Orientation of hollow core optical fiber for cleaving

Abstract

A process for initiating a cleave in a hollow core optical fiber with internal microstructures includes determining a first fuse location on a hollow core optical fiber. The first fuse location is the location where a first internal microstructure fuses to an internal surface of the hollow core optical fiber. Based on that first fuse location, a cleave endpoint location for a cleave on the hollow core optical fiber is determined. Then, based on the cleave endpoint location a cleave-flaw location on the hollow core optical fiber is determined. The hollow core optical fiber is positioned in an optical fiber cleaver such that the cleave-flaw location is positioned to receive a cleave initiator of the cleaver. Once the fiber is positioned, a cleave is initiated in the hollow core optical fiber.

Description

: MANGAN 11-2ORIENTATION OF HOLLOW CORE OPTICAL FIBER FOR CLEAVINGBACKGROUND

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 695,569, filed September 17, 2024, entitled “Orientation of HCF for cleaving using tensioning cleaver” with Cassandra Thalman as first named inventor, and Serial No. 63 / 696,666, filed September 19, 2024, entitled “Orientation of HCF for cleaving using tensioning cleaver” with Cass Thahnan as first named inventor the disclosures of which are hereby incorporated by reference.BACKGROUND

[0002] Various aspects of the present disclosure relate generally to cleaving optical fibers, and more specifically, cleaving hollow core optical fibers (HCF) with internal microstructures.

[0003] When splicing two optical fibers, each optical fiber needs to be cleaved to provide a flat surface that is perpendicular to a longitudinal axis of the optical fiber. Thus, the two ends can be spliced together. To produce a good cleave, a mechanical cleaver or a scribe may be used to initiate a cleave and tension based on a thickness of the fiber is applied to the optical fiber to break apart the fiber, producing a flat surface for splicing.BRIEF SUMMARY

[0004] According to aspects of the present disclosure, a process for initiating a cleave in a hollow core optical fiber with internal microstructures includes determining a first fuse location on a hollow core optical fiber. The first fuse location is the location where a first internal microstructure fuses to an internal surface of the hollow core optical fiber. Based on that first fuse location, a cleave endpoint location for a cleave on the hollow core optical fiber is determined. Then, based on the cleave endpoint location a cleaveflaw location on the hollow core optical fiber is determined. The hollow core optical fiber is positioned in an optical fiber cleaver such that the cleave-flaw location is: MANGAN 11-2 positioned to receive a cleave initiation from the cleaver. Once the fiber is positioned, a cleave is initiated in the hollow core optical fiber with the cleaver.

[0005] In some embodiments, axial stress is applied to the hollow core optical fiber while initiating the cleave in the hollow core optical fiber. In many of those embodiments, the axial stress is between 150 and 210 megapascals (MPa).

[0006] In several embodiments, a second fuse location is determined, where the second fuse location is where a second internal microstructure fuses to the internal surface of the hollow core optical fiber. In those embodiments, determining a cleave endpoint location on the hollow core optical fiber for a cleave based on the first fuse location includes determining the cleave endpoint location to be between the first fuse location and the second fuse location. In some of those embodiments, the cleave endpoint location is at least 5 micrometers (pm) from both the first fuse location and the second fuse location, and preferably at least 10 pm from both the first fuse location and the second fuse location.

[0007] In numerous embodiments, the cleave endpoint location is at least 5 micrometers (pm) from the first fuse location, and preferably at least 10 micrometers pm from the first fuse location.

[0008] In various embodiments, determining the first fuse location comprises inspecting the hollow-core optical fiber with a vision system that reveals a geometry of the internal microstructures in a sidewall of the hollow-core optical fiber.

