Patent Application
20170031110
The present disclosure relates to optical fiber processing, and in particular relates to a ferrule holder for an optical fiber processing tool, such as used for laser processing of optical fiber ends.
Optical fibers are used in a variety of optical and telecommunications applications. Optical fiber connectors are used to connect two optical fibers so that the optical communication can take place between the two connected fibers. Often the optical fiber connectors are installed in the field, with such connectors being referred to as “field-installable connectors.” As the name implies, the connectors are installed in less than ideal circumstances for precision assembly. Consequently, such connectors and assembly processes need to be simple and reliable while meeting stringent performance requirements. Also, the tools used for the connector installation need to be portable, easy to use, rugged and preferably battery operated.
The assembly of connectors involves several steps, including the end preparation of the optical fibers to be connectorized. In general, end preparation involves four main process steps: (1) stripping the polymer coating to expose a select length of the bare glass fiber; (2) precision cleaving the bare glass fiber section with controlled end angles and surface quality; (3) inserting the optical fiber in a ferrule of the connector to have a controlled protrusion distance from the ferrule; and (4) polishing the end face of the optical fiber that protrudes from the ferrule.
The first step is currently done manually using a mechanical stripper. This process can introduce flaws in the glass fiber that can reduce the optical fiber strength. Consequently, a non-mechanical coating stripping process that does not cause flaws in the glass fiber are desired. To get a controlled protrusion distance and a high-quality fiber end face, the end face of the optical fiber is polished after fixing the optical fiber in the connector ferrule. Generally, this involves several polishing steps with progressively finer polishing pads. The polishing pads need to be replaced after each connector assembly, particularly the final polishing pad. This is a time consuming process whose outcome is very much operator dependent.
One of the difficulties in the end face preparation or processing of optical fibers to be connectorized is that the ferrules that hold the optical fibers can vary in size, e.g., from 1.25 mm diameter for LC type connectors to 2.5 mm in diameter for SC type connectors. Consequently, the tool used to perform endface processing needs to readily accommodate different size ferrules while maintaining the tight lateral and longitudinal alignment tolerances for endface processing. These tolerances are about 10 microns for lateral offset and in the range from about 100 microns to 150 microns for longitudinal offsets.
An aspect of the disclosure is a ferrule holder for holding a ferrule of an optical fiber connector, wherein the ferrule holds an optical fiber having an end face to be processed by an optical fiber processing tool that uses light. The ferrule holder includes: a first face plate having a first magnetic feature, first kinematic alignment features and a conical bore with a wide proximal end and a narrow distal end that defines a narrow aperture; a second face plate having a second magnetic feature complementary to the first magnetic feature, second kinematic alignment features that are complementary to the first kinematic alignment features, and a central bore that closely accommodates the ferrule; and wherein, whenever the first and second face plates are interfaced, the first and second magnetic features magnetically engage and hold the first and second face plates together while the first and second kinematic alignment features operably align and make contact, thereby placing the fiber end face in axial alignment with and in proximity to the narrow aperture.
Another aspect of the disclosure is a ferrule holder for holding a ferrule of an optical fiber connector and for use with an optical fiber processing tool that includes a light source that emits light. The ferrule holder includes: a first face plate having a first front side, a first central axis and a conical bore along the first central axis, the conical bore having a narrow end that defines a first aperture at the first front side, with the first face plate being operably arranged relative to the optical fiber processing tool, the first face plate further including at least one magnetic feature and one or more first kinematic alignment features operably arranged on the first front side and symmetrically arranged about the first central axis; a second face plate having a second front side, a second back side and a second central axis and and having a cylindrical bore being aligned along the second central axis and sized to receive and closely accommodate the ferrule, the second face plate further including at least one second magnetic feature and one or more second kinematic alignment features operably arranged on the second back side and symmetrically arranged about the second central axis; and wherein the first and second face plates are configured to be removably interfaced with the first front side and the second back side confronting and with the first and second central axes being substantially coaxial so that the first and second magnetic features magnetically engage and hold the first the first and second face plates together while the respective first and second kinematic alignment features operably align and make contact.
