  A micro-pulse lidar at eye-safe wavelength is constructed based on an
up-conversion single-photon detector. The ultralow noise detector enables using
integration technique to improve the signal-to-noise ratio of the atmospheric
backscattering even at daytime. With the pulse energy of 110uJ, the pulse
repetition rate of 15 kHz, the optical antenna diameter of 100 mm and
integration time of 5 minutes, a horizontal detection range of 7 km is
realized. In the demonstration experiment, atmospheric visibility over 24 hours
is monitored continuously, with results in accordance with the weather
forecasts.