[0009] In many embodiments, positioning the hollow core optical fiber comprises changing an azimuthal orientation of the hollow-core optical fiber relative to the cleave initiator of the cleaver.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0010] FIG. 1 is an illustration of a cleave in a hollow core fiber with internal microstructures, according to various aspects of the present disclosure;

[0011] FIG. 2 A is a side view of a cleave of a hollow core fiber, where too little stress is placed on the hollow core fiber during the cleave, according to various aspects of the present disclosure;MANGAN 11-2

[0012] FIG. 2B is a side view of a cleave of a hollow core fiber, where an optimum amount of stress is placed on the hollow core fiber during the cleave, according to various aspects of the present disclosure; and

[0013] FIG. 3 is a flow chart illustrating a process for cleaving a hollow core optical fiber with internal microstructures, while minimizing a chance for harming the internal microstructures; according to various aspects of the present disclosure.DETAILED DESCRIPTION

[0014] Cleaving of solid optical fiber includes creating a mechanical flaw on the surface of the glass fiber to form a point of stress concentration and structural mechanical weakness. When tension is applied to the fiber at this flaw (creating an internal stress), either by fiber bending, axial tension, or both, a crack forms that propagates across the fiber cross section. With proper flaw depth and fiber stress, propagation of the fracture can result in a smooth, nearly flat surface that is nearly perpendicular to the fiber longitudinal axis.

[0015] A typical cleaver (e.g., mechanical cleaver with a striker, laser cleaver, etc.) provides an axial tensioning and scribe process. With solid core optical fibers, a cleave initiator initiates a break with a cleave initiator (e.g., a striker, laser, etc.) and the tensioning completes the break as the break propagates through a cross section of the solid core optical fiber. As the solid core optical fibers are essentially homogeneous at a cross section, there is no need to determine an azimuthal position (i.e., rotational positioning) of optical fiber within the cleaver. Thus, typical glass fiber cleaving does not involve rotational positioning of the fiber with reference to the cleave blade. Aspects of the present disclosure are directed toward cleaving hollow core optical fiber (HCF) with internal microstructures, where the internal microstructures are anti-resonant ring fibers (ARF) within the core, so a cross section of the optical fiber is not homogenous.

[0016] Turning now to the figures, FIG. 1 illustrates a hollow core optical fiber 100 including a cladding 102 (e.g., a glass cladding) and internal microstructures 104a-f (collectively, 104) in the form of anti-resonant ring fibers. Depending on where a cleave starts and ends on an ARF HCF fiber 100, the cleave can result in varying degrees of destruction of the microstructure features 104. For example, if a cleave ends at or near a; MANGAN 11-2 point 106a-f (collectively , 106) where the microstructure features 104 couple to the cladding 102, then there is a higher chance that the microstructure 104a-f at that point 106a-f will be damaged during the cleave.

[0017] In a HCF 100, when a cleave initiator initiates a cleave (e.g., at a cleave flaw location 108), the cleave propagates in both directions 110, 112 (i.e., clockwise and anticlockwise) at about the same speed to meet on an opposite side of the cladding 102 to create a cleave endpoint 114. The intersection of the two cleave propagations often results in a discontinuity in the fraction surface. As shown in FIG. 1 , the cleave endpoint 114 is between two microstructure features 104c, 104d, so the microstructure features are not damaged. Typically, to ensure that the cleave endpoint 114 is at a point that is not near a microstructure, once a desired endpoint 114 location is found, a location one- hundred-and-eighty degrees on the cladding 102 should be used as a cleave initiation point 108 under normal circumstances. The location of the cleave endpoint can be controlled by managing the stress field (radial, longitudinal, azimuthal) in the fiber, and by the location of the initial flaw'.

[0018] For example, as shown in FIG. 1, there are an even number of internal microstructures 104. As the cleave endpoint 114 is desired to be between two microstructures 104c and 104d, the cleave flaw point 108 (i.e., where the cleave initiator initiates the cleave) is also between two microstructures 104f and 104a. However, in a HCF with an odd number- of microstructures 104, the cleave flaw point 108 should still be one-hundred-and-eighty degrees from the desired endpoint (the desired endpoint being between two adjacent microstructures), which would result in a cleave flaw location at a point near one of the microstructures.

[0019] To ensure a cleave with undamaged microstructures, the HCF should be properly aligned in a cleaver using a rotational alignment device that rotates the HCF to be in proper alignment with the cleave initiator. Multiple types of cleavers are available that provide different combinations of fixed and adjustable levels of bending, torsion and axial tension, so in some cases, a cleaver type as well as a stressing setting can be tuned to particular HCF fiber designs. Such HCF designs can include a number and geometrical parameters (e.g. diameter and thickness) of internal microstructures, the: MANGAN 11-2 thickness of the outer surrounding cladding, and whether the cleave surface should be perpendicular or angled with respect to the longitudinal axis of the fiber.

