Multiplexer and demultiplexer for multi-core optical fiber and method for manufacturing the same

Abstract

The application belongs to the technical field of passive optical devices, and discloses a multiplexer / demultiplexer suitable for a multi-core optical fiber and a preparation method thereof. In the application, a small outer diameter optical fiber is fused at one end of a single-mode optical fiber. The cladding diameter of the small outer diameter optical fiber is smaller than the cladding diameter of the single-mode optical fiber, and the cladding diameter of the small outer diameter optical fiber is equal to the core spacing of the multi-core optical fiber to be matched. The mode field diameter of the small outer diameter optical fiber is consistent with the mode field diameter of each core of the multi-core optical fiber. The small outer diameter optical fiber is used as a transition optical fiber between the single-mode optical fiber and the multi-core optical fiber, high-precision matching between the single-mode optical fiber and the multi-core optical fiber is realized, the problems existing in the prior art preparation method can be avoided, and the application has the advantages of good scalability, simple preparation, high precision, and industrialized mass production.

Description

Technical Field

[0001] This invention belongs to the field of passive optical device technology, and more specifically, relates to a multiplexer / demultiplexer suitable for multi-core optical fibers and its preparation method. Background Technology

[0002] In optical communication networks, spatial division multiplexing based on multi-core optical fibers is one of the most effective methods to solve the current bottleneck in optical communication transmission capacity. Multi-core optical fibers are a new type of optical fiber with multiple independent cores in a common cladding region. Based on the spatial division multiplexing concept, multi-core optical fibers can transmit multiple optical signals simultaneously in a single fiber, which can greatly improve communication capacity and break through the current transmission capacity limit of ordinary single-mode optical fibers. Multi-core optical fibers can increase the channel and transmission capacity of the system by several times or even tens of times. Especially in the era of 5G cabling with rapidly developing transmission capacity, they can greatly save cabling space in high-density cabling in data centers and short-to-medium distance transmission.

[0003] A major challenge in the application of multi-core optical fibers is the fabrication of high-performance multiplexing / demultiplexing devices between multi-core and standard single-mode fibers. These devices enable each core of the multi-core fiber to connect with the single-mode fiber, achieving optical signal input and output. Therefore, multiplexing / demultiplexing devices adapted for multi-core fibers and their fabrication methods are extremely important, becoming one of the key technologies for promoting the practical application of multi-core fibers and reducing costs.

[0004] Currently, the main methods for manufacturing multiplexers and demultiplexers suitable for multi-core optical fibers are as follows:

[0005] Bundling method: Etched single-mode and multi-core optical fibers are inserted into cylindrical sleeves that have been mechanically drilled or laser-drilled. Alignment is achieved using an alignment platform, and then adhesive is applied to fix the fibers, thus fabricating the multi-core coupler. This fabrication method uses hydrofluoric acid to etch the optical fibers; the etching precision of the single-mode fiber affects the coupler's performance.

[0006] Tapering method: A single-mode fiber with its coating removed is inserted into a pre-tapered glass sleeve. The waist region of the capillary is tapered so that the diameter of the tapered single-mode fiber matches the core diameter of the multi-core fiber. The single-mode fiber and glass sleeve are then cut from the waist region and fused with the multi-core fiber. This fabrication method is technically complex and requires high precision control of the tapering and fusion splicing equipment, making mass production impossible. Summary of the Invention

[0007] This invention provides a multiplexer / demultiplexer suitable for multi-core optical fibers and its fabrication method, solving the problems of existing fabrication methods for multiplexers and demultiplexers suitable for multi-core optical fibers affecting device performance, having complex processing techniques, or requiring high-end equipment.

[0008] This invention provides a method for fabricating a multiplexer / demultiplexer suitable for multi-core optical fibers. The multiplexer / demultiplexer includes a first ferrule assembly, a second ferrule assembly, and a flange. The first ferrule assembly includes a first ferrule, a first tail shank, and a first sleeve. The first tail shank is fixedly connected to the first ferrule and is capable of rotating freely within the first sleeve. The second ferrule assembly includes a second ferrule, a second tail shank, and a second sleeve. The second tail shank is fixedly connected to the second ferrule and is capable of rotating freely within the second sleeve.

