Fiber optic components and their formation methods

Abstract

A method for forming an optical fiber assembly includes placing an adhesive in a ferrule assembly, heating the ferrule assembly by thermal induction, inserting an optical fiber into the ferrule hole during or after the heating step, and securing the optical fiber to the ferrule assembly using the adhesive. Thermal induction effectively renders or maintains the adhesive in a molten state to allow for optical fiber insertion.

Description

[0001] Priority application

[0002] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 284,086, filed November 30, 2021, pursuant to the Patent Act, and relies on the contents of that application, which are incorporated herein by reference in their entirety. Background Technology

[0003] This disclosure relates generally to optical connectivity, and more specifically to a method for forming an optical fiber assembly using an induction heating device, and the optical fiber assembly obtained by such method.

[0004] Fiber optic cables have a wide range of applications, including voice, video, and data transmission in the telecommunications industry. In telecommunications systems using fiber optics, fiber optic cables carrying the fiber are typically connected to equipment or other fiber optic cables in many locations. To facilitate these connections, fiber optic cables are usually provided with fiber optic connectors at their ends. The process of installing connectors at the ends of fiber optic cables is called “termination” because the ends of the fiber optic cables are terminated with connectors. The term “connectorization” is sometimes also used to refer to this process. Termination can be done at the factory, resulting in “pre-connectorized” or “pre-terminated” fiber optic cables, or it can be done in the field (e.g., using “field-installable” or “field-mountable” fiber optic connectors).

[0005] Regardless of where termination occurs, fiber optic connectors typically include a ferrule with one or more holes, each hole receiving one optical fiber. The ferrule supports the optical fiber and positions it relative to the connector body. When the connector is inserted into an adapter to mate with another connector, a retention mechanism (e.g., a latch) associated with the connector body engages with the adapter to hold the connector in place. An alignment mechanism (e.g., a sleeve within the adapter) receives or otherwise positions the ferrule such that the optical fiber in the ferrule can be aligned with the optical fiber supported by the ferrule of the mating connector.

[0006] A ferrule is used to position the optical fiber, as the fiber is typically secured to the ferrule during the termination process. Specifically, during termination, the fiber is inserted into the rear portion of the ferrule bore and advances to or past the front portion of the ferrule. Adhesive is typically used to secure (bond) the fiber to the ferrule (e.g., inside and / or behind the ferrule bore), to the ferrule holder extending above and beyond the rear portion of the ferrule holder, or to both the ferrule and the ferrule holder. Various techniques for inserting and bonding optical fibers to ferrules are known. Given the importance of such techniques to the termination process and their impact on cost, complexity, and final performance, there has been considerable interest in them.

[0007] One of the most common insertion and bonding techniques is the use of epoxy resin. Epoxy resin is injected into the ferrule and / or ferrule holder before or during fiber insertion. Once cured, the epoxy resin forms a strong bond between the fiber and the ferrule. However, the challenge with epoxy resin can lie in the time required for such curing. It can take 5 to 10 minutes or longer to achieve sufficient curing for subsequent processing (e.g., cutting and / or polishing the fiber end at the ferrule tip). The extended curing time can be partially offset by batch termination, where multiple ferrules with epoxy resin and inserted fiber cure simultaneously, but not all setups are conducive to such batch processing. For example, field termination is often limited to individual processing due to practical reasons or because multiple terminations are not required. Even some factory terminations may not be suitable for batch processing, given that other processing steps may be easier or designed to accommodate individual processing.

[0008] One epoxy resin alternative adhesive that has been used is a thermoplastic adhesive, also known as a "hot melt" adhesive. Such adhesives can be stored in a solid form, melted when needed for liquid processing, and then allowed to return to a solid form to bond surfaces in contact with the adhesive. For example, U.S. Patent No. 4,984,865 discloses injecting molten thermoplastic adhesive into a ferrule bore and then pushing an optical fiber through the bore, such that the adhesive: (i) occupies the space between the optical fiber and the ferrule bore, and (ii) forms a bead around the protrusion of the optical fiber at the end of the ferrule. U.S. Patent No. 7,147,384 is similar but discloses more possibilities for storing hot melt adhesive inside the connector prior to termination, different hot melt adhesive properties, and certain oven-based heating techniques. While the melting and subsequent setting / curing time of the adhesive may be faster than that of epoxy resin injection and curing, it still takes more than a minute.

[0009] Several adhesives have been proposed that offer even shorter processing times than hot-melt adhesives. For example, U.S. Patent No. 8,696,215 discloses a particular adhesive based on a partially cross-linked resin (e.g., polyphenylene sulfide) that can be heated and cured in less than one minute. Adhesives can also be pre-loaded into the ferrule in solid form. While such adhesives can speed up processing, they require heating to relatively high temperatures (e.g., above 250°C), which can be difficult to achieve because the adhesive's storage location within the ferrule and other components that may be present nearby (e.g., connector housing / body) may not be designed to withstand high temperatures.

[0010] Although many methods for inserting and bonding optical fibers to ferrules are known, there remains interest in new alternatives. Each known method has its own challenges and may not be suitable for a given application, or at least leaves room for improvement when used for a given application. Summary of the Invention

[0011] This disclosure provides a method for forming an optical fiber assembly. The method involves heating a ferrule holder and / or a ferrule in a specific manner to facilitate insertion and bonding of the optical fiber into the ferrule. During insertion and bonding, the ferrule and ferrule holder may be part of an optical connector assembly including a connector body in which the ferrule holder is positioned. Alternatively, such a connector body may be installed after the optical fiber has been inserted and bonded to the ferrule.

