News Column

Patent Issued for Cable Installation Using Optical Detection

May 7, 2014

By a News Reporter-Staff News Editor at Journal of Engineering -- British Telecommunications Public Limited Company (London, GB) has been issued patent number 8702064, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Barker, Philip Alfred (Ipswich, GB); Heatley, David John Taylor (Felixstowe, GB); Neild, Ian (Ipswich, GB).

This patent was filed on December 23, 2008 and was published online on April 22, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "Optical fibers are widely used within telecommunication systems for high-speed information transfer, particularly in the core or backbone network. With the advent of fiber to the premises (FTTP), the conduits will further extend to and into commercial and residential premises. Indeed it is a fundamental part of the push to FTTP in e.g. the UK, that substantially all the network comprises optical fiber, extending from the core network to as many end customers, both commercial and residential, as possible. This involves the installation of millions of kilometers of optical fiber across the network, especially at the local access level which had previously been served by copper. To achieve widespread take-up, the optical fiber installation process needs to be speedy, cost- and effort-efficient.

"An optical fiber unit, which could comprise a single optical fiber, or a bound bundle of typically 2 to 24 optical fibers, can be installed using what is known as the 'blown fiber' method, described in EP 108590. In this method, a fiber unit is propagated along a hollow tube pre-laid along the desired route, where compressed air is fed, or 'blown' into the mouth of the tube. The viscosity of the flow of air travelling along inside the tube, together with the friction on the outer surface of the fiber unit, helps to carry the fiber unit along the length of the tube.

"The tubes or conduits typically are made of plastic, each with a typical inner diameter of 2.5 to 6 mm or more, and are usually provided in a bound bundle comprising up to 24 or more tubes, which are held together within a protective outer sheath. The tubes usually comprise a continuous span between convenient access points such as surface boxes, inspection chambers down man holes, or near telephone poles. Each fiber conduit tube can receive at least one fiber unit comprising one or more individual optical fibers. Large numbers of tube conduits--and bundles of conduits--are pre-installed across the access network and the distribution network between the local exchanges and the customer premises, typically to locations which may require a future fiber connection.

"When it is decided to populate these pre-installed tubes, the fiber cable or unit is installed in each tubular span by blowing it down the conduit from one end; alternatively the unit could be blown down a concatenation of spans in a single step if circumstances permit. This is repeated for each span, or concatenation of spans, until a continuous fiber path has been laid between the end points of the whole route.

"A tubular path can be described between two access points, which may be hundreds of meters apart, by a single length of conduit tube. The conduit path may alternatively comprise a number of lengths of physically separate conduit tubes which are connected together, e.g. in series. Either way, it is crucial to choose the correct conduit path during installation, so that the fiber unit emerges at the desired destination end. During installation however, the operator at one of the installation points would be presented with a large and potentially confusing number of conduit tube openings, each representing a path leading to a destination. The tube openings are usually mapped to their destinations, e.g. by color-coding. If however the tube openings are wrongly mapped, or the records otherwise inaccurate, mistakes can result in attempts to identify the correct conduit path and the correct tube opening leading to the desired destination. This is especially so if the working conditions are poor, e.g. in adverse weather up a telephone pole or down a manhole or in poor lighting.

"Where the path comprises a number of tube lengths connectorized together, yet another problem may lie in broken connections between lengths of conduit tubes within the network, so that the fiber unit may get lost within the system during installation and never emerge at the destination. Yet another issue may be the possibility that the fiber unit, during installation, could be impeded by an imperfect connection or a tight bend or some other source of friction in the conduit, and again never emerge at the destination.

"For any of these or other reasons, the fiber unit may, during installation, emerge in the wrong place, or in an extreme case, not at all. Add to that some uncertainty about the exact length of the conduit route down which the fiber unit is being installed, so that the operator may not even know in a timely manner when something has gone wrong.

"The current response to this problem is to use two operators during installation, one at each end of the installation conduit path. The second operator at the destination end of the tubular path is required because the destination or remote end is often some distance away--up to a kilometer or more--from the head end. The operator at the head end is therefore unable to know the status of the remote end during an installation without a second operator located there reporting the status back to the head end.