[0009] The method includes the following steps:

[0010] Step 1: Strip the coating of n single-mode optical fibers to obtain n first intermediate components; fuse a small-diameter optical fiber to one end of each first intermediate component to obtain a second intermediate component; insert the n second intermediate components into the first ferrule, with the small-diameter optical fiber passing through the first ferrule and extending a first distance; after curing, grind the end face of the small-diameter optical fiber to obtain a third intermediate component; the cladding diameter of the small-diameter optical fiber is equal to the intercore spacing of the multi-core optical fiber to be matched, and the mode field diameter of the small-diameter optical fiber is consistent with the mode field diameter of each core in the multi-core optical fiber;

[0011] The coating layer of the multi-core optical fiber is stripped off, and one end of the multi-core optical fiber with the coating stripped off is inserted into the second ferrule. The multi-core optical fiber passes through the second ferrule and extends out a second distance. After curing, the end face of the multi-core optical fiber used for docking with the third intermediate component is polished.

[0012] Step 2: Place and fix the first sleeve and the second sleeve horizontally; rotate at least one of the first tail shank and the second tail shank to make the third intermediate part and each fiber core in the multi-core optical fiber be in a preset position, and then apply glue to fix the relative positions of the first tail shank and the first sleeve, and the relative positions of the second tail shank and the second sleeve.

[0013] Step 3: Connect the first ferrule assembly and the second ferrule assembly using the flange to complete the preparation.

[0014] Preferably, the mode field diameter of the small outer diameter optical fiber is in the range of 8 to 10 micrometers, and the cladding diameter of the small outer diameter optical fiber is in the range of 40 to 80 micrometers; the cladding diameter of the multi-core optical fiber is in the range of 125 to 250 micrometers.

[0015] Preferably, the cores of the multi-core optical fiber are arranged symmetrically.

[0016] Preferably, the multi-core optical fiber has a symmetrical ring-shaped core arrangement.

[0017] Preferably, the end faces of both the small-diameter optical fiber and the multi-core optical fiber used for docking are coated.

[0018] Preferably, in step 2, the position of each fiber core in the third intermediate component and the multi-core optical fiber is observed using an imaging system, and the position of the fiber core is adjusted by rotating at least one of the first tailstock and the second tailstock based on the observation results.

[0019] Preferably, in step 2, positioning the third intermediate component and each fiber core in the multi-core optical fiber in a preset position includes: positioning each fiber core in the third intermediate component in a one-to-one correspondence with the position of each fiber core in the multi-core optical fiber, and ensuring that the angle between the line connecting the two farthest fibers in the multi-core optical fiber and the horizontal axis reaches a preset value.

[0020] Preferably, the two farthest cores of the multi-core optical fiber are located on the horizontal or vertical axis.

[0021] Preferably, the outer diameter of the first ferrule is the same as the outer diameter of the second ferrule.

[0022] On the other hand, the present invention provides a multiplexer / demultiplexer suitable for multi-core optical fibers, which is prepared by the above-described preparation method for a multiplexer / demultiplexer suitable for multi-core optical fibers.

[0023] One or more technical solutions provided in this invention have at least the following technical effects or advantages:

[0024] (1) Typically, the cladding diameter of a single-mode fiber is larger than the intercore spacing of a multi-core fiber, making direct matching impossible. Existing technologies involve etching or tapering the single-mode fiber to achieve matching, which can affect device performance or lead to complex processing techniques and high equipment requirements. The fabrication method for a multiplexer / demultiplexer suitable for multi-core fibers proposed in this invention adopts a different approach from existing solutions. This invention fuses a small-diameter fiber at one end of the single-mode fiber. The cladding diameter of the small-diameter fiber is smaller than that of the single-mode fiber, and the cladding diameter of the small-diameter fiber is equal to the intercore spacing of the multi-core fiber to be matched. The mode field diameter of the small-diameter fiber is consistent with the mode field diameter of each core in the multi-core fiber. In other words, this invention uses the small-diameter fiber as a transition fiber between the single-mode fiber and the multi-core fiber, achieving high-precision matching between the single-mode fiber and the multi-core fiber, thus avoiding the problems existing in existing fabrication methods.

