Abstract:
The present invention relates to an arrangement for handling optical fibers in a confined space, such as connecting, reorganizing and/or cross-connecting several optical fibers contained in optical fiber cables in an insulated space. Controllable organization of the optical fiber cables can be achieved, by providing the insulated space ( 2, 3 ) with cable guiding and coiling means. The arrangement includes elastic and tight transits in openings ( 5, 6 ). The transits have a tapering centre part and will adapt to optical fiber cables of mutually different diameters and allow the cables to extend in different directions outside the insulated space.

Description:
This application claims priority under 35 U.S.C. §§119 and/or to 9901925-9 filed in Sweden on May 27, 1999; the entire content of which is hereby incorporated by reference. 
     FIELD OF INVENTION 
     The present invention relates to an arrangement for reorganising and/or connecting optical fibres in a limited or confined space. When handling optical fibres, and then particularly optical fibres included in optical fibre cables, it is necessary to be able to combine several optical fibre cables at a collecting point and there reorganise and/or connect together individual optical fibres in a sealed fashion. 
     DESCRIPTION OF THE BACKGROUND ART 
     It is known to bring several optical fibre cables together in a closed container for reorganising and/or connecting the fibres. Commercially available solutions for sealing the cable transits or lead-throughs of the container include sealing said transits with the aid of shrink hoses placed on the optical fibre cables, or sealing said transits with the aid of self-vulcanising tape wound on the optical fibre cables, said tape being wound around the cable to an appropriate size. One disadvantage with the use of shrink hoses lies in the primary requirement of heat. The hoses must either be heated electrically or with the aid of gas. The former often requires the provision of a power source at the place where the cables are to be connected, while the latter constitutes an explosion hazard. The drawback with self-vulcanising tape is that installation is operator-dependent and that addition material is often required when resealing a used container, such as a connecting box. 
     U.S. Pat. No. 5,224,199A teaches a connecting box intended for optical fibre cables and comprising a bottom part and a top part which can be joined to the bottom part, wherein the bottom part and the top part each include grooves which face one another and when said parts are joined one to the other define channels into which elastic plugs that carry optical fibre cables are inserted. The elastic plugs are slotted, so as to facilitate both fitting and removal of the cables and enable the elastic plugs to be first placed on the optical fibre cables, so that the top part of the box can be connected to its bottom part with the plugs carrying said cables placed in the channels between the box parts. Dismantling of the cable from the box is effected by first separating the top part of the box from its bottom part and then opening the plugs, which is easily done, and removing the plugs from the cables and therewith release the same. 
     U.S. Pat. No. 5,313,546 teaches the use of an hermetically sealed connection encapsulation intended for optical fibre cables and comprising a bottom part which includes seal-accommodating channels and a lid which is connectable to said bottom part, wherein the seals include holes for accommodating optical fibre cables inserted thereinto. The seals of this solution have also been slotted to facilitate insertion of the cables into the seals prior to fitting the seals into the channels in the bottom part of the encapsulation. 
     SUMMARY OF THE INVENTION 
     With the intention of facilitating handling of optical fibre cables in a limited or confined space, such as a closed space, for instance in a sealed fibre/cable connecting box arrangement for reorganising and/or connecting optical fibres in said cables, the closed space has been provided with means for guiding and coiling the cables prior to stripping respective cables and mutually separating the optical fibres enclosed therein. In addition to organising the cables in said space in an ordered and controllable fashion, the provision of means for guiding and coiling the cables in said confined space also ensures that essentially the same preparation lengths are obtained with respect to the different cables, regardless of the transit or lead through which they have been inserted into said space, while also enabling the bending radii of the optical fibre cables to be monitored. By providing the elastic transits, i.e. the cable seals between the cables and the closed space, such as a cable connecting box, to the closed space accommodating the optical fibre cables with a tapering opening, alignment of the optical fibre cables can be adapted with respect to coiling of the cables, therewith reducing the influence of the transit on said cables. The centre part of the tapering opening enables the optical fibre cable to be angled to some extent when placed in the transit without needing to influence the tightness of the transit against the cable and against said space. The taper in the centre part of the transit also enables cables of different diameters to be sealed effectively. The cable seals will preferably seal the incoming and outgoing cables against the ingress of moisture and water. 