[0012] Therefore, according to one embodiment, the optical fiber assembly includes a ferrule and a ferrule holder. The ferrule has a front portion defining a front end, a rear portion defining a rear end, and a ferrule aperture extending between the front and rear ends. The ferrule aperture can be in the form of a microaperture, i.e., having a very small diameter (<127 μm) covering most (>80%) or the entire length of the ferrule. Such ferrule designs are common and are generally less expensive compared to other ferrule aperture geometries, such as those involving countersunk hole configurations and shorter microapertures. The ferrule holder receives the rear portion of the ferrule and, together with the ferrule, constitutes the ferrule assembly. The ferrule holder is made of metal and has a ferrule holder channel communicating with the ferrule aperture.

[0013] In this exemplary embodiment, a method of forming an optical fiber assembly includes: placing an adhesive in a ferrule assembly, wherein the adhesive is placed in a ferrule support channel, a ferrule aperture, or both; heating the ferrule assembly by thermal induction, wherein heating causes the adhesive to become or remain in a molten state; inserting an optical fiber into the ferrule aperture during or after the heating step, wherein the temperature of the ferrule maintains the adhesive in a molten state during insertion; and securing the optical fiber to the ferrule assembly using an adhesive, wherein the adhesive solidifies during securing.

[0014] In some implementations, the insertion step includes inserting an optical fiber from the rear end of the ferrule and through a ferrule aperture such that the end of the optical fiber extends to or beyond the front end of the ferrule, and the insertion step does not cause adhesive to migrate to the end face of the ferrule, including the front end.

[0015] In some implementations, the adhesive is initially in solid form, at least during the placement step. A specific example is that the adhesive comprises monofilaments of a thermoplastic adhesive, which are inserted into a ring support channel, a ring hole, or both.

[0016] In other embodiments, the optical fiber can be coated with adhesive immediately before the insertion step, so that the placement and insertion steps occur simultaneously. One example of coating the optical fiber with adhesive is clamping the optical fiber in a molten pool of adhesive.

[0017] Thermoplastic adhesives may be particularly advantageous for the use of methods and optical fiber assemblies according to this disclosure due to their relatively low viscosity and relatively rapid curing ability over a reasonable temperature range. However, other adhesives are also feasible. More generally, adhesives having the following properties may provide similar advantages: (a) a melt viscosity in the range of about 500 centipoise (cp) to about 20,000 cp over a temperature range of 150°C to 300°C; or (b) a Shore D hardness of at least 60 at room temperature (23°C for the purposes of this disclosure). The adhesives according to this disclosure may also include one or more additives, such as antioxidants, color masterbatches, or viscosity modifiers, to further provide the desired properties.

[0018] In some implementations, the heating step may include: positioning the ring assembly relative to an induction coil; and flowing current through the induction coil, wherein the current generates a magnetic field that induces heat generation in the ring holder.

[0019] In some embodiments, the heating step may further include positioning a metal sleeve over the front portion of the ferrule. When current flows through the induction coil, the metal sleeve remains above the front portion of the ferrule so that the current induces heat generation within the metal sleeve. The metal sleeve helps transfer heat to the front portion of the ferrule, ensuring that the ferrule (which may comprise a ceramic material that cannot be effectively heated by induction) still reaches a sufficient temperature to maintain the adhesive in a molten state, at least during fiber insertion.

[0020] Alternatively, the following implementation scheme can be adopted: multiple optical fiber assemblies are formed simultaneously through a heating step and a fixing step, and the heating step includes positioning a corresponding collar assembly relative to the induction coil.

[0021] Additional features and advantages will be set forth in the detailed description below, and some of these features and advantages will be apparent to those skilled in the art of optical connection technology. It should be understood that the foregoing general description, the following detailed description, and the accompanying drawings are merely exemplary and intended to provide an overview or framework for understanding the nature and characteristics of the claims. Attached Figure Description

[0022] The accompanying drawings are included to provide further understanding and are incorporated in and form a part of this specification. The drawings illustrate one or more embodiments and, in conjunction with the specification, explain the principles and operation of each embodiment. Features and attributes associated with any embodiment shown or described may be applied to other embodiments shown, described, or understood based on this disclosure.

[0023] Figure 1 This is a 3D view of an example of a fiber optic connector.

[0024] Figure 2 yes Figure 1 Exploded 3D view of a fiber optic connector.

[0025] Figure 3 yes Figure 1 A cross-sectional side view of a fiber optic connector, showing the adhesive pre-loaded in the connector's ferrule holder.

[0026] Figure 4 yes Figure 1 A three-dimensional view of the arrangement of the fiber optic connectors relative to the induction heating device.

[0027] Figure 5 yes Figure 4 Side view of the arrangement in the middle.

[0028] Figure 6 yes Figure 4 The cross-sectional side view arranged in the middle also shows the optical fiber in the rear of the fiber optic connector.

