[0001] The invention relates to an integrated system of perimeter protection and data transmission
using optic fibres.
[0002] Various uses of fibre optic conductors in the field of alarm systems already exist
in the prior art. These materials are particularly suitable for a utilisation of this
kind, where absolute reliability is required, because of their immunity to natural
atmospheric agents, such as rain, snow and wind, as well as to electromagnetic interference.
[0003] The principal advantage of the choice of fibre optics lies in the impossibility of
short-circuits or of interference in its transmitted signal without the system control
unit noticing.
[0004] Of particular interest, with reference to the present case, are the prior art applications
relative to physical barrier systems using tensed cables.
[0005] A first use of fibre optics in alarm systems consisted in its sealing internally
to a channel, realised in metal foil and successively covered with adhesive tape.
[0006] The metal foil, which could be barbed or not, was then stretched between two support
posts. In this way, an alarm signal was received only when the optic fibre was cut,
but not when adjacent wires were in some way enlarged so as to permit a person's entrance.
To obviate this, wires were made which would break with only minimum variations in
their tension. In this way, however, every attempt at unauthorised entrance necessitated
the substitution of the forced wire with a consequent increase in the maintenance
costs.
[0007] Later, optic fibres were used in such a way as to exploit their characteristic of
altering the signal, even when only minimum deformations are made and not only when
a breakage occurrs. This process, called "microbending", consists in arranging the
optic fibre according to an arbitrary configuration and making the forcing of the
perimter wire correspond to deformations in the optic fibre itself.
[0008] In this way, the presence of the optic fibre in the perimeter fence serves only to
signal its cutting, as already happened in the above-mentioned oldest applications:
for this reason, the wires used are normal optic fibre cables and have only modest
mechanical characteristics.
[0009] The deformed optic fibre responsible for the signalling of the attempted forcing
of the fence, which might not even contain optic fibres, is found internally to the
posts which hold up the fence itself.
[0010] Considering a fence of about 100-150 metres in length, a post would be situated about
every 2 metres. One out of every two or three of these posts would exhibit internally
an optic fibre subject to microbending at the places where the wires pass through
the post; the remaining posts having the wire fixed normally and stably.
[0011] Unfortunately this is necessary because of the mediocre quality of the wire from
the mechanical point of view, necessitating a tensioning of the wire at each post
not containing the optic fibre, that is, at most every ten metres.
[0012] Consequently, the optic fibre must follow the development of the fence for its entire
length, with a significant increase in costs: this solution also requires considerable
installation work, because of the quantity of tensing imposed by the quality of the
wire used.
[0013] Apart from this, the device interpreting the signals indicating handling of the wire,
sending and receiving the signal sent from the optic fibre on a certain tract, is
normally connected to a control station by means of wires or the selfsame optic fibre.
It is obvious that by increasing the length of the fence the quantity of wires necessary
to connect the signal interpreting device of the various tract with the control station
also increases: furthermore, each further input also requires its own connection.
[0014] Consideration must also be given to the fact that a plant made in this way presents
other drawbacks, linked to possible false alarms: in the presence of thermal variations
caused by atmospheric conditions (for example due to the different degree of exposure
to the elements of the various tracts), or due to a progressive deterioration (after
bad weather), the wire deforms unevenly, modifying its tension, and this requires
a continual adjustment of the tension in the various tracts.
[0015] Finally, any use of the optic fibres internally to the fence wires to signal attempts
at intrusion by cutting the wire but without alterations to the tension at the posts
would appear to be an unjustified expense because of the insufficient use of the quality
of these components.
[0016] An aim of the present invention, as it is characterised in the claims that follow,
is thus that of elimination the above-mentioned drawbacks.
[0017] The invention solves the problem by providing a tensed-wire alarm system wherein
each tract of fencing comprises a single wire, fixed only at its ends, and a single
corresponding sensor group, connected to the control unit of the said tract.
[0018] One of the principal advantages offered by the invention consists in its self-balancing
with respect to thermal effects, so that false alarms are not induced.
[0019] A further advantage consists in the fact that during installation the time and the
operations necessary are considerably reduced. The quantity of fibre optic cable present
in the sensor posts is also reduced, with a consequent lowering of costs.
