FR2901890A1 - OPTICAL CABLE FOR CONNECTING TO A GENERAL DISTRIBUTION NETWORK AND CONNECTING METHOD THEREFOR - Google Patents

Abstract

The invention relates to an optical cable (10) comprising: - an outer envelope (15) whose inner surface (150) defines a cavity (151), - at least one elongated element extending in said cavity, intended to receive at least one an optical fiber, characterized in that it further comprises: - a profiled structure (16) extending inside said cavity (151) and defining at least one open compartment (160, 161, 162) which substantially extends in the longitudinal direction of the cavity and contains said at least one elongated member (11, 12, 13, 14, 17) and means (18) for maintaining said at least one elongated member therein of its compartment, and in that for each compartment, the sectional area of the elongated element (s) present in said compartment is less than 75% of the area of the section of said compartment.

Description

The invention relates to the field of optical cables which are intended for

  connect a distribution network to power points, located particularly with subscribers. The invention more particularly relates to optical cables intended to carry a large number of optical fibers. Several types of optical networks are known. Some networks have a tree architecture. In this type of architecture, optical cables connect each subscriber to a general distribution network by forming branches extending from cascaded connection points. Cables generally contain a decreasing number of optical fibers as the network divides to get closer to each subscriber. A disadvantage of this architecture is that it multiplies the number of connection points. The connection points require splicing to permanently connect cables to each other. These splices are a source of fragility of the network and especially a source of costs, related in particular to the installation time which is important compared to the cost of the optical fiber itself.

  Since the cost of fiber optics has been steadily decreasing, it has proved more interesting to install a large number of optical fibers during the installation of the network than to multiply the cables and cables. installation interventions that, especially in urban areas, generate significant expenses.

  Optical networks with star-ring architectures are also known. A network of this type comprises a ring general distribution artery in which extends a general distribution cable. The route connects a set of sub-distributors, each sub-distributor being intended to serve a given geographical area of distribution.

  Each sub-distributor performs a junction into the artery and a set of microconduits previously installed in a sheath that extends from the sub-distributor into the geographical distribution area. The microconducting installation in the sheath is performed by pulling, pushing or blowing. The microconduits therefore extend between connection points in the geographical distribution zone. Each connection point makes a junction between the set of microconduits and a distribution microcircuit to a subscriber located in the geographical area.

  From pre-existing microconduits, it is possible to make subscriber connections on demand. For this purpose, microcables containing optical fibers are inserted into microconduits, from the sub-distributor to a subscriber who wishes to be connected to the network.

  The insertion of the microcables into the microcards is conventionally carried out by pulling, pushing or blowing techniques. This type of architecture is particularly suitable for connecting professional subscribers for whom microcables containing a large number of optical fibers are used. However, this type of architecture is poorly suited when it is appropriate to install, in a given geographical area, a large number of microconduits. Indeed, the multiplication of microconduits makes complex the management of the connection points and requires bulky connection points. Furthermore, a disadvantage of this type of network architecture is that it requires the prior installation of a set of microdrivings and requires installation techniques in an urban environment that can be implemented only from dedicated and heavy equipment. The object of the invention is therefore to overcome these drawbacks by proposing an optical cable that can comprise a very large number of fibers, while making it possible to make a connection to a general distribution network, in a simpler way in terms of accessibility, tracking and security and more economical way. The invention thus relates to an optical cable comprising: an outer casing whose inner surface defines a cavity, at least one elongate element extending in said cavity, intended to receive at least one optical fiber, characterized in that it further comprises: a profiled structure extending within said cavity and defining at least one open compartment which extends substantially in the longitudinal direction of the cavity and which contains said at least one elongate member and means for maintaining said at least one elongate member within said compartment, and that for each compartment the sectional area of the elongate member (s) present in said compartment is less than 75% of the area of the section of said compartment. Within the scope of the present patent application, an elongated element will be understood to mean a micromodule, a microcable, a microtube or a unitary optical fiber, in particular a tight optical fiber 900 μm or an optical fiber 245 μm.

  Since the elongated elements present in each compartment of the profiled structure do not fill all the available volume in the compartment, a certain clearance exists between the different elements.

  Thus, when an elongated element is to be extracted, it can be easily identified and its extraction can be performed without disturbing the neighboring elongate elements, also present in the compartment. Moreover, the distribution of the elongate elements according to compartments, allows to limit the number of elements per compartment.

