A vibration detector (1) comprising at least one fiber optic sensor (2) mechanically coupled to a flexible support member (3). The vibration detector (1) is mounted on the outside of the pipeline and a signal from the fiber optic sensor is measured. This signal is indicative of whether the vibration detector is experiencing vibrations due to collisions of contaminant particles with each other and/or with the walls of the pipeline. A method for detecting particulate contaminants in a fluid flowing in a pipeline is also provided.