A scanning optical delay line includes an optical path element that rotates about its central axis, such that a face is intermittently incident a beam of light to be optically delayed. When the beam is not incident the face, it is reflected onto a reinsertion line which provides a second opportunity for the beam to intersect the optical path element. The optical path element may include one or more parallelogram prisms, or parallel reflective surfaces to provide a substantially linear optical path length variation during the scan, which is produced by the rotation of the optical path element. A highly linear part of the rotation can be maximally used providing a high duty cycle, high linearity scanning optical delay line that permits high quality, high data rate applications.