Another aspect of the disclosure is a tool assembly for processing an end face of an optical fiber held by a ferrule in an optical fiber connector. The tool assembly includes: an optical fiber processing tool having a light source, an optical system and a front end, wherein the light source generates light and the optical system directs the light to the front end; a ferrule holder operably arranged at the front end of the optical fiber processing tool, the ferrule holder having: a) a first face plate attached to or formed integrally with the front end of the laser tool and having a first magnetic feature, first kinematic alignment features and a conical bore with a wide proximal end and a narrow distal end that defines a narrow aperture and b) a second face plate having a second magnetic feature, second kinematic alignment features that are complementary to the first kinematic alignment features, and a central cylindrical bore, and also having a connector guide that receives a front end of the optical fiber connector so that the ferrule closely resides within the central cylindrical bore; and wherein, whenever the first and second face plates are interfaced, the first and second magnetic features magnetically engage and hold the first and second face plates together while the first and second kinematic alignment features operably align and make contact, thereby placing the fiber end face in axial alignment with and in proximity to the narrow aperture so that the focused light passes through the narrow aperture and to the fiber end face to process the fiber end face.
Another aspect of the disclosure is a method of processing an end face of an optical fiber held in a ferrule of an optical fiber connector. The method includes: generating light from a light source; directing the light through a conical bore of a first face plate in the direction from a wide end of the conical bore to a narrow end that defines a narrow aperture; closely holding the ferrule in a central bore of a second face plate that is magnetically attached to and kinematically aligned with the first face plate so that the narrow aperture is axially aligned with and immediately adjacent the fiber endface; and wherein the light passes through the narrow aperture and is incident upon the end face of the optical fiber with sufficient intensity to substantially polish the end face.
Additional features and advantages are set forth in the Detailed Description that follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the embodiments as described in the written description and claims hereof, as well as the appended drawings. It is to be understood that both the foregoing general description and the following Detailed Description are merely exemplary, and are intended to provide an overview or framework to understand the nature and character of the claims.
The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the Detailed Description serve to explain principles and operation of the various embodiments. As such, the disclosure will become more fully understood from the following Detailed Description, taken in conjunction with the accompanying Figures, in which:
Reference is now made in detail to various embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, the same or like reference numbers and symbols are used throughout the drawings to refer to the same or like parts. The drawings are not necessarily to scale, and one skilled in the art will recognize where the drawings have been simplified to illustrate the key aspects of the disclosure.
The claims as set forth below are incorporated into and constitute part of this Detailed Description.
Cartesian coordinates are shown in some of the Figures for the sake of reference and are not intended to be limiting as to direction or orientation.
In the discussion below, the term “magnetic” when describing a “magnetic feature” or a “magnetic element” can mean that the feature or element is made of either a magnetized material or a magnetizable material, such as a ferromagnetic material.
With this in mind,
The close-up inset 11 of
Consequently, after the coarse polishing step, end face 104 needs to be further polished to eliminate or minimize the scratch marks and other defects. However, this needs to be accomplished without substantially changing the protrusion distance DP. This is accomplished in one example using an optical fiber processing tool 200 (introduced and discussed below; see
Optical Fiber Processing Tool with Ferrule Holder
An example tool 200 includes a housing 210 having a central axis AH, a front end 212, a back end 214, an outside surface 218 and an interior 220. In an example, ferrule holder 300 is located at the front end 212 of housing 210. In an example, housing 210 is sized so that tool 200 can be hand-held by a user, such as a field technician.
The tool 200 includes a light source system 240 arranged in interior 220 along housing central axis AH and adjacent or towards housing back end 214. Light source system 240 generates light 242 having an operating wavelength suitable for processing (e.g., polishing by heating or melting) end face 104 of optical fiber 100. The light source system 240 can include a laser, such as a quantum cascade laser, vertical-cavity surface-emitting laser or VCSEL, a diode laser (i.e., a semiconductor laser), etc.
An optical system 250 that can include one or more optical elements (e.g., lens elements, mirrors, gratings, filters, beam splitters, etc.) is operably arranged between light source system 240 and housing front end 212. The optical system 250 is configured (and in an example is adjustable) to direct light 242 from the light source system to end face 104 of fiber 100. In an example, light 242 is made convergent or is otherwise focused by optical system 250 to form focus spot FS (see
With reference to
As best seen in
In an example, inner surface 332 of conical bore 330 is smooth, and further in the example is highly reflective (e.g., greater than 90% reflective, or greater than 95% reflective). In an example, inner surface includes a reflectivity coating (not shown) to provide optimum reflection for the operating wavelength or wavelengths of light 242 from light source system 240.
In an example, first face plate 310 includes at least one first magnetic feature 350. In an example, the at least one first magnetic feature 350 is constituted by one or more magnetic elements 352 operably disposed at or near front side 312 and symmetrically arranged about central axis AX1. In one example, two first magnetic elements 352 are employed, while in other examples three or four first magnetic elements are employed. In another example, the at least one first magnetic feature 350 is constituted by at least a portion of body 311 being magnetic or being made of a magnetizable (e.g., ferromagnetic) material.
