2. Low-coherence interferometry

In very general terms, temporal coherence tomography (OCT) measures backscatter contrast within complex 3D structures, and can distinguish the depth of these scattering events by indirectly measuring the propagation time of photons within the structure. This propagation time measurement is only possible using interferometric detection, which relies on several advantages offered by low-coherence interference.

In this chapter, the principle of low-coherence interferometry and the essential characteristics of optical interferometry will be developed. We will derive the link between the source spectrum and the temporal coherence length, which controls the axial resolution of OCT systems. Finally, the main OCT configurations will be introduced and compared, before a more detailed description of two main configurations in the following sections.