters achieve optical signal amplification through photoelectric conversion, electrical amplification, retiming, pulse shaping and electro-optical conversion. It is suitable for single wavelength, but not for high-speed multi-wavelength systems. Therefore, the research on various optical amplification technologies is of great significance to the development of optical fiber communication systems.

[0003] At present, the development of amplifiers can be divided into core pumping and cladding pumping according to the pumping method. Core pumping injects pump light into the core. For multi-core optical fibers, multiple single-mode pump sources need to work simultaneously to meet the demand, which is costly and bulky. Cladding pumping only requires a single multi-mode pump source to achieve simultaneous amplification of multiple core optical signals, greatly reducing costs and installed volume.

[0004] For multi-channel multi-core optical fibers, it is particularly important to reduce costs, achieve high gain, and reduce the gain difference between fiber cores. The existing cladding pumping scheme of multi-core amplifiers usually requires the design and production of double-clad multi-core active optical fibers, which has the problem of high cost. In addition, the signal input end of the cladding pumping scheme of the existing multi-core amplifier has an extended active optical fiber segment, and the active optical fiber segment absorbs signal light, which is not conducive to gain improvement. Summary of the invention

[0005] The present invention solves the problems in the prior art that the cladding pumping scheme for realizing multi-path signal amplification has high cost and the gain performance needs to be further improved by providing a side pump coupler and a preparation method thereof, a multi-core amplifier and a preparation method thereof.

[0006] In a first aspect, the present invention provides a side-pumped coupler, comprising: a plurality of double-clad single-mode passive optical fibers and a pump optical fiber; the pump optical fiber is a multimode optical fiber, a portion of the pump optical fiber is stripped of coating and tapered into a cone, and then spirally wound around the plurality of double-clad single-mode passive optical fibers with stripped coating to form a coupling region, and the coupling region is tapered and fused into one.

[0007] Preferably, the end side of the multiple double-clad single-mode passive optical fibers contained in the side pump coupler as the signal input end is connected to the light source for inputting signal light; the pump optical fiber is used for inputting pump light; the end side of the multiple double-clad single-mode passive optical fibers contained in the side pump coupler as the signal output end is corroded and bundled for adapting to the end face of the multi-core active optical fiber.

[0008] Preferably, the bundling process is to insert a plurality of corroded double-clad single-mode passive optical fibers into a capillary tube, wherein the capillary tube is made of a material selected from glass, metal and ceramic.

[0009] Preferably, the side pump coupler further comprises: a filling optical fiber; and a plurality of double-clad single-mode passive optical fibers with coatings stripped off are bonded to the outside of the filling optical fiber.

[0010] Preferably, the winding length of the pump optical fiber is 1 cm to 1.5 cm, and the number of winding turns is 7 to 10 turns; the taper length of the coupling zone taper when it is fused is 500um to 1000um.

[0011] Preferably, the side pump coupler further comprises: a packaging tube; the packaging tube is used to package the integrated structure obtained after the taper melting process.

[0012] In a second aspect, the present invention provides a method for preparing the side pump coupler as described above, comprising the following steps:

[0013] A double-clad single-mode passive optical fiber with a coating layer stripped off in a partial section is used as a first intermediate component, and a pump optical fiber with a coating layer stripped off in a partial section and tapered into a cone is used as a second intermediate component;

[0014] The plurality of the first intermediate pieces are closely arranged, the second intermediate piece is spirally wound on the plurality of the first intermediate pieces to form a coupling region, and the coupling region is subjected to tapered melting to obtain a side pump coupler.

[0015] In a third aspect, the present invention provides a multi-core amplifier, comprising: a multi-core active optical fiber, a fan-out device, and a side pump coupler as described above; one end of the multi-core active optical fiber is connected to the side pump coupler, and the other end of the multi-core active optical fiber is connected to the fan-out device; the side pump coupler is used to allow pump light and signal light to be simultaneously input into the multi-core active optical fiber, and the fan-out device is used to output amplified multi-path signal light.

