Extra long imaging range swept source optical coherence tomography using re-circulation loops

One of the main drawbacks of the swept source optical coherence tomography (SS-OCT) is its limited axial range. A novel interferometer configuration is proposed, equipped in each arm with an adjustable path length ring. By compensating the losses in the rings using semiconductor optical amplifiers, multiple paths A-scans can be obtained which when combined axially, can lead to an extremely long overall axial range. The effect of the re-circulation loops is equivalent with extending the coherence length of the swept source. In this way, the axial imaging range in SS-OCT can be pushed well beyond the limit imposed by the coherence length of the laser, to exceed in principle many centimeters.