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

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.