[0016] Preferably, the multi-core active optical fiber is doped with one or more rare earth elements selected from the group consisting of erbium, ytterbium, molybdenum and thulium.

[0017] In a fourth aspect, the present invention provides a method for preparing a multi-core amplifier, connecting the side pump coupler as described above to one end of a multi-core active optical fiber, and connecting the other end of the multi-core active optical fiber to a fan-out device to obtain a multi-core amplifier.

[0018] One or more technical solutions provided in the present invention have at least the following technical effects or advantages:

[0019] The side pump coupler provided by the present invention comprises a plurality of double-clad single-mode passive optical fibers and a pump optical fiber, wherein the pump optical fiber is a multimode optical fiber, and a portion of the pump optical fiber is stripped of its coating layer and tapered into a cone, and then spirally wound on the portion of the double-clad single-mode passive optical fibers stripped of its coating layer to form a coupling region, and the coupling region is tapered and fused into one. The corresponding present invention also provides a method for preparing a side pump coupler, wherein the double-clad single-mode passive optical fiber stripped of its coating layer is used as a first middle piece, and the pump optical fiber stripped of its coating layer and tapered into a cone is used as a second middle piece; multiple first middle pieces are closely arranged, and the second middle piece is spirally wound on the multiple first middle pieces to form a coupling region, and the coupling region is tapered and fused to obtain a side pump coupler. On the basis of providing a side pump coupler, the present invention also provides a multi-core amplifier and a corresponding preparation method, wherein the multi-core amplifier includes a multi-core active optical fiber, a fan-out device, and a side pump coupler, wherein one end of the multi-core active optical fiber is connected to the side pump coupler, and the other end of the multi-core active optical fiber is connected to the fan-out device; the side pump coupler is used to simultaneously input the pump light and the signal light into the multi-core active optical fiber, and the fan-out device is used to output the amplified multi-channel signal light. That is, the present invention proposes a multi-channel spiral pumped side pump coupler and a multi-core amplifier solution, which can use commercial (i.e. conventional) double-clad single-mode passive optical fiber to achieve multi-channel transmission of pump light, without the need to specially design double-clad single-mode passive optical fiber or double-clad multi-core optical fiber, and can simplify the process and reduce costs. In addition, the signal light enters the multi-core active optical fiber at the same time as the pump light after passing through the passive optical fiber and the coupler, and the active optical fiber without an extension section before input absorbs the signal light, which is conducive to obtaining high gain, and the multi-channel pump light is input into the multi-core active optical fiber from the fiber core, which is more conducive to reducing the gain difference. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the structure of a tapered pump fiber in a side-pump coupler provided in Example 1 of the present invention;

[0021] Figure 2 A schematic structural diagram of a coupling region in a side-pumped coupler provided in Example 1 of the present invention;

[0022] Figure 3 A schematic structural diagram of a side pump coupler package provided in Example 1 of the present invention;

[0023] Figure 4 A schematic diagram of the structure of a side pump coupler provided in Example 2 of the present invention;

[0024] Figure 5 A schematic diagram of the structure of a four-core amplifier provided in Embodiment 4 of the present invention;

[0025] Figure 6 A schematic diagram of the structure of the corroded optical fiber in the four-core amplifier provided in Example 4 of the present invention;

[0026] Figure 7 A schematic diagram of the structure of the corroded optical fiber bundle in the four-core amplifier provided in Example 4 of the present invention;

[0027] Figure 8 A schematic diagram of the structure of the connection area in the four-core amplifier provided in Embodiment 4 of the present invention;

[0028] Fig. 9 This is a schematic diagram of the structure of the connection area in the six-core amplifier provided in Example 4 of the present invention.

