In this paper, a rugged, low cost and very efficient fiber optic displacement sensor is proposed and demonstrated for the measurement of amplitude and frequency of heart rate signal. The proposed sensor is based on intensity modulation technique and uses a bundled POF as a probe. Among these sensors, optical fiber sensors (OFSs) stand out due to their remarkable properties, including resistance to electromagnetic interference. Nowadays, wearable devices are gaining broad interest for a continuous monitoring of the heart rate (HR). One of the most promising methods to estimate HR is the seismocardiography (SCG) which allows to record the thoracic vibrations with high non-invasiveness in out-of-laboratory settings.