  This makes it easier to visualize, by color or other, such as net or ring. This also allows to assign a compartment to a certain type of elongate elements, for example elements having a particular number of fibers. This further facilitates the choice of the elongated element for the operator and makes it possible to easily and securely manage the various elongated elements. One can also choose to allocate to each compartment the same number of elongate elements and then reference each elongated element by color, according to the number of fibers contained. Finally, the fact of maintaining the elongated elements in their compartment during the manufacture and installation of the cable prevents the distribution of elements in the profiled structure is not preserved after installation of the cable. This would indeed be very disturbing for the operator who would not be in front of the expected configuration.

  Preferably, said at least one compartment has a generally U-shaped shape. The structure advantageously has the form of a ribbon, in which extend substantially in the same plane, one or more compartments, separated by partitions.

  Preferably, said structure is transversely grooved to adjust its flexibility. In a first embodiment, the means for holding said at least one elongated element inside its compartment are constituted by a thin layer of easily peelable, breakable or tearable material which closes said compartment. In another embodiment, these holding means are constituted by a thin layer of an easily peelable, breakable or tearable material surrounding said at least one elongated member loosely.

  In another embodiment, these holding means consist of an easily peelable, breakable or tearable ribbon which surrounds the profiled structure and holds the elongated elements. Advantageously, said outer casing comprises reinforcements.

  This is preferable when the optical cable has a very large number of fibers, to protect them effectively. Preferably, if reinforcements are provided in the form of metal tapes, the outer envelope further comprises at least one synthetic tape, wound on said metal tapes.

  This makes it possible to decouple the metal reinforcements from the outer casing and thus to improve the flexibility of the cable. Thus, with the optical cable according to the invention, an elongated element can be extracted without difficulty by the operator. After its extraction, the elongate element will allow the connection of a power point, located for example in a subscriber or in a junction box. The operation of connecting a power point to the optical cable will not require the completion of connections between cables by splice or connector since the elongated element for the connection of the power point is directly taken from the main cable.

  The invention also relates to a method of connection by means of an optical cable as defined above, comprising the steps of:

  extracting a portion of an elongate element of the optical cable; connecting a feed point to the optical cable via the portion of the extracted elongated element. The steps of this method of connection do not require the realization of connections between cables by splice or connector since the elongate element is directly taken from the main cable to be diverted to a feed point. The method may comprise steps of: - selecting a portion of an elongated member extending between a first area of the cable and a second area of the cable, remote from the first area along the cable, -selecting the element lying at the first zone; pulling the elongated element at the second zone to extract the selected portion of the elongated element. To this end, the method advantageously comprises the preliminary steps of: - opening in the outer casing at the first and / or second zone and - removing the holding means at least opposite said 25 openings.

  The method may include a step of inserting the portion of the extracted elongated member into a conduit extending between the cable and the feed point. The method advantageously consists in placing on the opening at the first zone, means ensuring the tight closure of the cable. It is also preferably to place on the opening at the second zone, means ensuring the maintenance of the elongated element, its connection to the distribution cable and the sealing of the optical cable. The portion of the elongated element can be inserted into the pipe by pushing, pulling or blowing. The method may include a step of extracting a portion of an elongate member having a length of between a few meters and several tens of meters. Other features and advantages of the invention will emerge more clearly from the description which follows, which is given in a nonlimiting manner with reference to the accompanying drawings, in which: FIG. 1 schematically represents a network architecture conforming to a embodiment of the invention; FIG. 2 schematically represents a perspective view of a structure of an optical cable according to an embodiment of the invention, cut transversely, FIG. the various steps of a method of connecting a feed point, according to an embodiment of the invention. The elements common to the different figures will be designated by the same references.

  In Figure 1, the distribution network shown comprises an artery 1 of general ring distribution in which extends a cable 2 of general distribution. The cable 2 interconnects a set of sub-distributors or optical patching points 3 arranged along the artery 1, each sub-distributor 3 being intended to serve a geographic area 6 of distribution. The distribution network comprises a connection cable 10 extending from the sub-distributor 3 in a single main pipe 9. The cable 10 has two ends, each end being connected to the sub-distributor 3 so that the cable forms a connecting loop extending in the geographical zone 6. The distribution network also comprises a plurality of connection points 21, 22, 23, 24, 25, 26, 27, 28 distributed along the cable 10, each connection point being intended to allow the connection of a feed point 31, 32, 33, 34, 35, 36, 37 or 38 located in the geographical zone 6. The feeding points 31, 32, 33, 34, 35, 36 and 37 are for example localized power points in subscribers while the power point 38 is installed in a junction box.

  The feed point 38 installed in the junction box makes it possible to connect the cable 10 to a branch network 40. Such a branch network 40 makes it possible to connect one or more subscribers located outside of geographic area 6 or at a remote site. As illustrated in FIG. 1, the cable 10 comprises a plurality of microcables 11, 12, 13, 14. The microcables 11, 12, 13, 14 are connected to the general distribution cable 2 at the level of the sub-distributor 3, when the installation of the network. The sub-distributor 3 therefore does not require any subsequent connection.

