U.S. patent application number 10/550794 was filed with the patent office on 2006-08-24 for optical fiber cable distribution frame.
Invention is credited to Philip J. Barker, John Kerry, Christopher C. Taylor.
Application Number | 20060188209 10/550794 |
Document ID | / |
Family ID | 32299721 |
Filed Date | 2006-08-24 |
United States Patent
Application |
20060188209 |
Kind Code |
A1 |
Barker; Philip J. ; et
al. |
August 24, 2006 |
Optical fiber cable distribution frame
Abstract
A telecommunication distribution frames comprising a switch
connected to an optical fibre of an incoming cable, terminated at a
primary flexibility suite, via a secondary flexibility suite, where
the primary and secondary flexibility suites include means for
routing joined blown fibre tubes within the installation. A
continuous blown fibre unit extending through the joined blown
fibre tubes. A blown fibre tube flexibility module (14) has a
patching panel (11), which may be provided with connectors. Above
the panel (11) are a set of bend control vanes or mandrels (24),
one for each of the connector sites in the panel. Patching tubes
may pass down and out through the aperture (99) at the back of the
module.
Inventors: |
Barker; Philip J.; (Ipswich,
GB) ; Kerry; John; (Ipswich, GB) ; Taylor;
Christopher C.; (Cheltenham, GB) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Family ID: |
32299721 |
Appl. No.: |
10/550794 |
Filed: |
March 31, 2004 |
PCT Filed: |
March 31, 2004 |
PCT NO: |
PCT/GB04/01370 |
371 Date: |
September 22, 2005 |
Current U.S.
Class: |
385/135 |
Current CPC
Class: |
G02B 6/4459 20130101;
G02B 6/4464 20130101; G02B 6/4452 20130101; G02B 6/4478
20130101 |
Class at
Publication: |
385/135 |
International
Class: |
G02B 6/00 20060101
G02B006/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2003 |
GB |
0307394.7 |
Sep 25, 2003 |
GB |
0322490.4 |
Claims
1. A flexibility suite for routing optical fibres within a
telecommunications switch installation, the suite comprising: a
first flexibility point and a second flexibility point, the first
flexibility point including a first set of conduits each of the
conduits having a first end disposed in a first array and a second
end disposed in a second array; the second flexibility point
including a second set of conduits, each of the conduits having a
first end disposed in a third array and a second end disposed in a
fourth array; the flexibility suite being so arranged as to permit
the conduit ends on the second array to be interconnected with
conduit ends on the third array by means of tubular interconnects
so that, by selecting the conduits whose ends on the second and
third arrays are interconnected, a continuous path can be formed
between any conduit end in the first array and any conduit end in
the fourth array.
2. A flexibility suite as claimed in claim 1 wherein said tubular
interconnects are present and interconnect conduit ends on the
second and third arrays, and wherein means are provided to control
the paths taken by the tubular interconnects.
3. A flexibility suite as claimed in claim 1, wherein each of the
conduit ends on the second, third and fourth arrays is provided
with a connector for connection of the respective conduit end to a
tubular interconnect.
4. A flexibility suite as claimed in claim 3, wherein each
connector of the third array is provided by one end of a
double-ended connector, the other end of each connector providing
the corresponding connector of the fourth array, the bores of the
connectors providing the conduits of the second set.
5. A flexibility suite as claimed in claim 3, wherein each of the
conduit ends of the first array are also provided with a connector
for connection of the respective conduit end to a tubular
interconnect.
6. A flexibility suite as claimed in claim 5 wherein each connector
of the second array is provided by one end of a double-ended
connector, the other end of the connector providing the
corresponding connector of the first array, the bores of the
connectors providing the conduits of the first set.
7. A flexibility suite as claimed in claim 1, wherein the bores of
the conduits and the tubular interconnects are between 1.5 and 5
millimetres in diameter.
8. A flexibility suite as claimed in claim 7, wherein the bores are
between 2 and 4 millimetres in diameter.
9. A flexibility suite as claimed in claim 1, wherein the second
and third arrays or the first and fourth arrays are arranged side
by side.
10. A flexibility suite as claimed in claim 9, wherein the
side-by-side arrays are provided on two panels distinct from each
other.
11. A telecommunications switch or router installation comprising;
a telecommunications switch or router; a first and at least one
second flexibility suite according to claim 1; a sub-path being
defined through each of the flexibility suites from the first array
to the fourth array via an interconnection between the second and
third arrays; the fourth array of the first flexibility suite being
interconnected with the first array of the or one of the second
flexibility suite (s); a tubular pathway being provided between the
fourth array of the second flexibility suite or the last of the
second flexibility suites and the switch or router; the other
second flexibility suites, if any, being interconnected in series
with the first array of each of subsequent second flexibility suite
being interconnected with the fourth array of the preceding second
flexibility suite by means of a tubular interconnect, so that a
substantially continuous path is provided for installation of a
blown-fibre member between the first flexibility suite and the
switch or router; wherein the switch or router is optically
connected, via an optical fibre of a continuous blown-fibre member
which extends along said substantially continuous path, to an
optical fibre of an optical fibre cable which enters the
installation from an external telecommunications network.
12. An installation as claimed in claim 11, wherein the optical
fibre of the blown-fibre member is spliced to the fibre of the
incoming cable.
13. An installation as claimed in claim 11, wherein the optical
fibre of the blown-fibre member is spliced to a fibre of a cable or
fibre unit which is within the optical path between the incoming
cable and the blown-fibre member.
14. An installation according to claim 11, including a plurality of
secondary flexibility suites.
15. An installation according to claim 11, wherein a plurality of
telecommunications switches are connected, via the primary and
secondary flexibility suites, to optical fibres of several incoming
cables.
16. An installation according to claim 11, including bend control
means to control the bend radius of the blown fibre tube.
