It's a tad difficult to understand what exactly you mean and what your data structure is, but possibly the answer is to use, in your script,

Load YourField1, YourField2, Rx_optical_signal, Rx_optical_signal  as '8 AM', Rx_optical_signal  as '12 PM', Rx_optical_signal  as '4 PM', Rx_optical_signal  as '8 PM'

From YourTable;

You could then use e.g. Only ([8 AM]) or avg([8 AM]) to get the result that you seem to be describing.