The first face plate 310 further includes a plurality of first kinematic alignment features 360 disposed on or in front side 312, or formed in front side 312. In an example, the first kinematic features 360 are symmetrically arranged about central axis AX1. In an example, the first kinematic alignment features 360 include first alignment elements 362 such as spheres or balls or portions of a sphere, or bumps or protrusions that extend from front side 312. In an example, three first kinematic alignment features 360 are employed.
Also in an example, first face plate 310 can be formed as a part of (e.g., integrally with) tool 200 or can be configured as a separate piece to be added on to the front end 212 of the tool. In an example, first face plate 310 is precision mounted to or fixed or integrally fabricated with the front end 212 of housing 210 of tool 200 so that conical bore 330 and aperture 334 are precisely aligned along central axis AX and with optical system 250 and light source system 240. This allows for good alignment of the light source 240, optical system 250 and aperture 334 to be maintained when tool 200 is deployed in the field.
The second face plate 410 includes a central axis AX2, a body 411 and a generally planar front side 412, an opposite and generally planar back side 414, and top and bottom sides 416. Note that in the embodiment of
The second face plate 410 also includes at least one second magnetic feature 450, such as at least a portion of body 411 being magnetic or magnetizable (see, e.g.,
In another example such as shown in
Also in an example, one of the first and second magnetic elements 352 and 452 can be magnetic while the other can be a ferromagnetic material, i.e., the first and second magnetic elements 352 and 452 do not need to both be magnetic. This is because a ferromagnetic material becomes temporarily magnetized when subjected to the magnetic field. Some ferromagnetic materials (e.g., iron) can become permanently magnetized when subjected to a magnetic field. Also in an example, some of the magnetic elements 352 and/or 452 can be magnets while others can be magnetizable (e.g., made of a magnetizable material). In an example, a single magnetic element in the form of a ring or annulus can be employed. In an example, magnetic features 350 and 450 can each include alignment features (not shown) that facilitates alignment of the first and second face plates 310 and 410 when they are operably interfaced.
In another example, both first and second face plates 310 and 410 can be magnetic, or one face plate can be magnetic while the other face plate can be made of a ferromagnetic or otherwise magnetizable material. An advantage of using discrete magnetic elements 352 and/or 452 is that the remainder of the face plate body 311 or 411 can be made of a lightweight material, such as plastic, molded polymer, aluminum, etc.
The second face plate 410 further includes a plurality of second kinematic alignment features 460 disposed on or in front surface 412. The second kinematic alignment features 460 are complementary to the first kinematic alignment features 360 so that they can operably engage or otherwise operably make mechanical contact. The second kinematic alignment features 460 are arranged so that they axially align with and make mechanical contact the first kinematic alignment features 360 when the the second face plate is operably aligned with and engaged with first face plate 310, with central axes AX1 and AX2 of the respective first and second face plates being substantially co-axial with each other and with the central axis AX of ferrule holder 300.
In an example, second kinematic alignment features 460 comprise second alignment features 462, such as grooves formed in front surface 412 as shown in
In an example, second face plate 410 includes a connector guide 470 at front side 412. The connector guide 470 defines an opening 472 sized to receive and closely accommodate and otherwise support at least the front-end portion of connector housing 14 of connector 10 so that ferrule 20 of the connector aligns with and closely resides within central bore 430 so that fiber end face 102 is in a position to be processed by light 242 from tool 200.
The respective bodies 311 and 411 of first and second face plates 310 and 410 can be made of molded polymer and can include metal portions added thereto, including magnetic elements 352 and/or 452, or other magnetic features 350 and 450, as well as modular parts that define the conic bore 330 and the central bore 430. The respective bodies 311 and 411 can also be formed to include first and second kinematic alignment elements 362 and 462.
In practice, multiple second face plates 410 are fabricated, each with a different sized central bores 430 so that the appropriate second face plate can be used with tool 200, depending on the size (e.g., diameter d20) of ferrule 20 used in optical fiber connector 10.
As noted above, tool 200 is used to process the fiber end face 104 as part of a tool assembly 201. When performing processing of fiber end face 104 using tool 200, first and second face plates 310 and 410 are arranged (i.e., interfaced) with the front side 312 of the first face plate confronting the back side 414 of the second face plate. The central axes AX1 and AX2 are substantially coaxial with each other and with the central axis AX of the fiber holder 300 so that the respective first and second magnetic features 350 and 450 are operably aligned and magnetically engage, and the respective first and second kinematic alignment features 360 and 460 are aligned and come into mechanical contact. The ferrule 20 of connector 10 resides within the central bore 430, with the ferrule front-end surface 23 protruding slightly from the back side 414 of the second face plate 410.