17. A method of creating a connection in a telecommunications
switch or router installation, between a telecommunications switch
or router, and an optical fibre of an incoming cable connected to
and incoming from a telecommunications network, comprising the
steps of: installing lengths of blown fibre tube and joining the
ends of the lengths of blown fibre tube to form a path from a
primary flexibility suite to the telecommunications switch via a
secondary flexibility suite, where the primary and secondary
flexibility suites include means for routing joined blown fibre
tubes within the installation, and thereafter, installing, by
blowing, a continuous blown fibre unit through the path formed by
the joined blown fibre tubes, to provide an optical path between
the telecommunications switch and the optical fibre of the incoming
cable.
18. A method of re-routing an existing connection in a
telecommunications switch or router installation from a connection
between a first telecommunications switch or router and a primary
flexibility suite, to create a connection between a second
telecommunications switch or router and the primary flexibility
suite, comprising the steps of: breaking the connection between the
first telecommunications switch and the primary flexibility suite,
joining the ends of lengths of blown fibre tube to form a path from
the primary flexibility suite to the secondary telecommunications
switch via a secondary flexibility suite, where the primary and
secondary flexibility suites include means for routing joined blown
fibre tubes within the installation, and thereafter, installing, by
blowing, a continuous blown fibre unit through the path formed by
the joined blown fibre tubes thereby providing an optical path
between the second telecommunications switch or router and the
optical fibre of the incoming cable.
19. A method according to claim 17, wherein the primary flexibility
suite includes a line-side optical flexibility point and an
equipment-side blown fibre tube flexibility point located in
proximity to each other, and the secondary flexibility suite
includes a line-side blown fibre flexibility point and an
equipment-side blown fibre flexibility point located in proximity
to each other, wherein the path from the primary flexibility suite
to the telecommunications switch is formed by installing a blown
fibre tube from the equipment-side blown fibre flexibility point in
the primary flexibility suite to the line-side blown fibre
flexibility point in the secondary flexibility suite, installing a
blown fibre tube from the equipment-side blown fibre flexibility
point in the secondary flexibility suite to the telecommunications
switch, and interconnecting the line-side flexibility point to the
equipment-side flexibility point in flexibility suite.
20. A method according to claim 17, wherein the continuous blown
fibre unit is installed by blowing from an equipment rack housing
the telecommunications switch.
21. A method according to claim 17 wherein the continuous blown
fibre unit is pre-connectorised.
22. A method according to claim 17 wherein the continuous blown
fibre unit is installed by blowing from the line-side optical
flexibility point of the primary flexibility suite.
Description
[0001] This invention relates to telecommunications exchange or
router installations and to methods of creating connections and
re-routing connections in such installations.
[0002] A typical telecommunications exchange building houses a
large variety and quantity of equipment such as switches, typically
on equipment racks, and connected by cables to and from each other
and to the external telecommunications network. The trunk parts of
telecommunications networks are nowadays commonly all-fibre.
Increasingly, optical fibre use extends into the access network,
with fibre-to-the kerb, fibre-to-the-cabinet and even fibre-to-the
premises. Consequently, virtually all modern telephone exchange
installations involve a considerable proportion of fibre circuits
rather than wired circuits. Because optical fibre is sensitive both
to bend and strain, management of the optical interconnections
within an exchange installation is important.
[0003] One of the main functions of optical fibre plant within an
exchange or router building is to manage and route fibres from a
particular set of optical equipment to fibres from, for example, an
incoming cable from the external telecommunications network. As
optical fibre is deployed more abundantly and more generally in the
network, the routing and patching of such fibre, especially within
exchanges, is becoming increasingly troublesome. Major problems are
the growth in the amount of equipment and the sheer number of
connections required. These problems are exacerbated by growth,
upgrading and changes within the exchange which result in the need
to interconnect new equipment or systems. Although the physical
positions of incoming cables rarely change, additional cables may
be added and the new equipment or system will almost certainly be
in a different physical location from the old, and in any event
will typically need moving or different connections to be made.
[0004] The current method of fibre routing within exchange
buildings is achieved with Optical Flexibility Racks (OFRs), which
serve as junction or distribution points allowing cables to be
routed within the exchange building. OFRs can carry hundreds of
individually spliced fibres but when they are fully populated, as
is often the case, there is severe congestion at the OFRs. It is
often difficult to identify, locate and isolate individual fibres
in such cases when re-routing of the cable path is necessary,
making the task both time-consuming and complicated. Another
problem resulting from fibre overcrowding is that fibres are routed
across each other in close proximity so that the combined weight
presses down on fibres located near the base of OFRs, increasing
the risk of circuit failure through increased optical loss and even
of fibre breakage. This problem becomes even more critical as
higher bit rate systems are employed, as these tend to be more
sensitive to increases in optical loss.
[0005] The installation and maintenance of optical fibre cabling,
its routing and supporting structures such as OFRs take up a
significant portion of the total cost, time and effort of
installing and cabling a telecommunications exchange system. The
current methods to interconnect exchange equipment, or to connect
an incoming cable to a rack of exchange equipment typically involve
several lengths of optical fibre connected end to end either by
means of connectors or splices, or a combination thereof. The path
taken by the fibre from the incoming cable to an equipment rack
could involve a significant number of connections or splices,
especially if the destination equipment rack is physically distant
from the incoming cable, for example if the equipment sits on a
separate floor from the incoming cable within the exchange
building.
[0006] Such conventional methods are commonly known and described
in e.g. Modular Optical Plant for Access Network: Operational
Aspects by D. Brewer et. al (Proc. EFOC & N (Technology and
Infrastructure) 1995, at pages 164-167).
[0007] Problems associated with the existing method of creating
fibre paths by using connectors or splices arise from the
inherently delicate nature of joining fibre ends, which is time-
and cost-consuming in the need for specialist equipment and
expertise. Connections and splicing also inevitably involve optical
losses regardless of the quality of the joint. Other problems could
arise: for example, stored fibre could "run out" either side of the
splice, thereby reducing the number of fibre turns and hence the
opportunity to re-splice in the future.
