GB2293498A - Method and apparatus for installing an optical fibre element in a tube - Google Patents
Method and apparatus for installing an optical fibre element in a tube Download PDFInfo
- Publication number
- GB2293498A GB2293498A GB9519089A GB9519089A GB2293498A GB 2293498 A GB2293498 A GB 2293498A GB 9519089 A GB9519089 A GB 9519089A GB 9519089 A GB9519089 A GB 9519089A GB 2293498 A GB2293498 A GB 2293498A
- Authority
- GB
- United Kingdom
- Prior art keywords
- ribbon cable
- tube
- drive mechanism
- optical
- bore
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/46—Processes or apparatus adapted for installing or repairing optical fibres or optical cables
- G02B6/50—Underground or underwater installation; Installation through tubing, conduits or ducts
- G02B6/52—Underground or underwater installation; Installation through tubing, conduits or ducts using fluid, e.g. air
Abstract
An optical fibre element is introduced into the bore of a preformed tube (not shown), by means of a device which comprises: (i) a pressure vessel 1 with an input (2, Figure 1) for receiving compressed gas; (ii) an outlet 4 which can be attached to the tube and which allows both cable and gas to pass into the tube; and (iii) a mechanism (8) for driving the cable towards the outlet of the vessel. The element, a ribbon cable 3, is propelled along a tortuous path in the tube by fluid drag and comprises a plurality of optical fibres which are laid side-by-side in a single plane and which together are surrounded by a jacket. If the cable runs slack in the housing, an LED and photodiode 32 detect the slackness and send a signal to the cable supply device (Figures 5 to 7) to alter the speed of delivery. <IMAGE>
Description
Method and Apparatus for Installing an Optical
Fibre Element in a Tube
This invention relates to the introduction of optical fibre elements into the bore of a preformed tube.
Recently it has been proposed to provide buildings and the like with optical fibres by installing a tube in the building and then introducing a leading end of the fibre into the bore of the tube and propelling it along the tube by the viscous drag of a fluid medium. Such a method is described for example in European Patent Application No: 108590. The tube will normally have a tortuous path in three dimensions, that is to say, it will describe a path in which it extends in both horizontal directions and vertically as it passes along the floors, walls and ceilings of the buildings, such horizontal and vertical sections being joined by relatively short curved sections of typical radius 30 to 60mm.
If the fibre encounters a sharp bend or other obstruction in the tube it may slow down as it negotiates the bend or obstruction, and in view of this it has been proposed to incorporate a control mechanism in the gas propulsion (blowing) device that will detect the reduction in speed of the fibre and will reduce the rate at which the fibre is paid off the spool accordingly.
For example, one such control mechanism comprises means to detect bowing of the fibre within the blowing device due to the differences between the speed at which the fibre is taken off the spool and the speed at which it enters the bore of the tube.
In many cases it will be desired to install more than one optical fibre in the bore of the tube, for example in order to satisfy the demand for data transmission or to connect to different equipment. In view of this it has been proposed for more than one fibre to be installed in the form of a cable. However, although such cables can generally be installed satisfactorily, they suffer from the fact that they are of significantly reduced flexibility as compared with individual fibres, with the result that the leading edge of the cable can stop when it encounters a sharp bend or other obstruction in the tube. Also, if any bends or obstructions in the tube cause the cable to slow down, the cable may tend to bow or buckle in the tube rather than within the blowing device, which will render any control mechanism ineffective.The blowing device can be stopped manually if the operator can detect the buckling of the fibre in the tube visually, but this may occur at parts of the tube remote from the operator, and in addition visual detection of the buckling requires the tube to be transparent. However, the use of tubes with electrically conductive inner surfaces in order to prevent build up of static electricity within the tube and consequent sticking of the fibre, requires the tube to be opaque.
An alternative system that has been employed has been to install a number of individual, separate fibres (usually four fibres) simultaneously with one another. Such a system has the advantage that the fibres retain their original degree of flexibility, but has the disadvantage that particularly complex and expensive installation equipment is required. For instance, the control mechanism must cater for the fact that any one of the fibres may slow down as it is introduced into the tube and bow in the blowing device while the other fibres continue at their original speed.Furthermore, when the control mechanism causes the rate of feed of the fibres to be reduced in order to reduce the bowing of one fibre in the blowing device, it is quite possible for a different fibre to begin to bow at the same time as the first fibre straightens out, with the result that the control mechanism becomes "confused".
