Optical waveguides – Accessories – Splice box and surplus fiber storage/trays/organizers/ carriers
Reexamination Certificate
1999-02-19
2001-08-14
Spyrou, Cassandra (Department: 2872)
Optical waveguides
Accessories
Splice box and surplus fiber storage/trays/organizers/ carriers
C385S134000
Reexamination Certificate
active
06275639
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an optical fiber closure.
BACKROUND OF THE INVENTION
Optical fiber splice closures (which are sometimes called splice cases or enclosures) generally comprise a casing which provides a closed space for containing splices between optical fibers. Such closures normally must also contain significant lengths of the spliced optical fibers. These lengths of optical fibers (which may be called “excess fiber” ) are normally required in order to be able to carry out the fiber splicing operation, which is generally performed using splicing equipment next to the closure. Excess fiber may also be required in order to organize the fiber splices in the closure. Optical fiber splice closures normally include some means of storing the splices in an organized manner. The excess optical fiber associated with the organized splices needs to be stored in the closure in such a way that its bend radius does not fall below the critical bend radius of the fiber (which is typically about 30 nm). The critical bend radius of an optical fiber is the minimum safe radius at which the fiber may be bent without causing damage to the fiber or causing signal loss in the fiber.
International patent application WO 95/07480 (Raychem) discloses an extremely effective optical fiber splice closure. The closure comprises a casing consisting of a generally circular base and a dome-shaped cover which may be attached and sealed to the base to close the casing. In use, the optical fiber cables enter the casing through a plurality of cable ports in the base. The cable ports of a closure of this type are commonly sealed around the cables by means of heat-shrinkable sleeves which are heated by a gas torch to cause them to shrink and seal around the cables. The closure of WO 95/07480 includes a highly sophisticated optical fiber organizer which provides the highest degree of fiber and splice organization, by means of a series of trays which are hinged to a large base plate which itself guides the optical fibers to and from the trays in a highly organized manner.
International patent application WO 89/10648 (Raychem) discloses a much simpler splice closure which may be used for electrical conductors (e.g. wires) or optical fibers. The closure comprises two casing parts and a sealing material contained in the casing parts. The two casing parts are held and forced together by means of springs positioned around them. One or both casing parts has/have a deformable surface, and the springs are so shaped as to cause the deformable surface(s) to be deformed towards the sealing material, thereby putting the sealing material under compression. Optical fibers containing splices may be placed between two portions of the sealing material. The splices are simply arranged in a row in one of the casing parts directly on one of the portions of sealing material, and the optical fibers leading to the splices are separated in a comb-like article which is referred to as a conductor organizer. The other casing part, containing another portion of sealing material is then placed on top of the first casing part, sandwiching the optical fibers and splices between the two portions of sealing material.
SUMMARY OF THE INVENTION
According to a first aspect, the present invention provides an optical fiber splice closure, comprising:
(a) a casing for containing a plurality of optical fiber splices;
(b) a support which, at least in use, is contained in the casing and on which, in use, a plurality of optical fiber splices are located; and
(c) sealant which, at least in use, is contained in the casing and encapsulates at least part of the support.
The invention has the advantage that it provides a simple yet effective splice closure which provides firm location, and hence the possibility of effective and reliable organization, of optical fiber splices. This firm location of the optical fiber splices is provided by the support on which the splices may be located. Because the support is encapsulated in the sealant, the supported optical fiber splices are placed in a sealed and protective environment which is provided in a simple yet effective manner. The sealant preferably encapsulates substantially the entire support.
The support preferably includes a plurality of splice holders for holding the optical fiber splices. The splice holders may, for example, be arranged in at least one series along at least part of the support. The splice holders are preferably arranged such that splices held in them in use are substantially mutually parallel. The orientation of the splice holders is preferably such that splices held in them are substantially perpendicular to the direction in which the optical fiber cable(s) and/or optical fibers extend into the closure.
The term “optical fiber splices” as used in this specification includes optical fiber connectors, optical fiber splitters or couplers, or the like, in addition to optical fiber splices (e.g. fusion splices) as such.
The support preferably includes guide means for guiding optical fibers to and from the splices. The guide means preferably comprise one or more projections which project from one or more surfaces of the support. The projections may, for example be generally hook-like, and may be flexible in order to facilitate the location of one or more optical fibers in place. Other types of guide means which may additionally or alternatively be used include channels, grooves or other apertures, and tie wraps or other securement devices.
Advantageously, the support may be in the form of at least one tray. By a “tray” is meant a generally flat structure which may, for example, be generally plate-like or frame-like. There may be one or more walls or other projections extending above a major surface of the tray, for example one or more peripheral walls.
In some preferred embodiments, the support has a plurality of holes extending through it. More preferably, the support comprises at least one mesh or the like (which may, for example, be formed from a woven or non-woven fabric, or may be formed from a plastics material or a metal). The sealant can preferably extend through the holes in the support during use. This has the advantage that the sealant preferably can substantially completely encapsulate each optical fiber on the support. In a preferred arrangement, the support comprises at least two meshes between which the spliced optical fibers are located in use.
It has been found that when optical fibers contact each other, for example if they cross-over each other, the optical signals carried by the fibers may become attenuated. This is believed to be due, at least in part, to localized pressure on the fibers at their point of contact, which can result in localized bending and/or compression of the fibers. This belief is supported by the finding that if two fibers are pressed together at their point of contact the signal attenuation generally becomes more severe. Such pressing together of crossing (or otherwise contacting) optical fibers may arise in some conventional optical fiber organizers.
The inventors of the present invention have discovered that if two mutually contacting optical fibers are encapsulated in sealant and the sealant is subjected to a compressive force, signal attenuation in the optical fibers due to the mutual contact between them either does not occur at all, or occurs to a significantly lesser extent than would be the case if the two optical fibers were directly subjected to the same compressive force in the absence of the sealant. This phenomenon is believed to be due to the sealant distributing the compressive force substantially evenly around the periphery of each of the fibers. The phenomenon is most readily apparent in sealants which behave hydrostatically or pseudo-hydrostatically, such as gel sealants (which are described in more detail below), i.e. in sealants which distribute pressure similarly to liquids.
Embodiments of the invention in which the support is perforated (e.g. in the form of a mesh) exploit this phenomenon to prevent or reduce
Bolt Sidney Joseph
Buekers Valere
Daems Daniel
Ferris Ian
Macken Luk
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Curtis Craig
Spyrou Cassandra
LandOfFree
Optical fiber splice closure does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical fiber splice closure, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical fiber splice closure will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2452734