Optical waveguides – With disengagable mechanical connector – Optical fiber/optical fiber cable termination structure
Reexamination Certificate
1999-09-07
2002-07-09
Ullah, Akm E. (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber/optical fiber cable termination structure
Reexamination Certificate
active
06416236
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to ferrules for fiber optic connectors and associated fabrication methods and, more particularly, to ferrules designed to facilitate fiber-to-fiber contact once a pair of fiber optic connectors have been mated, as well as associated fabrication methods.
BACKGROUND OF THE INVENTION
Optical fibers are being increasingly utilized for a variety of applications including data transmission and the like. In order to interconnect the optical fibers, the fiber optic connectors that are typically mounted upon the opposed end portions of the optical fibers are appropriately mated. While the optical connections established by the mating of a pair of fiber optic connectors is generally quite good, some modern applications are placing increased performance and reliability demands upon optical fiber networks. In this regard, the optical connections established by mating a pair of fiber optic connectors preferably have relatively low attenuation and a small return loss.
In order to decrease the attenuation and return loss introduced by a fiber optic connector, conventional fiber optic connectors are designed such that fiber-to-fiber contact is established between the optical fibers upon which the respective fiber optic connectors are mounted. For example, fiber-to-fiber contact is preferably established between each optical fiber of a first fiber optic cable upon which a first fiber optic connector is mounted and a respective optical fiber of a second fiber optic cable upon which a second fiber optic connector is mounted once the first and second fiber optic connectors have been mated.
Unfortunately, the front faces of the ferrules of most fiber optic connectors have angular errors and are therefore not completely perpendicular to the optical fiber axes of the end portions of the optical fibers upon which the ferrules are mounted. In addition, the front faces of the ferrules of most fiber optic connectors are not perfectly flat. As such, the end portions of the optical fibers that are flush with the front face of the ferrule of a conventional fiber optic connector may not establish fiber-to-fiber contact with the corresponding optical fibers of another fiber optic connector since some portions of the front face of the ferrules may actually protrude outwardly beyond the end portions of the optical fibers. By protruding outwardly beyond the end portions of the optical fibers, portions of the front faces of the ferrules may contact before the optical fibers make fiber-to-fiber contact, thereby effectively preventing fiber-to-fiber contact. Likewise, dirt or other particles that settle upon the front face of the ferrule may prevent fiber-to-fiber contact in instances in which the end portions of the optical fibers are flush with the front face.
In order to overcome these problems and to provide for fiber-to-fiber contact, notwithstanding angular errors and dirt accumulation, the end portions of the optical fibers upon which the ferrules are mounted generally protrude or extend slightly beyond the front face of the respective ferrule. In this regard, the end portions of the optical fibers generally protrude by between about 500 nanometers and about 1,000 nanometers beyond the front face of the respective ferrule. As such, fiber-to-fiber contact can be established even if the front face has angular errors or if dirt or other particles have accumulated upon the front face.
In order to mount a fiber optic connector such that the end portions of the optical fibers extend beyond the front face of the ferrule by a predetermined protusion distance, the optical fibers are typically inserted through and epoxied or otherwise secured within the optical fiber bores defined by the ferrule such that the end portions of the optical fibers extend beyond the front face of the ferrule by more than the desired protrusion distance. The end portions of the optical fibers are then polished until the end portions of the optical fibers protrude beyond the front face of the ferrule by the desired protrusion distance. Upon mating a pair of fiber optic connectors, the end portions of the optical fibers that protrude beyond the front faces of the respective ferrules will generally make fiber-to-fiber contact.
Unfortunately, the fiber-to-fiber contact established by the mating of a pair of conventional fiber optic connectors having protruding optical fibers imparts forces to the optical fibers that may exceed the sheer stress of the epoxy that otherwise secures the optical fibers within the optical fiber bores of the ferrule in some circumstances. If the forces exerted upon an optical fiber exceed the sheer stress of the epoxy, the optical fiber will generally be pushed back into the ferrule such that the end portion of the optical fiber is flush with the front face of the ferrule or recessed within the respective optical fiber bore relative to the front face of the ferrule.
The likelihood that the epoxy bond will be broken typically increases as the temperature rises. In this regard, most ferrules are formed of a thermoset material that expands to a much greater degree than the optical fibers in response to heating. As such, the fit of the optical fibers within the respective optical fiber bores is loosened as temperatures increase such that the optical fibers are even more likely to be pushed back into the respective optical fiber bores defined by the ferrule.
In instances in which the optical fibers are pushed back into the respective optical fiber bores defined by the ferrules, intermateability problems may arise if the respective fiber optic connector is subsequently mated with another fiber optic connector. For example, a fiber optic connector in which the optical fibers have been pushed back into the respective optical fiber bores defined by the ferrule may fail to establish fiber-to-fiber contact in instances in which the fiber optic connector is decoupled and then mated with another fiber optic connector. As such, the attenuation and return loss of the resulting optical connection would be greatly increased relative to optical connections having fiber-to-fiber contact.
SUMMARY OF THE INVENTION
A ferrule is therefore provided that facilitates fiber-to-fiber contact without requiring the end portions of the optical fibers to protrude beyond the front face of the ferrule. Accordingly, the ferrule reduces the forces that are placed upon the optical fibers and prevents the optical fibers from being pushed back into the respective optical fiber bores defined by the ferrule. As such, the ferrule of the present invention serves to maintain fiber-to-fiber contact even in instances in which the fiber optic connector is decoupled from an original fiber optic connector and remated with another fiber optic connector. By maintaining fiber-to-fiber contact, the ferrule of the present invention also serves to maintain the attenuation and return loss of the resulting optical connection at a relatively low level, as desired in many applications.
The ferrule of the present invention includes a ferrule body having opposed front and rear faces. The ferrule body also defines at least one optical fiber bore extending between the front and rear faces and adapted to receive an optical fiber. In addition, each optical fiber bore opens through a medial portion of the front face of the ferrule body. Advantageously, the medial portion of the front face through which the optical fiber bores open protrudes outwardly beyond at least some peripheral portions of the front face. Although the medial portion can protrude outwardly beyond at least some peripheral portions of the front face by different amounts, the medial portion of one advantageous embodiment protrudes outwardly by about 1-5 millimeters relative to at least some peripheral portions of the front face.
Since only the medial portion of the front face of the ferrule, and not the entire front face, will make contact as a pair of fiber optic connectors are mated, fiber-to-fiber contact can be established between the optical fiber
Childers Darrell R.
Knecht Dennis M.
Luther James P.
Theuerkorn Thomas
Siecor Operations LLC
Ullah Akm E.
LandOfFree
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