Abstract
In this paper a low-cost all-fiber current sensor is described that fulfills the requirements of robustness, sensitivity, accuracy and cost required for the monitoring of catenary current in changeover sections of the high-speed railway network. Its optical configuration is simplified through the use of few devices with extremely simplified alignment. This allows high sensitivity for low current values and a resolution below the ampere level. The sensing head is packed in a compact box withstanding temperature and position variations without affecting the sensitivity of the set-up. The electronics incorporates self-referencing that makes it robust to small misalignments and power variations in the optical source. Field tests will be reported in the conference.