[0008] In a first aspect, the present invention provides a
flexibility suite for routing optical fibres within a
telecommunications switch installation, the suite comprising:
a first flexibility point and a second flexibility point, the first
flexibility point including a first set of conduits each of the
conduits having a first end disposed in a first array and a second
end disposed in a second array;
[0009] the second flexibility point including a second set of
conduits, each of the conduits having a first end disposed in a
third array and a second end disposed in a fourth array; the
flexibility suite being so arranged as to permit the conduit ends
on the second array to be interconnected with conduit ends on the
third array by means of tubular interconnects so that, by selecting
the conduits whose ends on the second and third arrays are
interconnected, a continuous path can be formed between any conduit
end in the first array and any conduit end in the fourth array.
[0010] Such an arrangement facilitates the use of blown fibre in an
exchange setting. This arrangement also facilitates the provision
of new paths through the re-use of existing partial paths simply by
changing the choice of "patches" made between the second and third
arrays.
[0011] Generally, the second set of conduits will be formed by the
bores of double-ended connectors. Similarly, the first set of
conduits will often be formed by the bores of double-ended
connectors. Preferably the connectors are push-fit connectors which
provide a sealing grip about or within the tubes which are used
between flexibility suites, to switches or routers and as patch
tubes. Such connectors are particularly good at facilitating the
rapid commissioning or re-commissioning of tube paths.
[0012] In a second aspect, the present invention provides a
telecommunications switch or router installation comprising; a
telecommunications switch or router connected to an optical fibre
of an optical fibre cable which itself is connected to and incoming
from an external telecommunications network; a first and at least
one second flexibility suite according to the first aspect of the
invention; a sub-path being defined through each of the flexibility
suites from the first array to the fourth array via an
interconnection between the second and third arrays; the fourth
array of the first flexibility suite being interconnected with the
first array of the or one of the second flexibility suite(s);
[0013] a tubular pathway being provided between the fourth array of
the second flexibility suite or the last of the second flexibility
suites and the switch or router; the other second flexibility
suites, if any, being interconnected in series with the first array
of each of subsequent second flexibility suite being interconnected
with the fourth array of the preceding second flexibility suite by
means of a tubular interconnect, so that a substantially continuous
path is provided for installation of a blown-fibre member between
the first flexibility suite and the switch or router.
[0014] In a third aspect the invention provides a method of
creating a connection in a telecommunications switch installation,
between a telecommunications switch, and an optical fibre of an
incoming cable connected to and incoming from a telecommunications
network, terminated at a primary flexibility suite, comprising the
steps of:
[0015] installing lengths of blown fibre tube and joining the ends
of the lengths of blown fibre tube to form a path from the primary
flexibility suite to the telecommunications switch via a secondary
flexibility suite, where the primary and secondary flexibility
suites include means for routing joined blown fibre tubes within
the installation, and thereafter, installing, by blowing, a
continuous blown fibre unit through the path formed by the joined
blown fibre tubes, thereby providing an optical path between the
telecommunications switch and the optical fibre of the incoming
cable.
[0016] In a fourth aspect, the present invention provides a method
of re-routing an existing connection in a telecommunications switch
installation from a connection between a first telecommunications
switch and a primary flexibility suite, to create a connection
between a second telecommunications switch and the primary
flexibility suite comprising the steps of:
[0017] breaking the a connection between the first
telecommunications switch and the primary flexibility suite at the
primary flexibility suite, installing lengths of blown fibre tube
and joining the ends of the lengths of blown fibre tube to form a
path from the primary flexibility suite to the secondary
telecommunications switch via a secondary flexibility suite, where
the primary and secondary flexibility suites include means for
routing joined blown fibre tubes within the installation, and
thereafter, installing, by blowing, a continuous blown fibre unit
through the path formed by the joined blown fibre tubes thereby
providing an optical path between the second telecommunications
switch and the optical fibre of the incoming cable.
[0018] Embodiments of the invention will now be described by way of
example only with reference to the accompanying drawings in
which:
[0019] FIG. 1 is a schematic drawing of a exchange installation
using optical fibre cables currently deployed according to the
current conventional method;
[0020] FIGS. 2A and 2B are schematic drawings showing the existing
method of re-routing the path between an incoming cable and the
destination equipment rack using optical fibre cables according to
the current conventional method;
[0021] FIG. 3 is a schematic drawing of an exchange installation
according to the present invention;
[0022] FIGS. 4A and 4B are schematic drawings showing a method of
re-routing the path between an incoming cable and the destination
equipment rack according to the present invention;
[0023] FIG. 5 is a schematic drawing of another embodiment of an
exchange installation according to the present invention;
[0024] FIG. 6 is a schematic drawing of a further embodiment of an
exchange installation according to the present invention;
[0025] FIG. 7 shows a blown fibre flexibility tube module (BFTFM),
and FIGS. 7A to 7F show configurations of BFTFMs in single-, two-,
three-, four-, five- and six-module builds respectively;
[0026] FIG. 8 depicts a suite of BFTFMs of the type shown in FIG. 7
partly populated with blown fibre tubes, and a view of the routes
taken by the patching tubes within and between the BFTFMs;
[0027] FIG. 9 shows a typical build sequence of an exchange
installation of the type as shown in FIG. 3 above;
[0028] FIG. 10 shows an instance of cable deployment in an exchange
according to current methods;
[0029] FIGS. 11 to 11D illustrate the use of positive tube bend
management in the BFTFMs;
[0030] FIG. 12 provides a close up view of the patching means
within the BFTFMs;
[0031] FIG. 13 depicts another, more preferred embodiment of the
patching means;
[0032] FIG. 14 depicts details of a tube connector used with the
patching means of FIG. 13; and
[0033] FIG. 15 is another view of the patching means of FIG. 13
mounted in a BFTFM.
[0034] FIG. 1 shows a typical layout of the current exchange
installation of a particular equipment rack (2) within an exchange
building, connected to an incoming cable (5). For the avoidance of
doubt, an "incoming cable" includes any cable which enters the
exchange to connect it with, for example external
telecommunications networks.
