A method for monitoring a torsional state of an electric cable (1; 36) having a central longitudinal axis, the method comprising - providing an electric cable including a torsion sensor longitudinally extending along the cable, said torsion sensor including a single-mode optical fibre arranged substantially along the central longitudinal axis (Z) of the cable (1; 36), characterised in that the cable comprises at least three longitudinal structural elements , at least one of the longitudinal structural elements being an electrically conductive core , wherein the torsion sensor is mechanically coupled with at least one of the longitudinal structural elements , and measuring a torsional state of the single-mode optical fibre by polarisation-sensitive optical reflectometry, said measuring comprising: - injecting a plurality of probe optical signals having distinct input polarisation states into an end of the single-mode optical fibre ; - detecting a plurality of backscattered optical signals, each of the plurality of backscattered optical signals having an output state of polarisation; - measuring the output states of polarisation of the backscattered optical signals; - calculating a birefringence angle function as a function of longitudinal position of the single-mode optical fibre from the measured output states of polarisation, and - calculating a rotational angle function of the single-mode optical fibre from the birefringence angle function as a function of the longitudinal position in the single-mode optical fibre , and - associating a torsional state of the single-mode optical fibre with the calculated rotational angle function, wherein the method comprises associating the torsional state of the cable (1; 36) along the central longitudinal axis (Z) with the measured torsional state of the single-mode optical fibre . - providing an electric cable including a torsion sensor longitudinally extending along the cable, said torsion sensor including a single-mode optical fibre arranged substantially along the central longitudinal axis (Z) of the cable (1; 36), characterised in that the cable comprises at least three longitudinal structural elements , at least one of the longitudinal structural elements being an electrically conductive core , wherein the torsion sensor is mechanically coupled with at least one of the longitudinal structural elements , and - injecting a plurality of probe optical signals having distinct input polarisation states into an end of the single-mode optical fibre ; - detecting a plurality of backscattered optical signals, each of the plurality of backscattered optical signals having an output state of polarisation; - measuring the output states of polarisation of the backscattered optical signals; - calculating a birefringence angle function as a function of longitudinal position of the single-mode optical fibre from the measured output states of polarisation, and - calculating a rotational angle function of the single-mode optical fibre from the birefringence angle function as a function of the longitudinal position in the single-mode optical fibre , and - associating a torsional state of the single-mode optical fibre with the calculated rotational angle function, <EOS>