Monitoring device, system and method for the monitoring of an area of building or land, using at least one light waveguide

1. A monitoring device used for the monitoring of an area of building or land by detecting monitoring data relating to an optical signal after a round trip in an optical strand, comprising:

an optical strand used as a sensor, comprising optical waveguides under mechanical prestress to such an extent that they are subjected to tensile stress even when subjected to little deformation;

one optical source for emitting an optical emission signal transmitted in the optical strand;

one optical analogue detector for detecting an intensity of an optical return signal corresponding to the optical emission signal returning from the optical strand, said optical analogue detector configured to calculate monitoring data solely from said intensity of the optical return signal; and

the monitoring device arranged as a compact unit and comprising control means for alternately activating and deactivating the emission of the optical source so that a ratio between the non-emission duration and the emission duration is greater than 5000;

the optical strand consisting in a component with optical waveguides that monitor the deformations of the component and are fastened on or in the component under mechanical prestress, the optical waveguides being firmly bounded to the component over at least part of its length and being prestressed to such an extent that the optical waveguides are subjected to tensile stress when deformations due to compression, shrinkage or creep occur in the component.

2. The monitoring device of claim 1 , wherein said control means for alternately activating and deactivating the emission of the optical source are arranged to periodically activate the emission of the optical source one microsecond per time period, said time period being between 5 and 100 milliseconds.

3. The monitoring device of claim 1 , wherein said control means for alternately activating and deactivating the emission of the optical source are arranged to periodically activate the emission of optical source one microsecond per time period, said time period being between 5 and 30 milliseconds.

4. The monitoring device of claim 1 , further comprising an electrical connector for transferring data and/or energy.

5. The monitoring device of claim 1 , further comprising wireless transmission means for transmitting monitoring data to a remote station.

6. A monitoring system comprising a monitoring device and a remote station, the monitoring device being used for monitoring an area of a building or land by detecting monitoring data relating to an optical signal after a round trip in an optical strand and comprising:

an optical strand used as a sensor, comprising optical waveguides under mechanical prestress to such an extent that they are subjected to tensile stress even when subjected to little deformation;

one optical source for emitting an optical emission signal transmitted in the optical strand;

one optical analogue detector for detecting an intensity of an optical return signal corresponding to the optical emission signal returning from the optical strand;

wireless transmission means for transmitting said intensity of the optical return signal to said remote station;

the monitoring device being arranged as a compact unit and comprising control means for alternately activating and deactivating the emission of the optical source so that a ratio between the non-emission duration and the emission duration is greater than 5000;

the optical strand consisting in a component with optical waveguides that monitor the deformations of the component and are fastened on or in the component under mechanical prestress, the optical waveguides being firmly bounded to the component over at least part of its length and being prestressed to such an extent that the optical waveguides are subjected to tensile stress when deformations due to compression, shrinkage or creep occur in the component;

the remote station comprising processing means for calculating, solely from an intensity variation of the optical return signal, monitoring data comprising a change in the length of the optical strand.

7. The monitoring system of claim 6 , comprising several monitoring devices, each comprising wireless transmission means for transmitting intensities of optical return signals to a same remote station.

8. The monitoring system of claim 6 , wherein the remote station comprises means for a user to activate said transmission of intensity of the optical return signal.

9. A method of monitoring an area of building or land carried out in a monitoring device according to claim 1 , comprising:

alternately activating and deactivating the emission of the optical source, so that a ratio between the non-emission duration and the emission duration is greater than 5000; and

calculating monitoring data based solely on an intensity of an optical return signal corresponding to the optical emission signal returning from the optical strand.

10. The method of claim 9 , further comprising a step of transmitting the intensity of the optical return signal from the monitoring device to a remote station.

11. The method of claim 10 , wherein said transmission step is periodically carried out.

12. The method of claim 10 , wherein said transmission step is carried out on demand.

13. The method of claim 11 , wherein said transmission step may also be carried out on demand.