  Quantum Optical Coherence Tomography (Q-OCT) presents many advantages over
its classical counterpart, Optical Coherence Tomography (OCT): it provides an
increased axial resolution and is immune to even orders of dispersion. The core
of Q-OCT is quantum interference of negatively correlated entangled photon
pairs obtained in a Hong-Ou-Mandel configuration. This two-photon interference
can be observed in the time domain in the form of dips or in the Fourier domain
by means of a joint spectrum. The latter approach proved to be practical in the
sense that it alleviated the requirement posed on light in Q-OCT to exhibit
strict negative correlations, since the negative correlations can be easily
extracted in the Fourier domain as the main diagonal of the joint spectrum. In
this work, we investigate the use of this spectral approach in which quantum
interference is obtained with classical low-intensity light pulses. We report
theoretical calculations and their experimental validation and show that
although such classical light is much easier to launch into an experimental
system, it offers limited benefits as compared to Q-OCT based on entangled
light. We analyse the differences in the characteristics of the joint spectrum
obtained with entangled photons and with classical light and explain the
origins of these differences.