[0020] The serial connection of the control units of the various tracts allows the plant
to be predisposed to exchange information with external acquisition sytems or data
processing systems, thus exploiting more adequately the optic fibres present in the
fence wires, to which the task of transporting any alarm information from the station
control unit is given.
[0021] Further characteristics and advantages of the present invention will better emerge
from the detailed description that follows, together with the accompanying drawings
which represent a preferred but not exclusive embodiment and in which:
- Figure 1 shows a particular of the invention in perspective view, with some parts
removed better to evidence others and some parts schematically represented;
- Figure 2 shows a section view of a particular of the invention;
- Figure 3 shows schematically the invention in its entirety;
- Figure 4 shows a part of the fence between contiguous tracts of the invention.
[0022] With reference to the drawings, the invention substantially consists of an integrated
perimeter protection and fibre optic data transmissionm system, comprising tracts
2 of fencing made with tensed wires 3 distributed on levels which are substantially
parallel among themselves, in a horizontal, vertical and oblique direction. Two adjacent
levels are distanced less than is necessary for the passage of a person. The integrated
system 1, represented by horizontal wires 3 parallel to the earth, comprises, for
each tract 2 of fencing, a single wire 3 with at its inside a first optic fibre 4,
rigidly fixed only at its ends 3a, 3b, so as to be tensed along all of the tract 2
with a single operation, acting on one end and keeping the other fixed. In this way
It is sufficient to have only one sensor group 6 for each tract of fencing 2 to which
the wire 3 is constrained, so that the sensor group 6 can perceive any pulling on
the wire 3.
[0023] The sensor group 6 is of the analog type and comprises at least one rotatable element
10 and a second optic fibre 11, arranged unilaterally with respect to the wire 3 containing
the first optic fibre 4. There will be a proportionate number of rotatable elements
10 for each tract 2 of fencing, normally double the number of levels that the wires
3 describe. The rotatable elements 10, represented in figure 1, will be arranged in
the posts which are situated at the ends 2a, 2b of each tract 2 of fencing, correspondingly
to the inversions of the arrangement of the wire 3, as is illustrated in figure 4.
The two posts of consecutive tracts 2 of fencing, of which only one is equipped with
an analog sensor group 6, represented in figure 4, can also be reduced to one post
alone of greater size. The rotatable elements 10 and the second optic fibre 11 are
mutually connected in such a way that any pulling on the wire 3 determines a rotation
of at least one rotatable element 10, so that the second optic fibre 11 is deformed;
the sensor group 6 comprises also a photodiode 22, situated at one end of the second
optic fibre 11 so as to read the luminous signal that crosses it, and is associated
to continuous monitoring means 12 of the same signal. A sensor group 6 of this kind,
particularly useful in the described application, could however be used also in systems
not using optic fibres internally, but with good mechanical charactristics in order
to be able to stand such a kind of tensing.
[0024] Each rotatable element 10 envisages a pivot 18 rotating about a horizontal axis and
a portion 19 of curved surface destined to be associated with the said wire 3 with
low friction. In the illustrated case the portion 19 of curved surface is equipped
with two wheels 23, situated on opposite sides of the rotation pivot 18, in correspondence
of which the rotatable element 10 is associated to the wire 3. This specification
is particularly useful during the tensing phase of the wire 3, as it reduces the friction.
Once the wire 3 is mounted, it is preferably blocked to the rotatable element 10 at
the pivot 18 in order to render local deformation of the second optic fibre 11 more
evident, which otherwise would distribute over the entire optic fibre 11 length. The
connection between rotatable elements 10 and second optic fibre 11 happens through
at least one appendage 20, but normally one for each end of the rotatable element
10, to deform the second optic fibre 11, contained inside a vertical guide 21 at a
rotation of a rotatable element 10. As can be seen in figure 1, the second optic fibre
11 is arranged on two branches, carrying the optic signal from one to the other of
its ends. The branch that runs inside the vertical guide 21 passes also through holes
made in the appendages 20 of the rotatable elements 10. When one of these rotates,
at least one appendage 20 chokes the second optic fibre 11 in at least one point,
modifying the signal carried by it. The photodiode 22 collects a different signal
from the one which had been originally carried. The continuous monitoring means 12,
downline of the photodiode 22, comprise at least one analog-digital convertor 13,
to sample the signal received from the said photodiode 22. The samples are processed
by an algorithm which considers very slow variations to be uninfluential, neutralising
the effects due to drift in the electronic components and to thermal expansion in
the mechanical parts.