[0020] The microstructures in the HCF may be found using a vision system (e.g., microscopy, shadowing) that reveals the geometry of the microstructure in sideview. Then based on where the microstructures 104 are present in the HCF, a mechanical (or electro-mechanical) system adjusts the relative position of a cleave initiator of the cleaver and the HCF by rotating the HCF, rotating the cleave initiator, or both.

[0021] For high probability of obtaining a cleave with high quality, the cleave endpoint should located a distance 118 at least 5 micrometers (pm), and preferably at least 10 pm, from the point 106 where the microstructure 104 is fused to the cladding 102.

[0022] Additionally, axial tension is applied during the cleave resulting in stress inside the HCF, and the resulting stress should range between about 150 megapascals (MPa) and 210 MPa. If the resulting stress is too low (because the applied tension is too low based on a cross-sectional area of the fiber), the resulting cleave is an angled cleave (220, FIG. 2A), as shown in FIG. 2A. However, if the resulting stress is too high, then hackle is created at edges of the HCF. Therefore, a balance is required to have a cleave (220, FIG. 2B) perpendicular to the axis and minimize hackle in the resulting cleave surface of the HCF as shown in FIG. 2B. In cases where an angled cleave is desired, the axial tension may be changed to produce that angled cleave. For example, as discussed above, a lower axial tension should produce an angled cleave.

[0023] Turning to FIG. 3, a flow chart is shown illustrating a process for cleaving a hollow core fiber (HCF). At 302, a first fuse location on a hollow core optical fiber is determined, the first fuse location being where a first internal microstructure fuses to an internal surface of the hollow core optical fiber (e.g., an inside of glass cladding of the HCF). In some embodiments, the first fuse location may be found using vision system that reveals a geometry of the internal microstructures in a sidewall of the hollow-core optical fiber.

[0024] At 304, a cleave endpoint location is determined on the hollow core optical fiber for a cleave based on the first fuse location. For example, as discussed above, theMANGAN 11-2 cleave endpoint should be at least 5 pm from the first fuse location, and preferably 10 pm from the first fuse location.

[0025] At 306, a cleave-flaw location is determined based on the cleave endpoint location. For example, as discussed above, under normal circumstances, a cleave travels equally clockwise and counterclockwise from the cleave-flaw location to meet at a point on the opposite side of the cladding of the HCF, Thus, the cleave-flaw location should be one-hundred-and-eighty degrees from the determined cleave endpoint location in normal cases. However, depending on levels of bending, torsion, and axial tension, the cleaveflaw location may be different than one-hundred-and-eighty degrees from the determined cleave endpoint.

[0026] At 308, the hollow core optical fiber is positioned in an optical fiber cleaver such that the cleave-flaw location is positioned to receive a cleave initiator of the cleaver. In various embodiments, the cleaver is a mechanical cleaver, where the cleave initiator is a striker. In other embodiments, the cleaver is a laser cleaver, where the cleave initiator is a laser. In some embodiments, the positioning of the HCF relative to the striker includes changing an azimuthal orientation of the hollow-core optical fiber relative to the cleave initiator of the cleaver. A mechanical or electromechanical system of the cleaver may rotate the HCF relative to the cleave initiator, rotate the cleave initiator relative to the HCF, or both.

[0027] At 310, a cleave is initiated in the hollow core optical fiber using the cleaver. The manner in which the cleave is initiated is determined by the cleaver type (e.g., mechanical cleaver, laser cleaver, etc.). In some embodiments, the process 300 includes providing an axial tension on the hollow core optical fiber while initiating the cleave in the hollow core optical fiber with the cleave initiator. Providing the axial tension helps complete the cleave and minimizes and angle of the cleave relative to the axial direction of the HCF. As discussed above, too little axial tension results in an angled cleave, while too much axial tension results in hackling. Thus, the axial tension should be based on a cross sectional area of the fiber to create a stress of between 150-210 MPa to minimize hackling and provide a perpendicular cleave.