"During a typical installation session, the first operator situated at the head end of the conduit fits a protective slug or bead on the tip of the fiber unit, then feeds this and compressed air into the mouth of the conduit with fiber installation apparatus--known in the art as a 'blowing head' which is described in general in WO88/00713. Meanwhile the second operator locates himself at the desired end point of the fiber installation. The process commences by directing compressed air into the mouth of the head end conduit. If the air is directed into the correct conduit so that the tubular path leads to the desired destination, the remote end operator can eventually sense the arrival of the air with an airflow meter temporarily connected to the end of the conduit, or more simply by feeling the airflow exiting the conduit against his hand if the airflow is sufficiently high. He then communicates this to the head end operator by radio or other means, to confirm to the head end operator that the air is applied to the correct conduit. The head end operator upon receiving the news, then blows the fiber unit into the conduit through to the remote end, whereupon the remote end operator advises his colleague on its arrival. The head end operator then turns off the air supply and the blowing head, and the installation process is complete.

"This process is labor-intensive as two operators must work on a single installation. This is in turn drives up the overall cost of optical fiber installation, a problem now especially significant in the FTTP context with the considerable installation volumes involved.

"Various methods requiring only a single operator installation of blown fiber have been developed, to obtain a significant saving in manpower and cost requirements. In the simplest method, the length of the conduit route is known, allowing the operator to know that the fiber has (probably) arrived at the remote end when the required length of fiber unit has been played out. This relies on the map record of conduit route being up to date and accurate, and presumes a completely smooth and obstruction-free conduit route. Neither of these can be guaranteed in practice.

"Another known practice is to install at the remote end of the conduit a barrier of porous material such as an 'airstone' which is constructed of a porous material which allows air through but which will stop further progress of the fiber unit. The airstone is temporarily placed at the mouth of the destination remote end of the tube conduit. When the fiber ceases to travel down the tube, this is an indication that the far end of the fiber may have reached the destination end and has been retained by the airstone barrier. However, lack of further progress is ambiguous as to whether the fiber unit has indeed reached the porous airstone at the destination end, or if instead the fiber unit is caught on an obstruction at some intermediate point along the length of the conduit.

"These, together with other methods like those described in WO9103756 or WO/9812588, also describe how fiber arrival can be detected by the single operator at the head end of the installation; the initial step of detecting that the compressed air fed into the head tube end is not addressed in the above techniques.

"One method, developed by the applicants of the present case and described in WO2006/103419 does describe a device which permits the detection of the arrival of both air as well as the remote end of the fiber unit at the opening of the remote tube end. The device uses a low-mass wind vane which rotates in the presence of airflow, and which rotation is stopped when the fiber end arrives and gets 'caught' in the blades of the wind vane. The change in status of the wind vane can be captured as indicia of air or fiber arrival."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "In general, embodiments provide methods and devices for aspects relating to the installation of cables such as optical fiber units into conduit tubes using, e.g. the blown fiber method, so that a single operator can operate substantially on his own at one end, to determine if compressed air and/or the fiber unit fed into a conduit has reached its intended destination. Embodiments can be used where the operator has to choose between one of a number of conduits, or where there is a single conduit but where it is desirable to unambiguously confirm that the air and/or the fiber unit will reach or reaches the intended destination. In view of the possible volumes that may be deployed in FTTP initiatives, embodiments also address the need for cost-efficiency in being relatively cheap to manufacture and simple to operate.

"An embodiment provides a device for use with a conduit having a first conduit end and a conduit second end, into which conduit a cable can be installed using a flow of air into the first conduit end, the devices, being suitable for confirming that the flow of air is exiting the second conduit end, the device comprising a housing, means to enable connection of the device to the second conduit end, a light source, a detector arranged to detect a presence or absence of a light signal, and a light shield, wherein in use, the flow of air entering the device causes the light shield and at least one of the light source or the detector, to move to and to stay at a position relative to the other, permitting the detector to detect detections comprising one or more of a presence or absence of the light signal, an intensity level of the light signal, a change in the presence or absence of the light signal, or a change in the intensity level of the light signal.