[0029] Figure 7 It is shown in the Figure 6 After the optical fiber passes through the adhesive and through the ferrule of the optical fiber connector, the optical fiber is secured to the optical fiber connector with adhesive (cross-sectional side view).

[0030] Figure 8 This is a schematic three-dimensional view of multiple fiber optic connectors positioned relative to the induction heating device.

[0031] Figure 9 It is positioned relative to the induction heating device according to the alternative implementation scheme. Figure 1 A cross-sectional side view of a fiber optic connector.

[0032] Figure 10 yes Figure 9 A top view of the induction heating device. Detailed Implementation

[0033] In the following description, various embodiments will be illustrated by example. Generally, this specification relates to optical fiber assemblies capable of being formed in short cycle times, and methods for such formation. The optical fiber assembly includes an optical fiber secured relative to a ferrule, which may be part of or used in an optical fiber connector. The method involves using and treating an adhesive in a specific manner during the optical fiber termination process to secure the optical fiber to the ferrule. Examples relating to securing a single optical fiber to a corresponding ferrule will be described, but this disclosure is not limited to such examples. For example, aspects of this disclosure may also be applicable to ferrules for multi-fiber connectors.

[0034] Therefore, in the claims described below, the use of “a” or “an” in relation to an element (e.g., an optical fiber) means “one or more” of the elements, unless otherwise expressly stated.

[0035] Furthermore, in this disclosure, the term "fiber optic connector" refers to an assembly comprising a ferrule and a connector body, wherein the ferrule is designed to facilitate fiber alignment for optical coupling, and the connector body is designed to facilitate mechanical connection (e.g., to an adapter). Other components may be included as part of the assembly, but are not necessarily required in the preceding claims described below. In this disclosure, the terms "connector assembly," "connector subassembly," "optical connector," and "connector" are considered to be interchangeable with "fiber optic connector."

[0036] Furthermore, the term "nominal" used in this disclosure with respect to measurement or dimensional characteristics (e.g., diameter) refers to the specified or expected value of the characteristic. The actual value of the characteristic may be within acceptable manufacturing tolerances.

[0037] The term “heat distortion temperature” or “HDT” in this disclosure means the value at 1.82 MPa according to ASTM D648, unless otherwise stated.

[0038] The term "monofilament" in this disclosure refers to a preform produced by melting, extruding, and cooling an adhesive in a manner that produces a solid preform. The term does not preclude post-extrusion processing; only a solid preform with a substantially constant shape is required.

[0039] The first example will now be described based on the principles described above. For example... Figure 1 and Figure 2 As shown, the first example relates to an optical connector 10 (“connector 10”) in the form of a simplex LC connector (e.g., according to IEC 61754-20:2012). However, the description is not intended to be limited to any particular connector type, but can be applied to a wide variety of connector designs. These include, for example, simplex, duplex, and multi-fiber connector designs. A specific example is a simplex SC connector (e.g., according to IEC 61754-4:2013).

[0040] Connector 10 includes a configuration for supporting optical fibers ( Figure 1 and Figure 2The diagram shows a ferrule 12 (not shown) and a connector body 14 extending therefrom. More specifically, the ferrule 12 is part of a ferrule assembly 16, which also includes a ferrule holder 18 received on a rear portion of the ferrule 12. The connector body 14 includes a front connector body 20 in which the ferrule holder 18 is positioned and a rear connector body 22 coupled to the rear of the front connector body 20. Thus, in the illustrated embodiment, the connector body 14 is a two-piece connector body, but embodiments with a single-piece connector body are also possible. Furthermore, the term "connector body" in this disclosure is interchangeable with "connector housing".

[0041] The front connector body 20 includes a latching arm 26 extending outward and rearward from a front portion of the front connector body 20. The latching arm 26 is configured to bend toward other portions of the front connector body 20 to allow the connector 10 to be inserted into and removed from an adapter (not shown), a dust cover (not shown), and / or other structure or component. The rear connector body 22 includes a trigger arm 28 (also referred to as an "actuator arm") that a user can press to bend the latching arm 26 toward the front connector body 20. The trigger arm 28 is optional, as other embodiments may include different types of rear connector bodies or a single connector body, as described above.

[0042] Still referencing Figure 1 and Figure 2 A spring 32 located within the rear connector body 22 extends into the front connector body 20 and biases the ferrule holder 18 into a forward position within the front connector body 20. The internal geometry of the front connector body 20 defines a stop for the ferrule holder 18 in the forward position, thereby retaining the ferrule holder 18 within the front connector body 20. The ferrule 12 extends from the ferrule holder 18 and has a front portion protruding beyond the front end 34 of the front connector body 20.

[0043] refer to Figure 3 This allows for a better understanding of the relationship between the ferrule assembly 16 and the connector body 14, as well as additional details of the components themselves. For example... Figure 3As shown, the ferrule 12 includes a ferrule aperture 40 extending between the rear end 42 and the front end 44 of the ferrule 12. The ferrule aperture 40 includes a tapered inlet portion 46 extending from the rear end 42, but its diameter is smaller compared to the ferrule 12 itself. This small-diameter portion of the ferrule aperture 40 may be referred to as a micro-hole or micro-aperture, and is typically designed to be close in size to the nominal diameter of the optical fiber to which the ferrule 12 is intended to terminate. For example, for an optical fiber with a nominal diameter of 125 μm, the micro-aperture portion of the ferrule aperture 40 may have a diameter of 127 μm or smaller, 126 μm or smaller, or even 125.5 μm or smaller. In the example shown, the micro-aperture occupies the majority of the ferrule aperture 40. In some embodiments, the micro-aperture may extend to at least 80% (between the front end 44 and the rear end 42), at least 85% of the total length of the ferrule 12, or at least 90% of the total length of the ferrule 12.