[0029] Among them, 1-pump fiber, 2-double-clad single-mode passive fiber, 3-coupling region, 4-packaging tube, 5-filling fiber, 6-connection region, 7-multi-core active fiber, 8-fan-out device, and 9-capillary. DETAILED DESCRIPTION

[0030] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0031] Embodiment 1:

[0032] Embodiment 1 provides a side pump coupler, see Figure 1 to Figure 2 , comprising: a plurality of double-clad single-mode passive optical fibers 2 and a pump optical fiber 1; the pump optical fiber 1 is a multimode optical fiber, and a portion of the pump optical fiber 1 is stripped of its coating layer and tapered into a cone (the schematic diagram of the structure of the pump optical fiber tapered into a cone is shown in Figure 1) is spirally wound around the sections of the plurality of double-clad single-mode passive optical fibers 2 from which the coating layers are stripped to form a coupling region 3, and the coupling region 3 is tapered and fused into one.

[0033] Among them, the multiple double-clad single-mode passive optical fibers 2 contained in the side pump coupler are connected to the light source as the end side of the signal input end, and are used to input signal light; the pump optical fiber 1 is used to input pump light; the multiple double-clad single-mode passive optical fibers 2 contained in the side pump coupler are used as the end side of the signal output end and are corroded and bundled for adaptation to the end face of the multi-core active optical fiber.

[0034] The side-pumped coupler provided by the present invention is used to realize multi-channel signal amplification, which belongs to the cladding pumping scheme. The pump light input end and the signal light input end are located on one side, and the signal light output end is located on the other side. The signal light output end is easy to be bonded with the multi-core active optical fiber for refractive index matching after corrosion and bundling. On this basis, a multi-core amplifier can be further formed. The content of the multi-core amplifier is specifically described in Example 4.

[0035] The double-clad single-mode passive optical fiber 2 in the present invention can adopt commercial double-clad single-mode passive optical fiber, and there is no need to specially design double-clad single-mode passive optical fiber or double-clad multi-core optical fiber. For example, the structure of the commercial double-clad single-mode passive optical fiber includes a core, an inner cladding, a depressed cladding, an outer cladding, a low-fold cladding and a coating layer from the inside to the outside. The diameter range of the core is 3um to 10um, and the range of the relative refractive index difference Δ1 of the core is: 0.85%≤Δ1≤0.96%. The diameter range of the inner cladding is 5.5um to 12.5um, and the range of the relative refractive index difference Δ2 of the inner cladding is: -0.1%≤Δ2≤0.1%. The diameter range of the depressed cladding is 12.5um to 19.5um, and the range of the relative refractive index difference Δ3 of the depressed cladding is: -0.5%≤Δ3≤0.3%. The diameter of the outer cladding is in the range of 105um to 250um, and the relative refractive index difference Δ4 of the outer cladding is in the range of 0≤Δ4≤0.3%. The refractive index of the low-fold cladding is in the range of 1.35 to 1.39. The above design is suitable for matching and coupling with multimode optical fiber.

[0036] The pump fiber 1 is a large core diameter fiber, preferably a multi-mode pump source pigtail. The pump fiber 1 is made into a tapered fiber by tapering, and then wound around multiple double-clad single-mode passive optical fibers and heated to taper, so that one pump light can be coupled into the multi-core active optical fiber.

[0037] The bundling process is to insert multiple corroded double-clad single-mode passive optical fibers into a capillary. The capillary is made of a material selected from glass, metal, and ceramic. The capillary is preferably made of metal. The good heat dissipation effect of metal can further extend the life of the device.

[0038] The winding length of the pump optical fiber 1 is 1 cm to 1.5 cm, and the number of winding turns is 7 to 10 turns; the taper length of the coupling region 3 when the taper is fused is 500 um to 1000 um.

[0039] In addition, the side pump coupler may further include: a packaging tube 4; the packaging tube 4 is used to package the integrated structure obtained after the taper melting process, see Figure 3 .

