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+.
Yes. There is also an adapter that would allow me to use a SFP+ in a QSFP+ port. But I’m trying to work out if I can make an easily interoperable system where a wall jack fed from a 40G switch can act as a both a 10G or 40G port as needed. Hence the question.
This is almost the setup I’m looking for. Except example is using MMF. I want to know is this setup can be done to one SFP over SMF.
Unless specifically stated, generally fiber transceivers only run at the stated rate and would expect every channel to negotiate unless it had a 4x10 mode supported by both the transceiver and the device you put it in (which is what that DAC splitter is for), though once you split the lanes this way, a single pair would only ever run at 10g
Additionally the nature of CWDM on a single pair means the 10g side will see all four signals simultaneously as there are no filters on that side of the connection. QSFP+ runs like this because it’s cheaper to manufacture and a single transmit/receive pair is only necessary in much longer range transport which typically uses more specialized expensive hardware for better long range signal integrity.
In short: no, this won’t work and transceivers generally only ever run in one mode et once as configure by the switch/router they’re inserted in, and the modes you’re asking a qsfp+ to run in are mutually exclusive based on type (single lc pair cwdm at 40g vs 4x10g MPO/MTP with changeable modes). Fiber doesn’t have the same “negotiation” features that copper Ethernet does.
I didnt ask his question, though i a want to thank you for answering it. I learned a lot in this thread :D