[0035] The incoming cable (5) is typically terminated at a cable
chamber joint (CCJ) (8) by a splice (10f) to an internal cable
(1c). The CCJ is typically located within same building as the
equipment rack (2) although this is not necessarily the case. The
CCJ represents the "line-side" of the exchange for purposes of
fibre routing within the exchange. The equipment rack represents
the "equipment-side" for purposes of fibre routing within the
exchange.
[0036] The internal cable (1c) is spliced at one end to the
incoming cable at the CCJ, and the other end to a line-side
flexibility point such as an Optical Flexibility Rack (OFR)
(4d).
[0037] Flexibility points serve various functions, mainly as a
junction or distribution point to allow a user to select and
connect a point to any other point within the exchange e.g. from
any piece of exchange equipment to any other piece of equipment, or
from/to an incoming cable. Flexibility points also provide an
interface between the typically high fibre count incoming cable and
internal cables (which may be single-fibre or may contain many
fibres), terminate incoming fibres onto splice trays for safe
storage, provide easy access to each individual fibre and serve as
testing points. We are however for present purposes interested only
in their ability to connect line-side fibre to equipment-side
fibre. Typically, at least two flexibility points are used
together, more usually in side-by-side pairs, to facilitate the
routing of fibres within the exchange--one on the line-side and one
on the equipment-side. Such groupings of flexibility points are
within this patent called flexibility suites. For the avoidance of
doubt, "flexibility points" and "flexibility suites" in this
discussion are generic references to OFRs and OFR suites for fibre
cables, and to Blown Fibre Tube Flexibility Modules (BFTFMs) and
BFTFM suites (discussed below in connection with FIG. 3
onwards).
[0038] OFR suites (4a and 4b, 4c and 4d) allow fibres terminated in
line-side flexibility points and equipment-side flexibility points
to be spliced to each other on a splice tray dedicated to a fibre
or pair of fibres. Fibre jumpers (3a, 3b) are spliced between the
pair of OFRs which typically make up a suite. Another fibre cable
(1b) connects an equipment-side OFR (4c) to the next line-side OFR
(4b). The first OFR suite (comprising 4c and 4d) in FIG. 1 is
located near the CCJ, and the last suite (comprising 4a and 4b) is
that located near the destination equipment rack. In an actual
exchange, a number of OFR suites distribute and route optical
cable; the "last OFR suite" (comprising 4a and 4b) would be the
suite located closest to the destination equipment rack (2).
[0039] The prior art shown FIG. 1 depicts the most basic layout
involving two pairs of OFRs (i.e. two suites). In practice,
depending on the exchange building layout and the complexity and
length of the optical path, any number of OFR suites can be used to
describe the optical path to the equipment rack, which would have
an effect on the number of splices or connections in the optical
path. For the basic configuration shown in FIG. 1, a minimum of six
splices (10a to 10f is required.
[0040] FIGS. 2A and 2B illustrate how, according to current
practices, an optical path is re-routed from a first equipment rack
(2) to second equipment rack (12) in a conventional optical fibre
installation.
[0041] In the installation shown in FIG. 2A, an optical path
connects the incoming cable (5) to the existing equipment rack (2).
There are six splices (10a to 10f) between the incoming cable (5)
and the equipment rack (2). To re-route the optical path to the new
equipment (12) at a different location, the splice at the OFR (10e)
will have to be broken in the old path. The other splices along the
old path (10a to 10d) could be broken if required. FIG. 2B shows
the optical path to the new equipment rack (12) through two OFR
suites (4). Five new splices (10h to 10l) are made to create the
new optical path from the line side OFR (4d) adjacent to the CCJ
(8). As discussed above, splicing is a time-consuming and hence
expensive procedure requiring considerable specialist skill. Each
splice will inevitably give rise to signal attenuation and the
creation of new splices will necessarily involve the risk of a
poorly-made joint in the optical path. The cable used in the old
optical path may be removed and if not suitable for re-use, as is
generally the case, it will be discarded. Alternatively it may be
left in place, thus further adding to the problem of overcrowding
within the exchange.
[0042] FIG. 3 shows a first embodiment of the invention. Instead of
separate lengths of fibre connecting the OFRs which need to be
joined (e.g. 1a, 3a, 1b, 3b and 1c in FIG. 1), a blown fibre unit
(BFU) is installed from the OFR (4) to the equipment rack (2) to
effect the connection between the incoming cable (5) and the
equipment rack (2).
[0043] The incoming cable (5) is terminated at a first line-side
OFR (4) in the usual way as described in connection with FIG. 1
above. An internal cable (1) is spliced to the incoming cable at
the CCJ and will be spliced at its other end on a splice tray
housed in a conventional line side OFR (4) in the usual way as
described in connection with FIG. 1 above. From the line-side OFR
(4), lengths of blown fibre tube (BFT) or bundles thereof (16) are
patched through to the equipment rack (2) via a number of
flexibility points for BFTs which we will refer to as Blown Fibre
Tube Flexibility Modules (BFTFMs) (14). These BFTFMs typically
comprise a single tube and push-fit BFT connectors. Suitable
push-fit connectors can be obtained from the John Guest company. As
noted above in connection with FIG. 1, BFTFMs are flexibility
points allowing the production, within the exchange building, of a
blown fibre installation path from any point to any other point by
routing and joining lengths of blown fibre duct. As with OFRs,
BFTFMs will most commonly be employed in pairs, or suites, one on
the line-side (14b) and one on the equipment-side (14a). The OFR
(4) at which the internal cable (1) is spliced forms one half of a
flexibility suite, the other half of the suite being a BFTFM (14c)
on the equipment side. We will refer to this flexibility suite as
the primary flexibility suite. Within the blown fibre path between
the primary flexibility suite and the switch/router there will be
one or more other flexibility suites and these will be referred to
as secondary flexibility suite(s).