[0044] When the ferrule holder 18 is in the forward position, it is received on the rear portion of the ferrule 12 and abuts against the inner surface 50 of the front connector body 20. A portion of the ferrule holder 18 extends to the rear of the ferrule 12 and includes a ferrule holder channel 52 communicating with the ferrule bore 40. In the example shown, the ferrule assembly 16 includes an adhesive 54 disposed within the ferrule holder channel 52. Figure 3 The adhesive 54 is schematically shown, intended to represent a solid material. Adhesive 54 can be placed in this solid form within the ferrule assembly 16 before or during the fiber termination process. In other words, adhesive 54 can be pre-loaded into the ferrule support channel 52 before the termination process begins, or as a step in the termination process. In some embodiments, adhesive 54 can be provided as a monofilament. This means the adhesive has been melted, extruded, and cooled in some way to produce a solid preform / body. Initially, such extrusion may produce an elongated solid preform, which can then be cut to shorter lengths for use in corresponding optical components. Although... Figure 3 The illustration shows adhesive 54 placed only in the ring support channel 52; however, in alternative embodiments, adhesive 54 may be placed only in the ring hole 40, or simultaneously in both the ring support channel 52 and the ring hole 40. Further details regarding adhesive 54 and alternatives to these examples will be described in more detail below.

[0045] Connector 10 has been generally described; now, an example method for forming an optical fiber assembly including connector 10 will be described. The optical fiber assembly is the result of a termination process, i.e., a process of terminating optical fibers with components (e.g., some or all of the components of connector 10). This process utilizes thermal induction to heat the ferrule assembly 16 and melt the adhesive 54. In an alternative embodiment, the adhesive 54 is not pre-loaded but injected or otherwise placed into the ferrule assembly 16 in a molten (liquefied) form, and the process can be used to maintain this molten form during other steps. Optical fiber 102 ( Figure 6 Insert it into the ferrule assembly 16 and through the molten adhesive into the ferrule hole 40, as will be described in further detail below.

[0046] to this end, Figures 4 to 6 The diagram illustrates the positioning of connector 10, sleeve 110, and induction heating device 112 relative to each other. Sleeve 110 is received on the front end 44 of ferrule 12, but is small enough to also extend along the front portion of ferrule 12 and into the space between the outer surface of ferrule 12 and the inner surface of the front connector body 20. Connector 10 and sleeve 110 are arranged such that ferrule assembly 16 and sleeve 110 are located on axis A of induction coil 114 extending through induction heating device 112. In other words, sleeve 110, ferrule assembly 16, or both are at least partially located within induction coil 114. Sleeve 110 and connector 10 may be supported by corresponding fasteners (not shown), the position of which can be controlled by suitable equipment to form... Figures 4 to 6 The layout shown.

[0047] In some embodiments, the ferrule holder 18 is made of metal. This allows the induction heating device 112 to effectively heat and melt the adhesive 54 placed in the ferrule holder channel 52. More specifically, the induction heating device 112 can be used to generate a current flowing through the induction coil 114. The current, in turn, generates a magnetic field that excites electrons in the ferrule holder 18 and heats them, consistent with the principle of induction heating. This heat then causes the adhesive 54 to melt (i.e., to be in a molten form). In embodiments where the adhesive 54 is already in a molten form when placed in the ferrule holder channel 52, the heat from the ferrule holder 18 keeps the adhesive 54 in a molten form. The molten form of the adhesive 54 allows the optical fiber 102 to be inserted through the adhesive 54.

[0048] to this end, Figure 6The diagram illustrates the insertion of an optical fiber 102 into a connector 10 from the rear side of the rear connector body 22. The optical fiber comprises a glass wire 120 surrounded by one or more polymer coatings 122 (e.g., acrylate). The coating 122 is removed from the end of the optical fiber 102 to create a “bare” glass end 124, as is standard practice in optical fiber termination processes. Once the adhesive 54 is in a molten state through the induction heating steps described above, the glass end 124 can be passed through the adhesive 54 into the ferrule hole 40. The adhesive 54 can move with the optical fiber 102 toward the rear end 42 of the ferrule 12. Additionally, some adhesive 54 may be pulled into the ferrule hole 40 to fill the space between the glass end 124 and the ferrule hole 40. The result after the optical fiber 102 is fully inserted may resemble... Figure 7 The figure shows adhesive 54 surrounding the optical fiber 102, adjacent to the rear end 42 of the ferrule 12, within the ferrule support channel 52. Due to the level of detail in the figure, adhesive 54 occupying the space between the optical fiber 102 and the sleeve aperture 40 is not shown. Ultimately, adhesive 54 cools and solidifies, at which point the optical fiber 102 is secured to the ferrule assembly 16, specifically the ferrule 12, by adhesive 54. Cooling can be achieved passively, simply by allowing adhesive 54 to return to room temperature. Alternatively, active cooling techniques can be used to accelerate the curing time.

