Therefore, by default SFP+ modules don't have CDR, and XFP modules must have CDR. (3) For transceivers used on a switch, there is little difference between the two. You can choose with CDR or without CDR. HTF is a professional manufacture of optical transceiver, you can check the features of 10G. Clock and Data Recovery (CDR) is a core function that ensures stable, error-free transmission for optical modules. What is CDR (Clock and. The optical module serves as a crucial component in optical fiber communication systems, operating at the physical layer, which is the lowest layer in the OSI model. Its primary function is to achieve optoelectronic conversion by converting electrical signals into optical signals and vice versa. Mux is also only used in optical modules that require wavelength division multiplexing.