[0044] As an alternative to the configuration of the primary
flexibility suite described above, the primary flexibility suite
could also comprise two BFTFMs (as opposed to an OFR and a BFTFM).
The main function of the OFR in the primary flexibility suite is to
receive the incoming cable (5), which could comprise up to e.g. 144
fibres, and provide a break out point for the individual fibres of
that cable. It is possible for the individual fibres of the
incoming cable to be broken out at, for example, a CCJ (8), or at
any point between the CCJ and the primary flexibility suite. It
would not however normally be desirable so to do, as this would
mean bringing up to e.g. 144 individual fibres to the primary
flexibility suite for treatment. For the purposes of this
description therefore, the primary flexibility suite will be
discussed as being an OFR-BFTFM pair although it should be
understood that this is not the only arrangement possible.
[0045] The BFTs (16a, 16b) in this embodiment are installed between
one equipment-side BFTFM to the next line-side BFTFM along the path
to the equipment rack. The path is completed by installing BF patch
tubes (17a, 17b) within the flexibility suites (14c and 4, 14a and
14b), so that a completed BFT path is created between the OFR (4)
and the equipment rack, ready to receive a blown fibre unit (BFU).
BFU is then installed by blowing from one or other end of the path,
i.e. from the equipment rack (2) or from the first OFR (4).
[0046] In a preferred version of the invention, EPFU (Enhanced
Performance Fibre Unit) as generally described in EP-B-052170 is
used. The BFT or duct used as patch tubes typically has an internal
bore diameter in the range 1.5 to 5 mm, more usually between 2.0
and 4 mm, especially 2.5 to 3.5 mm. A particularly preferred bore
diameter is 2.5 mm, and a tube with this bore size can conveniently
be made to have an outer diameter of 4 mm. Of course, the use of
circular internal cross sections is not essential, nor is the use
of circular external cross sections although these will often be
used. Generally, the fibre unit to be used will contain only a
single fibre, but there will be occasions where higher fibre counts
will be used. Often fibre units can be made more stable if they
contain an even number of fibres, for example 2-fibre, 4-fibre,
8-fibre, but odd-fibre counts can of course be used. The use of
fibre units with multiple fibres may, for example, be useful where
the multiple fibres are to be terminated at the same destination
rack and/or where they serve the same customer.
[0047] FIG. 3 shows just two flexibility suites in use, but as
discussed above, further flexibility suites can be employed
depending on the physical distance, building layout and path taken
from the originating point to the destination point.
[0048] By way of example, if the scenario involves the CCJ (8)
being located in the basement, the primary flexibility suite (4) on
the ground floor and the equipment rack (2) on the first floor, the
installation could involve the following steps: [0049] 1. Install
the CCJ (8). [0050] 2. Terminate the incoming cable (5) on the CCJ.
[0051] 3. Install an internal cable (1) between the CCJ and the OFR
of the primary flexibility suite (4) [0052] 4. At the CCJ splice
all fibres from incoming cable (5) to the internal cable (1).
[0053] 5. Terminate all the fibres from the internal cable (1) on
the OFR (4). [0054] 6. Install BFT (16b) from the equipment side of
the BFTFM (14c) in the primary flexibility suite to the line-side
BFTFM (14b) on first floor. [0055] 7. Install BFT (16a) from the
equipment rack (2) on the first floor to the equipment side of the
first floor BFTFM (14a). [0056] 8. Patch the BFT path at the
flexibility suites using BF patch tubes (17a, 17b), typically cut
to length on site. "Patch tubes" are generally short lengths of
tube to provide a "patch" between a BFT on the equipment side of
the BFTFM to a BFT on the line side of the BFTFM. [0057] 9. Install
the BFU. Blowing will usually be carried out from either the
equipment rack (2) or from the OFR (4), although blowing out from
some intermediate point may also be possible. [0058] 10. At the OFR
splice the internal cable (1) to the installed BFU. [0059] 11. At
the equipment rack splice the pigtails from the equipment rack (2)
to the installed BFU (of course if the equipment pigtails are
connectorised--i.e. have connectors, then it is useful for the BFU
to be pre-connectorised, so that the connector(s) of the BFU(s) can
be coupled to those of the pigtails).
[0060] It will be clear to the skilled person that a major
advantage of using a single unbroken length of blown fibre unit to
interconnect optical equipment to the external network, is the
removal of lossy splices and/or connectors. Their removal also
eliminates these known reliability weak points. In the basic
arrangement described in this FIG. 3, there are only three splices
(10a, 10b, 10c) per fibre between the CCJ and the equipment rack,
compared to six in the conventional arrangement described in FIG.
1. Time- and cost-savings are achieved as expensive and delicate
splicing and connectorising are significantly reduced.
[0061] FIGS. 4A and 4B show how an optical path connecting an
incoming cable (5) to an existing equipment rack (2) can be changed
to the new equipment rack (12) in accordance with the
invention.
[0062] FIG. 4A shows the existing optical path between the incoming
cable (5) and the old equipment rack (2) though two flexibility
suites (14). FIG. 4B shows how only two splices (10a, 10b) have to
be broken in the existing optical path, which compares favourably
with equivalent under the conventional method which requires five
breaks (see FIG. 2). After the splices are broken (or, more
generally, the fibre cut) the blown fibre unit is removed. The path
is then re-configured, using BFT (16) between flexibility suites
(14d and 14e, 14c and 4), and single tube BFT patch leads (17c,
17d) between the flexibility points within a suite. BFU is then
installed as described above in connection with FIG. 3, by blowing
from one or other end of the path, i.e. from the new equipment rack
(12) or from the OFR (4). Only two new splices are made (10c, 10d),
at the OFR and the new equipment rack.
[0063] It can be seen that yet another advantage of the invention
is flexibility in re-routing and user-friendliness, compared to
conventional techniques requiring installation of heavy cables.
[0064] FIGS. 5 and 6 show refinements of the arrangements described
in FIG. 3 above, being embodiments of the invention which further
reduce the number of splices required.
