Optical waveguides – With optical coupler – Plural
Reexamination Certificate
2000-12-26
2003-02-18
Sircus, Brian (Department: 2839)
Optical waveguides
With optical coupler
Plural
C385S031000, C439S502000
Reexamination Certificate
active
06522804
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates to fiber optic cable systems and, more specifically, to a fiber optic drop for providing continuous, uninterrupted fiber optic service from a service provider central office to a subscriber premises.
2. Definitions
The following definitions and descriptions are provided to clearly define the intended meanings of certain terms used throughout this application.
1. Primary fiber optic strand—a fiber optic strand that is connected to an electronic device in the central office of a service provider. A primary fiber optic strand supports a single fiber optic electronic device in the central office and up to 32 different fiber optic electronic devices external to the central office, i.e., one fiber optic strand can be split into 32 different strands for connection to 32 different fiber optic electronic devices.
2. Fiber optic cable—a cable that contains a multiple number of fiber optic strands.
3. Distribution splitter—a splitter used in the intermediate portion of a deployment network, where fiber optic strands are separated and directed to different locations. Distribution splitters divide a single fiber optic strand into multiple numbers of strands.
The number of splitters in a network depends on the total number of strands in the fiber optic cable leading into a central office. The total number of strands in the cable is at least equal to the number of fiber optic electronic devices connected at the central office.
For purposes of describing the present invention, it is understood that, although only two levels of splitting are described herein, any number of levels could be used to divide a primary fiber optic strand into multiple strands. In fact, instead of using distribution splitters and local terminals, a single primary fiber optic strand could go directly to a local terminal with a 1×32 splitter, in which case the local terminal splits the strand into 32 separate strands which may be connected to 32 individual fiber optic drops leading to one or more subscriber premises.
4. Secondary fiber optic strand—the strands that are separated from a primary fiber optic strand. When a primary fiber optic strand goes through a first distribution splitter, the separated strands are referred to as secondary fiber optic strands. The number of secondary fiber optic strands in the network depends upon the configuration of the splitter, e.g., a 1×8 splitter would split a primary fiber optic strand into eight secondary fiber optic strands. Through each set of splitters, the number of fiber optic electronic devices supported becomes progressively smaller until there is only one device per strand.
5. Splice case or splicer—case that attaches to a fiber optic cable and separates one or more fiber optic strands from the cable to be diverted away from the cable in a different direction. A splice case contains fiber optic splices or permanent connections between two fiber optic strands.
6. Local terminal—an outside plant cable terminal used in the prior art for terminating one or more fiber optic strands near one or more subscriber premises for connection to copper wire drops into each subscriber premises. Under the current invention, a local terminal includes a splitter-terminal apparatus that splits a final fiber optic strand into multiple strands, each fitted with a connectorized termination for joining one fiber optic drop.
7. Fiber optic drops—small fiber optic cables that contain one or two fiber optic strands connecting, for example, the local terminal to a fiber optic interface device or a fiber optic interface device to an optical network terminal.
8. Connectorized termination—a fitting for a fiber optic cable or strand that facilitates quick connections between two different cables or strands. The fittings are typically plastic connectors with a male and female side, e.g., SC connectors.
9. Pigtail—in the context of a splitter-terminal, pigtail refers to a short length of jacketed fiber optic strand permanently fixed to a component at one end and a connectorized termination at the other end, such that the pigtail provides a flexible fiber optic connection between the component and the connectorized termination. When used in the context of a fiber optic drop, pigtail refers to a short length of jacket (the fiber optic strand is described separately) fixed to a component (sheath) at one end and a connectorized termination at the other end.
BACKGROUND OF THE INVENTION
The telecommunications industry has long recognized the many advantages fiber optic cabling and transmission devices hold over traditional copper wire and transmission systems. Fiber optic systems provide significantly higher bandwidth and greater performance and reliability than standard copper wire systems. For example, fiber optic systems can transmit up to 10 gigabits per second (Gbps), while copper lines transmit at typically less than 64 kilobits per second (Kbps). Optical fibers also require fewer repeaters over a given distance to keep a signal from deteriorating. Optical fibers are immune to electromagnetic interference (from lightning, nearby electric motors, and similar sources) and to crosstalk from adjoining wires. Additionally, cables of optical fibers can be made smaller and lighter than conventional copper wire or coaxial tube cables, yet they can carry much more information, making them useful for transmitting large amounts of data between computers and for carrying bandwidth-intensive television pictures or many simultaneous telephone conversations.
Despite the many advantages, extremely high installation costs have discouraged network providers from providing continuous fiber optic networks extending from central office facilities all the way to subscriber premises. As used herein, “fiber to the home” (FTTH) refers to this continuous deployment of fiber optic lines directly to subscriber premises. On the main distribution lines of a telecommunications network, the volume of traffic and number of customers often justify the high installation cost of fiber optic lines. However, thus far, the costs of deploying fiber optic lines to individual subscriber premises have far outweighed any potential benefits to network providers.
Therefore, instead of implementing FTTH networks, service providers have developed strategies to provide some of the benefits of fiber optic networks without actually deploying fiber all the way to the home (or other end-subscriber location). One such strategy is known as fiber to the curb (FTTC), in which fiber optic lines extend from the service provider to local terminals (also referred to as outside plant cable terminals) that are situated in areas having a high concentration of subscribers. Service providers complete the last leg of the network, i.e., from the local terminals into a subscriber premises, using copper wire drops and perhaps a high speed data connection, such as an Asynchronous Digital Subscriber Line (ADSL).
Such FTTC systems provide the benefits of fiber optic systems as far as the fiber extends, but deprive the subscriber of the full benefit of fiber optic networks because of the copper wire drops. Indeed, as the weakest link, the copper wire drops limit the bandwidth capacity for the entire system. Thus, the only way to gain the full benefit of fiber optic networking is to use a continuous fiber optic connection from the service provider's equipment to the subscriber's equipment.
Despite the bandwidth limitations, network providers favor copper wire drops because of the prohibitively high cost of installing fiber optic drops using conventional systems and methods. The bulk of these costs can be attributed to the highly skilled labor and time required to install fiber optic splitters and to join fiber optic drops to fiber optic strands coming from the splitters. In conventional systems and methods, fiber optic networks use fiber optic splitters and splice cases to route fiber optic strands throughout a distribution network. The fiber optic splitters and splice cases allow a fiber
Bellsouth Intellectual Property Corporation
Shaw Pittman LLP
Sircus Brian
Zarroli Michael C.
LandOfFree
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