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EP-3683609-B1 - SHEATHED OPTICAL RIBBON CABLE ASSEMBLY

EP3683609B1EP 3683609 B1EP3683609 B1EP 3683609B1EP-3683609-B1

Inventors

  • ZITSCH, DWIGHT DAVID
  • Rabi, Zaheer

Dates

Publication Date
20260513
Application Date
20200116

Claims (14)

  1. A cable assembly (100) comprising: a ribbon cable (101) comprising a plurality of optical fibers having endfaces (101a); an elastomeric sheathing (104) being disposed over at least a portion of said ribbon cable (101) and terminating at a sheathing end (103) short of said endfaces (101a) such that said endfaces (101a) protrude beyond said sheathing end (103); a ferrule (102) having a mating surface (102a) presenting said endfaces (101a), a rear end (102b), having a rear opening (112) through which said optical fibers pass, and a window configured to allow adhesive to be injected into said ferrule (102) through said window such that adhesive flows around the optical fibers to secure the fibers to said ferrule (102); and cured adhesive disposed in said ferrule (102) to secure said optical fibers to said ferrule (102), characterised that said cable assembly (100) does not have a boot and said rear end (102b) of said ferrule (102) contacts said sheathing end (103) to form an adhesive-tight seal sufficient to prevent liquid adhesive in said ferrule (102) from flowing out of said rear opening (112).
  2. The cable assembly (100) of claim 1, wherein said elastomeric sheathing (104) is a halogen-based material.
  3. The cable assembly (100) of any preceding claim, wherein said elastomeric sheathing (104) is a fluoropolymer material.
  4. The cable assembly (100) of any preceding claim, wherein said elastomeric sheathing (104) is one of polyvinylidene fluoride or polyvinylidene difluoride (PVDF), fluorinated ethylene propylene (FEP), perfluoroalkoxy polymer (PFA), or polytetrafluoroethylene (PTFE).
  5. The cable assembly (100) of claim 1, wherein said elastomeric sheathing (104) is a silicone-based rubber material.
  6. The cable assembly (100) of any preceding claim, wherein the elastomeric sheathing (104) is a heat shrink material.
  7. The cable assembly (100) of any preceding claim, wherein said elastomeric sheathing (104) is extruded over said ribbon cable (101).
  8. The cable assembly (100) of any preceding claim, wherein said ferrule (102) is an MT ferrule
  9. The cable assembly (100) of any preceding claim, further comprising a convoluted tubing around said elastomeric sheathing (104).
  10. A method of preparing a cable assembly (100), said method comprising disposing elastomeric sheathing (104) over a ribbon cable (101) having a plurality of optical fibers; stripping said optical fibers and said sheathing (104) to form stripped optical fibers (202) that protrude beyond an end (103) of said sheathing (104); inserting said stripped optical fibers (202) through a rear opening (112) at a rear (102b) of a ferrule (102) such that endfaces (101a) of said stripped optical fibers (202) protrude beyond a mating face (102a) of said ferrule (102); disposing liquid adhesive in said ferrule (102) by injecting adhesive through a window of said ferrule (102) such that the adhesive flows around the optical fibers to secure the fibers to the ferrule (102); and causing said liquid adhesive to cure, characterised in that the cable assembly (100) does not have a boot and said end (103) of said sheathing (104) contacts said rear (102b) of said ferrule (102) to form an adhesive-tight seal between said ferrule (102) and said sheathing (104).
  11. The method of claim 10, wherein disposing said sheathing (104) around said ribbon cable (101) comprises heat shrinking said sheathing (104) around said ribbon cable (101).
  12. The method of claim 10 or 11, wherein disposing said sheathing (104) around said ribbon cable (101) comprises slipping sections of said sheathing (104) over the ribbon cable (101) to form overlapping joints between said sections, and then sealing said overlapping joints.
  13. The method of claim 10, 11 or 12 wherein disposing said sheathing (104) around said ribbon cable (101) comprises pulling a length of said sheathing (104) over the ribbon cable (101).
  14. The method of claim 10, wherein disposing said sheathing (104) around said ribbon cable (101) comprises extruding said sheathing (104) around said ribbon cable (101).