[0049] The sleeve 110 can serve multiple purposes in the steps described above. For example, in some embodiments, the sleeve 110 may be made of metal to assist in the heating process described above. In such embodiments, considering the position of these components relative to the induction coil 114, operating the induction heating device 112 results in both the ferrule support 18 and the sleeve 110 being heated. Heating the sleeve 110 helps to heat the front portion of the ferrule 12 surrounded by the sleeve 110. In fact, the sleeve 110 can be received tightly on the front portion of the ferrule 12 to provide more efficient heat transfer to the ferrule 12 (e.g., by radiation). By heating the front portion of the ferrule 12 with the sleeve 110 and the rear portion of the ferrule 12 with the ferrule support 18, the ferrule 12 can be heated more uniformly / consistently. This makes it easier and faster to bring the relevant portions of the ferrule 12 to a sufficient temperature to maintain the adhesive 54 in a molten form when the optical fiber 102 is inserted through the ferrule hole 40. For example, if the front portion of the ferrule 12 is not maintained at such a temperature, there is a risk that the adhesive 54 present in the ferrule 12 (e.g., if initially placed there and / or pulled in by the fiber 102) may solidify before the fiber is fully inserted. This could prevent full insertion or introduce properties that adversely affect the bond strength / performance. In embodiments where the microhole occupies the majority of the sleeve aperture 40, controlling the temperature to maintain the molten form of the adhesive 54 during fiber insertion is particularly advantageous. Furthermore, the induction heating device 112 can rapidly heat the sleeve 110 and the ferrule holder 18, thereby rapidly melting the adhesive 54, thus reducing the time associated with the heating step compared to other techniques.

[0050] Furthermore, in some embodiments, before and / or during operation of the induction heating device 112, the sleeve 110 can be used to push the ferrule assembly 16 rearward relative to the connector body 14. This can be achieved by sizing the sleeve 110 to fit through an opening 128 in the front connector body 20, which is larger than the ferrule 12 but smaller than the ferrule holder 18, thereby allowing the sleeve 110 to advance to push the ferrule holder 18 rearward. In other embodiments, the sleeve 110 may be sized to grip or otherwise engage the ferrule 12 to push the ferrule 12 (and therefore the ferrule holder 18) rearward. The advantage of removing the ferrule holder 18 from its forward position is that the ferrule holder 18 no longer contacts the inner surface 50 of the front connector body 20. The front connector body 20 is typically made of a molded polymer material, such as... 1010, and may not be able to withstand the same temperatures as metal components such as the ferrule holder 18. The temperature required to melt the adhesive 54 in the ferrule 12 may deform the front connector body 20. Therefore, by removing the ferrule holder 18 from contact with the inner surface 50 of the front connector body 20 before operating the induction heating device 112 (and maintaining the space when operating the induction heating device 112), the risk of heat from the ferrule holder 18 damaging the front connector body 20 is reduced.

[0051] Some embodiments of this disclosure may even involve heating the ferrule assembly 16 to a temperature higher than the heat deflection temperature (HDT) of the connector body 14. Taking connector 10 as an example, the front connector body 20 may include a molded polymer material having a specific HDT measured according to ASTM D648 at 1.82 MPa. Due to the rapid, concentrated heating of the induction heating device 112, and because the ferrule assembly 16 does not contact the front connector body 20 during heating, the ferrule assembly 16 can be heated to a temperature higher than the HDT of the front connector body 20. This means that, if desired, the adhesive 54 can be selected from materials with a melting point higher than the HDT of the front connector body 20. In some embodiments, the melting point of the adhesive 54 may be at least 10°C, at least 20°C, at least 30°C, at least 50°C, or more higher than the HDT of the front connector body 20. Therefore, in the case of the front connector body 20 comprising an HDT of 213°C... In embodiments using materials such as 1010, materials with melting points higher than 213°C, higher than 220°C, higher than 250°C, etc., can be used as adhesive 54. This principle can be extended to allow the use of cheaper materials with lower HDT as connector body 14. For example, the front connector body 20 comprises polybutylene terephthalate (e.g., B4300 G3 (the material is manufactured by BASF SE AG, Ludwigshafen, Germany) has an HDT of 185°C. The adhesive 54 in this embodiment may have a melting point higher than 185°C, higher than 200°C, higher than 220°C, higher than 250°C, etc.

[0052] Regardless of the HDT of the connector body 14 and the melting point of the adhesive 54, the sleeve 110 can also be used as part of an active cooling step. For example, after operating the induction heating device 112 and inserting the optical fiber 102 into the desired position, the sleeve 110 can be used to deliver pressurized air or other gas to the ferrule 12. Forced convection can accelerate heat dissipation from the ferrule 12, which in turn allows the adhesive 54 to cure / solidify more quickly. Rapid curing also helps to shorten cycle time, which can be advantageous when forming large quantities of optical fiber assemblies using the methods according to this disclosure.

[0053] While the additional advantages that may arise from using sleeve 110 have been mentioned above, this disclosure is not limited to embodiments using sleeve 110. In other words, the method according to this disclosure is feasible in which the collar assembly 16 is sufficiently heated by the induction coil without the need to place a sleeve on the collar 12.

