A magnetic resonance (MR) system 10 includes at least one cable (30, 32, 34) that has at least one optic fiber component (31C, 31E, 33B, 35B) and an optical monitoring unit (37) in communication with the at least one optic fiber component (31C, 31E, 33B, 35B). The optical monitoring unit (37) is configured to determine temperatures at each of a plurality of positions along the at least one optic fiber component (31C, 31E, 33B, 35B). The optical monitoring unit (37) is further configured to halt an operation of the MR system (10) in response to at least one determined temperature. In accordance with the invention, the temperature of one or more cable traps forming part of the cable can be monitored and a faulty cable trap can be detected.