  A key question of quantum optics is how nonclassical bi-photon correlations
at low power evolve into classical coherence at high-power. Direct observation
of the crossover from quantum to classical behavior is desirable, but difficult
due to the lack of adequate experimental techniques that cover the ultra-wide
dynamic range in photon flux from the single photon regime to the classical
level. We investigate bi-photon correlations within the spectrum of light
generated by broadband four-wave mixing (FWM) over a \emph{large dynamic range
of $\sim80dB$ in photon flux} across the classical-to-quantum transition using
a two-photon interference effect that distinguishes between classical and
quantum behavior. We explore the quantum-classical nature of the light by
observing the interference contrast dependence on internal loss and demonstrate
quantum collapse and revival of the interference when the FWM gain in the fiber
becomes imaginary.