[0054] Referring more generally to adhesive 54 in the steps described above, those skilled in the art of optical bonding will understand that adhesive 54 comprises a polymeric material that can be melted and / or maintained in a molten form by induction heating of the collar holder 18. Thermoplastic hot melt adhesives are particularly advantageous due to their melt viscosity, relatively fast curing time, and bond strength. Examples of such hot melt adhesives include those from Henkel Corporation. PA 2692 and Kraton Corporation's (Houston, Texas) UNI-REZ TM 2626. Various other hot melt adhesives are disclosed in U.S. Patent Nos. 4,984,865 and 7,147,384, the disclosures of which are incorporated herein by reference. As described in U.S. Patent No. 7,147,384, hot melt adhesives suitable for fiber optic connectors may comprise polyamides or other polymeric materials having one or more of the following properties: (a) a melt viscosity of 1,000 to 20,000 centipoise (cp) over an operating temperature range of 210°C to 250°C; (b) a Shore D hardness of 50 to 85 at room temperature; or (c) a crystallinity of 15% to 35% to provide excellent adhesive stability in fiber optic connectors.

[0055] In some embodiments according to this disclosure, the adhesive 54 may be in monofilament form when placed in the ferrule holder 18. Many adhesives, especially polyamide-based thermoplastic adhesives, are available in monofilament form. A short section of monofilament can be cut from a spool or the like and inserted into the ferrule holder channel 52 before or as part of the termination process. Figure 3 For example, a monofilament approximately 2 mm in length and 1 mm in diameter can be cut from a spool and placed in the ferrule support channel 52 near the rear end 42 of the ferrule 12. When the induction heating device 112 is operated, the ferrule support 18 can be rapidly heated to a temperature higher than the melting point of the adhesive 54 due to the metal construction of the ferrule support 18. Therefore, the monofilament of the adhesive 54 within the ferrule support channel 52 can melt rapidly.

[0056] In other embodiments according to this disclosure, and as previously described, the adhesive 54 may already be in a molten form when placed into the ferrule assembly 16. For example, the adhesive 54 may be melted and injected into the ferrule support channel 52 before the optical fiber 102 is inserted into the ferrule assembly 16. Alternatively, the adhesive 54 may be applied to the glass end 124 of the optical fiber 102 before the optical fiber 102 is inserted into the ferrule assembly 16. For example, the adhesive 54 may be applied by immersing the optical fiber 102 in a molten pool of adhesive 54 before insertion, or by spraying molten adhesive 54 onto the glass end 124 before insertion. In such embodiments, the optical fiber 102 carries the adhesive 54 into the ferrule support channel 52 and ultimately into at least a portion of the ferrule aperture 40. Thus, the steps of placing the adhesive 54 into the ferrule assembly 16 and inserting the optical fiber 102 occur simultaneously. Different techniques for placing the adhesive 54 into the ferrule assembly 16 are not necessarily mutually exclusive, as multiple techniques may be used in some embodiments if desired.

[0057] Furthermore, certain aspects of this disclosure may be applicable to adhesives other than thermoplastic hot-melt materials. For example, the adhesive types disclosed in U.S. Patent No. 8,696,215, cited in the background section above, may be used in some embodiments, including, for example, polyphenylene-sulfide (PPS) based adhesives. The ferrule assembly 16 may still be heated using the induction heating device 112 in the same manner as described above.

[0058] Generally, adhesives having one or more of the following properties may be particularly suitable for the methods according to this disclosure: (a) a melt viscosity of 500 to 20,000 cp in an operating temperature range of 150°C to 300°C; or (b) a Shore D hardness of at least 60 at room temperature. In some embodiments, the adhesive may include one or more additives that help provide the desired processing properties. Example additives include, but are not limited to, antioxidants, color masterbatches, and viscosity modifiers. Another possibility is that the adhesive contains metal particles, which may be particularly advantageous for the methods according to this disclosure. For example, before extruding the molten adhesive to form a monofilament, the molten adhesive may be mixed with a metal paste, etc., such that the monofilament contains metal particles. When the monofilament adhesive is positioned in the ferrule holder 18 and / or ferrule 12 as described above and the induction heating device 112 is operated, the metal particles may be heated by the magnetic field generated by the induction coil 114. This can make the adhesive melt faster and more uniformly when forming the optical fiber assembly. Even in embodiments where the adhesive is already in a molten form when it is placed into the ring assembly 16, the adhesive can be premixed with metal particles to help maintain the molten form during operation of the induction heating device 112. Figure 9The diagram illustrates how connector 10 and sleeve 110, according to an alternative embodiment, can be used with induction heating device 212. Induction heating device 212 still includes coil 214, but coil 214 has a helical pattern entirely located within plane P. Although... Figure 10 The coil 214 is shown in the shape of an Archimedes spiral, but in other embodiments, the spiral pattern of the coil may be different.

[0059] like Figure 9 As shown, connector 10 and sleeve 110 are positioned near coil 214, generally parallel to plane P, rather than arranged to extend through coil 214. In some embodiments, connector 10 may even be placed on coil 214. Figures 4 to 6 Similar to the implementation scheme, the sleeve 110 and connector 10 can be supported by corresponding fixing devices (not shown), the position of which can be controlled by suitable equipment to form... Figure 9 The arrangement is shown. Although not inside coil 214, bushing 110 and ring support 18 may still be located within the magnetic field generated by the current flowing through coil 214. Therefore, coil 214 can function the same as coil 212 and still heat bushing 110 and ring support 18. The above-mentioned reference can still be performed using induction heating device 212. Figures 4 to 6 The basic steps discussed are for forming fiber optic assemblies.

