Optical waveguides – With disengagable mechanical connector – Optical fiber/optical fiber cable termination structure
Reexamination Certificate
1999-12-28
2002-10-15
Kim, Ellen E. (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber/optical fiber cable termination structure
C385S056000, C385S070000
Reexamination Certificate
active
06464408
ABSTRACT:
FIELD OF INVENTION
The present invention relates to the field of fiber optics, and more specifically relates to improvements in connector components and methods for making those improved components.
BACKGROUND OF THE INVENTION
Fiber optic communication systems send messages in the form of pulses of light along thin strands of transparent material, referred to as fiber optics. One common application for such systems is in carrying digital data between computers in a network or between portions of a large computer. In a typical system, a device referred to as an optical transmitter includes a laser that emits light. The intensity of the light is varied in accordance with the information to be sent. The emitted light is focused on an end of an optical fiber so that the light is transmitted along the fiber. At the other end of the fiber, the light is directed onto a photodetector, which transforms the light into an electrical signal. The electrical signal also varies in accordance with the information being sent. A “duplex” system typically uses two fibers in parallel, and has a transmitter and a receiver at each end of the system so that information can be sent in opposite directions along the two fiber optics. The transmitter and receiver at each end typically are combined in a single device referred to as a “transceiver.” Optical communication systems can transmit data at rates many times faster than systems using electrical wires, and offer other advantages.
Typically, the optical fibers are provided in optical cables. The fibers themselves are covered by protective coatings or “sheathing.” The cable includes one or more individual sheathed fiber optics, covered by an external jacket and may also include components for protecting the cable against physical strain. To set up an optical communications system, cables of this type are connected to optical devices such as transceivers and to one another in much the same way as electrical cables are connected to electronic devices and to one another to set up an electronic system. However, connecting an optical cable requires that the individual optical fibers be precisely aligned with the mating fibers or devices. The optical fibers commonly are as small as 0.125-mm (0.005 inches) in diameter. To connect two fibers end-to-end, the mating ends should be aligned with one another within a few microns, i.e., within hundred-thousandths of an inch, and should be butted against one another with essentially no gaps. Even slight deviation from these tolerances can cause appreciable loss of light transmitted along the fibers and degradation of the signal. Likewise, when an optical cable is connected to a transceiver or other device, the fibers must be precisely positioned relative to the optical elements of the device. Optical cables are provided with devices referred to as “connectors” which can be engaged with mating connectors on other cables, or with mating features on transceivers or other devices, to align the fibers with the required precision.
One known type of fiber optic connector is a so-called “MT” type. The MT connector has a connector housing with a front end and a ferrule movably mounted in the housing. The ferrule is biased by a spring to a forward position. When the ferrule is in the forward position, a front face of the ferrule projects from the housing. A multi-fiber cable extends into the housing. The individual fibers of the cable extend through the ferrule to the front face. The front face of the ferrule, and the ends of the fibers, are polished to form a flat surface. The fiber ends are precisely located within the ferrule. The ferrule also has pin-receiving bores. A male MT-type connector has pins in these bores projecting beyond the front face, whereas a female MT connector has the bores empty. Two cables may be connected to one another by engaging male and female MT connectors with one another so that the pins of the male connector enter the pin receiving bores of the female connector. The ferrules are free to “float” or move slightly relative to the housing of the connectors and hence are brought into precise alignment with one another by the pins. Also, because each ferrules is free to move rearwardly relative to its housing against the spring bias, the ferrules can be brought into abutting, face to face contact despite tolerances in the housings. These connectors can provide the good connection between the individual fibers of the two cables, with low optical transmission losses.
One type of connector that has been proposed is referred to in the industry as an MT-RJ connector. U.S. Pat. No. 5,926,596 depicts a typical MT-RJ connector. Reference is made to the '596 patent without admission as to whether or not such patent constitutes prior art against the present invention. As shown in the '596 patent, a typical MT-RJ connector includes an exterior housing which resembles the exterior housing of the common “RJ” plug used to connect a home telephone to a wall outlet. The housing has a flexible catch on its exterior. A “ferrule” is movably mounted within the housing at a forward end of the housing, so that a forward face of the ferrule is exposed to the exterior of the housing. A spring inside the housing urges the ferrule in the forward direction. The ferrule has a pair of fiber bores for receiving two individual fibers of the cable, and a pair of pin holes for receiving alignment pins. A “male” MT-RJ connector has alignment pins permanently disposed in its alignment pin holes, whereas a “female” MT-RJ connector has empty pin holes. The connectors may be permanently installed on the ends of fiber optic cables by the cable manufacturer. The cable manufacturer positions the fibers in the fiber bores and polishes the ends of the fiber precisely flush with the front of the ferrule.
To connect two cables end-to-end, male and female connectors are inserted into opposite ends of a hollow double-ended socket so that the catches on their housing engage with the socket and the socket physically holds the housings in crude alignment with one another. The pins on the ferrule of the male connector engage the pin holes in the ferrule of the female connector, and hold the ferrules, and hence the fibers, in precise alignment with one another. The springs in the housings urge the ferrules forwardly so that the front faces of the ferrules, and hence the ends of the fibers, abut one another. Devices such as transceivers are equipped with single-ended sockets adapted to receive the housing of a connector. Such sockets are equipped with pins corresponding to the pins of a male MT-RJ connector for engaging the ferrule of a female connector so as to hold the ferrule and hence the fibers of the cable in precise alignment with the device.
Despite considerable effort devoted by the art to development of fiber optic connectors, sockets and related components, there are still needs for further improvements.
There exists a need for further improvement to the housing of an MT-RJ connector that would allow easier insertion and removal of the connector. Currently, the housing of MT-RJ connectors are quite small and do not provide adequate surface area for a technician to grasp the connector. However, any extension of the surface area of the housing or variation in shape must conform to industry standards for these connectors. A connector that is too large may interfere with neighboring connectors or sockets by limiting access to those connectors, as in a network hub or other computer systems employing fiber optics.
There is also a need to improve the latch mechanism to prevent accidental releases of the connector from the socket.
Regarding the socket, a need exists to provide a socket design that allows a technician to visually determine, or by touch, the orientation of the socket to ensure that the connector is rotated to the correct position to have proper alignment of the fiber optics. In a typical MT-RJ connector, there is only one orientation for both the connector and the socket that will properly position the fiber optics. As su
Computer Crafts, Inc.
Kim Ellen E.
Lerner David Littenberg Krumholz & Mentlik LLP
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