There could be many reasons that can cause a fibre link lossing the connection. It could be HBA issue, SFP, cable or switch problem.
For more SAN switch trouble shooting, see Brocade SAN switch trouble shooting commands, Here show some tips to determine whether the SFP or a cable is the cause of the loss of connectivity, perform the following:
Check the output of "porterrshow " from the switch.
"enc out " errors alone imply primarily cable problem.
"enc out " and "crc err " combination imply primarily GBIC/SFP problem.
To find out if source or destination SFP is causing the error, Check the Output of "portshow x" where x is the port number.
If the pair of "Lr_in " and "Ols_out " as well the "Lr_out " and "Ols_in " values are "quite" equal, it is a normal case.
If one counter is significantly higher than the other, the link problems either "reached" the switch ("in" > "out") or are caused by the switch ("out" > "in").
Note: If the "Ols_in value is higher than the "Lr_out one, then the "problem source is, in most cases, more related to the attached device (sending those offline sequences) and the switch responds to them with a "link reset".
enc_out ; Encoding error outside of frames
crc err ; Frames with CRC errors Lr_in ;
Link reset In (primitive sequence), does not apply to FL_Port Lr_out ;
Link reset Out (primitive sequence), does not apply to FL_Port Ols_in ;
Offline reset in (primitive sequence), does not apply to FL_Port Ols_out ;
Offline reset out (primitive sequence), does not apply to FL_Port