[0060] It will be apparent to those skilled in the art of optical connections that various modifications and variations can be made based on this disclosure. For example, although shown in the figures and described above as having the ferrule assembly 16 positioned within the connector body 14 during the formation of the fiber optic assembly, in alternative embodiments, the ferrule assembly 16 can be processed independently to form the fiber optic assembly. In other words, the ferrule assembly 16 can be positioned relative to the induction heating device 112 and heated in the absence of the connector body 14. After the fiber optic cable 102 is inserted and secured to the ferrule assembly 16, the connector 10 can then be formed around the resulting fiber optic assembly. Specifically, the fiber optic assembly can then be assembled with the connector body 14 and possibly other components as part of assembling the connector 10. Processing the ferrule assembly 16 independently of the assembly of the connector 10 is an alternative method to keeping the ferrule support 18 spaced apart from the inner surface of the connector body 14 during operation of the induction heating device 112.

[0061] Furthermore, although the heating of a single collar assembly 16 is described above as being achieved by an induction heating device 112, in alternative embodiments, multiple collar assemblies 16 can be heated simultaneously. For example, Figure 8 Multiple connectors 10 are shown, with corresponding ferrule assemblies 16 ( Figure 2 and Figure 3The ring assembly 16 is positioned relative to the induction coil 214 of the induction heating device 212. The shape of the induction coil 214 allows each ring assembly 16 to be located within the induction coil 214. Furthermore, each ring assembly 16 remains associated with a corresponding sleeve 110. When the induction heating device 212 is operating, the ring support 18 of each ring assembly 16 is based on the above-mentioned... Figures 4 to 6 Heating is performed on the same principle as described above. The collar 12 of each collar assembly 16 is also connected via a corresponding sleeve 110 to the collar described above. Figures 4 to 6 Heating in the same manner as described.

[0062] Those skilled in the art of optical connections will recognize that many other alternatives and variations exist. For this reason at least, the invention should be construed as encompassing all contents within the scope of the appended claims and their equivalents.

Claims

1. A method of forming an optical fiber assembly, wherein the optical fiber assembly includes a ferrule and a ferrule holder, the ferrule having a front portion defining a front end, a rear portion defining a rear end, and a ferrule aperture extending between the front end and the rear end, and wherein the ferrule holder receives the rear portion of the ferrule and defines a ferrule assembly together with the ferrule, the ferrule holder comprising metal and having a ferrule holder channel communicating with the ferrule aperture, the method comprising: The placement step involves placing a thermoplastic adhesive in the ferrule assembly, wherein the thermoplastic adhesive is placed in the ferrule support channel, the ferrule hole, or in both the ferrule support channel and the ferrule hole; A heating step, wherein the collar assembly is heated by thermal induction, wherein the heating step causes the thermoplastic adhesive to present or remain in a molten form, and wherein the heating step includes: Positioning the collar assembly relative to the induction coil and a metal sleeve separate from the induction coil, wherein the positioning includes receiving a front portion of the collar within the metal sleeve, and wherein the positioning causes the metal sleeve to be positioned between the collar and the induction coil; and A current is passed through the induction coil, wherein the current generates a magnetic field that induces heat in the collar support to cause the thermoplastic adhesive to take on or remain in a molten state, and wherein when the current is passed through the induction coil, the metal sleeve remains above the front portion of the collar so that the current induces heat in the metal sleeve. The insertion step involves inserting the optical fiber into the ferrule hole during or after the heating step, wherein the temperature of the ferrule maintains the thermoplastic adhesive in its molten form during the insertion step; and In the fixing step, the optical fiber is fixed to the ferrule assembly using the thermoplastic adhesive, wherein the thermoplastic adhesive solidifies during the fixing step.

2. The method of claim 1, wherein the insertion step comprises inserting the optical fiber from the rear end of the ferrule and through the ferrule hole such that the end of the optical fiber extends to or beyond the front end of the ferrule, and wherein the insertion step does not cause the thermoplastic adhesive to migrate to the end face of the ferrule including the front end.

3. The method of claim 1, wherein the thermoplastic adhesive is initially in a solid form at least during the placement step.

4. The method of claim 3, wherein the placement step comprises: The monofilament of the thermoplastic adhesive is inserted into the ferrule support channel, the ferrule hole, or the ferrule support channel and the ferrule hole.

5. The method of claim 1, further comprising: The coating of the thermoplastic adhesive is applied to the optical fiber, wherein the placement step and the insertion step are performed simultaneously.

6. The method of claim 5, wherein the coating of the thermoplastic adhesive is applied to the optical fiber by immersing the optical fiber in a molten pool of the thermoplastic adhesive.

7. The method of claim 1, wherein the ferrule has a total length between the front end and the rear end of the ferrule, and wherein the ferrule hole has a diameter of less than 127 μm and a length of at least 80% of the total length of the ferrule.

8. The method of claim 1, wherein the induction coil has a helical pattern, and wherein the positioning of the collar assembly relative to the induction coil causes the collar assembly to extend along an axis extending through the induction coil.