[0025] (2) This invention addresses the difficulty of connecting single-mode fiber and multi-core fiber by improving the connection method. The ferrule assembly used in this invention includes a ferrule, a tail shank, and a sleeve. That is, a ferrule with a tail shank is designed. After the sleeve is placed horizontally and fixed, the tail shank is rotated to ensure that each fiber core in the two fibers (i.e., the small-diameter fiber bundle and the multi-core fiber) is in a preset position. This enables direct, fast, and low-insertion-loss connection and alignment of the fibers, making the time-consuming, labor-intensive, and difficult task of connecting multi-core fiber and single-mode fiber (since in this invention, single-mode fiber is connected to small-diameter fiber, and the small-diameter fiber is used as a transition fiber between single-mode fiber and multi-core fiber, it is actually a connection between small-diameter fiber bundle and multi-core fiber) simple and fast.

[0026] (3) In this invention, the end faces of the two optical fibers (i.e., the small outer diameter fiber bundle and the multi-core fiber) that are aligned and bonded are also coated, which can effectively improve the return loss of the multiplexer and demultiplexer suitable for multi-core optical fibers and improve the device performance.

[0027] (4) The multiplexer and demultiplexer for multi-core optical fibers and its preparation method provided by the present invention have the characteristics of good scalability, simple preparation, high precision, and industrial mass production. Attached Figure Description

[0028] Figure 1 A schematic diagram of a multiplexer / demultiplexer suitable for multi-core optical fibers provided by the present invention;

[0029] Figure 2 This is a schematic diagram illustrating the alignment and positioning of a multiplexer / demultiplexer suitable for four-core optical fibers provided in Embodiment 1 of the present invention.

[0030] Figure 3 This is a schematic diagram illustrating the alignment and positioning of a multiplexer / demultiplexer suitable for a seven-core optical fiber, as provided in Embodiment 2 of the present invention.

[0031] Figure 4 This is a schematic diagram illustrating the alignment and positioning of a multiplexer / demultiplexer suitable for a 19-core optical fiber, as provided in Embodiment 3 of the present invention. Detailed Implementation

[0032] 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.

[0033] This invention provides a method for fabricating a multiplexer / demultiplexer suitable for multi-core optical fibers, see [link to documentation]. Figure 1The multiplexer / demultiplexer includes a first insert assembly, a second insert assembly, and a flange 3. The first insert assembly includes a first insert 101, a first tail shank 102, and a first sleeve 103. The first tail shank 102 is fixedly connected to the first insert 101 and can rotate freely in the first sleeve 103. The second insert assembly includes a second insert 201, a second tail shank 202, and a second sleeve 203. The second tail shank 202 is fixedly connected to the second insert 201 and can rotate freely in the second sleeve 203.

[0034] The method for fabricating the multiplexer / demultiplexer suitable for multi-core optical fibers includes the following steps:

[0035] Step 1: Strip the coating of n single-mode optical fibers 4 to obtain n first intermediate components; fuse a small-diameter optical fiber 5 to one end of each first intermediate component to obtain a second intermediate component; insert the n second intermediate components into the glue-filled first ferrule 101, with the small-diameter optical fiber 5 passing through the first ferrule 101 and extending a first distance; after curing, grind the end face of the small-diameter optical fiber 5 to obtain a third intermediate component; the cladding diameter of the small-diameter optical fiber 5 is equal to the core spacing of the multi-core optical fiber 6 to be matched, and the mode field diameter of the small-diameter optical fiber 5 is consistent with the mode field diameter of each core in the multi-core optical fiber 6; strip the coating of the multi-core optical fiber 6, insert the stripped end of the multi-core optical fiber 6 into the glue-filled second ferrule 201, with the multi-core optical fiber 6 passing through the second ferrule 201 and extending a second distance; after curing, grind the end face of the multi-core optical fiber 6 used for docking with the third intermediate component.

