How to choose equipment for CWDM?

Question

Computer networks

There are two such multiplexers that you need to install CWDM SFP modules on the receiving and transmitting sides for the assembly to work properly (if it is possible to schematically show the connections).
And why on CWDM SFP modules, for example, from this catalog, only the transmission wavelength is indicated? What then is the receive wavelength, or is it the same as the transmit wavelength?
I will ask the guys who personally work with CWDM / DWDM equipment to answer.

Answer 1

A laser is used for transmission, generating a signal at a single frequency (wavelength). Broadband photodetector for reception, receives at all frequencies. Accordingly, you need two pairs of color modules for two channels: 1510 and 1530 for the first 1550 and 1570 for the second. Choose the distance for yourself.