A side-pump coupler and its fabrication method, and a multi-core amplifier and its fabrication method.

Abstract

This invention belongs to the field of optical fiber communication technology and discloses a side-pump coupler and its fabrication method, as well as a multi-core amplifier and its fabrication method. The side-pump coupler provided by this invention includes multiple double-clad single-mode passive optical fibers and one pump fiber. The pump fiber is a multi-mode fiber. A portion of the pump fiber has its coating removed, is tapered, and then spirally wound around the coated sections of the multiple double-clad single-mode passive optical fibers to form a coupling region. The coupling region is tapered and fused together. The multi-core amplifier provided by this invention includes a multi-core active optical fiber, a fan-out device, and a side-pump coupler. One end of the multi-core active optical fiber is connected to the side-pump coupler, and the other end is connected to the fan-out device. The side-pump coupler allows pump light and signal light to be simultaneously input into the multi-core active optical fiber, and the fan-out device outputs amplified multi-channel signal light. This invention simplifies the process, reduces costs, and improves gain performance.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber communication technology, and more specifically, relates to a side-pumped coupler and its fabrication method, and a multi-core amplifier and its fabrication method. Background Technology

[0002] The development of optical fiber communication has brought great convenience to information exchange. However, in recent years, with the increase in data transmission capacity, traditional single-mode optical fiber transmission network systems have reached their limits. How to expand capacity has become an urgent issue. Space division multiplexing, using mode division multiplexing and multi-core multiplexing schemes, allows a single optical fiber to be divided into multiple transmission channels, enabling the simultaneous transmission of multiple signals. It is a highly promising solution for overcoming capacity limitations in the future. Among them, multi-core multiplexing uses multi-core optical fibers with multiple cores as the backbone network, carrying multiple channels of signals for simultaneous transmission. It has the characteristics of good stability and low crosstalk, and has attracted much attention in recent years. However, its long-distance transmission still incurs losses, requiring regeneration and relay of attenuated optical signals at certain intervals. Traditional repeaters amplify optical signals through photoelectric conversion, electrical amplification, retiming, pulse shaping, and electro-optical conversion, which is suitable for single wavelengths, but not for high-speed multi-wavelength systems. Therefore, research on various optical amplification technologies is of great significance to the development of optical fiber communication systems.

[0003] Currently, amplifier development can be categorized into core-pumped and cladding-pumped methods based on the pumping mechanism. Core-pumped amplifiers inject pump light into the fiber core, requiring multiple single-mode pump sources to operate simultaneously for multi-core fibers, resulting in high cost and large size. In contrast, cladding-pumped amplifiers only require a single multimode pump source to simultaneously amplify optical signals from multiple fiber cores, significantly reducing cost and installation size.

[0004] For multi-channel, multi-core optical fibers, reducing costs, achieving high gain, and minimizing the gain difference between fiber cores are particularly important. Existing cladding pumping schemes for multi-core amplifiers typically require the design and manufacture of double-clad multi-core active optical fibers, resulting in high costs. Furthermore, existing cladding pumping schemes for multi-core amplifiers have an extended active fiber segment at the signal input end, and this active fiber segment absorbs signal light, which is detrimental to gain improvement. Summary of the Invention

[0005] This invention addresses the problems of high cost and insufficient gain performance in existing cladding pumping schemes for multi-channel signal amplification by providing a side-pumped coupler and its fabrication method, as well as a multi-core amplifier and its fabrication method.

[0006] In a first aspect, the present invention provides a side-pump coupler, comprising: multiple double-clad single-mode passive optical fibers and a pump optical fiber; the pump optical fiber is a multimode optical fiber, and a portion of the pump optical fiber, after having its coating removed and tapered into a cone shape, is spirally wound around the coated portions of the multiple double-clad single-mode passive optical fibers to form a coupling region, wherein the tapered coupling region is fused together.

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

[0008] Preferably, the bundling process involves inserting multiple etched double-clad single-mode passive optical fibers into a capillary tube, wherein the capillary tube is made of one of the following materials: glass, metal, or ceramic.

