Optical waveguides – With disengagable mechanical connector – Optical fiber/optical fiber cable termination structure
Reexamination Certificate
1999-10-06
2001-09-25
Font, Frank G. (Department: 2877)
Optical waveguides
With disengagable mechanical connector
Optical fiber/optical fiber cable termination structure
C385S076000, C385S139000
Reexamination Certificate
active
06293710
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical connector for use with optical fibers and, more particularly, to an optical connector for use with optical fibers that has a one-piece housing.
BACKGROUND OF THE INVENTION
Optical fiber connectors are an essential part of substantially any optical fiber communication system. For instance, such connectors may be used to join segments of fiber into longer lengths; to connect fiber to active devices such as radiation sources, optical amplifiers, detectors and repeaters; or to connect fiber to passive devices such as switches and attenuators. The central function of an optical fiber connector is the maintenance of two optical fiber ends such that the core of one of the fibers is axially aligned with the core of the other fiber; and consequently, all of the light from one fiber is coupled to the other fiber. This is a particularly challenging task because the light-carrying region (core) of an optical fiber is quite small. In singlemode optical fibers the core diameter is about 8 microns where 1 micron=1 &mgr;m=10
−3
mm. Another function of the optical fiber connector is to provide mechanical stability and protection to the junction in its working environment. Achieving low insertion loss in coupling two fibers is generally a function of the alignment of the fiber ends, the width of the gap between the ends, and the optical surface condition of either or both ends. Stability and junction protection is generally a function of connector design (e.g., minimization of the different thermal expansion and mechanical movement effects). An optical fiber connector typically includes a small capillary cylinder with a glass or plastic fiber installed along its central axis. This cylinder is interchangeably referred to as a ferrule or a plug.
In a connection between a pair of optical fibers, a pair of ferrules are butted together end-to-end and light travels from one to the other along their common central axis. In this conventional optical connection, it is highly desirable for the cores of the glass fibers to be precisely aligned in order to minimize the loss of light (insertion loss) caused by the connection; but as one might expect, it is presently impossible to make routine perfect connections. Manufacturing tolerances may approach “zero,” but practical considerations such as cost, and the fact that slight misalignment is tolerable, suggest that perfection in such matters may be unnecessary.
One known design of an optical fiber connector is shown in U.S. Pat. No. 4,793,683; and its basic components comprise a precision molded plastic conical plug having an optical fiber centered therein, a compression spring disposed about a cylindrical portion of the plug, and a retention collar surrounding the plug and spring. The collar includes external threads that enable it to couple with another connector via a fixture having a precision molded alignment sleeve whose shape is best described as “biconic.” This design has been superseded by the connector shown in U.S. Pat. No. 4,934,785 which comprises a cylindrical plug, a base member that holds the plug, a compression spring, and a cap that surrounds the plug and spring. In this design, only the cylindrical plug needs to be of high precision and is typically made from a ceramic material. When joining two of these plugs together, an alignment sleeve is used which comprises a split, thin-walled cylinder made of metal, ceramic or even plastic material. This alignment sleeve need not be as precise as the above-described biconic alignment sleeve.
And while the above connectors perform satisfactorily, further improvements are desirable. For example, because of the growing acceptance of optical fiber as the transmission media of choice for television, data, and telephone (multi-media) communications, the need to provide higher density interconnection arrangements has emerged. All of the above-mentioned simplex optical connectors are constructed in such a way that the ability to stack a large number of them together is limited by the need to manually grasp both sides during insertion and removal from a receptacle or coupling device. Known duplex optical connectors, such as the one shown in U.S. Pat. No. 4,787,706, also require manual access to the opposite sides of its housing during removal from the receptacle or coupling device which precludes high density optical fiber interconnection arrays. Furthermore, it is always desirable to reduce cost while still providing a connector that is immediately acceptable to customers. With these latter desires in mind, reference is made to the art of electrical connectors where, perhaps, the most used and accepted connectors are the ones known as RJ11-type plugs/jacks that are typically used in corded telephone products. These connectors have achieved widespread acceptance because they are inexpensive, they operate reliably, and their operation is readily understood by customers. However, because of the high precision and low insertion loss requirements associated with optical interconnections (particularly between singlemode fibers), RJ11-type designs have been unacceptable for optical connectors. Examples of such electrical connectors are shown in U.S. Pat. Nos. 3,761,869 and 3,954,320.
Another known design of an optical fiber connector is disclosed in U.S. Pat. No. 5,212,752. The optical connector comprises a ferrule assembly that includes a ferrule portion having a passageway for an optical fiber and a plug frame in which the ferrule assembly is disposed. Once the ferrule assembly has been disposed in the plug frame, the plug frame is assembled within another portion of the optical connector called a grip. The plug frame may be assembled within the grip in a plurality of rotational orientations with respect to the grip in such a way that the direction of eccentricity is aligned with a key of the grip. Once the plug frame has been coupled within the grip, the optical connector may be inserted into a coupling housing. The coupling housing is configured to allow two identical optical connectors to be inserted therein to provide an optical connection between two optical fibers terminated by ferrule assemblies within the optical connectors.
One of the advantages of the optical connector disclosed in U.S. Pat. No. 5,212,752 is that when the plug frame is inserted within the grip, the optical connector is provided with good side-loading characteristics due to the design of the grip and the manner in which the plug frame couples with the grip. One of the disadvantages associated with this optical connector is that, once the grip is installed, it cannot be removed. This is a disadvantage if, for some reason, tuning must be re-adjusted. The coupling housing is adapted to receive the grip. Although it may be possible to insert the plug frame into the coupling housing even when the plug frame is not disposed within the grip, removing the plug frame from the coupling housing once it has been inserted would be difficult, if not impossible without a special tool, due to the fact that there is no mechanism for detaching the plug frame from the coupling housing once it has been inserted. Furthermore, if the plug frame is not disposed within the grip, the side-loading characteristics of the optical connector are diminished.
Another disadvantage of this optical connector is that it is possible for certain components of the optical connector to be improperly assembled during the assembly process. This can be seen with reference to FIG. 2 of U.S. Pat. No. 5,212,752. A cable retention member is adapted to receive a barrel and spring of the ferrule assembly during the assembly process. The cable retention member includes a collar which is chamfered such that when the cable retention member is inserted within the plug frame, the side portions of the collar are received within windows of the plug frame. However, the plug frame has a cylindrical, or annular, opening that does not include any type of keying mechanism for ensuring that the side
Driscoll Elizabeth J.
Lampert Norman Roger
May John Francis
Nielson Jeffrey Dale
Subh Naif Taleb
Font Frank G.
Lucent Technologies - Inc.
Punnoose Roy M
Thomas, Kayden, Hortsemeyer & Risley, LLP
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