  As can be seen in FIG. 1, the feed points 31, 32, 33 and 34 are connected to the cable 10 via a microcable portion extracted from the cable 10 from one of the connection 21, 22,23,24.

  More specifically, the feed points 31, 32, 33 and 34 are respectively connected to the connection cable 10 via portions of the microcables 11, 12, 13 and 14 extracted from the cable 10 at the connection points 21, 22, 23, 24, so that no junction operation between cables is required at connection points 21, 22, 23, 24. Figure 2 schematically shows a perspective view of an optical cable. according to the invention, cut transversely. The optical cable 10 comprises a closed outer envelope 15 whose inner surface 150 defines a cavity 151. Preferably, the outer envelope 15 is reinforced, given the very large number of optical fibers that it is likely to contain. By way of illustration, this envelope may be made of commonly used materials, such as PE, PVC or PP, and the reinforcements may be in the form of metal ribbons or else non-metallic reinforcing fibers. They bear the reference 152 in FIG. 2. In the case of reinforcements in the form of metal ribbons, the flexibility of the cable can be improved by decoupling the metal strip from the outer casing by juxtaposing one or more synthetic ribbons such as polyester ribbons. These ribbons are then wound on the metal reinforcements.

  Inside this cavity 151, extends a profiled structure 16 which has the form of a ribbon. Preferably, the profiled structure 16 is grooved transversely along its length to provide more flexibility to the optical cable 10. This structure defines, in this embodiment, three compartments 160, 161 and 162, through partitions 163. the embodiment shown in Figure 2, these compartments have a generally U-shaped cross section and extend substantially in the longitudinal direction of the cavity 151. Inside each compartment of the profiled structure 16, are provided several microcables 17, such as microcables 11, 12, 13, 14 which are, in this example, all four in the compartment 160.

  Each of these microcables is intended to receive at least one optical fiber. On the profiled structure 16, there are also provided means 18 for maintaining the microcables inside their respective compartment.

  In the example illustrated in Figure 2, these means consist of a thin film easily peelable, breakable or tearable, which closes the compartments 160 to 162 of the profiled structure 16. These means could also be used to cover, loosely , the packets of microcables placed in each of the compartments. These means could also comprise an easily peelable, breakable or tearable ribbon which surrounds the profiled structure 16.

  This thin film or this tape may in particular be made of a thermoplastic polymer or paper. The microcables 17 are arranged in the compartments of the profile 16, so as to have a sufficient clearance to facilitate their identification and extraction. The clearance in each compartment is such that the area of the sum of the sections of all the microcables contained in a compartment is less than 75% of the area of the section of the same compartment.

  As an indication, for the cable illustrated in Figure 2 which is substantially rectangular in section, the outer dimensions are 15.5 x 30.5 mm for a reinforced cable containing 684 optical fibers and 13.5 x 28.5 mm for an unreinforced cable containing the same number of optical fibers.

  As explained above, the compartment 160 may contain microcables of 8 optical fibers, the compartment 161 of the microcables of 12 optical fibers and finally the compartment 162, microcables 18 fibers. In this case, the category of microcables assigned to a given compartment, for example the compartment 160, can be identified by a mark placed on the edge 164 of one of the partitions 163 forming this compartment 160. If each compartment comprises microcables of different capacity, this capacity can be identified by a specific color for the sheath of each microcable. The optical cable shown in Figure 2 comprises microcables. The invention is not limited to this embodiment. It could also comprise other elongated elements such as micromodules, microtubes or even a unit optical fiber, in particular a tight optical fiber 900pm or an optical fiber 245pm. The invention also relates to a method of connection by means of an optical cable according to the invention.

