Is it possible to use the CDT-TX-02M-R / CDT-RX-03M for data communication?

No. The CDT module is only for transmitting ON-OFF signals. It does not accept any form of serial data. It is possible to use all 6 inputs as a parallel interface to input 6 different binary signals. These will be output as parallel on the RX end. Note that the time to sample the input can take as long as 63ms. See operation guide for details.