[0025] The rotation pivot 18 is equidistant from the centres of the wheels 23 so as not
to induce moments when there are uniformly distributed pulls on the wire 3.
[0026] A tensing of this kind is possible because of the special structure of the wire 3,
which improves its performance from the mechanical point of view: it comprises, as
can be seen from a transversal section show in figure 2, apart from at least one first
optic fibre 4 to transfer an optic signal, at least two coverings 7a and 7b in low-elastic
material, one on the left 7b and one on the right 7a, to reduce the torque reaction
due to the tension of the wire 3. The external surface is constituted by a plastic
sheath 8.
[0027] In the illustrated example the two coverings 7a and 7b comprise lines 5 in galvanised
carbon steel with a resistance of about 2,000 Newtons per square millimetre and the
external sheath 8 is in PVC 80.
[0028] In order better to exploit the properties of the optic fibres, while the second optic
fibre 11 reads the alarm perturbations, the first optic fibre 4 transports the signal.
An analysing unit 9 is associated to each tract 2 of fencing. Since for each tract
2 of fencing there is only one post with a sensor group 6 and the ends 3a, 3b of the
wire 3 are fixed to the opposite ends 2a, 2b of the same tract 2 of fencing, the analysing
units 9 can be connected in series among themselves: two conseccutive analysing units
9 situated at the ends 2a, 2b of a tract 2 of fencing communicate by means of the
said single wire 3 with optic fibre 4.
[0029] In this way, as is shown in figure 3, a single analysing unit 9 is connected to a
central control unit 17, which collects and visualises the data coming from all of
the fencing.
[0030] Furthermore, each analysing unit 9 is equipped with an interface, which exchanges
information with external acquisition systems 16 or external data processing systems
16, so as to transfer from one analysing unit 9 to another, and thus to the central
command unit 17, information of various kinds.
[0031] To guarantee that portions of the entire integrated system 1 of perimeter protection
and fibre optic data transmission do not remain isolated because of any eventual defects
in the fibre optic 4 wire 3, the presence of a further wire 14 is envisaged, identical
to the preceding, but independent of it, for each tract 2 of fencing, to realise a
counter-rotating double ring topology. The signal transferred from one analysing unit
9 to another travels in both directions and if a tract 2 of fencing is handled, the
information relative to it continue to arrive at the central command unit 17, thanks
to an automatic reconfiguration of the system.
1. An integrated system of perimeter protection and data transmission using optic fibres,
comprising tracts (2) of fencing realised with wires tensed and distributed on levels
which are substantially parallel among themselves, adjacent levels being distanced
less than is necessary for the passage of a person, the said system characterised
in that it comprises, for each tract (2) of fencing, a single wire (3), with at its
inside at least one first optic fibre (4), rigidly fixed only at its ends (3a, 3b),
so that the said optic fibre (4) can be tensed over all the said tract (2) of fencing
by one operation only, and constrained to a single sensor group (6), aimed at perceiving
any pulling whatsoever on the said single wire (3).
2. An integrated system of perimeter protection and data transmission using optic fibres,
comprising tracts (2) of fencing realised with tensed wires (3) and distributed on
levels which are substantially parallel among themselves, adjacent levels being distanced
less than what is necessary for the passage of a person, characterised in that it
comprises, for each tract (2) of fencing, a single wire (3) rigidly fixed only at
its ends (3a, 3b), so that the said optic fibre (4) can be tendsed over all the tract
(2) of fencing with a single operation, being constrained to a single sensor group
(6), aimed at perceiving any pulling whatsoever on the said single wire (3) and comprising
at least one rotatable element (10) and a second optic fibre (11), arranged unilaterally
with respect to the said wire (3) containing the first optic fibre (4), mutually connected
so that any pulling on the said wire (3) determines a rotation of at least one rotatable
element (10), in such a way as to deform the said second optic fibre (11).
