If you use this method, what happens if the pulse is reflected multiple times? Then the result would be a distorted pulse, caused by the addition of multiple reflections?
Also, you would need to be careful with the pulse width because otherwise the reflected pulse will arrive back at the input before the source pulse has finished.
In my opinion, if you have access to both ends of the cable, it is easier to send a periodic wave and measure the phase difference between them. The far end of the cable would need to be terminated, of course.
Brian