Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
  • G02B6/4439—Auxiliary devices
  • G02B6/444—Systems or boxes with surplus lengths
  • G02B6/4453—Cassettes
  • G02B6/4454—Cassettes with splices

Definitions

• the invention relates to a cassette for optical fibres of the kind stated in the preamble of claim 1.
• Such a cassette shaped substantially as a circular disc, is previously known from the patent specification SE-B-457 021, wherein the fibre cables are placed with retained shields and with a number of loops in an external storage space, which is situated outside an external side wall and is externally free, wherefrom the cables are drawn with their bare end portions, i.e. with their bare fibres, via two helical lead-through portions through the side wall into a radially internal storage space.
• this internal storage space which is inwardly limited by an internal circular ring wall, the bare fibres are placed in curved, substantially circular loops up to a joining or branching place.
• the fibres are securely protected inside the cassette.
• a cassette according to said patent specification SE-B-457 021 is relatively easy to handle, and the insertion of the fibre loops into the internal storage space can be carried out without serious problems.
• a careful handling is required, and it is necessary to observe great care and accuracy when removing the insulation and placing the fibre into the helical lead-through portion while securing the shielded cable loops in the external storage space, e.g. with an elastic string of cellular rubber.
• the fibre In the lead-through portion itself, the fibre must be secured in its groove by placing a piece of rubber in the upper part of the groove, so that the fibre can slide in the groove without engaging with the wall of the groove. Internal tensions in the fibre will also cause losses.
• ribbon- or band-like fibre cables are being used to an increasing extent, i.e. cables with a number of fibres, e.g. up to twelve fibres, grouped into a ribbon or band. To avoid losses it is necessary to prevent such ribbons or bands from being twisted.
• the ribbon or band may be bent as a whole provided that the bending radius is sufficiently large, e.g. 35 mm.
• the main object of the present inven ⁇ tion is to achieve an improved cassette, which enables an easy insertion of a bare fibre or fibre band into the cassette, a greater bending radius of the fibre loops in the storage space of the cassette, a secure holding of the end portions or bare fibres or fibre bands of the cable at the two inlet openings of the cassette, so that the risk of causing sharp bends or tensions is reduced outside as well as inside the cassette.
• Additional objects are to enable a deflection of a fibre loop into an opposite circum ⁇ ferential direction inside the cassette, and - a very swift and easy handling of the fibre loops when inserting the same into the cassette and taking them out again.
• the cable end portion may be inserted in a simple manner into the cassette and be held in a well-defined posi ⁇ tion, which secures that the fibre loops will obtain a large bending radius in this region and will be situated at a dis ⁇ tance from the external side wall of the cassette immediately outside the inlet opening as well as immediately inside the inlet opening.
• posi ⁇ tion which secures that the fibre loops will obtain a large bending radius in this region and will be situated at a dis ⁇ tance from the external side wall of the cassette immediately outside the inlet opening as well as immediately inside the inlet opening.
• Fig. 1 illustrates in a perspective view a lid of a cassette according to the invention
• Fig. 2 illustrates in a perspective view a cassette according to the invention (to which the lid of figure 1 fits) ;
• Fig. 3 illustrates in a planar view the cassette according to figure 2 with two inserted optical fibre bands and a joint
• Fig. 4 shows schematically in a planar view a modified embodi ⁇ ment of the cassette.
• cassettes 1 and 2 are intended to be used essentially in the same way as the cassette according to the above-mentioned patent specification 457.021.
• a number of such cassettes e.g. six of them, are stacked one on top of the other in a two-part cable box.
• the latter may be of the same kind as described in said patent specification and does not form any part of the present invention.
• Two or more optic fibre cables which are to be joined to each other and/or form a branch, are inserted in sealed lead-through portions in the cable box, and the end portions of the cables are inserted into the cassette, where they form loose, curved loops and are mutually joined to each other or branched.
• the cassette 100 is manufactured by injection moulding of thermoplastic material and has a substantially circular configuration.
• it is made up of a substantially circular disc-like bottom wall 101, which at its outer peri ⁇ phery has an upright, external side wall 102, inlet openings 103a, 103b, guides 104a, 104b adjacent to each inlet opening, various internal guide elements (to be explained below) , a holding device 105 for connection sleeves and a central tubular hub 106, by means of which the cassette is threaded onto a non- illustrated pin in the cable box.
• the lid 200 Upon mounting of the lid 200, the external configuration of which corresponds to the external configuration of the cassette and which is provided with a central hole 206, the cassette can be stacked with its lid together with other cassettes in the cable box.
• the external side wall 102 follows the outer contour of the bottom wall 101 - compare also figure 3 - and forms a circular portion 102a, which extends in an angular region of about 120°, approximately rectilinear portions 102b and 102c adjoining thereto, each extending about 30°, and furthermore two adjoi ⁇ ning circular portions 102d and 102e, respectively, each extending in an angular region of about 60° relative to the circular centre point 107 (somewhat displaced from the tubular hub 106) but having a centre of curvature situated at a radial distance from these centres 106, 107, so that the respective corner point 102f, 102g is situated at a greater radial dis- tance from the circular centre 107 than the circular portion
• the side wall 102 ends in these corner points 102f, 102g, and the bottom wall 101 forms in these regions a step-like shoulder adjoining a radially recessed portion of a correspon ⁇ ding, circular side wall portion 102h, which extends in an angular region of about 60°, and there is also a small overlap ⁇ ping region of the side walls, each of about 10-15°.
• the side wall portion 102h is situated at the same radial distance from the circular centre 107 as the circular portion 102a.