3. An integrated system of perimeter protection and data transmission according to claim
1, characterised in that the said wire (3) comprises:
- at least one first optic fibre (4), to transfer an optic signal;
at least two coverings (7a, 7b), in low-elastic material, of which coverings one is
on the left (7b), and one is on the right (7a) to reduce torque reaction due to tension
on the wire (3);
- an external sheath (8) in plastic material;
so as to optimise the mechanical performance of the said wire (3).
4. An integrated system for perimeter protection and data transmission using optic fibres
according to claim 1, of the type wherein to each tract (2) of fencing a unit (9)
of analysis of the transmitted signals is associated, characterised in that the said
units (9) of analysis are connected serially among themselves, two units (9) of analysis
consecutive, situated at the ends (2a, 2b) of a tract (2) of fencing, communicating
by means of the said single wire (3) containing the said first optic fibre (4), the
ends (3a, 3b) of the said wire (3) being fixed to the opposite ends (2a, 2b) of the
said tract (2) of fencing.
5. An integrated system of perimeter protection and data transmission using optic fibres
according to claim 1, characterised in that the said sensor group (6) is of analog
type, comprising at least one rotatable element (10) and a second optic fibre (11),
arranged unilaterally with respect to the said wire (3) containing the first optic
fibre (4), mutually connected in such a way that any pulling on the said wire (3)
determines a rotation of at least one rotatable element (10), in such a way as to
deform the second optic fibre (11), the said analog sensor group (6) comprising also
a photodiode (22), situated at an end of the said second optic fibre (11) so as to
read a luminous signal crossing it and being associated to continuous monitoring means
(12) of the said signal.
6. An integrated system of perimeter protection and data transmission using optic fibres
according to claim 3, characterised in that the said two coverings (7a, 7b) comprise
lines (5) made of galvanised carbon steel with a resistance of about 2,000 Newtons
per square millimetre.
7. An integrated system of perimeter protection and data transmission using optic fibres
according to claim 3, characterised in that the said external sheath (8) is made in
PVC 80.
8. An integrated system of perimeter protection and data transmission using optic fibres
according to claim 4, characterised in that it envisages a further wire (14), identical
to the preceding one, but hanging from it, for each tract (2) of fencing, so as to
realise a double counter-rotating ring topology.
9. An integrated system of perimeter protection and data transmission using optic fibres
according to claim 4, characterised in that each of the said units (9) of analysis
is equipped with an interface for the exchanging of information with external acquisition
systems (16) or external data processing systems, so as to transfer from one unit
(9) of analysis to another information of various kinds.
10. An integrated system of perimeter protection and data transmission using optic fibres
according to claim 4, characterised in that one alone of the said units (9) of analysis
is connected to a control station (17) which collects and visualises the data arriving
from each tract (2) of fencing.
11. An integrated system of perimeter protection and data transmission using optic fibres
according to claims 2 or 5, characterised in that each rotatable element (10) envisages
a pivot (18) of rotation about a horizontal axis and a portion (19) of curved surface,
destined to be associated to the said wire (3) with a small degree of friction, each
rotatable element (10) further more exhibiting at least one appendage (20) interfering
with the said second optic fibre (11), contained inside a vertical guide (21) in such
a way as to deform it when a rotation is imparted to the rotatable element (10).
12. An integrated system of perimeter protection and data transmission using optic fibres
according to claim 2 or 5, characterised in that the said continuous monitoring means
(12) comprise at least an analog-digital converter (13) for the sampling of the signal
received from the said photodiode (22).
13. An integrated system of perimeter protection and data transmission using optic fibres
according to claim 11, characterised in that the said rotatable element (10) comprises
two wheels (23), situated on opposite sides with respect to the said rotation pivot
(18), whereas the wire (3) is associated to the rotatable element (10).
14. An integrated system of perimeter protection and data transmission using optic fibres
according to claim 13, characterised in that the said rotation pivot (18) is equidistant
from the centres of the said wheels (23), so as not to induce moments connected with
pullings uniformly distributed on the wire (3).