  A correlation optical time-domain reflectometry (COTDR) method is presented,
which measures the propagation delay with an accuracy of a few picoseconds.
This accuracy is achieved using a test signal data rate of 10 Gbit/s and
employing cross-correlation and pulse fitting techniques. In this paper we
introduce and evaluate the basic signal processing steps, investigate the
measurement accuracy, and discuss applications for monitoring link delay and
chromatic dispersion of long fiber spans as well as temperature sensing
applications.
