Hi feras, If you are referring to the decision component, here’s the explanation I found on the help section:
The Decision component processes the I and Q electrical signal channels received from the DSP stage, normalizes the electrical amplitudes of each I and Q channel to the respective m-PSK or m-QAM grid and performs a decision on each received symbol based on normalized threshold settings. It supports the following modulation formats: BPSK, QPSK, 8PSK, 16PSK, 16QAM and 64QAM. The Decision component supports single or dual polarization (SP/DP) multiplexing schemes
Please ask any further questions you might find.