Patent Application
20060105684
1. Field of the Invention
The present invention is directed to an apparatus and method for polishing terminated optical fiber connectors, in particular, field terminable ferrule-based optical connectors having a thermoplastic adhesive.
2. Related Art
Mechanical optical fiber connectors for the telecommunications industry are known. In recent years, an emphasis has been placed on the use of small form factor (SFF) optical fiber connectors. For example, LC (“Lucent Connectors”) optical-type connectors have been described in U.S. Pat. Nos. 5,481,634; 5,719,977; and 6,318,903. Other SFF connectors include MU-type and LX5-type optical connectors. These connectors are used for joining optical fiber segments at their ends and for connecting optical fiber cables to active and passive devices. The LC form factor is about 50% smaller (e.g., with a ferrule polishing area of about 0.5 mm2) than the form factors for other conventional optical connectors, such as ST, FC, and SC (e.g., with a ferrule polishing area of about 3.2 mm2), which can be referred to as large form factor (LFF) connectors.
Commercially available SFF connectors are not well suited for field installations. Conventional adhesive materials include thermosets, anaerobic and UV curing adhesives, as well as two-part epoxies and acrylates. For example, LC connectors typically use epoxy-based resins (e.g., two part epoxies) for fiber retention within the ferrule portion of the connector. These epoxies require about 10 to 15 minutes to heat cure after application. Once set, the fiber cannot be removed from the ferrule without breaking the fiber, thus making resetting of the optical fiber in the ferrule impractical.
In addition, because of their small size, most SFF connectors utilize 50% reduced diameter ceramic ferrules for fiber alignment, resulting in about six times reduction in available polishing area. Due to this reduced polishing area, it is more difficult to control the important parameters of SFF connector ferrule geometry, namely the radius of curvature (or “ROC”), the fiber height, and the (radius) apex offset.
According to a first aspect of the present invention, a polishing apparatus for an optical fiber connector that includes an optical fiber ferrule and a connector housing, comprises a polishing puck having an aperture to permit passage of the ferrule therethrough and a mount to hold the connector housing at a predetermined angle. The polishing apparatus further includes a stabilizer having a first portion mountable on the polishing puck to provide a grip separate from the connector housing. The polishing apparatus further includes a weighting device, at least a portion of which is disposed in the stabilizer, to provide a direct force on the connector housing.
According to another embodiment, a method of polishing an optical fiber connector that includes an optical fiber ferrule and a connector housing, comprises providing the polishing apparatus described above. The stabilizer is mounted on the polishing puck. The method further includes disposing the optical fiber connector in the mount, wherein at least a portion of the ferrule extends through an aperture in the polishing puck. The weighting device is then placed in the stabilizer, where a portion of the weighting device directly contacts at least a portion of the connector housing. The polishing apparatus is then translated across at least one polishing surface for a predetermined amount of polishing strokes.
The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and the detailed description that follows more particularly exemplify these embodiments.
The present invention will be further described with reference to the accompanying drawings, wherein:
While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.
The present invention is directed to an apparatus and method for polishing terminated optical fiber connectors, in particular, field terminable ferrule-based optical connectors having a thermoplastic adhesive.
According to an exemplary embodiment of the present invention, a polishing device or apparatus, such as shown in
Polishing puck 110 further includes a connector mount 114 that is configured to receive a SFF connector, such as an LC-type connector 10, having a fiber connector housing 30 and having an optical fiber terminated in the connector ferrule 14. Typically, ferrule 14 is formed from a ceramic, glass, plastic, or metal material to support an optical fiber inserted therein. In an exemplary embodiment, the SFF connector 10 is preloaded with a thermoplastic adhesive that can rapidly soften at a sufficient elevated temperature and that can rapidly harden when exposed to ambient (e.g., room) temperature. For example, the thermoplastic adhesive utilized can be a thermoplastic resin, such as described in U.S. Pat. No. 4,984,865, incorporated by reference herein in its entirety. In addition, the thermoplastic adhesive can be an ultra high temperature (UHT) thermoplastic adhesive material which provides a high softening point and that is capable of satisfying environmentally stringent Telcordia GR-326 specifications. The construction of an exemplary LC-type optical connector, other suitable adhesives and the pre-loading of an exemplary LC-type optical connector are further described in commonly-owned and co-pending U.S. patent application Ser. No. 10/811,437, incorporated by reference herein in its entirety. An exemplary method of terminating a fiber in a SFF connector is described in a commonly-owned and co-pending U.S. Patent Application entitled “Field Termination Apparatus and Method For Small Form Factor Optical Connectors with Thermoplastic Adhesive” (Attorney Docket No. 60093US002), incorporated by reference herein in its entirety.
Alternatively, in other embodiments, the connector may be any SFF or LFF connector. In additional alternative embodiments, the fiber terminating process may be accomplished utilizing a thermoplastic adhesive or a thermoset, e.g., a cyanoacrylate, an anaerobic and/or UV curing adhesive, or a two-part epoxy or acrylate.
Mount 114 provides a snug, slidable fit to hold connector 10 at a predetermined angle, e.g., 90° with respect to the polishing surface or at a small angle from perpendicular (about 5° to about 12°) for angle polished connectors. When in use, a terminated optical fiber connector 10 is placed in mount 114, so that a portion of ferrule 14 of the optical fiber connector 10 extends through aperture 113 of puck 110. The bottom surface 115 of puck 110 can then be moved or slid across an appropriate polishing media (not shown) so that the fiber and ferrule end face 15 is suitably polished (e.g., flat or angled), within permissible/compliant ROC and apex offset tolerances. Conventional LC polishing pucks suitable for the apparatus of the present invention are commercially available from optical connector vendors such as OFS (Georgia, USA).
