Broad Bandwidth Light Sources in Optical Coherence Tomography (OCT)

Optical coherence tomography (OCT) is a 3D volumetric imaging modality based on low-coherence interferometry, which achieves unprecedented axial resolving capability through the low temporal-coherence property of broad bandwidth light sources. Since the first demonstration in the early 1990s, OCT has evolved rapidly and being widely used in different biomedical fields, as a powerful imaging modality that provides resolution on the order of microns. One key enabling factor that drives the advancement and widespread of the OCT technique is the development of broadband sources. This chapter provides a review of different types of most frequently used broadband sources for OCT systems, including femtosecond lasers, swept sources, supercontinuum sources, and superluminescent diodes. These sources operate with different physics principles and have very different characteristics. The key parameters of broadband sources will be discussed in this chapter, including centre wavelength, spectral bandwidth, noise, instantaneous linewidth of a swept source, and the repetition/swept rate, as well as the indications of these source parameters for OCT imaging performance.