DP83TD510E-EVM: long distance communication fails (the distance is 1200 meters)

hello TI team:

  I bought two sets of DP83TD510E-EVM last month, the test communication cable is pair of twisted wire from CAT5E. The communication is set up when the distance is 900 meters, but when the distance is 1200 meters, communication fails. The MSE detect is good when distance is 900 meters, but MSE detect is poor (over 660h). Could you offer me a script txt to solve the problem?

Thanks.

Regard

WEI