[0065] In FIG. 5, the CCJ (8) and the splice thereat are removed.
The incoming cable (5) is instead directly spliced to the blown
fibre unit (when installed) at the line side OFR (4). In this
arrangement, there are only two splices per fibre between the
incoming cable and the switch/router. By way of example, the
following are typical steps that can be taken to create this
installation where the incoming cable enters the building in the
basement, the primary flexibility suite (4) is on the ground floor
and the equipment rack is located on the first floor: [0066] 1.
Route the incoming cable (5) from cable chamber to the OFR of the
primary flexibility suite (4). [0067] 2. Terminate all fibres of
the incoming cable (5) on the OFR (4). Install BFT (16a) from the
equipment side of the ground floor BFTFM (14c) of the primary
flexibility suite to the line-side BFTFM (14b) on first floor.
[0068] 3. Install BFT from the equipment rack (2) to the equipment
side of the first floor BFTFM (14a). [0069] 4. Provide a BFT path
through all BFTFMs using BF patch tubes (17a, 17b), typically cut
to length on site. [0070] 5. Install BFU. Blowing will generally be
carried out from either the equipment rack or from the first OFR.
[0071] 6. At the OFR splice the incoming cable (5) to the installed
BFU. [0072] 7. At the equipment rack splice pigtails from the
equipment rack (2) to the installed BFU or, if connectorised, join
the connectors of the BFU to those of the pigtails.
[0073] The arrangement in FIG. 6 allows a connection between the
equipment rack (2) and the incoming cable (5) with just a single
splice (10) at the OFR (4). In this case, BFT is installed directly
from the equipment rack to the equipment side of the BFTFM located
nearest to the equipment rack (14a). BFU is installed in the manner
discussed above with reference to FIG. 3. By way of example, the
following are typical steps that can be taken to create this
installation where the incoming cable enters the building in the
basement, the primary flexibility suite (4) is on the ground floor
and the equipment rack is located on the first floor: [0074] 1.
Route the incoming cable (5) from cable chamber to the OFR (4) of
the primary flexibility suite. [0075] 2. Terminate all fibres of
the incoming cable on the OFR (4). [0076] 3. Install BFT (16b) from
the equipment side of ground floor BFTFM of the primary flexibility
suite (14c) to the line-side BFTFM on first floor (14b). [0077] 4.
Install BFT (16a) from the equipment rack (2) to the equipment side
of the first floor BFTFM (14a). [0078] 5. Patch a BFT path through
all BFTFMs using BF patch tubes (17a, 17b), usually cut to length
on site. [0079] 6. Install pre-connectorised BFU by blowing from
the equipment rack of the switch or router. [0080] 7. At the OFR
splice the incoming cable (5) to the BFU.
[0081] FIG. 7 shows an embodiment of a BFTFM (14). This has a
patching panel (11), shown here with no connectors, although these
would generally be provided, in double-ended form (as for example
shown in FIG. 14), within each of the holes shown in the panel 11.
Above the panel 11 are shown a set of bend control vanes or
mandrels 24, one for each of the connector sites in the panel 11.
It will be seen that these are configured to receive tubes which
approach the BFTFM from the left, the tubes then being bent down to
reach a connector site on the panel 11. These tubes could be the
patching tubes or they could be tubes coming from an earlier suite
or going to a later one. The other ends of the connectors, when
fitted into the panel 11, face downwards and tubes (typically
patching tubes) are mated to these connectors and then lead on to
connectors of another BFTFM (typically the one that provides the
other part of the same suite). The arrangement shown in FIG. 7 is
intended to be used with a matching BFTFM as shown in FIG. 7B. In
such an arrangement, the patching tubes typically pass down and out
through the aperture 99 at the back of the BFTFM. The curved faces
of the three-sided structure shown generally as 77 serves to
provide a bending mandrel for the patch tubes that join the two
BFTFM of the suite. The end portions 76 and 78 provide some lateral
confinement of the patch tubes as well as providing another curved
guiding mandrel. Preferably the bend management mandrels 24 are
provided as a unitary structure to suit a particular size of
patching panel. Also, it is preferable if the bend management
mandrels or the assembly of these can be fitted in either hand,
that is to accept tubes from left of the suite or from right of the
suit. A bend mandrel arrangement or assembly could be provided to
accept tubes both from the left and from the right (that is, in
FIG. 7 the left hand part of assembly 24 could be as shown, while
the right hand part could have the mandrels or vanes with a bend
towards the right (e.g. the mirror-image of the left). Clearly,
such an arrangement need not be symmetrical, with the left half of
the mandrels bending left and the right half bending right, but
could be arranged one-third two-thirds or one-fifth four-fifths,
for example.
[0082] Preferably a BFTFM occupies about the same area and space as
an existing OFR or other generic flexibility rack currently used in
exchanges, for ease of replacement. In the UK in the exchanges of
British Telecommunications plc therefore, it is anticipated that
BFTFMs will be approximately 1000 cm wide, 400 cm deep and 830 cm
tall. This build of BFTFMs is expected to be stacked up three
modules high each on the line- and equipment sides, as shown in
FIG. 7F, to occupy a total height of about 2500 cm. It is of course
possible to size and configure the BFTFMs according to the
particular requirements of the situation.
[0083] As noted briefly above, it is preferable that BFTFMs
incorporate positive tube bend management (e.g. the mandrels 24)
for optimised BFU installation. Further discussion of this
technique is provided below in the discussion of FIGS. 10 and 11,
but in brief this helps prevent installed optical fibres from being
bent at less than their minimum permissible bend radius.
[0084] FIGS. 7A to 7F show possible build configurations of the
BFTFM of FIG. 7 into BFTFM suites, from a single module to a
six-module build. While a single BFTFM may be used as a flexibility
point, multiple-modules are preferred (e.g. to provide one or more
suites) and their modularity allows flexibility in use and scope
for expansion.
[0085] FIG. 7A shows a single module BFTFM. Two versions are
available that respectively allow cable entry from left or right.