Because central bore 430 and conical bore 330 are each centered on central axis AX, and because central axes AX1 and AX2 are substantially coaxial, the fiber end face 104 is axially aligned with aperture 334 of the conical bore and resides in close proximity thereto. The conical bore 330 and its reflective inner surface 332 can serve as a guiding taper that directs light 242 to aperture 334. Thus, even if there is a small directional error for light 242 coming from optical system 250, the light will be funneled to aperture 334 via reflection from inner surface 332 of conical bore 330. In an example, most if not all of the reflections from reflective inner surface are at a grazing incidence, which is known in the art to have a high reflectance, especially from a smooth surface.
The use of first and second magnetic features 350 and 450 to magnetically engage and keep the the first and second face plates 310 and 410 pressed together allows the second face plate to be easily removed from the first face plate. This in turn allows for a different second face plate 410 having a different sized central bore 330 to be exchanged for the original second face plate of ferrule holder 300. Meanwhile, the first and second kinematic alignment features 360 and 460 provide for precise mechanical alignment of fiber end face 104 with aperture 334 when the first and second faceplates 310 and 410 are magnetically engaged and the kinematic alignment features come into contact. This ensures that fiber end face 104 substantially coincides with focus spot FS formed by tool 200.
In an example, the alignment between the first and second faceplates 310 and 410 is in the range from 5 microns to 20 microns for a lateral offset and in the range from about 50 microns to 150 microns for a longitudinal offsets. In another example, the alignment is 10 microns or better for a lateral offset and 100 microns or better for a longitudinal offset.
Because light 242 is directed toward (e.g., focused substantially at) aperture 334, the focus spot FS will substantially coincide with the fiber end face 104, which is located immediately adjacent aperture 334 of conical bore 330. Furthermore, as noted above, some of light 242 can reflect from the reflective inner surface 332 of conical bore 330 and be directed through aperture 334, thereby making efficient use of the light and further contributing the intensity of focal spot FS.
The aperture 334 associated with conic bore 330 (see, e.g.,
Whenever the first and second face plates 310 and 410 of
The ferrule holder 300 disclosed herein has a number of advantages. One advantage is that it is configured to accommodate different size ferrules 20 used in different connectors 10 by being able to exchange one second face plate 410 for another having a different central bore diameter. Another advantage is that the ferrule holder 300 is configured so that the second face plate 410 can be removed manually and quickly from the first face plate 310 because a magnetic force is used to attach the two face plates. This is important because in an example, the entire connectorization process (including fiber end face processing) is preferably carried out in the field within about two minutes or so per connector. Another advantage is that the first and second kinematic alignment features 360 and 460 provide for the precise lateral and longitudinal alignment required when the first and second face plates 310 and 410 are interfaced so that the processing of fiber end face 104 is efficient and does not need to be repeated.
Another advantage is that the first and second face plates 310 and 410 can be formed using a molding process that offers low cost as well as precision construction. The molding process also allows for modular parts to be added to each of the face plates, such as modular metal members that define the central bore 430 that support ferrule 20 or the conical bore 330 that guides light toward aperture 334 and to fiber end face 102.
Another advantage is that the conical bore 330 of first face plate 310 can guide or funnel light 242 toward aperture 334 even if there is an offset in light beam 242 relative to the tool central axis AX. The tool 200 typically has a limited pointing angle accuracy, e.g., of about 1 degree or so, which leads to a corresponding lateral misalignment of the focused light 242 with respect to aperture 334 of conical bore 330. Here, conical bore 330 can serve to guide any misdirected light 242 through aperture 334 by grazing-incidence reflection from the inner wall 332. Because grazing-incidence reflection has a high reflectivity, the optical loss due to reflection is negligible. Further, because the fiber end face 104 is located immediately adjacent aperture 334, the intensity of focus spot FS at the fiber end face will not be substantially reduced by the small angular misalignments of light beam 242.
It will be apparent to those skilled in the art that various modifications to the preferred embodiments of the disclosure as described herein can be made without departing from the spirit or scope of the disclosure as defined in the appended claims. Thus, the disclosure covers the modifications and variations provided they come within the scope of the appended claims and the equivalents thereto.
This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Ser. No. 62/198,821, filed on Jul. 30, 2015, the content of which is relied upon and incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62198821 | Jul 2015 | US |
