How should a frequency for signals that can be transmitted by a high-speed IC coupler be estimated?

For IC couplers for communications, propagation delay times t_PLH and t_PHL are specified. By using the maximum values for these times and the following formulas, a rough frequency for signals that can be transmitted (nonreturn-to-zero (NRZ)) can be estimated.

(bps)≒1/t_PLH (or t_PHL) or (Hz)≒1/t_PLH (or t_PHL)