On 27/11/2025 11:32, Joel Busch wrote:
Oh that's actually the first I've heard of a manufacturer using
different grids for their ER4 lite vs their ER4! Now I get why you
were telling me not to combine ER4 lite and ER4, in your experience
they use nLWDM and LWDM respectively.
Not quite.
Both ER4 and ER4-Lite are nLWDM, because of the chromatic dispersion
sensitivity when using PAM4 modulation above 10km.
My impression was the opposite, that each seller sticks to one grid
for both. Examples below:
So Smartoptics use different wavelengths for ER4 and ER4-Lite:
https://smartoptics.com/product/tqd031-sn4c-so/
https://smartoptics.com/wp-content/uploads/2023/10/ds-tqd023-sl4c-so-qsfpdd-400g-er4-lite-c4-r6.1.pdf
And they are using nLWDM for both.
The LWDM is primarily used for 100G-LR4, as there is no concern of
chromatic dispersion below 10km.
I don't have the insight into who actually manufactures and who sells
who's stuff, so these examples might contain duplicate entries for
what any one manufacturer does.
It's quite possible.
On our end, we've generally gone to 400G-ZR+ coherent for 400G
requirements, even in the metro. So we've only had to deal with a
handful of 400G-ER4/ER4-Lite plugs, and only from Smartoptics. We
haven't tried to mix vendors, not for any reason other than there was no
benefit in doing so.
I was talking to them before starting this thread and they confirmed
that the nLWDM spacing is correct. They also let me know that they
tested their ER4 lite against their ER4 and they were compatible. So
unfortunately it's not so simple. We have a mess in the market, I think.
So do they explain why they are using the same sets of wavelengths for
what they market as ER4 and ER4-Lite?
And is there an appreciable difference in price between both types of plugs?
Looking at Flex's web site, the ER4-Lite page says "not interoperable
with D.164HG.30", which is odd because D.164HG.30 is Flex's ER4-Lite:
https://www.flexoptix.net/en/d-164hg-30-e.html?option875=1
I think there is a documentation issue with Flex, but again, I could be
wrong :-).
Mark.
_______________________________________________
NANOG mailing list
https://lists.nanog.org/archives/list/[email protected]/message/GFNLQK7OVTPMSCL34M33ITTFUAYKW3NB/
