You could also look at light levels on both sides on the link you are trying to get up if you are using a current switch with optics that support this... You need to also look at duplex settings if it is a sfp+ port.
Command is
show port # transceiver info detail
example
PLW_X430_WWaterTP_Homestead.1 # sh02 port 25 transceiver info detail
Port : 25
Media Type : ZX_1550 (Industrial Temperature)
Vendor Name : SOURCEPHOTONICS
Part Number : SPGBZXIDFBEX
Serial Number : F2R2017123
Wavelength : 1550 nm
Temp (Celsius) : 42.53 Status : Normal
Low Warn Threshold : -40.00 High Warn Threshold : 100.00
Low Alarm Threshold : -45.00 High Alarm Threshold : 105.00
Voltage AUX-1/Vcc (Volts) : 3.27 Status : Normal
Low Warn Threshold : 3.00 High Warn Threshold : 3.60
Low Alarm Threshold : 2.90 High Alarm Threshold : 3.70
Tx Power (dBm) : 2.23 Status : Normal
Low Warn Threshold : 0.00 High Warn Threshold : 5.00
Low Alarm Threshold : -1.00 High Alarm Threshold : 6.00
Rx Power (dBm) : -8.36 Status : Normal
Low Warn Threshold : -23.01 High Warn Threshold : -3.00
Low Alarm Threshold : -23.98 High Alarm Threshold : -2.00
Tx Bias Current (mA): 10.53 Status : Normal
Low Warn Threshold : 0.20 High Warn Threshold : 60.00
Low Alarm Threshold : 0.10 High Alarm Threshold : 70.00