According to one aspect, the present invention provides a method of introducing an optical fibre element into the bore of a preformed tube that has a tortuous path in three dimensions, which comprises introducing a leading edge of the element into an open end of the bore and propelling the element along the bore of the tube by fluid drag of a gaseous medium, wherein the optical fibre element is an optical ribbon cable comprising a plurality of optical fibres which are laid side-by-side in a single plane and which together are surrounded by a jacket, and ribbon cable is introduced into the bore of a tube by means of a device which comprises:
( i) a pressure vessel with an input for
receiving compressed gas;
( ii) an outlet which can be attached to the tube
and which will allow both ribbon cable and
the gas to pass into the tube; and
(iii) a drive mechanism for driving the ribbon
cable toward the outlet of the pressure
vessel.
The method according to the invention has the advantage that it enables a number of fibres to be installed in the bore of a tube in the form of a single optical element which is relatively flexible in one direction (i.e. normal to the plane of the ribbon cable) so that a relatively simple control mechanism relying on bowing of the cable can be employed in the blowing device without the control mechanism needing to take into account independent bowing of separate optical fibres. The present invention is based in part on our observation that, as the ribbon cable progresses along the tube, it is able to pass through bends in the tube in both orthogonal directions that are perpendicular to the bore of the tube (and the length of the ribbon cable) notwithstanding the fact that the ribbon cable is very stiff and resistant to bending in the same direction as its plane.That is to say, even though the ribbon cable is flexible in only one direction normal to its plane - it can accommodate bends in the tube in two directions, thereby allowing the tube to have a tortuous path in which it extends in three dimensions. The reason why this is the case appears to be due to the fact that the ribbon cable is able to twist about its axis as it progresses along the tube, thereby enabling it to pass through all the bends in the tube by bending in a direction normal to its plane.
In its simplest form the ribbon cable need only include a pair of optical fibres, although it is possible for it to include four, six, eight, twelve or more optical fibres. The fibres may be single mode or multi-mode fibres, and together are surrounded by a jacket that aids propulsion of the cable by viscous drag of the gas. Such a jacket is described in European Patent Specification No.
345968. It is necessary to employ a single jacket that surrounds the assembly of optical fibres as a cable in order to enable the jacket to be stripped off the assembly of optical fibres for provision of an optical ribbon connector thereto. If desired the ribbon cable may include an optical connector on its leading end, and also if desired on its trailing end. Such a method enables the connectors to be incorporated on the ribbon cable under factory conditions rather than in the field.
In the device employed in the method, the pressure vessel will normally have a region in its interior through which the ribbon cable passes between the drive mechanism and the outlet, which region has an internal lateral dimension in one direction that is sufficiently large to allow the ribbon cable to bow in that direction if the speed at which the ribbon cable enters the bore of the tube is less than the speed at which the drive mechanism drives it toward the outlet of the pressure vessel, the device including a detector for detecting bowing of the ribbon cable, and a feedback arrangement for controlling the drive mechanism in response to the detector. The detector preferably comprises means for producing a beam of electromagnetic radiation that is attenuated or not depending on the degree to which the ribbon cable bows, and means for detecting the beam of electromagnetic radiation.
It is possible to employ a bank of photodetectors that will detect radiation from one or more radiation emitting devices, for example LEDs, so that the extent to which the optical fibre bows can be determined and the drive mechanism be controlled accordingly, although it is not necessary for the control mechanism to be of such complexity. Indeed, it is preferred for the sake of simplicity and cost for the means for detecting the beam of electromagnetic radiation to comprise a single photodetector, e.g. in the form of a photodiode and the drive mechanism to be controlled in accordance with the degree to which the radiation beam is attenuated by the cable.