     The object of the invention is to integrate an optical fibre handling function in the moulded bottom part of a cable connecting box in all essential aspects. The purpose of this function is to provide a unitary measurement for all optical fibre cable preparations on the one hand, and to hold an installed optical cable in position in the bottom part of the box and prevent uncontrolled bending of the cables and to seal the cable transits on the other hand. 
     The invention will now be described in more detail with reference to preferred embodiments thereof and also with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a connecting box arrangement for optical fibre cables arranged in accordance with the invention. 
     FIG. 2 shows a bottom part of the box arrangement of FIG. 1 from above. 
     FIG. 3A illustrates with the aid of arrows the directions in which incoming and outgoing optical fibre cables are inserted into the bottom part of the box shown in FIG. 2 for correct placement of the fibres/cables in the guide grooves in said bottom part. 
     FIG. 3B illustrates from one side an optical fibre cassette in accordance with the present invention. 
     FIG. 3C illustrates from above an optical fibre cassette, and shows with the aid of arrows the directions in which the optical fibres are inserted for correct placement of the optical fibres/cables in said optical fibre cassette. 
     FIGS. 4A-D illustrate respectively an inventive elastic transit from one short side, from one long side, in cross-section and in perspective. 
     FIG. 5 illustrates from one short side an elastic transit that includes several holes. 
     FIG. 6 illustrates a plug for sealing an opening in a transit, in accordance with the invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 illustrates an openable cable connecting box arrangement  1  according to the invention, which includes a bottom part  2 , a top part  3  and several optical fibre cassettes  4  for organising and coiling the optical fibres. The box arrangement can be connected with optical fibre cables that are sealed by cable seals, by inserting the cables through openings  5 ,  6  at respective ends of the connecting box. The bottom part of the box can be joined to its top part with the aid of locking or latching means for instance, so as to obtain an easily opened connecting box arrangement. In order to provide a positive and tight connection of the optical fibre cables, the ends of the top and bottom parts of the box may be provided with mutually coacting and openable nut and bolt joints and a sealing device, such as an O-ring, may be placed between the respective mutually facing connecting surfaces of the top and bottom parts of the box. The bottom part of the box includes a space which accommodates means for guiding and coiling incoming and outgoing optical fibre cables. When the top part  3  of the box is given an appropriate height, several optical fibre cassettes  4  can be stacked on the lower part and accommodated in said top part. One or more openings for sealed transit of the optical fibre cables may be provided on each side of the ends of the bottom part of the box. The top and bottom parts of the connecting box arrangement will preferably be made of a plastic material, such as polycarbonate, polyphenyl oxide, polybutiene terephthalate, polypropylene or the like. 
     FIG. 2 shows the bottom part  2  of the box arrangement from above. Both short sides of the lower box part  2  include openings  5 ,  6 , such as apertures, for insertion of optical fibre cables into cable seals. The illustrated openings have smooth sides and a semi-cylindrical bottom so as to conform fully with the cross-sectional shape of the cable seals, therewith enabling the cable transits to be made completely tight. Provided at the ends of the bottom part are holes  7  for receiving screws or the like fasteners for fixing the top part  3  to the bottom part  2  and for clamping intermediate cable seals enclosing optic fibre cables to prevent the ingress of moisture into the interior space of the connecting box arrangement. Arranged in the central portion of the bottom part of the box are two cable coiling and guiding devices  8 ,  9  which function to coil or wind the incoming and outgoing cables. An undulating guide element  10  is provided on one side of the inside of the bottom part of the box arrangement. The arrangement also includes various holes for receiving screws or like fasteners for securing devices that hold the cassettes  4  disposed on the bottom part  2  of the box interior. 