[0040] Embodiment 2:

[0041] Embodiment 2 provides a side pump coupler. The difference between Embodiment 2 and Embodiment 1 is that Embodiment 2 further includes a filling optical fiber; a plurality of double-clad single-mode passive optical fibers with coatings stripped off are bonded to the outside of the filling optical fiber.

[0042] See also Figure 4 Embodiment 2 provides a side pump coupler, comprising: a plurality of double-clad single-mode passive optical fibers 2, a pump optical fiber 1 and a filling optical fiber 5; a plurality of double-clad single-mode passive optical fibers 2 with coatings removed are bonded to the outside of the filling optical fiber 5, the pump optical fiber 1 is a multimode optical fiber, and a portion of the pump optical fiber 1 is stripped of its coating and tapered into a cone (for a schematic diagram of the structure of the pump optical fiber tapered into a cone, see Figure 1 ) are spirally wound around the sections where the coating layers of the plurality of double-clad single-mode passive optical fibers 2 are stripped to form a coupling zone, and the coupling zone is tapered and fused into one.

[0043] Embodiment 3:

[0044] Embodiment 3 provides a method for preparing a side pump coupler, comprising the following steps:

[0045] A double-clad single-mode passive optical fiber with a coating layer stripped off in a partial section is used as a first intermediate component, and a pump optical fiber with a coating layer stripped off in a partial section and tapered into a cone is used as a second intermediate component;

[0046] The plurality of the first intermediate pieces are closely arranged, the second intermediate piece is spirally wound on the plurality of the first intermediate pieces to form a coupling region, and the coupling region is subjected to tapered melting to obtain a side pump coupler.

[0047] Among them, if the coupling area formed by spirally winding the second middle piece around multiple first middle pieces is used as the third middle piece, the subsequent steps can be understood as performing high-temperature taper fusion on the third middle piece to obtain the fourth middle piece. After obtaining the fourth middle piece, low-refractive index glue can be used for dispensing at both ends to form a side pump coupler.

[0048] Specifically, the method for preparing the side pump coupler provided in Example 3 may be the method for preparing the side pump coupler as described in Example 1 or Example 2. If it is the method for preparing the side pump coupler as provided in Example 2, the above-described method for closely arranging the plurality of first intermediate pieces is specifically implemented by adding a filling optical fiber in the middle of the plurality of first intermediate pieces, and bonding the plurality of first intermediate pieces to the outside of the filling optical fiber. This operation makes it easier for the first intermediate piece to contact and fuse with the second intermediate piece.

[0049] Embodiment 4:

[0050] Embodiment 4 provides a multi-core amplifier, see Figure 5 , comprising: a multi-core active optical fiber 7, a fan-out device 8, and a side pump coupler as described in Example 1 or Example 2; one end of the multi-core active optical fiber 7 is connected to the side pump coupler, and the connection structure forms a connection area 6, and the other end of the multi-core active optical fiber 7 is connected to the fan-out device 8; the side pump coupler is used to allow pump light and signal light to be simultaneously input into the multi-core active optical fiber 7, and the fan-out device 8 is used to output amplified multi-path signal light.

[0051] Example 4 On the basis of obtaining a side pump coupler, the end of the double-clad single-mode passive optical fiber is corroded and bundled to adapt to the end face of the multi-core active optical fiber, that is, aligned and bonded with the multi-core active optical fiber, so that the signal light and the pump light can be injected into the multi-core active optical fiber from multiple double-clad single-mode passive optical fibers at the same time, and the end of the multi-core active optical fiber is connected to the signal light after the fan-out device outputs the gain, thereby forming the multi-core amplifier, which can realize multi-channel signal amplification. The multi-core amplifier provided by the present invention allows the pump light and the signal light to be injected into the multi-core active optical fiber at the same time, which is conducive to improving the gain and reducing the gain difference between the cores, and does not require the additional design of the double-clad multi-core optical fiber, which can simplify the production process and reduce the production cost.