Thus according to another aspect, the invention provides a device for installing an optical ribbon cable in the bore of a preformed tube, which comprises:
( i) a pressure vessel with an input for
receiving compressed gas;
( ii) an outlet which can be attached to the tube
and which will allow both the optical ribbon
cable and the gas to pass into the tube;
(iii) a drive mechanism for driving the ribbon
cable toward the outlets; the pressure vessel having a region in its interior through which the ribbon cable passes between the drive mechanism and the outlet, which region has an internal lateral dimension in one direction that is sufficiently large to allow the ribbon cable to bow in that direction if the speed at which the ribbon cable enters the bore of the tube is less than the speed at which the drive mechanism drives it toward the outlet of the pressure vessel, the device including:
( iv) a detector for detecting bowing of the
ribbon cable which comprises means for
producing a beam of electromagnetic
radiation that is attenuated or not
depending on the degree of bowing of the
ribbon cable, and a single photodiode for
detecting the beam of electromagnetic
radiation; and
( v) a feedback arrangement for controlling the
drive mechanism in response to the detector.
A method of installing an optical ribbon cable and device suitable for installing ribbon cable in accordance with the present invention will now be described by way of example with reference to the accompanying drawings in which:
Figure 1 is a perspective view of a blowing device
used according to the invention;
Figure 2 is a side sectional elevation of the device
shown in figure 1;
Figure 3 is a top plan view of the device shown in
figure 1;
Figure 4 is an isometric view of the control
mechanism employed in the blowing device;
Figure 5 is a top plan view of a device for supplying
optical ribbon cable to the blowing device;
Figure 6 is a sectional view of the ribbon supply
device taken along the line V-V of figure 5;
and
Figure 7 is a side view of the ribbon supply device
of figure 5.
Referring to the accompanying drawings, a device for blowing optical fibre ribbon cable 3 into the bore of a tube comprising an aluminium housing 1 of generally elongate shape having a screw threaded air pressure inlet 2 for attachment to the nozzle of an air compressor and an air outlet 4 provided with a connector 6 for attachment to a tube (not shown) into which the ribbon cable 5 is to be blown. The housing 1 is provided with a transparent plastics top cover that can be attached and removed by means of screws that engage threaded screw holes 6.
Outside the housing 1 and on the side opposite the outlet 4 is located a ribbon cable drive mechanism 8 which comprises a drive roller 10 that is powered by a 12V dc motor 12 via a gearbox 14, and an idle roller 16 in contact with the drive roller 10 so that ribbon cable can be fed through the nip between the rollers and passed into the housing 1 via an inlet cannula 18 and air seal 20.
The housing contains a ribbon cable speed control mechanism 22 placed in line with the inlet cannula 18 and the outlet 4 so that ribbon cable will pass through the control mechanism as it is blown into the tube. The control mechanism is formed from a pair of aluminium blocks 24 and 26 that can be secured together and which together define an internal passageway for the ribbon cable which, over a region thereof, opens out into a chamber 28 of sufficient lateral dimensions that the ribbon cable 3 can bow as shown if the drive mechanism 8 supplies the ribbon cable faster than it enters the tube. The control mechanism 4 has a slot 30 provided in the blocks 24 and 26 at the downstream end of the chamber 28 in which is located an LED that will generate a beam of light across the path of the ribbon cable, and a single photodiode 32 arranged to detect the beam.
Ribbon cable is supplied to the drive mechanism 8 by means of a supply device shown in figures 5 and 7. The device includes a frame 34 that supports a spindle 36 on which a spool (not shown) of ribbon cable is located. The spindle can be driven by a 12V electric motor 38, although this is not used in normal installation operation and the spool and spindle 36 are merely allowed to idle. the frame 34 also supports a dancer arm 40 that is spring biassed to a downward position in which the arm applies a breaking effect on the spindle 36 by means of a rubber belt 42 that extends around a drum 44 on the spindle. The device may also include a counter 46 for determining how far the ribbon cable has been blown.
In operation a spool of ribbon cable is located on the spindle 36 and the leading end of the ribbon cable is threaded through an eye 48 at the end of the dancer arm 40, through the nip of the rollers 10 and 16 and through the control mechanism 22. During installation the drive mechanism 8 feeds the ribbon cable through the control mechanism 22 and into the tube whereupon it is caused to progress along the tube by the flow of air that is supplied by a compressor via inlet 2. If the passage of the ribbon cable within the tube momentarily slows for any reason, the cable will be caused to bow in the chamber 28, and this bowing will be detected by the photodiode 32 whereupon a signal will be sent to cause the motor 12 to stop or slow down.If the speed of the ribbon cable is constant, demand for the ribbon cable by the drive mechanism will cause the dancer arm 40 to be raised against its bias. However, if the drive mechanism 8 slows, slack in the ribbon cable between the supply spool and the drive mechanism will allow the dancer arm 40 to drop and apply a breaking effect on the spindle 36.