[0009] Preferably, the side-pump coupler further includes: a filler fiber; multiple double-clad single-mode passive fibers with stripped coatings are bonded to the outside of the filler fiber.

[0010] Preferably, the pump fiber has a winding length of 1cm to 1.5cm and a winding number of 7 to 10 turns; the tapering length during the tapering and melting of the coupling region is 500um to 1000um.

[0011] Preferably, the side pump coupler further includes: an encapsulation tube; the encapsulation tube is used to encapsulate the integral structure obtained after tapered melting treatment.

[0012] Secondly, the present invention provides a method for fabricating a side-pump coupler as described above, comprising the following steps:

[0013] The first intermediate component is a double-clad single-mode passive optical fiber with a portion of its coating removed, and the second intermediate component is a pump optical fiber with a portion of its coating removed and tapered.

[0014] Multiple first intermediate components are arranged closely together, and a second intermediate component is spirally wound around the multiple first intermediate components to form a coupling region. The coupling region is then subjected to tapered melting to obtain a side pump coupler.

[0015] Thirdly, 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 simultaneously input pump light and signal light into the multi-core active optical fiber, and the fan-out device is used to output amplified multi-channel signal light.

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

[0017] Fourthly, the present invention provides a method for fabricating a multi-core amplifier, wherein a side-pump coupler as described above 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.

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

[0019] The side-pump coupler provided by this invention includes multiple double-clad single-mode passive optical fibers and one pump optical fiber. The pump optical fiber is a multimode optical fiber. A portion of the pump optical fiber has its coating removed and is tapered before being spirally wound around the coated portions of the multiple double-clad single-mode passive optical fibers to form a coupling region. The coupling region is then tapered and fused together. Correspondingly, this invention also provides a method for fabricating the side-pump coupler. A portion of the coated double-clad single-mode passive optical fiber is removed as a first intermediate component, and a portion of the coated pump optical fiber is removed and tapered as a second intermediate component. Multiple first intermediate components are arranged closely together, and the second intermediate component is spirally wound around the multiple first intermediate components to form a coupling region. The coupling region is then tapered and fused to obtain the side-pump coupler. Based on the side-pump coupler, this invention also provides a multi-core amplifier and its corresponding fabrication method. The multi-core amplifier includes a multi-core active fiber, a fan-out device, and a side-pump coupler. One end of the multi-core active fiber is connected to the side-pump coupler, and the other end is connected to the fan-out device. The side-pump coupler allows pump light and signal light to be simultaneously input into the multi-core active fiber, and the fan-out device outputs amplified multi-path signal light. In other words, this invention proposes a multi-channel spiral-pumped side-pump coupler and multi-core amplifier scheme, which can use commercially available (i.e., conventional) double-clad single-mode passive fiber to achieve multi-path transmission of pump light without the need for specially designed double-clad single-mode passive fiber or double-clad multi-core fiber, thus simplifying the process and reducing costs. Furthermore, after passing through the passive fiber and coupler, the signal light enters the multi-core active fiber simultaneously with the pump light. The active fiber, without an extension section before input, absorbs the signal light, which is beneficial for obtaining high gain. Moreover, the multi-path pump light is input into the multi-core active fiber from the fiber core, further reducing gain difference. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the tapered pump fiber in a side-pump coupler provided in Embodiment 1 of the present invention;

[0021] Figure 2 This is a schematic diagram of the coupling region in a side pump coupler provided in Embodiment 1 of the present invention;

[0022] Figure 3 This is a schematic diagram of a side pump coupler package provided in Embodiment 1 of the present invention;

[0023] Figure 4 This is a schematic diagram of a side pump coupler provided in Embodiment 2 of the present invention;

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

[0025] Figure 6 This is a schematic diagram of the etched optical fiber in the four-core amplifier provided in Embodiment 4 of the present invention;

[0026] Figure 7 This is a schematic diagram of the etched fiber bundle structure in the four-core amplifier provided in Embodiment 4 of the present invention;