• the circular arc portions 102a and 102h are thus concentric relative to the circular centre 107, whereas the centre point of the circular arc 102a (opposite to the holding device 105) and the corner points 102f, 102g are approximately situated on a circle having a larger radius with a centre in the tubular hub 106.
• the cassette will thus fit inside a cable box having an internal cylindrical space, the cylinder radius of which somewhat exceeds the radius of the last-mentioned circle having its centre in the tubular hub 106.
• the external portions of the bottom wall 101 and the side wall portions 102b, 102c, 102d, 102e form ear-like protrusions 108, 109 which, inside the corner points 102f, 102g, form inlet openings for optical fibres between the partially (at a mutual radial distance) overlapping side wall portions 102d, 102e and 102h.
• These inlet openings denoted with arrows 103a and 103b in figure 3, are tangentially directed and thus enable a well- defined guidance of the end portions or bare fibres of the cable through these openings 103a, 103b.
• guides 104a, 104b which consist of an insert body 110 and 111, respectively, of plastic material, e.g. cellular rubber, with guiding grooves extending tangentially in relation to the circular centre 107.
• These guiding grooves 112 and 113, respectively, are also parallel to the side wall portions 102h and 102d and 102e, respectively, so the bands Fl and F2 are kept upright and are therefore drawn as full lines only in figure 3.
• each fibre band Fl, F2 is securely held in position and extends at a distance outside the side wall portion 102a immediately outside the inlet opening 103a and 103b, respectively, (in the region between the openings 103a and 103b they are also somewhat twisted and bent downwards from the plane of the cassette, although this is not illu ⁇ strated in figure 3, so that they adjoin smoothly from the lead-through openings of the enclosing cable box, the lead- through openings normally being situated in a different plane than the particular cassette) and extend further in parallel to and at a distance inside the external side wall portion 102d, 102e, respectively, of the ear-like protrusion 108, 109.
• the fibre bands Fl, F2 extend relatively close to the inside of the side wall portion 102a and extend further approximately in a circular arc adjacent to the opposite side wall portion 102h and, finally, approximately another half turn to the holding device 105, where they are connected in a joint in a connecting sleeve S, which is inserted into the space between two of the mutually parallel partitions 105a-g thereof.
• the cassette On the upper edges of the side wall portions 102a and 102h, there are a number of inwardly directed, relatively short holding tongues 113a, 113b and 113c, 113d, respectively, and three elongated holding tongues 114a, 114b, 114c, by means of which the loop-formed fibre bands Fl, F2 are held in position when the cassette is being handled.
• the cassette may be handled at will and may even be turned upside down without involving any risk that the fibre bands fall out.
• the elongated holding tongues 114a, 114b, 114c are swung up about hinges formed by material recesses adjacent to the side wall 102a, 102h, so that the loops can be inserted from above and be secured in the guiding grooves of the insert bodies 110, 111 and be inserted below the fixed, shorter holding tongues 113a, 113b, 113c, 113d.
• the width of the fibre bands Fl, F2 (or height thereof when oriented upright as in figure 3) is substantially smaller than half the height of the side walls 102a-102h, so that the bands may cross each other, as shown in figure 3 adjacent to the tongues 114a and 113d.
• fibre bands Fl, F2 are illustrated.
• a large number of fibre bands may be inserted, in particular pairwise, into the inlet ope ⁇ nings 103a, 103b and be laid in circular loops with joints in the holding device 105.
• a number of guiding pins 115a, 115b, 115c, 115d, 115e, 115f serve as an internal guiding means in the radial direction, these guiding pins being arranged in a circle around the circular centre 107 and being provided with upper holding tongues 116a, 116b, 116c, 116d, 116e, 116f, which are parallel to the bottom wall 101 as are the other holding tongues.
• the guiding pins 105a-f are displaced circumferentially rela ⁇ tive to the elongated holding tongues 114a, 114b, 114c. These guiding pins 115a-f may also be used if one wishes to shift the circumferential direction of a fibre. In such a case, the fibre is inserted radially inwards past a guiding pin, e.g. 115a, past the central hole 107 and past an opposite guiding pin 115d at the other side, as indicated by a dotted line in figure 3.
• the guiding pins 117a and 117b are disposed at the same radial distance as the wall portions 102a and 102h.
• the whole storage space inside the external side wall 102a-102h can be used for protected storage of fibre loops.
• the fibre loops may be arranged with a very large bending radius, namely approximately corresponding to the radius of the cassette.
• the fibre loops Upon mounting and securing the lid 200 shown in figure 1 (by means of non-illustrated screws) , the fibre loops are secured in position, though loosely, in their inserted positions.
• the fibre loops may be secured in position at the respective inlet opening by means of threads or the like being inserted through holes 119 in the bottom wall 101.
• holding device 105 or connecting sleeves which are preferably inserted into the grooves between the partition walls 105a-g and are secured by means of non-illustrated locking bodies, e.g. pieces of plastic material, it is possible to dispose branching devices or other coupling devices in the rectangular recesses 120 and/or 121 in the bottom wall 101.
• the outer contour of the cassette 100 may be constituted by a large circular arc 102'a, extending along an angular region of about 300° and a radially recessed smaller circular arc 102 'h , extending along the remaining 60°, instead of the irregular configuration described above.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Light Guides In General And Applications Therefor (AREA)
• Mechanical Coupling Of Light Guides (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=20389920

Family Applications (1)

Country Status (3)

Families Citing this family (7)

Family Cites Families (1)

• 1993
  • 1993-05-12 SE SE9301639A patent/SE500679C2/sv unknown
• 1994
  • 1994-04-26 EP EP94915723A patent/EP0698222A1/en not_active Withdrawn
  • 1994-04-26 WO PCT/SE1994/000373 patent/WO1994027176A1/en not_active Application Discontinuation

Non-Patent Citations (1)

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