cross-posted from: https://aussie.zone/post/2534398

The 10GBase-LR is 1310nm and the QSFP-40G-LR4 CWDM channels are 1271, 1291, 1311 and 1331 nm. Are the 1310nm and 3rd channel 1311nm technically compatible?

I have a 10Gb and (will eventually have) a 40Gb switch both fitted with basic LR (Q)SFP+ transceivers and want to know if I can directly connect them or will I have to use an adapter to fit an SFP+ in an QSFP+ port?

I’m looking at using the XQX2502 QSFP+.

EDIT: The goal of this exercise is I’m trying to work out if I can make an easily interoperable system where a singlemode fiber wall jack fed from a 40G switch can act as a both a 10G or 40G port as needed.