  We consider the use of single-photon counting detectors in coherence-domain
imaging. Detectors operated in this mode exhibit reduced noise, which leads to
increased sensitivity for weak light sources and weakly reflecting samples. In
particular, we experimentally demonstrate the possibility of using
superconducting single-photon detectors (SSPDs) for optical coherence-domain
reflectometry (OCDR). These detectors are sensitive over the full spectral
range that is useful for carrying out such imaging in biological samples. With
counting rates as high as 100 MHz, SSPDs also offer a high rate of data
acquisition if the light flux is sufficient.
