  To guarantee the angular resolution, the Large High Altitude Air Shower
Observatory (LHAASO) requires a 500ps (rms) timing synchronization among the
6866 detect units for its KM2A sub-detector array. The White Rabbit technology
is applied which combines sub-nanosecond precision timing transfer and gigabit
Ethernet data transfer over the same fiber media. Deployed on a wild field at
4300m a.s.l. altitude, the WR network must maintain the precision over a wide
temperature range. The temperature effect on a small WR link is measured, and
contributions from different components like optical fiber, SFP module, fixed
delay on PCB and ICs are separately studied and analyzed. An online real-time
temperature correction method was applied based on the result which
significantly reduce the synchronization variation from 300 ps to 50 ps in a
temperature range of 50 degrees centigrade.
