  A novel and efficient method for fiber transfer delay measurement is
demonstrated. Fiber transfer delay measurement in time domain is converted into
the frequency measurement of the modulation signal in frequency domain,
accompany with a coarse and easy ambiguity resolving process. This method
achieves a sub-picosecond resolution, with an accuracy of 1 picosecond, and a
large dynamic range up to 50 km as well as no measurement dead zone.