The example shown allows cable to be fed from the left. A single
unit like this would be mounted on the back of a flexibility point
such as an OFR to provide the first building block of flexibility
suite, in particular the suite most adjacent to the CCJ or the
incoming cable.
[0086] FIG. 7B shows two BFTFM modules mounted back to back to
create a flexibility suite with a line-side and an equipment-side.
Generally, two modules are the optimum to provide line and
equipment side flexibility.
[0087] FIG. 7C shows a further BFTFM module mounted on top of the
arrangement of FIG. 7B. Such an arrangement may be required for
example, where there is uneven growth of the demand for the
equipment-side modules, compared to that for line-side modules.
[0088] FIG. 7D shows that further build can also be carried out to
the side from one end of the suite. In this case as cable entry is
from the left-hand side, further modules would be added to the
right.
[0089] FIGS. 7E and 7F show five- and six-module configurations to
illustrate the potential for growth in the use of BFTFMs.
[0090] The drawing on the right in FIG. 8 depicts another view of a
suite of BFTFMs (14) partly populated with blown fibre patch tubes
(17). This is a three-high build of line-side and equipment-side
modules. As described elsewhere, the BFTFMs perform a junctioning
or distribution function to allow users to make connections between
points in an exchange. The BFTFMs include a patch panel (11)
comprising patching tube connectors (13). In this embodiment, the
ends of the patch tubes are push-fit into the receivers to define
connection paths. In a preferred embodiment, the patching panel
comprises 19 tube connectors across and 14 deep in a grid or matrix
formation or array.
[0091] The patch panels of the pair of BFTFMs (such as 14a and 14b
in FIG. 3) allow a user considerable scope and flexibility in
directing and re-directing fibre connections within the exchange.
After a tube path is created by push-fitting the tube ends into the
relevant tube connector, fibre can then be blown along the path
from source (e.g. an incoming cable 5) to destination (e.g. an
equipment rack 2)--or in the opposite direction--via the BFTFM(s).
The fibre connection can be easily removed and/or redirected by
withdrawing the fibre from the tube path, pulling out the tubes
from the tube connector in the relevant BFTFM, and then if required
by repeating the above steps to create the path from the new source
or to the new destination.
[0092] The schematic diagram on the left in FIG. 8 shows the side
view of the BFTFM suite (shown on the right of the same page and
discussed above), with details of the tube patching between the
patching panels located on each BFTFM. It can be seen that the
patching tubes exit the connectors 13 downwards. In the suite on
the lower level of the assembly, patch tube link the front and back
(or, as shown, the left and right) of the suite. It can also be
seen that the top right BFTFM has been interconnected with the
middle-left BFTFM using a patching tube. Similarly, each of the
middle tier of BFTFMs is connected to the lowest tier of the stack.
Clearly the figure is merely illustrative and in general much
higher densities of patch tube connection will be used in real
life.
[0093] The paths of the patching tubes (17) can be traced between
the different levels of BFTFMs in the figure.
[0094] FIG. 9 shows a typical build sequence for the installation
described in FIG. 6 above using a generic type of OFR. The
following steps accord with the numbering against the drawings:
Installing the Primary Flexibility Suite (4 and 14c of FIG. 3)
[0095] 1. Install the OFR (the rear covers have been removed in the
drawing for clarity) (4). Install the incoming cables (5) and
terminate their fibres on splice trays, preferably single-circuit.
Cables can enter either from above or below. [0096] 2. Install one
BFTFM (14c) adjacent to the rear of the OFR. Each BFTFM can
typically accommodate 384 individual BF tubes, the equivalent of
4.times.96 fibre cables. A second and third BFTFM can be added to
the flexibility suite to accommodate typically 1152 individual BF
tubes. [0097] 3. Install the vertical cable tray (20), the mandrel
adapter (22) and the internal bend mandrel (24). The mandrels
positively manage the fibre tube bend to prevent over-bending. In
this instance the cable routes upwards. Installing Subsequent
Secondary Flexibility Suite (e.g. 14a and 14b of FIG. 3) [0098] 4.
Install vertical cable tray (26), support-frame uprights (28) and
frame strap (30) on exchange floor. [0099] 5. Add the outer bend
mandrel (32) and the line-side BFTFM (14b). [0100] 6. Install a
second vertical cable tray (26), equipment-side BFTFM (14a),
mandrel adapter and internal bend mandrel.
[0101] The secondary flexibility suite is now ready to accept BF
tubing. The installation shown can accommodate up to 384 BF patch
tubes.
Installing BF Tubing
[0102] 7. The butt of the BF tube (16) is cut level with the edge
of the BFTFM (14). Each tube contained is routed over the plastic
tube mandrels so that its bend radius is controlled. Tubes are then
cut to length and plugged into the push-fit bulkhead fittings which
are in turn located into the appropriate hole in the patch panel.
[0103] 8. An illustration of interface with the vertical cable
tray--upwards. [0104] 9. An illustration of interface with the
vertical cable tray--downwards.
[0105] We turn now to FIGS. 10 and 11 which help explain the use of
positive bend management in the context of a telecommunications
exchange. As noted above, this technique addresses problems arising
from bending a fibre at a radius smaller than its minimum
permissible bend radius. As is well known, bending an optical fibre
too tightly is likely to result in significant optical losses
and/or mechanical fibre damage. Bundles of optical fibre have
larger minimum permissible bend radii than those of their
constituent fibres. Controlling and managing the fibre bend (as
opposed to simply allowing the fibre to find its own path from
flexibility suite to flexibility suite) helps prevent optical tubes
or fibres from being kinked or bent to a tight radius which may
impede blown fibre installation and/or optimal fibre performance.
The fibre could be confined within a prescribed path, or simply
guided along a curve describing an ideal radius that could be at or
near the minimum permissible bend limit.
