<p>A sensor assembly for detecting the presence of a sheet document in a transport path is disclosed. The sensor assembly comprises an optical transmitter (1), an optical receiver (2) and an optical fibre (3). The optical transmitter (1) and optical receiver (2) are each associated with and lie opposite a respective end (8a, 8b) of the optical fibre (3). At least one of the optical transmitter (1) and the optical receiver (2) is disposed across the transport path from the associated end (8a, 8b) of the optical fibre (3).</p>