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

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

[0029] Among them, 1-pump fiber, 2-double-clad single-mode passive fiber, 3-coupling region, 4-encapsulation tube, 5-filled fiber, 6-connection region, 7-multi-core active fiber, 8-fan-out device, 9-capillary tube. Detailed Implementation

[0030] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0031] Example 1:

[0032] Example 1 provides a side-pump coupler, see [link to example]. Figures 1 to 2 It includes: multiple double-clad single-mode passive optical fibers 2 and one pump optical fiber 1; the pump optical fiber 1 is a multimode optical fiber, and a portion of the pump optical fiber 1 has its coating removed and is tapered (see the schematic diagram of the tapered pump optical fiber). Figure 1The coupling region 3 is formed by spirally winding the coated sections of multiple double-clad single-mode passive optical fibers 2, and the coupling region 3 is tapered and fused together.

[0033] The side-pump coupler contains multiple double-clad single-mode passive optical fibers 2, which are connected to the light source as 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 in the side-pump coupler are etched and bundled as the signal output end and are used to adapt to the end face of the multi-core active optical fiber.

[0034] The side-pump coupler provided by this invention is used to realize multi-channel signal amplification. It 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. After being etched and bundled, the signal light output end is easy to be bonded to the multi-core active optical fiber for refractive index matching. On this basis, a multi-core amplifier can be further formed. The details of the multi-core amplifier are explained in Example 4.

[0035] The double-clad single-mode passive fiber 2 in this invention can be a commercially available double-clad single-mode passive fiber, eliminating the need for specially designed double-clad single-mode passive fibers or double-clad multi-core fibers. For example, the structure of a commercially available double-clad single-mode passive fiber, from the inside out, includes a core, inner cladding, recessed cladding, outer cladding, low-fold cladding, and a coating layer. The core diameter ranges from 3 μm to 10 μm, and the relative refractive index difference Δ1 of the core ranges from 0.85% to 0.96%. The inner cladding diameter ranges from 5.5 μm to 12.5 μm, and the relative refractive index difference Δ2 of the inner cladding ranges from -0.1% to 0.1%. The recessed cladding diameter ranges from 12.5 μm to 19.5 μm, and the relative refractive index difference Δ3 of the recessed cladding ranges from -0.5% to 0.3%. The diameter of the outer cladding ranges from 105 μm to 250 μm, and the relative refractive index difference Δ4 of the outer cladding ranges from 0 ≤ Δ4 ≤ 0.3%. The refractive index of the low-fold cladding ranges from 1.35 to 1.39. The above design is suitable for matched coupling with multimode optical fibers.

[0036] The pump fiber 1 is a large-core fiber, preferably a multimode pump source pigtail. The pump fiber 1 is tapered into a tapered fiber and then wound around multiple double-clad single-mode passive fibers and heated to tapere, which enables one pump light to be coupled into the multi-core active fiber.

[0037] The bundled processing involves inserting multiple etched double-clad single-mode passive optical fibers into a capillary tube. The capillary tube is made of one of the following materials: glass, metal, or ceramic. Preferably, the capillary tube is made of metal, which has good heat dissipation properties and can further extend the lifespan of the device.

[0038] The pump fiber 1 has a winding length of 1cm to 1.5cm and a winding number of 7 to 10 turns; the coupling region 3 has a tapered length of 500um to 1000um during tapering and melting.

[0039] In addition, the side pump coupler may also include: an encapsulation tube 4; the encapsulation tube 4 is used to encapsulate the integral structure obtained after tapered melting treatment, see [link to documentation]. Figure 3 .

[0040] Example 2:

[0041] Example 2 provides a side-pumped coupler. The difference between Example 2 and Example 1 is that Example 2 also includes a filler fiber; multiple double-clad single-mode passive fibers with stripped coatings are bonded to the outside of the filler fiber.

