TITLE

A multipurpose cable.

TECHNICAL FIELD The present invention discloses a multipurpose cable with an inner and an outer electrical conductor.

BACKGROUND

In present day telecommunications systems, there is a need and a desire to modernize existing equipment in fixed installations. One such modernization involves exchanging fixed components which communicate with other fixed components via electrical signals for components which use optical signals to communicate with other fixed equipment. If and when such a modernization is undertaken, there will also be a need to install optical cables to/from the modernized equipment.

The installation of optical fibres is costly, not only because of the cost of the cable as such, but also because of the work involved, as well as the need for equipment to shield and house the optical cable so that it is protected against mechanical damage, as well as from environmental factors such as rain, wind etc. In addition, it might be desired to give the optical cable a mechanical housing which will increase its protection from so called wiretapping or illegal access.

In addition, even if new equipment which uses optical signals is installed to replace older equipment, there will still be a need to supply power to the new equipment.

SUMMARY As explained above, there is a need for an inexpensive solution by means of which optical cables can be installed between equipment which uses optical signals to communicate with each other.

Preferably, the solution should be inexpensive both when it comes to the work involved, as well as the equipment necessary for the installation. In addition, the solution in question should also offer an inexpensive and easy way of supplying power to the equipment in question.

Such a solution is disclosed by the present invention, in that it discloses a multipurpose cable which comprises an inner and an outer electrical conductor, both of which are circular and hollow.

In addition to said conductors, the cable of the invention also comprises a first layer of a dielectric material in order to separate the inner and the outer conductor. The outer conductor is also covered by a second layer of a dielectric material.

The inner conductor is arranged inside the first layer of a dielectric material, and the cable of the invention additionally comprises a first optical cable housed inside the inner electrical conductor. Accordingly, the inner and outer electrical conductors, as well as the first and second layers of dielectric material, serve to house and shield the first optical cable. In addition, the inner and outer conductors of the inventive cable are adapted to transport power and/or an electrical signal.

Thus, the invention provides an inexpensive way of connecting components by means of an optical cable, in addition to which the invention also provides a way of protecting and shielding the optical cable, as well as a way of supplying power or electrical signals to the components which are connected by means of the optical cable.

The low cost offered by the invention is obtained largely due to the fact that existing cabling which is used for the transmission of electrical signals prior to the installation of components which communicate via optical signals may be

used as a part of the invention. Since existing cabling can be used, the cost for the modernization is reduced.

Suitably, although not necessarily, the inner and outer conductors of the inventive cable are arranged concentrically with respect to each other.

Also, in one embodiment, the cable of the invention comprises connection possibilities, e.g. terminals, for the inner and outer conductors, for connecting a power supply or an electrical signal which it is desired to transmit using the inner and outer conductors.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail in the following, with reference to the appended drawings, in which

Fig 1 shows an application of a cable the invention, and

Fig 2 shows an open view of a part of a cable of the invention, and

Figs 3-5 show open views of a cable of the invention.

DETAILED DESCRIPTION

Fig 1 shows an overview of an installation in which the invention may be applied. The installation comprises a radio base station 110, i.e. a transceiver which is adapted to act as the controlling node of a cell in a cellular communications system. The cellular system in which the invention is applied may be of a wide variety of standards, such as, for example, GSM, WCDMA, TD-SCDMA, LTE etc.

All of the possible cellular systems in which the invention may be applied will not be enumerated here, and it should also be pointed out that the invention is not restricted to being used in cellular systems, but may be used in almost any application in which it is desired to connect optical cables between two components in a system.

Returning now to fig 1 , there is shown the base station 110, as well as a number of antennas, in this case three antennas, said antennas being numbered 120, 130,140.

As is also shown in fig 1 , each of the antennas has an "electronics box", arranged in direct connection to the antenna. These boxes are numbered 121 , 131 ,141. The function of the electronics box may vary between different applications, but in one example, the function of the box is to receive signals on radio frequency from the antenna and to demodulate the received signals so that a baseband signal is obtained, or, alternatively, the function of the box may be to convert the signal from RF, radio frequency, to a lower, intermediate frequency, a so called IF-frequency.

In most applications, the electronics box will be "reciprocal", i.e. a box which can demodulate signals from the antenna will also have as its function to modulate signals. Similarly, an electronics box which can convert signals from RF to IF will also be able to convert IF signals to RF-frequency, which are then supplied to the antenna for transmission.

However, the signals between the antennas (the word "antenna" here and in the following being used as a generic term for the combination of antenna and electronics box) are exchanged as electrical signals on a so called feeder cable. A number of feeder cables are shown in fig 1 , one feeder cable 122, 132, 142 leading to each antenna 120, 130,140.

If the operator or owner of the installation 100 in fig 1 wishes to modernize the base station 110 for a more modern one which uses optical signals as input/output towards the antennas, it will be necessary to install optical cables to all of the antennas 120, 130, 140. (It is assumed here that the antennas can accept optical signals as input/output, although it is perfectly possible to envision a modernization which comprises exchanging the

electronics boxes of the antennas for new ones, which use optical input/output signals instead of electrical ones.)

The installation of optical cables will be costly, which is to a significant extent caused by the cost of the installation as such. An optical cable needs to be mechanically guided during the installation, and also needs to be protected from mechanical damage after the installation.