[0052] Wherein, the multi-core active optical fiber 7 is doped with one or more rare earth elements selected from erbium, ytterbium, molybdenum and thulium.

[0053] The double-clad single-mode passive optical fiber is corroded and bundled by stringing a plurality of corroded optical fibers into a capillary tube, and the corroded optical fibers are bundled and tightly arranged in the capillary tube with almost no gaps. The diameter of the capillary tube is consistent with that of the multi-core active optical fiber, and the thickness ranges from 10um to 50um. The capillary tube can be made of high temperature resistant materials such as glass, metal, and ceramic.

[0054] Embodiment 5:

[0055] Example 5 provides a method for preparing a multi-core amplifier, connecting the side pump coupler described in Example 1 or Example 2 to one end of a multi-core active optical fiber, and connecting the other end of the multi-core active optical fiber to a fan-out device to obtain a multi-core amplifier.

[0056] The preparation method of the multi-core amplifier provided in Example 5 is also the preparation method corresponding to the multi-core amplifier provided in Example 4. The following takes the multi-core active optical fiber as a four-core active optical fiber and a six-core active optical fiber as examples, and describes them respectively in combination with whether the side pump coupler includes a filling optical fiber.

[0057] (1) Four-core amplifier.

[0058] The preparation method of the four-core amplifier comprises the following steps:

[0059] S1. Take four double-clad single-mode passive optical fibers with a core / cladding diameter ratio of 10 / 125um and a length of 1.2m to 2.6m, strip off the coating layer of 1.0±0.1cm in the middle, and obtain four sections of bare optical fiber as the first intermediate piece.

[0060] S2. Take a multimode optical fiber with a core / cladding diameter ratio of 105 / 125um and a length of 1.2m to 2.6m, strip off the coating layer in the middle of 2.0±0.1cm to obtain a bare optical fiber, and taper the bare optical fiber into the following Figure 1 The structure shown serves as the second middleware.

[0061] S3, take the second middle piece and wrap it around the four first middle pieces to form a coupling area, see Figure 2 , as the third middleware.

[0062] S4, taking the third middle piece, performing high-temperature taper fusion, and using the obtained structure as the fourth middle piece.

[0063] S5, take the fourth intermediate piece, put it into the packaging tube by using low refractive index glue at both ends to make a side pump coupler, see Figure 3 .

[0064] S6. The signal input ends of the four double-clad single-mode passive optical fibers included in the side pump coupler are connected to the light source for signal light input, and the pump input ends are used to input pump light. The signal output ends of the four double-clad single-mode passive optical fibers included in the side pump coupler are corroded, bundled, and bonded with the four-core active optical fiber with a refractive index matching adhesive to form a connection area, so that the pump light and the signal light are simultaneously input into the four-core active optical fiber. The tail end of the four-core active optical fiber is connected to a fan-out device to output the amplified signal light, thereby forming a four-core amplifier, see Figure 5 .

[0065] Among them, see Figures 6 to 8 , Figure 6 This is a schematic diagram of the structure of the corroded optical fiber in the four-core amplifier. Figure 7 This is a schematic diagram of the structure of the corroded optical fiber bundle in the four-core amplifier. Figure 8The schematic diagram of the structure of the connection area in the four-core amplifier is as follows. Specifically, the signal output ends of the four double-clad single-mode passive optical fibers 2 can be etched to 41um, and then inserted into a capillary 9 with a diameter of 102um and a wall thickness of 30um to arrange the etched optical fibers closely, and finally the bundled etched optical fibers are aligned with the cores of the four-core active optical fibers (i.e., the multi-core active optical fibers 7) and bonded with an adhesive having a matching refractive index.

[0066] (2) Six-core amplifier.

[0067] Similar to the preparation method of the four-core amplifier, after the side-pump coupler is prepared, the signal output ends of the six double-clad single-mode passive optical fibers are corroded and bundled and bonded with the six-core active optical fibers with a refractive index-matched adhesive to form a connection area, so that the pump light and the signal light are simultaneously input into the six-core active optical fiber. The tail end of the six-core active optical fiber is connected to a fan-out device to output the amplified signal light, thereby forming a six-core amplifier.