[0042] See Figure 4 Example 2 provides a side-pumped coupler, comprising: multiple double-clad single-mode passive optical fibers 2, one pump optical fiber 1, and one filler optical fiber 5; the multiple double-clad single-mode passive optical fibers 2 with their coatings removed are all bonded to the outside of the filler optical fiber 5; the pump optical fiber 1 is a multimode optical fiber, and a portion of the pump optical fiber 1 has its coating removed and is tapered (see schematic diagram of the tapered pump optical fiber). Figure 1 The coupling region is formed by spirally winding the coated sections of multiple double-clad single-mode passive optical fibers 2, and the coupling region is tapered and fused together.

[0043] Example 3:

[0044] Example 3 provides a method for fabricating a side-pump coupler, comprising the following steps:

[0045] The first intermediate component is a double-clad single-mode passive optical fiber with a portion of its coating removed, and the second intermediate component is a pump optical fiber with a portion of its coating removed and tapered.

[0046] Multiple first intermediate components are arranged closely together, and a second intermediate component is spirally wound around the multiple first intermediate components to form a coupling region. The coupling region is then subjected to tapered melting to obtain a side pump coupler.

[0047] If the coupling area formed by spirally winding the second intermediate component around multiple first intermediate components is used as the third intermediate component, the subsequent steps can be understood as performing high-temperature tapering fusion on the third intermediate component to obtain the fourth intermediate component. After obtaining the fourth intermediate component, it can be encapsulated by dispensing low-refractive-index adhesive at both ends to form a side pump coupler.

[0048] Specifically, Embodiment 3 may provide a method for fabricating a side-pump coupler as described in Embodiment 1 or Embodiment 2. If the method for fabricating a side-pump coupler is as described in Embodiment 2, the specific implementation of the above-described method of closely arranging multiple first intermediate components is as follows: a filler fiber is added between the multiple first intermediate components, and the multiple first intermediate components are bonded to the outside of the filler fiber. This operation facilitates the contact and fusion of the first and second intermediate components.

[0049] Example 4:

[0050] Example 4 provides a multi-core amplifier, see [link to example]. Figure 5 It includes: a multi-core active optical fiber 7, a fan-out device 8, and a side-pump coupler as described in Embodiment 1 or Embodiment 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; 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 simultaneously input pump light and signal light into the multi-core active optical fiber 7, and the fan-out device 8 is used to output amplified multi-channel signal light.

[0051] In Example 4, based on the side-pump coupler, the ends of the double-clad single-mode passive optical fibers are etched, bundled, and then adapted to the end faces of multi-core active optical fibers, i.e., aligned and bonded to the multi-core active optical fibers. This allows signal light and pump light to be simultaneously injected from multiple double-clad single-mode passive optical fibers into the multi-core active optical fiber. The ends of the multi-core active optical fibers are connected to fan-out devices to output the enhanced signal light, thus forming the multi-core amplifier, which can realize multi-channel signal amplification. The multi-core amplifier provided by this invention allows pump light and signal light to be injected into the multi-core active optical fiber simultaneously, which is beneficial for improving gain, reducing inter-core gain difference, and eliminating the need for additional double-clad multi-core optical fiber design, thereby simplifying the manufacturing process and reducing production costs.

[0052] 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 etching and bundling of double-clad single-mode passive optical fibers can specifically involve threading multiple etched optical fibers into a capillary tube, and then bundling the etched fibers together so that they are tightly arranged within the capillary tube with almost no gaps. The diameter of the capillary tube is the same as that of the multi-core active optical fiber, and the thickness ranges from 10µm to 50µm. The capillary tube can be made of high-temperature resistant materials such as glass, metal, or ceramics.

[0054] Example 5:

[0055] Example 5 provides a method for fabricating a multi-core amplifier, wherein a side-pump coupler as described in Example 1 or Example 2 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.

[0056] The fabrication method of the multi-core amplifier provided in Example 5 is the same as the fabrication method of the multi-core amplifier provided in Example 4. The following explanation will take four-core and six-core active optical fibers as examples, and will be further elaborated on whether or not the side-pump coupler contains filler fiber.

[0057] (1) Four-core amplifier.

