Optical waveguides – Accessories – Splice box and surplus fiber storage/trays/organizers/ carriers
Reexamination Certificate
1999-03-22
2003-01-14
Font, Frank G. (Department: 2877)
Optical waveguides
Accessories
Splice box and surplus fiber storage/trays/organizers/ carriers
C385S136000, C385S137000
Reexamination Certificate
active
06507691
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of fiber optics and, more particularly, to the storage and organization of fiber optic splices and associated slack.
BACKGROUND OF THE INVENTION
Optical fiber communications systems are used extensively in the telecommunications industry because of their large information carrying capacity, their virtually noise-free performance, and the long span distances achievable with optical fibers before regeneration and amplification of the signal is required. Practical limits on the lengths of optical fiber cables that can be manufactured and installed typically require that many splice points be included over the total cable route.
At each splice location, the optical fibers are separated from the other protective cable components for splicing and are, thus, more susceptible to damage. In addition, the optical fibers at a splice point are handled by a technician who must splice the fibers and then store the splice and associated slack in a protective enclosure.
Although an optical fiber cable can carry signals over relatively long distances without requiring repeaters, one common architecture includes one or more drop locations along a main cable route. In other words, it may be desirable to connect certain fibers to drop cables along the main cable route. Each such drop or splice point requires the protection of the cable ends and individual splices. More particularly, a splice closure is typically provided for terminating the cables and storing the splices.
Accordingly, enclosures for protecting optical fiber splices have been developed and are readily available. Typically, these enclosures include one or more splice organizers, or splice trays as they are also called, on which the individual splices and associated slack are mounted. For example, the assignee of the present invention manufacturers a conventional splice enclosure and splice organizer under the model designation FOSC 100. Siecor Corporation of Hickory, N.C. makes splice enclosures under the model designations SC2 and SC4-6.
U.S. Pat. No. 4,679,896 to Krafcik, for example, discloses a butt splice closure where the ends of two cables to be spliced together are routed through one end plate of a generally cylindrical housing. The housing is provided by a pair of generally circular end plates, and a tubular cover connecting the two end plates. Raychem, the assignee of the present invention, also manufactures butt splice closures wherein the cables to be spliced are brought in from a single end of the housing. A series of pivotally mounted splice organizers are provided. The pivotally connected splice organizers permit organizers to be moved to a raised position to facilitate access to an underlying organizer. A fixed slack basket may be positioned under the splice organizers to store slack buffer tubes, for example. An example includes U.S. Pat. No. 5,323,480 to Mullaney et al., the disclosure which is hereby incorporated by reference in its entirety, assigned to the present assignee, the disclosure which is hereby incorporated by reference in its entirety.
Another general type of splice closure is the in-line closure wherein cables enter the overall housing from opposing ends. An in-line splice closure may be particularly desirable for a drop or branch cable location where the main cable includes a significant number of fibers that can pass through the closure without requiring splicing. Only those fibers that need to be dropped are spliced and the remaining fibers can be stored within the housing.
For example, U.S. Pat. No. 4,805,979 to Bossard et al. discloses such an in-line fiber optic splice closure. The closure includes two mating shell portions which are secured together to define an overall protective housing. Cable entry ports are provided at each end of the housing and are defined by arcuate wall portions between the base and cover housing portions. A slack storage area is defined in the base by a pair of inwardly extending retaining brackets connected at a medial portion of the base. The cable ends are terminated adjacent the cable ports. A series of splice organizers are connected to the base above the slack storage area. Each splice organizer stores a number of individual fiber splices.
A splice organizer is typically limited in the amount of space it may occupy although it must permit the mounting of the individual splices and permit storage of the slack optical fibers in a relatively neat configuration. To hold a sufficient amount of slack to permit splicing, a splice organizer typically accommodates one or more bends of slack optical fiber in slack loops that cannot be sharply bent and thereby exceed the minimum bend radius for the optical fiber. Exceeding the bend radius causes microbending losses, that is, increased attenuation of the optical signal. In addition, the optical fibers may be physically damaged by exceeding the minimum bend radius. An approach to storing a sufficient length of slack is to use multiple loops for each individual fiber. See, for example, U.S. Pat. No. 4,373,776 to Purdy and U.S. Pat. No. 4,765,709 to Suillerot et al.
The slack loops of conventional splice organizers are frequently permanently entangled with each other as part of the normal course of splicing and routing of the slack for storage on the splice organizer. Unfortunately, it is very difficult to access an individual splice after all of the splices have been completed because of the entangling of the slack optical fibers. In almost all fiber optic communications systems, it is critical that high quality and high reliability splices be obtained. Fusion and mechanical splicing techniques and equipment have been developed that permit low loss, high quality, and durable splices to be obtained. However, it may sometimes be necessary to remake or repair splices to achieve the desired splice quality. The inability to readily reaccess a splice, such as to remake the splice, is a significant shortcoming of conventional fiber optic splice organizers.
Fiber cables are also available of a ribbon type, such as manufactured by AT&T, wherein several optical fibers are arranged in side-by-side relation and secured together by an adhesive layer. However, another difficulty with conventional splice organizers and techniques is that organizers for ribbon-type fiber optic cables require that every fiber in a given ribbon be spliced to every correspondingly positioned fiber of another fiber optic ribbon. Thus, any flexibility in interconnecting a predetermined individual optical fiber to an optical fiber in a different position or on a different ribbon is simply not available. Moreover, should it be necessary to repair only a single optical fiber splice of the ribbon, all of the splices must then be broken and remade. Thus, unnecessary communications systems downtime is experienced because of the need to work with all of the fibers in the ribbon, rather than being able to efficiently access only one optical fiber from the ribbon.
In many new fiber optic communications applications, such as in campus-type networks or cable TV networks, high fiber counts and a large number of drop points are required. Unfortunately, since conventional fiber optic organizers cannot accommodate splices between individual optical fibers when ribbon cables are used, interconnection flexibility for such a system is severely limited.
U.S. Pat. No. 5,278,933 to Huntsinger et al., issued Jan. 11, 1994, the disclosure which is hereby incorporated by reference in its entirety, provides a splice organizer and method for securing optical fiber splices and slack of the cables, which also permits ready separation of the optical fibers even after all the splicing has been completed, such as to facilitate remaking the splice. It also allows break out and splicing of individual optical fibers in the ribbons to enhance interconnection flexibility and permit the repair of individual optical fibers from an optical fiber ribbon.
In this structure, the fiber optic splice organizer includes a generally rectangular base
Greenlee Timothy A.
Hunsinger Terrance D.
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Font Frank G.
Mooney Michael P.
Tyco Electronics Corporation
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