[0036] Step 2: Place and fix the first sleeve 103 and the second sleeve 203 horizontally; rotate at least one of the first tail shank 102 and the second tail shank 202 to make each fiber core of the third intermediate component (i.e., small outer diameter fiber bundle) and the multi-core fiber 6 be in a preset position, and then apply glue to fix the relative positions of the first tail shank 102 and the first sleeve 103, and the relative positions of the second tail shank 202 and the second sleeve 203.

[0037] Step 3: Connect the first ferrule assembly and the second ferrule assembly using the flange 3 to complete the preparation.

[0038] The mode field diameter of the small-diameter optical fiber 5 ranges from 8 to 10 micrometers, and the cladding diameter of the small-diameter optical fiber 5 ranges from 40 to 80 micrometers. The cladding diameter of the multi-core optical fiber 6 ranges from 125 to 250 micrometers.

[0039] The cores of the multi-core optical fiber 6 are arranged symmetrically. For example, the cores of the multi-core optical fiber 6 are arranged in a symmetrical ring pattern.

[0040] In addition, the end faces of the small-diameter optical fiber 5 and the multi-core optical fiber 6 that are connected can also be coated to increase the transmission or reflection efficiency of optical signals and improve the insertion loss and return loss performance of the multiplexer / demultiplexer.

[0041] Specifically, in step 2, the positions of the cores in the third intermediate component and the multi-core optical fiber 6 are observed using an imaging system (e.g., a microscope). Based on the observation results, at least one of the first tailstock 102 and the second tailstock 202 is rotated to adjust the positions of the cores. Positioning the cores in the third intermediate component and the multi-core optical fiber 6 at preset positions includes: ensuring a one-to-one correspondence between the positions of the cores in the third intermediate component and the positions of the cores in the multi-core optical fiber 6, and ensuring that the angle between the line connecting the two farthest cores in the multi-core optical fiber 6 and the horizontal axis reaches a preset value. For example, positioning the two farthest cores in the multi-core optical fiber 6 on either the horizontal or vertical axis.

[0042] The present invention will be illustrated below with reference to specific embodiments.

[0043] Example 1:

[0044] Example 1 describes the fabrication of a multiplexer / demultiplexer suitable for four-core optical fibers. The ferrule in the ferrule assembly is fixedly connected to the tailstock, which can rotate freely axially within the sleeve. The four-core optical fiber has a core pitch of 42 micrometers with an error of less than ±0.5 micrometers, and a cladding diameter of 125 micrometers with an error of less than ±0.5 micrometers. The cladding diameter of the smaller outer diameter fiber is equal to the core pitch of the multi-core fiber, and the mode field diameter of the smaller outer diameter fiber is consistent with the mode field diameter of each core in the multi-core fiber. The cladding diameter of the smaller outer diameter fiber is 42 micrometers with an error of less than ±0.5 micrometers.

[0045] The inner hole shape of the first ferrule is determined by the cladding diameter of the small-diameter optical fiber and the arrangement of the small-diameter optical fibers in the first ferrule. The inner hole of the first ferrule is a circular through hole, and the space of the inner hole can accommodate four small-diameter optical fibers simultaneously. The inner hole size of the second ferrule is determined by the cladding diameter of the four optical fibers. The inner hole diameter of the second ferrule is 125 micrometers, with an error of less than ±0.5 micrometers.

[0046] The coating of the single-mode fiber is stripped off. A small-diameter fiber is fused to the end face of the single-mode fiber. The four fused fibers are then inserted into the inner hole of the first ferrule, which is filled with adhesive, with the small-diameter fiber passing through the end face of the first ferrule for a certain distance. The coating of the four-core fiber is then stripped off. The four-core fiber is then inserted into the inner hole of the second ferrule, which is filled with adhesive, with the multi-core fiber passing through the end face of the ferrule for a certain distance. The first and second ferrules are then heated and cured separately. After curing, the fiber end faces are polished, typically to a flat surface.

