A method of sensing electromagnetic (EM) fields downhole may include filtering a voltage signal induced in a coil antenna by an EM field to produce a filtered signal, said filtering being performed by a resonance tuning filter, and applying the filtered signal to a piezoelectric element to modify a strain of an optical fiber. A sensing system may include a cable deployed downhole and coupled to an interface unit. The cable has an optical fiber coupled to an array of downhole sensors, each sensor having a coil antenna coupled by a resonance tuning filter to a piezoelectric element that modifies a strain in the optical fiber in accordance with a signal induced in the coil antenna by an electromagnetic field. The interface unit measures a backscattered light to monitor the signal from each sensor in the array.