Returning now to the feeder cable which is used prior to the modernization, an open view of a typical such cable 200 is shown in fig 2: the cable 200 comprises an inner 210 and an outer 220 circular electrical conductor. As the names imply, the inner conductor 210 has a smaller diameter than the outer one 220, and the inner conductor is arranged inside the outer conductor, with a layer 230 of a dielectric material to keep the two conductors apart.

In addition, the cable 200 also comprises an outer "cover" 240 for the outer conductor 220.

A factor which is important here, and which can be seen in fig 2, is that the two conductors are not only circular but also hollow. This creates a "hollow" 250 inside the inner conductor 210 essentially along the entire length of the cable 200.

The fact that cables 121 , 131 , 141 , which have a cross section similar to that of the cable 200, are installed between the base station 110 and the antennas 120, 130, 140 is capitalized upon by the invention: the feeder cable

121 , 131 , 141 can be disconnected at both ends, and the optical cable which will be used by the new equipment can be inserted into the hollow 250 inside the inner conductor 210 at one end of the cable 200, for example at "the base station end".

The optical cable can then be fed into the cable, and accessed at the other end of the cable. The base station and the antenna can then be connected to the ends of the optical cable, and a weatherproof housing which can also serve as mechanical protection is then suitably installed to cover the connection points at both ends of the optical cable.

Following this procedure, the optical cable is now installed between the two points which it is desired to connect by means of the optical cable, and is housed inside the cable 200, which now serves as housing and as mechanical protection for the optical cable, without any additional expense being incurred for the housing and the mechanical protection.

In addition, the use of the existing cable to guide the optical cable between the points that are to be connected will also serve to greatly reduce the cost of the work carried out during the installation.

It can also be pointed out that an additional advantage is provided by the use of the existing feeder cable as housing and shield for the optical cable: the existing feeder cable 200 is typically quite coarse, i.e. the materials used in it have a high durability and high mechanical strength. This means that the housing which is obtained for the optical cable will be highly tamper-proof, i.e. it will be highly difficult for anybody who wishes to illegally access the cable in order to eavesdrop on the traffic, or to damage the optical cable.

Fig 3 shows an open view of a cable 300 of the invention. Parts or components which the cable 300 has in common with the cable 200 of fig 2 have retained their reference numbers from fig 2, and will not be described explicitly again. As can be seen in fig 3, the cable 300 is similar to the cable 200, but shows an optical cable 310 inside the inner electrical conductor 210, shielded mechanically by the two conductors 210, 220, as well as by the two layers 230, 240 of dielectric material.

Fig 4 shows an open view of the cable 300 of the invention, with the reference numbers from figs 2 and 3. This drawing has been added in order to illustrate a further aspect of the invention:

As has been stated above, the invention facilitates connecting two components with an optical cable, and provides protection for the optical cable. Another advantage which is gained by the invention is in the power supply to the antennas which use optical signals as input and/or output, but which still need a power supply: The feeder cable which is used as part of the inventive cable has, as shown in figs 2-4, an outer 220 and an inner 210 electrical conductor.

According to the invention, the conductors 210, 220 are used to feed electrical power to the antennas. This is accomplished by means of using the conductors 210, 220 as leads for electrical power from one point of the cable 300 to another point of the cable, as shown in fig 4: fig 4 shows the cable 300, but indicates that one of the conductors, in this case the inner conductor 210, is used as the "negative" terminal 410 for the electrical power, and the outer conductor 220 is used as the "positive" terminal 420 for the electrical power.

Thus, in the same way that the optical cable 310 is attached at either end of the connection, a power supply may be connected to the inner and outer conductors 210, 220, and the electrical power supply may be accessed at the other end of the cable in a similar manner, i.e. by accessing the inner and outer conductors 210, 220. This may be done by attaching connection terminals to the conductors, in order to facilitate the connection of power leads to/from the cable, or it may simply be done by attaching the power leads directly to the conductors of the cable.

Fig 5 shows an open view 500 of the inventive cable, with electrical leads attached to the terminals 510, 520, and with the optical cable 310 installed inside the hollow 250 of the inner conductor.

The invention is not limited to the examples of embodiments described above and shown in the drawings, but may be freely varied within the scope of the appended claims. For example, it is entirely possible to house more than one optical cable inside the feeder cable, depending of course on the diameter of the inner conductor 210, and the diameter of the optical cables.

In addition, the use of the electrical conductors 210, 220 to transport electrical power may be expanded to include the use of electrical signals. Such signals are then transported in the conductors together with the power supply, or, alternatively, the conductors of the inventive cable may be used for transporting electrical signals only.

It should also be pointed out that although the invention has been illustrated above as connecting a modernized base station with (possibly modernized) antennas, the invention can be used in order to obtain an optical connection between more or less any two pieces of equipment between which there extends an electrical cable with suitable characteristics regarding, for example, the inner hollow 250 shown in fig 2.

Also, it is of course possible to use the invention "from scratch", i.e. in cases when there is no electrical cable installed previously. In such cases, an electrical cable with suitable properties, i.e. essentially those described above in connection with fig 2, can be used in order to obtain a housing as well as mechanical protection for an optical cable.