If for any reason it is desired to remove the ribbon cable from the tube, a gas compressor can be attached to the remote end of the tube to blow the ribbon in the reverse direction, and the electric motor 38 can be switched on to allow the ribbon cable to be taken up by the spool located on the spindle 36.
The LED and photodiode 32 are located at the downstream end of the chamber 28 since this is the position at which the ribbon cable will begin to bow, and so the control mechanism will be activated before the bowed portion of the ribbon cable has reached the top of the chamber 28.
Claims (9)
1. A method of introducing an optical fibre element into the bore of a preformed tube that has a tortuous path in three dimensions which comprises introducing a leading edge of the element into an open end of the bore and propelling the element along the bore of the tube by fluid drag of a gaseous medium, wherein the optical fibre element is an optical ribbon cable comprising a plurality of optical fibres which are laid side-by-side in a single plane and which together are surrounded by a jacket, and the ribbon cable is introduced by means of a device which comprises:
( i) a pressure vessel with an input for receiving
compressed gas;
( ii) an outlet which can be attached to the tube and
which will allow both ribbon cable and the gas to
pass into the tube; and
(iii) a drive mechanism for driving the ribbon cable
toward the outlet of the pressure vessel.
2. A method as claimed in claim 1, wherein the ribbon cable comprises at least 4 optical fibres.
3. A method as claimed in claim 2, herein the ribbon cable comprises at least 8 optical fibres.
4. A method as claimed in any one of claims 1 to 3, wherein the ribbon cable includes an optical connector on at least its leading end.
5. A method as claimed in any one of claims 1 to 4, wherein the pressure vessel has a region in its interior through which the ribbon cable passes between the drive mechanism and the outlet, which region has an internal lateral dimension in one direction that is sufficiently large to allow the ribbon cable to bow in that direction if the speed at which the ribbon cable enters the bore of the tube is less than the speed at which the drive mechanism drives it toward the outlet of the pressure vessel, the device including a detector for detecting bowing of the ribbon cable, and a feedback arrangement for controlling the drive mechanism in response to the detector.
6. A method as claimed in claim 5, wherein the detector comprises means for producing a beam of electromagnetic radiation that is attenuated or not depending on the degree to which the ribbon cable bows, and means for detecting the beam of electromagnetic radiation.
7. A method as claimed in claim 6, wherein the means for detecting the beam of electromagnetic radiation comprises a single photodiode.
8. A device for installing an optical ribbon cable in the bore of a preformed tube, which comprises:
( i) a pressure vessel with an input for receiving
compressed gas;
( ii) an outlet which can be attached to the tube and
which will allow both the optical ribbon cable and
the gas to pass into the tube;
(iii) a drive mechanism for driving the ribbon cable
toward the outlets; the pressure vessel having a region in its interior through which the ribbon cable passes between the drive mechanism and the outlet, which region has an internal lateral dimension in one direction that is sufficiently large to allow the ribbon cable to bow in that direction if the speed at which the ribbon cable enters the bore of the tube is less than the speed at which the drive mechanism drives it toward the outlet of the pressure vessel, the device including:
( iv) a detector for detecting bowing of the ribbon
cable which comprises means for producing a beam
of electromagnetic radiation that is attenuated
or not depending on the degree of bowing of the
ribbon cable, and a single photodiode for
detecting the beam of electromagnetic radiation;
and
( v) a feedback arrangement for controlling the drive
mechanism in response to the detector.