"In an embodiment, air fed through from the head end flows through the conduit, and upon exiting the remote end of the conduit, enters the device housing. An increase in the air pressure within the substantially air-tight housing causes the light shield in the form of, e.g. a piston to move away from blocking the light beam emanating from the light source, at which position the light shield stays. The light beam is detected by the optical detector, and in an embodiment, this detection is signaled back to the operator at the head end, providing a confirmation that air is flowing out of the conduit at the far end. A number of types of detections are possible: the detector can be configured to detect the presence or absence of the light signal, or else it can be arranged to detect certain levels of intensity from the light signal or beam.

"In further embodiments, the light shield piston moves specifically between two positions, wherein the change of positions creates a change in the light signal detected by the detector. In an embodiment, means such as a magnetic and compression spring arrangement is used to urge the light shield to move to, and to stay at, one or the other of the positions. Air vents are opened up while the piston is in a certain position to allow the air exiting the remote end of the conduit to flow out of the device housing.

"Embodiments can be used to detect air arrival alone, without the need to subsequently use the same device to detect cable arrival, although there are of course advantages in using the same one device for both purposes.

"In another embodiment, there is provided a device for use with a conduit having a first conduit end and a conduit second end, into which conduit a cable can be installed using a flow of air into the first conduit end, the device being suitable for confirming that the cable is exiting the second conduit end, the device comprising a housing, means to enable connection of the device to the second conduit end, a light source, and a detector arranged to detect a light signal, wherein in use, the cable entering the housing of the device interferes with the detection by the detector of the light signal from the light source.

"Embodiments can confirm that the fiber unit cable fed into the conduit at the head end has reached the remote end of the conduit. This is performed by detecting an interference of the detector's detection of the light beam or signal from the light source. In embodiments, the light beam emanates transversely through the tubular housing, which is disturbed by the entry of the cable and a bead travelling along the longitudinal axis of the housing.

"No light shield piston is required for the working of this embodiment. It is possible for this method to detect cable arrival with an air arrival detection other than the method claimed, although as the devices for air- and fiber arrival are virtually identical, there is a strong obvious synergy and advantage in deploying both methods, one after the other, using the same device.

"Accordingly, in an embodiment, a device is configured for the detection of both air and fiber, unit cable at the remote end of the conduit, where a first light signal indicative of air arrival is detected, and then a subsequent detection comprising an interruption or interference of the light signal is detected which indicates fiber arrival.

"In embodiments the intensity of the light signal leaving the light source may be steady or modulated with a known signal. The further benefit of the latter is to deliver a more distinctive signal to detector when the light path is uninterrupted. In some practical situations where stray light from outside enters the sensor enclosure through for example the conduit if the external light is particularly strong and the conduit is partially transparent, the detector can more reliably distinguish a detected signal that contains a known intensity modulation, compared with a signal that has a substantially steady intensity.

"In further embodiments, there are provided systems for use with a conduit having a first conduit end and a conduit second end, into which conduit a cable can be installed using a flow of air into the first conduit end, for confirming that the flow of air is exiting the second conduit end, comprising any one of the devices as claimed, wherein apparatus at the first conduit end is configured to receive and to automatically respond to the transmitted status signal.

"In systems including the use of the devices for air-only, cable-only, or air-and-cable arrival detection, the apparatus at the head end which feeds the air and/or cable into the conduit is configured to receive a status signal indicating the respective arrivals at the remote end. In a further embodiment, the head end apparatus is arranged to be automatically turned off upon receipt of the relevant signal.

"In further embodiments, there are provided methods corresponding to the claimed devices and systems."

For the URL and additional information on this patent, see: Barker, Philip Alfred; Heatley, David John Taylor; Neild, Ian. Cable Installation Using Optical Detection. U.S. Patent Number 8702064, filed December 23, 2008, and published online on April 22, 2014. Patent URL:

Keywords for this news article include: British Telecommunications Public Limited Company.

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Source: Journal of Engineering

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