  This method will now be described with reference to FIG. 3, which schematically represents a portion of a cable 10 conforming to that of FIG. 2, also seen in perspective. This method consists in general of extracting a portion 110 of a microcable 11 present for example in the compartment 160 to connect a feed point to the optical cable, via this extracted portion 110. Thus, this method consists of make a first opening 190 in the outer casing 15 at a first zone 22 of the cable 10 and another opening 191 at the second zone 21 of the cable 10. These two zones are distant from each other , so that the portion 110 of the microcable that will be extracted may be between a few meters and several tens of meters. Once the openings are made, the holding means 18 closing the compartment 160 are removed opposite the openings 190 and 191, to allow access to the microcable 11. The microcable 11 is then cut at the first zone 22, through the opening 190. The microcable 11 is then pulled at the second zone 21, so as to extract the selected portion 110 of the microcable by the opening 191. The method finally involves inserting the microcable into a pipe ( not shown) extending between the cable and the feed point 31. In the case where the feed point is at a substantial distance from the cable 10, the insertion of the microcable into the pipe can be carried out from a stuffing device supplemented by a compressed air carrying device. For this, it will be advantageous to place on the opening 191 at the second zone 21, adaptation means (not shown) ensuring both the maintenance of the microcable, its connection to the distribution cable and the sealing of the Similarly, to protect and seal the cable 10 at the opening 190, appropriate means (not shown) 10 will be placed on this opening. Thus, the cable according to the invention makes it possible, by arranging the elongate elements by compartments, to facilitate their identification and thus to increase the capacity of the optical cable in terms of the number of optical fibers.

It will also be noted that a rectangular-shaped cable, such as that illustrated in FIG. 3, allows optimized storage along the compartments, with respect to a round-section cable. It thus makes it possible to access a very large number of optical fibers. The reference signs inserted after the technical features appearing in the claims are only intended to facilitate understanding of the latter and can not limit its scope.

Claims (17)

claims   An optical cable (10) comprising: - an outer shell (15) whose inner surface (150) defines a cavity (151), - at least one elongate member extending into said cavity, for receiving at least one optical fiber, characterized in that it further comprises: - a profiled structure (16) extending inside said cavity (151) and defining at least one open compartment (160, 161, 162) which substantially extends in the longitudinal direction of the cavity and which contains said at least one elongated member (11, 12, 13, 14, 17) and - means (18) for maintaining said at least one elongate member at the within its compartment, and in that for each compartment, the sectional area of the elongate element (s) present in said compartment is less than 75% of the area of the compartment. section of said compartment.   2. Optical cable according to claim 1, characterized in that said at least one compartment (160, 161, 162) has a general U shape.   3. Optical cable according to one of claims 1 or 2, characterized in that said profiled structure (16) has the form of a ribbon, in which extend substantially in the same plane, one or more compartments (160, 161, 162), separated by partitions (163). 25   4. Optical cable according to one of claims 1 to 3, characterized in that said structure (16) is grooved transversely to adjust its flexibility.   5. Optical cable according to one of claims 1 to 4, characterized in that the holding means (18) of said at least one elongated member within its compartment, comprise a thin layer of an easily peelable material, breakable or tearable that closes said compartment.   6. Optical cable according to one of claims 1 to 4, characterized in that said holding means comprise a thin layer of a readily peelable, breakable or tearable material which surrounds said at least one elongate member loosely.   7. Optical cable according to one of claims 1 to 4, characterized in that said holding means comprise an easily peelable, breakable or tearable tape which surrounds said profiled structure (16).   8. Optical cable according to one of claims 1 to 7, characterized in that said outer casing (15) comprises reinforcements (152).   9. Optical cable according to claim 8, wherein said outer casing comprises reinforcements (152) metal, characterized in that at least one synthetic tape is wound on said metal reinforcements.   10. A method of connection by means of an optical cable according to one of claims 1 to 9, comprising the steps of: - extracting a portion (110) of an elongated element (11) of the optical cable (10) connecting a feed point (31-38) to the optical cable (10) via the extracted elongated element portion (110). 25   The method of claim 10, comprising the steps of: - selecting a portion (110) of an elongated member (11) extending between a first zone (22) of the cable (10) and a second zone (21) of the cable (10), spaced from the first zone (22) along the cable, -selecting the elongated element (11) at the first zone - pulling the elongate element at the second zone (21) of the in order to extract the selected portion (110) of the elongate member (11).   The method of claim 11, comprising the steps of: - opening (190, 191) at the first and / or second zone (22, 21) and - removing the holding means (18) at least opposite said openings.   13. Method according to one of claims 10 to 12, characterized in that it comprises a step of inserting the portion (110) of the extracted elongated element in a pipe extending between the cable (10) and the feeding point (31).   14. The method of claim 13, characterized in that the portion of the elongate element (110) can be inserted into the pipe by pushing, pulling or blowing. 20   15. Method according to one of claims 12 to 14, characterized in that it consists in placing on the opening (190) at the first zone (22), means ensuring the tight closure of the cable (10). .   16. Method according to one of claims 12 to 15, characterized in that it consists in placing on the opening (191) at the second zone (21), means ensuring the maintenance of the elongated element , its connection to the distribution cable and the sealing of the optical cable.   17. Method according to one of claims 10 to 16, characterized in that it comprises a step of extracting a portion of an elongated element having a length of between a few meters and several tens of meters.