[0028] In some embodiments, the process also comprises determining a second fuse location on the hollow core optical fiber, the second fuse location being where a second: MANGAN 11-2 internal microstructure fuses to the internal surface of the hollow core optical fiber. If a second fuse location is known, then the cleave endpoint location can be determined to be between the first fuse location and the second fuse location, while ensuring that the cleave endpoint location is at least 5 micrometers from both fuse locations to ensure that the associated microstructures are not damaged during the cleave. In various embodiments, cleave endpoint location is at least 10 micrometers from both fuse locations.

[0029] The processes described herein result in better cleaves for hollow core fibers with internal microstructures. Poor cleaves must be repeated, which requires cutting off another portion of the fiber, resulting in variability in the fiber length protruding from the cable sheath. When splicing cables that contain multiple fibers, this can be problematic in packaging the splice points. Similar issues arise when packaging splice points in optical devices comprising HCF, such as fiber lasers or other devices that take advantage of the properties of HCF (latency, dispersion, nonlinearity and the like). Thus, increased probability of obtaining high quality cleaves simplifies installation of any HCF.

[0030] The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems and methods according to various embodiments of the present disclosure. It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and / or flowchart illustration, and combinations of blocks in the block diagrams and / or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

[0031] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and / or “comprising,” when used in this specification, specify the presence of: MANGAN 11-2 stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0032] The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. Aspects of the disclosure were chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.

Claims

: MANGAN 11-2CLAIMSWhat is claimed is:

1. A process comprising: determining a first fuse location on a hollow core optical fiber, the first fuse location being where a first internal microstructure fuses to an internal surface of the hollow core optical fiber; determining a cleave endpoint location on the hollow core optical fiber for a cleave based on the first fuse location; determining a cleave-flaw location on the hollow core optical fiber based on the cleave endpoint location; positioning the hollow core optical fiber in an optical fiber cleaver such that the cleave-flaw location is positioned to receive a cleave initiation from the cleaver; and initiating a cleave in the hollow core optical fiber with the cleaver.

2. The process of claim 1 further comprising: providing an axial tension on the hollow core optical fiber while initiating the cleave in the hollow core optical fiber.

3. The process of claim 2, wherein the axial tension is based on a cross-sectional area of the hollow core optical fiber.

4. The process of claim 1 further comprising: determining a second fuse location on the hollow core optical fiber, the second fuse location being where a second internal microstructure fuses to the internal surface of the hollow core optical fiber; wherein determining a cleave endpoint location on the hollow core optical fiber for a cleave based on the first fuse location includes determining the cleave endpoint location to be between the first fuse location and the second fuse location.MANGAN 11-25. The process of claim 4, wherein the cleave endpoint location is at least 5 micrometers (pm) from both the first fuse location and the second fuse location.

6. The process of claim 5, wherein the cleave endpoint location is at least 10 pm from both the first fuse location and the second fuse location.

7. The process of claim 1 , wherein the cleave endpoint location is at least 5 micrometers (pm) from the first fuse location.

8. The process of claim 7, wherein the cleave endpoint location is at least 10 pm from the first fuse location.

9. The process of claim 1, wherein: determining the first fuse location comprises inspecting the hollow-core optical fiber with a vision system that reveals a geometry of the internal microstructures in a sidewall of the hollow-core optical fiber.

10. The process of claim 1 , wherein: positioning the hollow core optical fiber comprises changing an azimuthal orientation of the hollow-core optical fiber relative to the cleave initiator of the cl eaver.

11. An optical fiber cleaver comprising: a portion to receive an optical fiber for cleaving; a cleave initiator; an inspection system that reveals a geometry of the internal microstructures in a sidewall of the hollow-core optical fiber; and a system that changes an azimuthal direction of the optical fiber for cleaving relative to the cleave initiator.

12. The optical fiber cleaver of claim 1, wherein the cleave initiator is a striker.Page to of 12 LIG 2501 USUA1 - 1925MANGAN 11-213. The optical fiber cleaver of claim 1, wherein the cleave initiator is a laser.

14. The optical fiber cleaver of claim 1, wherein the system at changes an azimuthal direction of the optical fiber for cleaving relative to the cleave initiator is a mechanical system.

15. The optical fiber cleaver of claim 1, wherein the system at changes an azimuthal direction of the optical fiber for cleaving relative to the cleave initiator is an electromechanical system.

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