It is not recommended that the ST2 and SC2 boards be interconnected because they have different rates and encoding formats (CIM used by the SC2 board and FEC used by the ST2 board). The SC1 and SC2 boards use the same rate and encoding format and therefore can be interconnected.
The TN13OBU103 board can substitute for the TN11OBU103 board on OptiX OSN 6800. After the substitution, the TN13OBU103 board provides only the functions of the TN11OBU103 board, but the VOA is unavailable. Depending on the NE version and gain, the TN12OBU or TN13OBU board can substitute for the TN11OBU103 board so that the integration attenuation can be configured for the OBU.