Description

The present invention relates, generally, to optical ribbon cable, and, more specifically, to a sheathed optical ribbon cable terminated with a ferrule, which is abrasion and/or chemical/heat resistant. Optical ribbon cable is used commonly to connect optical components together and is a convenient solution for applications having space and weight limitations. A conventional ribbon comprises optical fibers, which are placed side-by-side and encapsulated with a coating or a tape, for example, Mylar, to form a strip of optical fibers. A single ribbon may contain, for example, 4, 8, 12, or more optical fibers. The advantage of utilizing ribbon fiber cables resides in the ability to achieve a much higher density in a patch panel, cable routing/ducting, and device connection environments, without compromising the quality or quantity of the connection. Because the ribbon contains only coated optical fibers, this type of cable takes up much less space than individually buffered optical fibers. As a result, ribbon cables are denser than any other cable design. They are ideal for applications where limited space is available, such as in an existing conduit that has very little room left for an additional cable. Although ribbon cable is a good solution for high density optical applications, the absence of a buffer makes them susceptibility to abrasion, which necessitates taking certain precautions that complicate the assembly/installation process. Specifically, ribbon cable cannot rub against other objects, and, thus, in environments involving vibration, the cable must be secured with tiedowns and other mechanical means to prevent it from rubbing against other objects. The need for such tiedowns not only introduces additional steps/expense in the installation process, but also often presents challenges because a purchase point for a tiedown is not often available. Accordingly, the applicant has identified the need for an abrasion resistant ribbon cable that minimizes the need for tiedowns and other mechanical restraints. Furthermore, as the use of ribbon cables becomes more prevalent in rugged and demanding applications, such as aerospace, the applicant has also identified the need for a ribbon cable that is chemically and thermally resistant. The present invention fulfills these needs, among others. A prior art ribbon cable assembly (on which the preamble of claims 1 and 11 are based) is disclosed in patent JP 07-43560 A. The assembly comprises a fiber optic connector including a resin body with a passage into which stripped optical fibers of an optical fiber ribbon cable are inserted. The stripped ends are sandwiched between a lower ceramic substrate, with V-shaped fiber receiving grooves, and an upper ceramic substrate. A passage in the resin body allows adhesive to be injected in order to adhere the ribbon cable to the resin body and the stripped ends of the optical fibers to the ceramic substrates A prior art ribbon assembly is also disclosed in US 2015/0346435 A1 comprised of a ferrule and a ribbon cable comprised of an elastomeric sheathing. According to the invention there is provided a cable assembly according to claim 1 and a method of preparing a cable assembly according to claim 10. Fig. 1 shows one embodiment of the ribbon cable assembly of the present invention.Fig. 2 shows a side-by-side comparison of the sheathed ribbon cable of the present invention (prior to termination of a ferrule) compared to conventional ribbon cable having a boot (also prior to termination of a ferrule).Figs. 3a - 3d show various steps of the process of stripping a conventional ribbon cable and stripping the sheathed ribbon cable of the present invention for termination ofFig. 4 shows a side-by-side comparison of the stripped sheathed ribbon cable of the present invention and a stripped conventional ribbon cable.Figs. 5a - 5b show a side-by-side comparison of applying adhesive to a ferrule attached to the sheathed ribbon cable the present invention and to a ferrule attached to a conventional ribbon cable.Fig. 6 shows a side-by-side comparison of the almost complete cable assemblies of a conventional ribbon cable terminated with a ferrule and the sheathed ribbon cable of the present invention terminated with a ferrule, with stripped fibers protruding from the mating face of each ferrule.Fig. 7 shows a side-by-side comparison of the completed cable assembly of a traditional ferrule terminated ribbon cable and a ferrule terminated sheathed ribbon cable of the present invention. The invention will now be described by way of example with reference to the accompanying drawings in which: Referring to Fig. 1, one embodiment of the cable assembly 100 of the present invention is shown. In this embodiment, the cable assembly 100 comprises a ribbon cable 101, comprising a plurality of optical fibers (not shown) having fiber endfaces 101a, and an elastomeric sheathing 104 being disposed over at least a portion of the ribbon cable and termin