A deformation monitoring system for measuring at least the tensile strain of a plurality of electric cables comprising: a sampling apparatus (100; 143) for measuring spectral changes of Brillouin scattered light comprising a first and a second optical input/output port (101, 102; 163, 164), the first input/output port (101; 163) being apt to emit a first optical signal and the second input/output port (102; 164) being apt to emit a second optical signal, and a first plurality of electric cables (85; 104, 106, 108, 110; 146, 147, 148, 151) including a first and a last electric cable, characterised in that each cable of the plurality comprising a strain sensor including a strain optical fibre and a temperature sensor including a temperature optical fibre, the strain and temperature sensors extending longitudinally along the respective cable, the strain optical fibre and temperature optical fibres having proximal ends and distal ends, the proximal ends being positioned at a proximal end of the respective electric cable, wherein: the distal ends of the strain optical fibre and the temperature optical fibre of each electric cable are optically connected one to another, the proximal end of the strain optical fibre of the first electric cable of the first plurality is in optical communication with the first input/output (101; 163) of the sampling apparatus (100; 143) and the temperature optical fibre of the last electric cable of the first plurality is in optical communication with the second input/output port (102; 164) of the sampling apparatus (100; 143), and the proximal end of the temperature optical fibre of the first electric cable is optically connected with the proximal end of the strain optical fibre of the last electric cable, so as to form an optical fibre loop in which the strain optical fibre and the temperature optical fibre of each electric cable of the plurality are in optical communication with both the first and the second input/output ports (101, 102; 163, 164) of the sampling apparatus (100; 143) and the first and second optical signals enters the optical fibre loop in opposite directions. a sampling apparatus (100; 143) for measuring spectral changes of Brillouin scattered light comprising a first and a second optical input/output port (101, 102; 163, 164), the first input/output port (101; 163) being apt to emit a first optical signal and the second input/output port (102; 164) being apt to emit a second optical signal, and a first plurality of electric cables (85; 104, 106, 108, 110; 146, 147, 148, 151) including a first and a last electric cable, characterised in that each cable of the plurality comprising a strain sensor including a strain optical fibre and a temperature sensor including a temperature optical fibre, the strain and temperature sensors extending longitudinally along the respective cable, the strain optical fibre and temperature optical fibres having proximal ends and distal ends, the proximal ends being positioned at a proximal end of the respective electric cable, wherein: the distal ends of the strain optical fibre and the temperature optical fibre of each electric cable are optically connected one to another, the proximal end of the strain optical fibre of the first electric cable of the first plurality is in optical communication with the first input/output (101; 163) of the sampling apparatus (100; 143) and the temperature optical fibre of the last electric cable of the first plurality is in optical communication with the second input/output port (102; 164) of the sampling apparatus (100; 143), and the proximal end of the temperature optical fibre of the first electric cable is optically connected with the proximal end of the strain optical fibre of the last electric cable, so as to form an optical fibre loop in which the strain optical fibre and the temperature optical fibre of each electric cable of the plurality are in optical communication with both the first and the second input/output ports (101, 102; 163, 164) of the sampling apparatus (100; 143) and the first and second optical signals enters the optical fibre loop in opposite directions. the distal ends of the strain optical fibre and the temperature optical fibre of each electric cable are optically connected one to another, the proximal end of the strain optical fibre of the first electric cable of the first plurality is in optical communication with the first input/output (101; 163) of the sampling apparatus (100; 143) and the temperature optical fibre of the last electric cable of the first plurality is in optical communication with the second input/output port (102; 164) of the sampling apparatus (100; 143), and the proximal end of the temperature optical fibre of the first electric cable is optically connected with the proximal end of the strain optical fibre of the last electric cable, so as to form an optical fibre loop in which the strain optical fibre and the temperature optical fibre of each electric cable of the plurality are in optical communication with both the first and the second input/output ports (101, 102; 163, 164) of the sampling apparatus (100; 143) and the first and second optical signals enters the optical fibre loop in opposite directions.