[0068] See also Fig. 9 , Fig. 9 The figure is a schematic diagram of the structure of the connection area in the six-core amplifier. Specifically, the signal output ends of the six double-clad single-mode passive optical fibers 2 can be etched to 43um, and inserted into a capillary 9 with a diameter of 125um and a wall thickness of 50um together with the filling optical fiber 5, so that the etched optical fibers are closely arranged at the edge of the filling optical fiber 5. The bundled etched optical fibers are aligned with the cores of the six-core active optical fiber (i.e., the multi-core active optical fiber 7) and then bonded with an adhesive with a matching refractive index.

[0069] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A side pump coupler, characterized in that: include: A plurality of double-clad single-mode passive optical fibers and a pump optical fiber; the pump optical fiber is a multimode optical fiber, a portion of the pump optical fiber is stripped of coating, tapered into a cone, and then spirally wound around the portions of the double-clad single-mode passive optical fibers from which the coatings are stripped to form a coupling region, and the coupling region is tapered and fused into one.

2. The side pump coupler according to claim 1, characterized in that: The multiple double-clad single-mode passive optical fibers contained in the side pump coupler are connected to the light source as the end side of the signal input end, and are used to input signal light; the pump optical fiber is used to input pump light; the multiple double-clad single-mode passive optical fibers contained in the side pump coupler are used as the end side of the signal output end, which are corroded and bundled, and are used to adapt to the end face of the multi-core active optical fiber.

3. The side pump coupler according to claim 2, characterized in that: The bundling process is to insert a plurality of corroded double-clad single-mode passive optical fibers into a capillary tube, wherein the capillary tube is made of a material selected from glass, metal and ceramic.

4. The side pump coupler according to claim 1, characterized in that: Also includes: Filling optical fiber; multiple double-clad single-mode passive optical fibers with coatings stripped off are bonded to the outside of the filling optical fiber.

5. The side pump coupler according to claim 1, characterized in that: The winding length of the pump optical fiber is 1 cm to 1.5 cm, and the number of winding turns is 7 to 10 turns; the taper length of the coupling zone taper when it is fused is 500um to 1000um.

6. The side pump coupler according to claim 1, characterized in that: Also includes: Packaging tube; the packaging tube is used to package the integrated structure obtained after the cone melting process.

7. A method for preparing a side pump coupler according to any one of claims 1 to 6, characterized in that: The following steps are involved: A double-clad single-mode passive optical fiber with a coating layer stripped off in a partial section is used as a first intermediate component, and a pump optical fiber with a coating layer stripped off in a partial section and tapered into a cone is used as a second intermediate component; The plurality of the first intermediate pieces are closely arranged, the second intermediate piece is spirally wound on the plurality of the first intermediate pieces to form a coupling region, and the coupling region is subjected to tapered melting to obtain a side pump coupler.

8. A multi-core amplifier, characterized in that: include: A multi-core active optical fiber, a fan-out device, and a side-pumped coupler as claimed in any one of claims 1 to 6; One end of the multi-core active optical fiber is connected to the side pump coupler, and the other end of the multi-core active optical fiber is connected to the fan-out device; the side pump coupler is used to allow pump light and signal light to be simultaneously input into the multi-core active optical fiber, and the fan-out device is used to output amplified multi-path signal light.

9. The multi-core amplifier according to claim 8, characterized in that: The multi-core active optical fiber is doped with one or more rare earth elements selected from erbium, ytterbium, molybdenum and thulium.

10. A method for preparing a multi-core amplifier, characterized in that: The side pump coupler according to any one of claims 1 to 6 is connected to one end of a multi-core active optical fiber, and the other end of the multi-core active optical fiber is connected to a fan-out device to obtain a multi-core amplifier.

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