What Does the OH Warning Indication Mean?
The triangular OH icon is an indication to remind users that the OTN Overhead bytes have been manually modified.
In the OTU3 or OTU4 with Ethernet & Bulk Payloads test modes, the triangular OH warning or reminder icon will be displayed when the Overhead Generation feature is used to manually modify any bits or bytes on the OTN test signal. The modified bytes, on the Overhead Generator page will also turn red, to show which ones have been modified.
To reset the overhead to its standard default values, go to >OTN Tools >Overhead and select the Overhead Generation tab.
The 
Reset OH button can be used to bring all the overhead bytes back to their standard states.