9. A device for installing an optical ribbon cable in the bore of a preformed tube, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9419079A GB9419079D0 (en) | 1994-09-22 | 1994-09-22 | Method and apparatus for installing an optical fibre element in a tube |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9519089D0 GB9519089D0 (en) | 1995-11-22 |
| GB2293498A true GB2293498A (en) | 1996-03-27 |
Family
ID=10761720
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9419079A Pending GB9419079D0 (en) | 1994-09-22 | 1994-09-22 | Method and apparatus for installing an optical fibre element in a tube |
| GB9519089A Withdrawn GB2293498A (en) | 1994-09-22 | 1995-09-19 | Method and apparatus for installing an optical fibre element in a tube |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9419079A Pending GB9419079D0 (en) | 1994-09-22 | 1994-09-22 | Method and apparatus for installing an optical fibre element in a tube |
Country Status (1)
| Country | Link |
|---|---|
| GB (2) | GB9419079D0 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998012588A1 (en) * | 1996-09-19 | 1998-03-26 | British Telecommunications Public Limited Company | Blowing head |
| CN100414335C (en) * | 2004-06-24 | 2008-08-27 | 法国电信公司 | Small-sized micro-cable-laying device |
| EP1978389A1 (en) * | 2007-04-02 | 2008-10-08 | BRITISH TELECOMMUNICATIONS public limited company | Blown cable installation |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0292037A1 (en) * | 1987-04-28 | 1988-11-23 | Koninklijke KPN N.V. | Method and device for introducing a cable into a cable guide tube |
| US4856760A (en) * | 1986-07-16 | 1989-08-15 | British Telecommunications | Control method and apparatus |
| US4948097A (en) * | 1982-11-08 | 1990-08-14 | British Telecommunications Public Limited Company | Method and apparatus for installing transmission lines |
| GB2235595A (en) * | 1989-07-28 | 1991-03-06 | Bicc Plc | Overhead electric and optical transmission system |
| EP0445622A2 (en) * | 1990-02-28 | 1991-09-11 | Sumitomo Electric Industries, Ltd. | Method for laying optical fiber unit and apparatus therefor |
| EP0508016A1 (en) * | 1991-04-10 | 1992-10-14 | Kiyoshi Horii | Cabel or fiber installation device |
| WO1994009538A1 (en) * | 1992-10-20 | 1994-04-28 | Meab Mobile Equipment Ab | A method of inserting cables into tubing |
-
1994
- 1994-09-22 GB GB9419079A patent/GB9419079D0/en active Pending
-
1995
- 1995-09-19 GB GB9519089A patent/GB2293498A/en not_active Withdrawn
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4948097A (en) * | 1982-11-08 | 1990-08-14 | British Telecommunications Public Limited Company | Method and apparatus for installing transmission lines |
| US4948097C1 (en) * | 1982-11-08 | 2001-05-01 | British Telecomm | Method and apparatus for installing transmission lines |
| US4856760A (en) * | 1986-07-16 | 1989-08-15 | British Telecommunications | Control method and apparatus |
| EP0292037A1 (en) * | 1987-04-28 | 1988-11-23 | Koninklijke KPN N.V. | Method and device for introducing a cable into a cable guide tube |
| GB2235595A (en) * | 1989-07-28 | 1991-03-06 | Bicc Plc | Overhead electric and optical transmission system |
| EP0445622A2 (en) * | 1990-02-28 | 1991-09-11 | Sumitomo Electric Industries, Ltd. | Method for laying optical fiber unit and apparatus therefor |
| EP0508016A1 (en) * | 1991-04-10 | 1992-10-14 | Kiyoshi Horii | Cabel or fiber installation device |
| WO1994009538A1 (en) * | 1992-10-20 | 1994-04-28 | Meab Mobile Equipment Ab | A method of inserting cables into tubing |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998012588A1 (en) * | 1996-09-19 | 1998-03-26 | British Telecommunications Public Limited Company | Blowing head |
| US6364290B1 (en) | 1996-09-19 | 2002-04-02 | British Telecommunications Public Limited Company | Blowing head including a buckle detector |
| CN100414335C (en) * | 2004-06-24 | 2008-08-27 | 法国电信公司 | Small-sized micro-cable-laying device |
| EP1978389A1 (en) * | 2007-04-02 | 2008-10-08 | BRITISH TELECOMMUNICATIONS public limited company | Blown cable installation |
| WO2008119976A1 (en) * | 2007-04-02 | 2008-10-09 | British Telecommunications Public Limited Company | Blown cable installation |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9419079D0 (en) | 1994-11-09 |
| GB9519089D0 (en) | 1995-11-22 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |