Optical waveguides – With disengagable mechanical connector – Structure surrounding optical fiber-to-fiber connection
Reexamination Certificate
2001-08-23
2002-09-24
Sanghavi, Hemang (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Structure surrounding optical fiber-to-fiber connection
C385S072000, C385S078000
Reexamination Certificate
active
06454464
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 use in making connections in fiber optic systems, to loopback devices for use in testing optical devices, and to methods of using such devices.
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 optical fibers. 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 fibers. 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 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 create more economical connectors. Anything which can be done to eliminate parts and assembly expense in the connector and in the process for attaching the connector to the cable at the factory would be desirable.
It would be desirable to provide a field-installable connector which can be attached to a raw, newly cut cable end by a technician in the field. Such a connector should be compatible with the factory-prepared connectors and with the sockets used for such connectors. Moreover, such a field-installable connector should fit within the space available for installation according to industry standards. Such a connector should be relatively easy for the technician to install and should provide a good optical connection.
There are also needs for improvement in loopback testing of optical transceivers. As well known in the art, many optoelectronic components such as network hubs and interfacing devices incorporate numerous optical transceivers. Each transceiver has a transmitter arranged to send optical signals and a receiver arranged to receive the optical signals and convert the same back to electronic signals.
The transceivers commonly are tested by a “loopback” test. In a loopback test, a single fiber is connected to the transmitter and receiver of a single transceiver so that light sent by the transmitter is received by the receiver. If the transceiver can send signals to itself this manner, then both the transmitter and receiver incorporated in the transceiver are operational. Such a test can be conducted by connecting both ends of a single fiber to a standard MTRJ connector to form a local loop and inserting that connector into the socket associated with a transceiver. Several problems are encountered using this approach. The optical power appearing at the receiver may be too great for the receiver to handle. Typically, the transmitter is designed to send an optical signal strong enough to propagate over tens, hundreds or thousands of meters of fiber, whereas the fiber in a local loop may be a meter or less in length. Thus, the signal reaching the receiver from the transmitter over the local loop is far stronger than the receiver can accommodate. Also, where numerous transceivers incorporated in a single assembly are to be tested, connectors with such local loops must be inserted into sockets associated with all of these transceivers. All of these loops form a tangle of fibers overlying the surface of the assembly and making it
Computer Crafts, Inc.
Lerner David Littenberg Krumholz & Mentlik LLP
Rojas Omar
Sanghavi Hemang
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