In some embodiments, a method and apparatus, as well as an article, may operate to determine downhole properties based on detected optical signals. An optical detection system can include a fiber optic cable having a sensing location to generate a reflected measurement signal representative of measurement parameters. The optical detection system can further include a light source to transmit a measurement signal to cause the sensing location to provide the reflected measurement signal. The optical detection system can further include an optical detector comprising a single-photon detector (SPD) for detecting the reflected measurement signal received over the fiber optic cable. The optical detection system can further include a housing for enclosing the optical detector and to optically shield the optical detector, the housing including an aperture for passage of the fiber optic cable. Additional apparatuses, systems, and methods are disclosed.