9. The method of claim 1, wherein the induction coil has a spiral pattern in a plane, and wherein the positioning of the loop assembly relative to the induction coil causes the loop assembly to be positioned near the induction coil outside the plane.

10. The method of claim 1, wherein a plurality of optical fiber assemblies are formed simultaneously by the heating step and the fixing step, and wherein the heating step includes positioning a corresponding collar assembly relative to the induction coil.

11. The method of claim 1, wherein at least during the heating step, the ferrule assembly is part of an optical connector assembly, the optical connector assembly including a connector body in which the ferrule holder is positioned.

12. The method of claim 11, wherein the optical connector assembly further comprises a spring that biases the collar holder to a forward position abutting against an inner surface of the connector body, and wherein the method further comprises: The ring holder is moved from the forward position to the retracted position, wherein the ring holder is maintained in the retracted position at least during the heating step.

13. The method of claim 11, wherein the connector body has a heat distortion temperature of 1.82 MPa according to ASTM D648, and wherein the heating step comprises heating the ferrule assembly above the heat distortion temperature of the connector body.

14. The method of claim 13, wherein the melting point of the thermoplastic adhesive is at least 20°C higher than the heat distortion temperature.

15. The method of claim 1, wherein the thermoplastic adhesive has a viscosity between 500 cP and 20,000 cP in a temperature range of 150°C to 300°C.

16. The method of claim 1, wherein the thermoplastic adhesive has a Shore D hardness of at least 60 at a temperature of about 23°C.

17. An optical fiber assembly is formed as follows: The placement step involves placing the adhesive into the ring assembly, which includes the ring and the ring holder, wherein: The collar has a front portion defining a front end, a rear portion defining a rear end, and a collar hole extending between the front end and the rear end. The collar bracket is received on the rear portion of the collar, the collar bracket comprising metal and having a collar bracket channel communicating with the collar hole. The adhesive is placed in the ring support channel, the ring hole, or the ring support channel and the ring hole; A heating step, wherein the ferrule assembly is heated by thermal induction, wherein the heating step causes the adhesive to present or remain in a molten form, and wherein the heating step includes: Positioning the collar assembly relative to the induction coil and a metal sleeve separate from the induction coil, wherein the positioning includes receiving a front portion of the collar within the metal sleeve, and wherein the positioning causes the metal sleeve to be positioned between the collar and the induction coil; and A current is flowed through the induction coil, wherein the current generates a magnetic field that induces heat in the collar support to cause the adhesive to take on or remain in a molten form, and wherein when the current is flowed through the induction coil, the metal sleeve remains above the front portion of the collar so that the current induces heat in the metal sleeve. The insertion step involves inserting the optical fiber into the ferrule hole during or after the heating step, wherein the temperature of the ferrule maintains the adhesive in a molten state during the insertion step; and The fixing step involves using the adhesive to fix the optical fiber to the ferrule assembly, wherein the adhesive solidifies during the fixing step.

18. The optical fiber assembly of claim 17, wherein the insertion step comprises inserting the optical fiber from the rear end of the ferrule and through the ferrule bore such that the end of the optical fiber extends to or beyond the front end of the ferrule, and wherein the insertion step does not cause the adhesive to migrate to the end face of the ferrule including the front end, such that the adhesive remains within the ferrule bore and spaced from the end face after the fixing step.

19. The optical fiber assembly of claim 17, wherein the ferrule has a total length between the front end and the rear end of the ferrule, and wherein the ferrule hole has a diameter of less than 127 μm and a length of at least 80% of the total length of the ferrule.

20. The optical fiber assembly of claim 17, wherein the adhesive has a viscosity between 500 cP and 20,000 cP in a temperature range of 150°C to 300°C.

21. The optical fiber assembly of claim 17, wherein the adhesive has a Shore D hardness of at least 60 at a temperature of about 23°C.

22. The optical fiber assembly of claim 17, further comprising a connector body, the ferrule holder being positioned within the connector body, wherein the connector body comprises a polymer material having a heat distortion temperature of 1.82 MPa according to ASTM D648, and wherein the adhesive has a melting point at least 20°C higher than the heat distortion temperature.

23. The optical fiber assembly of claim 17, wherein the adhesive comprises a thermoplastic adhesive.

24. An optical fiber assembly formed by the method according to any one of claims 1 to 16, comprising: optical fiber; A ferrule for terminating optical fibers, wherein the ferrule has a front portion defining a front end, a rear portion defining a rear end, and a ferrule hole extending between the front end and the rear end. A collar bracket is received above the rear portion of the collar, wherein the collar bracket comprises metal and has a collar bracket channel communicating with the collar hole. A connector body, wherein the ferrule holder is positioned within the connector body, wherein the connector body comprises a polymer material having a heat distortion temperature at 1.82 MPa according to ASTM D648; and An adhesive that secures the optical fiber to the rear end of the ferrule and at least a portion of the ferrule hole, wherein the melting point of the adhesive is higher than the heat distortion temperature of the connector body.

25. The optical fiber assembly of claim 24, wherein the melting point of the adhesive is at least 20°C higher than the heat distortion temperature of the connector body.

26. The optical fiber assembly of claim 24, wherein the heat distortion temperature of the connector body is less than 200°C.

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