Polishing apparatus 100 further includes a stabilizer or grip 120. Stabilizer 120 includes a body 124 that is constructed of a rigid material, such as a metal or molded polymer, which is mountable on polishing puck 110. As shown in the exemplary embodiment of
As shown in
Stabilizer 120 is configured to provide a field technician (who performs polishing in the field) with a stable gripping surface during the polishing procedure, so that force is transferred substantially uniformly to the polishing puck 110, to help maintain ferrule/end face surface 15 in a substantially flat orientation on the polishing surface or media. In addition, outer surface 126 of stabilizer 120 can include a textured surface 127 to provide for easier gripping by a field technician. Stabilizer 120 can have any convenient shape for gripping. For example, as shown in
Conventional field mountable SFF connectors can be supplied with a flat ferrule end face or a ferrule having a pre-radius. During polishing of a SFF connector ferrule with a flat end face, a ferrule radius can begin to form. However, as the investigators have determined, utilizing conventional polishing pucks and polishing procedures (such as those utilized with LFF connectors, which have much larger polishing areas, and can undergo many more polishing strokes without significantly changing ROC and apex offset) can lead to the creation of a very small radius, of less than 7 mm, that is offset from the fiber core by more than 50 μm. For example, SFF connectors, which have a ferrule polish area about six times less than the polish area of LFF connectors, can be readily polished in 50 strokes or less, in which ROC may reduce to 4-6.5 mm, and apex offset can drift to 75-100 μm.
These example dimensions can fall outside of industry acceptable standards, such as Telcordia GR 326 (Issue 3, core) specifications, which require a ROC of 7-25 mm, an apex offset of 0-50 μm, and a fiber height (i.e., distance of fiber tip to ferrule end face) of +50 nm to −125 nm (depending on the radius). Thus, for consistent field polishes that yield standards-compliant connectors, the polishing apparatus 100 of exemplary embodiments of the present invention is configured to allow the field technician to impart a more uniform (and/or less random) force on the polishing puck 110 during field polishing. The polishing apparatus 100 of exemplary embodiments can also reduce technician bias and reduce connector to connector polishing variations and/or technician to technician polishing variations.
As shown in
As shown in
In addition, in this exemplary embodiment, the weighting device 130 can be formed to have a center of gravity near, at or below the contact portion 30A of the connector housing to provide even more stability. For example, as shown in
When in use, the weighting device 130 can be substantially disposed within the stabilizer 120, such as illustrated in
As the investigators have determined through machine polishing, a force of about 0.25 lbf per connector with a polishing pad having 70-72 durometer (Shore A) can be applied to an LC-type connector. Preferably, from about 0.1 lbf (0.44 N) to about 0.5 lbf (2.22 N) depending on the durometer of the polishing pad can be applied to an LC-type connector having a pre-radiused ferrule. A flat ferrule may require additional polishing strokes to yield a ferrule ROC of about 8 mm-14 mm. The application of more weight can yield a smaller ROC and the application of less weight can yield a larger ROC. Thus, according to the present invention, weighting device 130 can be designed to provide the appropriate amount of force to the connector during polishing, depending on the desired application and polishing pad used beneath polishing media.
In addition, according to an alternative embodiment, the weighting device can be designed as a spring loaded mechanism, either separate from or integral with the stabilizer, to provide a pre-set force to the connector housing during polishing.
Thus, as would be apparent to one of ordinary skill in the art, the components of polishing apparatus 100 can vary in shape and size. For example,
A polishing-yield comparison test was performed on two groups of LC connectors having terminated fibers (single mode and multi-mode fibers were utilized in each test group) with a thermoplastic (or Hot Melt) adhesive, available from 3M Company, St. Paul. Minn. The hand-polishing method included one or more of the following steps:
As shown in Table 1, a first group of LC-Connectors having pre-radiused ferrules ranging from 9-16 mm were polished. The LC connectors of this group were terminated using a thermoplastic adhesive, such as described in commonly-owned and co-pending U.S. patent application Ser. No. 10/811,437, incorporated by reference above. The LC connector fiber terminated ferrules were polished (as per the above method) using only a polishing puck, similar to polishing puck 110 shown in
Table 2 below displays the average results a second group of LC connectors having pre-radiused ferrules ranging from 9-16 mm. The second group of LC connectors, also terminated using a thermoplastic adhesive, were polished (as per the above method) using a polishing apparatus similar to polishing apparatus 100 shown in
Thus, the above polishing method and polishing apparatus of the present invention can be used to enable manual, field polishing technicians to achieve predictable high quality and yield performance. This method and apparatus can aid installers of fiber optic networks, such as Local Area Networks (LANs) or Premise buildings, for the field termination of small form factor connectors, such as the exemplary LC connectors described above. In addition, the above method and apparatus can be utilized for the field polishing of flat or pre-radiused ferrule-base large form factor connectors, such as ST connectors, FC connectors, and SC connectors. The reliability of the above method and apparatus can reduce the need to use costly interferometers to measure the ferrule geometry, as installers are usually blind to the geometry results of a field polish.
The present invention should not be considered limited to the particular examples described above, but rather should be understood to cover all aspects of the invention as fairly set out in the attached claims. Various modifications, equivalent processes, as well as numerous structures to which the present invention may be applicable will be readily apparent to those of skill in the art to which the present invention is directed upon review of the present specification. The claims are intended to cover such modifications and devices.