     FIG. 3A shows with arrows in the bottom part of the box the insertion directions of the optical fibre cables and optical fibres. As shown at  11 , the incoming cables containing optical fibres are passed into the bottom part of the box arrangement through the openings  5 ,  6  and are first guided towards a channel  12  and over the first coiling device  8  and then beneath the second coiling device  9  and then to overlying tray/cassettes for accommodating optical fibres or for further coiling of the cable around the second coiling device. The coiling devices  8 ,  9  enable individual cables to be coiled for storage in the box arrangement, or for obtaining lengths of optical fibre cable which are equivalent to the length of the optical transport paths in an optical fibre system. As shown at  14 , the optical fibres of the outgoing optical fibre cables are passed into the bottom part of the box arrangement and first guided up towards the channel  15  and over the second coiling device  9 , and from there up to the overlying trays/cassettes, for instance. 
     FIGS. 3B and 3C illustrate from one side and from above, respectively, a cassette  4  in which one or more optical fibres can be coiled/wound while leaving room for connecting and/or redirecting the optical fibres with the minimum of fibre intersection. The arrows  16  illustrate directions in which the optical fibre/optical fibres of the optical fibre cables is/are coiled. 
     FIGS. 4A-D illustrate a cable seal from different directions and in cross-section. FIG. 4A is a view of the cable seal  17  from one short side thereof and shows the seal to include a semi-cylindrical underside  18  and flat longitudinal sides  19 ,  20 . The upper side  21  has a high centre part and low side edges. Consequently, when the cable seal  17  is in place in an opening  5 ,  6 , it will be pressed down more in its centre than at its sides when securing the top part  3  of the box arrangement to its bottom part  2 , therewith improving clamping, and also sealing, of the cable transit that leads into the interior of the box arrangement  1 . As will be seen from FIG. 4, the cable seal includes a centre hole  22  through which the optical fibre cable can be passed and the conical shape of which has been reproduced in the figure by means two closely adjacent and concentrical circles. The tapering shape/conicity of the cable seal enables the seal to be adapted to cables of different diameters and permits a cable passing through the cable seal to be angled without being broken and while maintaining an effective seal. The possibility of angling the cable is beneficial when the cable shall be guided to one or the other side externally of the box arrangement, after having passed the cable through the cable seal. The slot is preferably made oblique, so as to provide greater tightness as it encloses an optical fibre cable in the channel on the bottom part of the box arrangement. 
     FIG. 4B is a side view of the cable seal  17 . It will be seen that the cable seal is long in relation to its width, which provides effective guidance of a cable passing therethrough and also stable fixation of the cable even when it is necessary to angle the cable in towards the box arrangement. The elevated centre part of the cable seal is shown at  24 . 
     FIG. 4C is a cross-sectional view of the cable seal  17  and shows the hole  22  tapering towards a circular-cylindrical opening  25 . 
     FIG. 4D is a perspective view of the cable seal  17  and shows the longitudinal slot  23  and the elevated centre part  24  of said seal. FIG. 5 illustrates a cable seal  26  that includes several holes  27 ,  28 , seen from one short side of the seal. The cable seal has a semi-cylindrical underside  29  and flat longitudinal sides  30 ,  31 . The upper side  32  has a high centre part and lower side edges, which, when the cable seal is in place in an opening  5 ,  6 , cause the cable seal to be pressed down more in its centre region than at the sides thereof as the top part of the box is tightened against the bottom part thereof, therewith improving clamping, and also sealing, of the optical fibre cables passing through said seal and into the interior of the box arrangement  1 . The conical shape of the holes  27 ,  28  have been illustrated in the figure by means of two mutually adjacent and concentrical circles. Openable slots  33 ,  34  have been provided obliquely in the upper part of the cable seal and on one side thereof, for insertion of the optical fibre cables into the cable seal. 
     FIG. 6 illustrates a connecting device  35  for an unused cable transit comprising two combined plugs  36 ,  37  which are operative in closing two different hole diameters in a sealing cable transit. Because respective plugs have been given a tapering centre part  38 ,  39  adapted to the shape of the hole in the transit, the hole will be closed positively and sealingly after the plug has been inserted into the hole in the cable transit. In the event of pressure differences between the interior space and the surroundings, the configuration of the plug and the hole will coact to keep the plug in the hole. The plugs may be used conveniently for closing the connecting box arrangements during their transportation prior to use. 
     It will be understood that the invention is not restricted to the aforedescribed and illustrated embodiments thereof and that modifications can be made within the scope of the accompanying Claims.