[0047] With both ferrule assemblies placed horizontally, a high-precision microscopic imaging system is used to observe the end faces of the four-core fiber and the small-diameter fiber bundle under a microscope. By rotating the tailstock, any two farthest cores of the four-core fiber and the small-diameter fiber bundle are positioned on either the horizontal axis or both on the vertical axis. Furthermore, the core positions of the four-core fiber and the small-diameter fiber bundle are ensured to be the same. (See [link to documentation]). Figure 2 .

[0048] The outer diameter of the first ferrule is the same as that of the second ferrule. The first ferrule assembly and the second ferrule assembly are placed horizontally, connected by flanges and fixed with glue to complete the preparation of the multiplexer.

[0049] Example 2:

[0050] Example 2: Fabrication of an optical fiber multiplexer / demultiplexer suitable for seven-core optical fibers.

[0051] Example 2 differs from Example 1 in that: the multi-core optical fiber is a seven-core optical fiber with a core spacing of 42 micrometers (error less than ±0.5 micrometers) and a cladding diameter of 150 micrometers (error less than ±0.5 micrometers). The cladding diameter of the small-diameter optical fiber is equal to the core spacing of the seven-core optical fiber, and the mode field diameter of the small-diameter optical fiber is consistent with the mode field diameter of each core of the seven-core optical fiber. The cladding diameter of the small-diameter optical fiber is 42 micrometers (error less than ±0.5 micrometers).

[0052] The inner hole shape of the first ferrule is determined by the cladding diameter of the small-diameter optical fiber and the arrangement of the small-diameter optical fibers in the first ferrule. The inner hole of the first ferrule is a circular through hole, and the space of the inner hole can accommodate seven small-diameter optical fibers simultaneously. The inner hole size of the second ferrule is determined by the cladding diameter of the seven optical fibers. The inner hole diameter of the second ferrule is 150 micrometers, with an error of less than ±0.5 micrometers.

[0053] A schematic diagram of alignment and positioning for a multiplexer / demultiplexer suitable for seven-core optical fibers is shown below. Figure 3 As shown, this ensures that any two of the farthest cores of the seven-core fiber and the small-diameter fiber bundle are located on the vertical axis.

[0054] Example 3:

[0055] Example 3: Preparation of a multiplexer / demultiplexer suitable for 19-core optical fibers.

[0056] Example 3 differs from Example 1 in that: the multi-core optical fiber is a nineteen-core optical fiber, with a core spacing of 42 micrometers (error less than ±0.5 micrometers) and a cladding diameter of 250 micrometers (error less than ±0.5 micrometers). The cladding diameter of the small-diameter optical fiber is equal to the core spacing of the nineteen-core optical fiber, and the mode field diameter of the small-diameter optical fiber is consistent with the mode field diameter of each core of the nineteen-core optical fiber. The cladding diameter of the small-diameter optical fiber is 42 micrometers (error less than ±0.5 micrometers).

[0057] The inner hole shape of the first ferrule is determined by the cladding diameter of the small-diameter optical fiber and the arrangement of the small-diameter optical fibers in the first ferrule. The inner hole of the first ferrule is a circular through hole, and the space of the inner hole can accommodate nineteen small-diameter optical fibers simultaneously. The inner hole size of the second ferrule is determined by the cladding diameter of the nineteen optical fibers. The inner hole diameter of the second ferrule is 250 micrometers, with an error of less than ±0.5 micrometers.

[0058] A schematic diagram of alignment and positioning for a multiplexer / demultiplexer suitable for 19-core optical fibers is shown below. Figure 4 As shown, the angle between the line connecting any two of the farthest cores of the 19-core fiber and the small outer diameter fiber bundle and the horizontal axis is the same preset value, that is, the same angle is achieved, thus completing the alignment and positioning.

