need to transmit two differential pecl clocks with precise phase relationships,

I need to send 2 differential timing signals over 50 feet. Need to keep phase and timing relationship - I can calibrate out a fixed phase offset for the 2 but I am also dithering the clock phases by very precise amounts. The distance used to be just 5 feet, now 50 feet. 16 MHz basic rate, with phase increments as small as 1.6 picoseconds and as large as 2 nanoseconds.Using LVPECL. Can also be LVDS.