[0058] The fabrication method of a four-core amplifier includes 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. Remove the coating layer with a length of 1.0±0.1cm in the middle to obtain four bare optical fiber segments, which will serve as the first intermediate component.

[0060] S2. Take a multimode optical fiber with a core / cladding diameter ratio of 105 / 125µm and a length of 1.2m to 2.6m. Strip the coating layer in the middle for a length of 2.0±0.1cm to obtain a bare optical fiber section. Taper the bare optical fiber as shown. Figure 1 The structure shown serves as the second middleware.

[0061] S3. Take the second intermediate component and wrap it around the four first intermediate components to form a coupling region. See [link / details]. Figure 2 It serves as a third middleware.

[0062] S4. Take the third intermediate component and fuse it at high temperature to form a tapered structure, and use the resulting structure as the fourth intermediate component.

[0063] S5. Take the fourth intermediate component, apply low-refractive-index adhesive to both ends of the encapsulation tube, and fabricate a side pump coupler. See [link to documentation]. Figure 3 .

[0064] S6. The signal input ends of the four double-clad single-mode passive optical fibers in the side-pump coupler are connected to a 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 in the side-pump coupler are etched, bundled, and bonded to the four-core active optical fibers with a refractive index-matched adhesive to form a connection area, allowing the pump light and signal light to be simultaneously input into the four-core active optical fibers. The tail end of the four-core active optical fibers is connected to a fan-out device to output the amplified signal light, thus forming a four-core amplifier. See [link to relevant documentation]. Figure 5 .

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

[0066] (2) Six-core amplifier.

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

[0068] See Figure 9 , Figure 9 This is a schematic diagram of the connection area in a six-core amplifier. Specifically, the signal output ends of the six double-clad single-mode passive optical fibers 2 are etched to 43µm and inserted together with the filler optical fibers 5 into a capillary tube 9 with a diameter of 125µm and a wall thickness of 50µm, so that the etched optical fibers are closely arranged at the edge of the filler optical fibers 5. After the bundled etched optical fibers are aligned with the cores of the six-core active optical fiber (i.e., multi-core active optical fiber 7), they are bonded with an adhesive that matches the refractive index.

[0069] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A side-pump coupler, characterized in that, include: The fiber comprises multiple double-clad single-mode passive optical fibers and one pump fiber; the pump fiber is a multimode optical fiber, and a portion of the pump fiber has its coating removed and is tapered into a cone shape before being spirally wound around the coated portions of the multiple double-clad single-mode passive optical fibers to form a coupling region, which is then tapered and fused together.

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

3. The side-pump coupler according to claim 2, characterized in that, The bundled processing involves inserting multiple etched double-clad single-mode passive optical fibers into a capillary tube, which is made of one of the following materials: glass, metal, or ceramic.

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

5. The side-pump coupler according to claim 1, characterized in that, The pump fiber has a winding length of 1cm to 1.5cm and a winding number of 7 to 10 turns; the tapering length of the coupling region during tapering and melting is 500um to 1000um.

6. The side-pump coupler according to claim 1, characterized in that, Also includes: Encapsulation tube; the encapsulation tube is used to encapsulate the integral structure obtained after tapered melting treatment.

7. A method for fabricating a side-pump coupler as described in any one of claims 1-6, characterized in that, Includes the following steps: The first intermediate component is a double-clad single-mode passive optical fiber with a portion of its coating removed, and the second intermediate component is a pump optical fiber with a portion of its coating removed and tapered. Multiple first intermediate components are arranged closely together, and a second intermediate component is spirally wound around the multiple first intermediate components to form a coupling region. The coupling region is then subjected to tapered melting to obtain a side pump coupler.

8. A multi-core amplifier, characterized in that, include: Multi-core active optical fiber, fan-out device, and side-pump coupler as described in any one of claims 1-6; 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 simultaneously input pump light and signal light into the multi-core active optical fiber, and the fan-out device is used to output amplified multi-channel 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 fabricating a multi-core amplifier, characterized in that, A multi-core amplifier is obtained by connecting the side-pump coupler as described in any one of claims 1-6 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.

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