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Can I attach a 10GBase-LR to QSFP-40G-LR4 (CWDM)? (aussie.zone)

submitted 1 year ago* (last edited 1 year ago) by ky56@aussie.zone to c/homelab@lemmy.ml

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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+.

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[–] Sailing7@lemmy.ml 2 points 1 year ago* (last edited 1 year ago) (1 children)

I'm not thaat into networking so excuse my possibly dumb question: is there a DAC Cable on the market, that would enable you to skip all that?

To this topic i found this:

English Article Version: https://community.fs.com/blog/how-to-convert-a-port-from-qsfp-to-sfp-port.html

German Article Version: https://community.fs.com/de/blog/how-to-convert-a-port-from-qsfp-to-sfp-port.html

The pictures suggest, that you could do exactly that (SFP+ to QSFP+). I'm not sure though, what that cable would be.

Edit: the article is in german. Try the new firefox translate feature, it should work. Edit2: added the english version of the article

[–] ky56@aussie.zone 1 points 1 year ago (1 children)

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.

QSFP+ to SFP+: MTP/MPO-LC Breakout Cable

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.

[–] gramathy@lemmy.ml 3 points 1 year ago (1 children)

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.

[–] Sailing7@lemmy.ml 2 points 1 year ago

I didnt ask his question, though i a want to thank you for answering it. I learned a lot in this thread :D