[0106] This characteristic of optical fibre is a particular problem
in large telecommunications exchanges. By way of example, British
Telecommunications plc has to date more than 4,000 exchanges
throughout the United Kingdom, of which some 200 serve over 20,000
customers each. The largest exchanges have multiple floors,
hundreds of equipment racks and a very high number of fibre and
copper cables routed around and throughout the exchange building.
As time progresses, the exchange becomes more heavily populated and
changes to equipment, customer needs etc., necessitate re-routing
and re-termination of cables. It has been found that the routes
taken by cables, if uncontrolled, may impair the performance of the
optical fibre. For example, if a jumper cable is re-used it will
have to be cut and re-connected--very often it may be too short to
reach easily between the two sides and may have to be stretched
tight thus compromising minimum bend radius dimensions, as shown in
FIG. 10. This of course affects fibre and circuit performance, but
is a common occurrence in exchanges owing to changes in the needs
of the customers served by the exchange, e.g. equipment upgrades
requiring cable path changes, and growth in numbers of cables
populating the exchange.
[0107] FIG. 11 shows the BFTFMs discussed in connection with FIG. 9
above, and illustrates how the technique of positive tube bend
management may be used. FIGS. 11A and 11B show where cable bend can
be controlled and managed (40) in a typical BFTFM set-up.
[0108] Tube bend management apparatus can take the form of curved
guides or mandrels--(e.g. 24 in FIG. 9)--around or against which
the tubes are wrapped. The degree of curve depends on the exact
type of cable tube being used but in the UK this would typically be
a radius of about 50 mm.
[0109] FIGS. 11C and 11D show where and how tubes (16) can be
subject to positive tube bend management in a BFTFM of the type
discussed in connection with FIG. 9. The bend control mandrels (24)
allow the optical fibre (16) to be guided in a controlled manner
around a curve of a radius suitable for it, preventing overly tight
cable routing.
[0110] FIG. 12 provides details of one application of positive tube
bend management on the BFTFM. On the right side of this figure is a
close-up view of an embodiment of a patching unit on a patching
panel (11). Other means for controlling fibre bend radius include
the use of bend limiting tube (or bend-limiting boots on an
ordinary tube); selection of tube sheath materials (i.e. using
stiffer or more rigid materials); and thicknesses can which
discourage excessive bend (i.e. using wall thicknesses which at the
lengths typically used for patching are much less likely to be bent
at a radius which represents an excessive bend); and so on. In this
embodiment, guides (15) are positioned on or next to the tube
connectors to accommodate and control the bend radius of tube and
fibre passing through the receivers. These help to prevent the type
of overbend depicted in FIG. 10.
[0111] FIG. 13 depicts another, preferred embodiment of the
patching unit of the invention, as mounted onto a BFTFM. In this
embodiment, the unit comprises two main parts, the first being a
connector body (19) configured to receive a BFT (17) entering (or
exiting) the module, and the second being the tube connector (13)
fitted to the body. The connector body includes a channel shaped
and functioning as a guide (15) to prevent BFT and fibre overbend.
As in the case of the patching unit depicted in FIG. 12, BFTs are
push-fit on the tube connectors (13). The tube connector is fixed
to the connector body (19), and only one of the two receiving
portions (21) is visible in this FIG. 13.
[0112] The tube connector is shown unfixed from the rest of the
patching unit and further detailed in FIG. 14. It essentially
comprises a connector tube (23) with two receiving portions (21),
one each on opposite ends of the connector tube.
[0113] When installed on the BFTFM, the patching units form a
matrix on the patching panel (11) allowing a user to create a
tubular path between two BFTFMs, and thus in the broader context of
the exchange, to form part of the tubular path between the incoming
cable (5) and the destination equipment rack (2). Another view of
this embodiment of the patching unit is shown in FIG. 15, which
show the patching unit mounted on a BFTFM, and the part of the path
taken by the BFT (17) through the tube connector (13). As noted
above e.g. in connection with FIG. 8, the tubes in the present
embodiment are connected on the patch panel in a push-fit
arrangement. While push fit connectors are very convenient to use,
clamped or screw-down connectors could be used as could, for
example, gluing or welding to fix and seal the tubes to the patch
panels--although such permanent or semi-permanent would compromise
the re-routing flexibility which the invention potentially
provides.
[0114] FIG. 15 shows the patching unit sitting in a position
provided for it in the patch panel of the BFTFM so that its arms
(25) point upwards, and the tube connector (13) downwards. As noted
above in connection with FIG. 8, up to 266 such patching units (19
across and 14 deep in one patching panel) can be accommodated in
the embodiment of the BFTFM under discussion. A BFT ultimately
leading from or to the incoming cable (5) or the equipment rack (2)
is positioned so that it lies on the connector body between the
connector arms. The channel acting as a guide (15) leads the BFT to
the tube connector (13) and prevents cable overbend. The BFT is
push-fit onto the receiving portion (21) of the tube connector (13)
located at the end of the channel (not visible from the drawings).
The other tube connector on the opposite end of the connector unit
may simultaneously or separately receive another length of BFT to
continue the tubular path away or from the BFTFM.
[0115] Although the foregoing discussion concerns mainly a
connection created by the invention between an equipment rack and
an incoming cable connecting the exchange to the external
telecommunications network, the skilled person would easily
recognise that the invention can be deployed with similar effects
or advantages to connect any other originating point to any
destination point within or outside of the exchange. Furthermore,
while the specific description is made in the context of
telecommunication exchange buildings, it would be clear that the
invention can have applications in any other environment where
blown fibre technology according to the invention can be used in
place of conventional connectorised and/or spliced optical fibre or
current BFT management practices. In particular, the invention may
be used in a Local Area Network (LAN) environment.
[0116] The skilled person would also appreciate that the invention
is not limited to use in a new set-up ready to be cabled, nor to
one which is already cabled in a manner as described herein. The
inventive aspect concerning re-routing of optical paths, in
particular, can be applied even in a conventional installation, to
gradually migrate the inventive method into such convention
set-ups. The benefits of using the invention can be realised even
in such applications.
* * * * *