[0059] 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 method for fabricating a multiplexer / demultiplexer suitable for multi-core optical fibers, characterized in that, The multiplexer / demultiplexer includes a first insert assembly, a second insert assembly, and a flange; the first insert assembly includes a first insert, a first tail shank, and a first sleeve, the first tail shank being fixedly connected to the first insert and capable of rotating freely within the first sleeve; the second insert assembly includes a second insert, a second tail shank, and a second sleeve, the second tail shank being fixedly connected to the second insert and capable of rotating freely within the second sleeve. The method includes the following steps: Step 1: Strip the coating of n single-mode optical fibers to obtain n first intermediate components; fuse a small-diameter optical fiber to one end of each first intermediate component to obtain a second intermediate component; insert the n second intermediate components into the first ferrule, with the small-diameter optical fiber passing through the first ferrule and extending a first distance; after curing, grind the end face of the small-diameter optical fiber to obtain a third intermediate component; the cladding diameter of the small-diameter optical fiber is equal to the intercore spacing of the multi-core optical fiber to be matched, and the mode field diameter of the small-diameter optical fiber is consistent with the mode field diameter of each core in the multi-core optical fiber; The coating layer of the multi-core optical fiber is stripped off, and one end of the multi-core optical fiber with the coating stripped off is inserted into the second ferrule. The multi-core optical fiber passes through the second ferrule and extends out a second distance. After curing, the end face of the multi-core optical fiber used for docking with the third intermediate component is polished. The end faces of the small-diameter optical fiber and the multi-core optical fiber used for docking are respectively coated. Step 2: Place and fix the first sleeve and the second sleeve horizontally; use the imaging system to observe the position of each fiber core in the third intermediate component and the multi-core optical fiber; based on the observation results, rotate at least one of the first tail shank and the second tail shank so that each fiber core in the third intermediate component and the multi-core optical fiber is in a preset position; then apply glue to fix the relative positions of the first tail shank and the first sleeve, and the relative positions of the second tail shank and the second sleeve. Step 3: Connect the first ferrule assembly and the second ferrule assembly using the flange to complete the preparation.

2. The method for fabricating a multiplexer / demultiplexer suitable for multi-core optical fibers according to claim 1, characterized in that, The mode field diameter of the small-diameter optical fiber ranges from 8 to 10 micrometers, and the cladding diameter of the small-diameter optical fiber ranges from 40 to 80 micrometers; the cladding diameter of the multi-core optical fiber ranges from 125 to 250 micrometers.

3. The method for fabricating a multiplexer / demultiplexer suitable for multi-core optical fibers according to claim 1, characterized in that, The cores of the multi-core optical fiber are arranged symmetrically.

4. The method for fabricating a multiplexer / demultiplexer suitable for multi-core optical fibers according to claim 3, characterized in that, The multi-core optical fiber has a symmetrical ring-shaped core arrangement.

5. The method for fabricating a multiplexer / demultiplexer suitable for multi-core optical fibers according to claim 1, characterized in that, In step 2, making each fiber core in the third intermediate component and the multi-core optical fiber in a preset position includes: making the position of each fiber core in the third intermediate component correspond one-to-one with the position of each fiber core in the multi-core optical fiber, and making the angle between the line connecting the two farthest fibers in the multi-core optical fiber and the horizontal axis reach a preset value.

6. The method for fabricating a multiplexer / demultiplexer suitable for multi-core optical fibers according to claim 5, characterized in that, The two farthest cores in the multi-core optical fiber are positioned on the horizontal or vertical axis.

7. The method for fabricating a multiplexer / demultiplexer suitable for multi-core optical fibers according to claim 1, characterized in that, The outer diameter of the first ferrule is the same as that of the second ferrule.

8. A multiplexer / demultiplexer suitable for multi-core optical fibers, characterized in that, It is prepared using the fabrication method for a multiplexer / demultiplexer suitable for multi-core optical fibers as described in any one of claims 1-7.

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