Absolute time position of picosecond laser pulse

We are presenting some new aspects of detection of absolute time position of picosecond laser pulses. The ground-space optical links for precise and accurate time scale synchronization are running or preparing in frame of several space agencies. We are involved in several projects in position of single photon detector and timing designer. The typical optical link consists of ground segment - picosecond laser pulse transmitter, telescope, single photon avalanche detector, timing electronics, and time reference; and space segment - corner cube retroreflectors, single photon sensitive optical receiver with event timer board, and time reference to be synchronized. To ensure absolute time position we have to calibrate absolute internal delay of several semiconductor photodiodes in picosecond range detecting picosecond laser pulses on several wavelengths. The experimental results demonstrating unobvious dependence on detector type and entire experiment arrangement and its possible theoretical interpretation will be presented.