On 11/28/25 08:36, Mark Tinka via NANOG wrote:
On 28/11/2025 11:34, Joel Busch wrote:
Yes we're seeing the same. And when I ask a customer if they would
like their uplinks to be 100G-LR4 or 100G-LR they ask me what 100G-LR
is 🙂
Wait when SFP-DD starts to become a thing 🙂. We have started shipping
these to some customers in Africa. Great for density when you can slot
44x 100G ports into a 1U line card.
Single-lambda 100G is definitely the way to go. LR4 just eats up too
much space and pays the data centres a lot more in x-connects than I'd like.
This ^
The other major advantage to the PAM4 is that it all has Forward Error
Correction (FEC). At 100g, a 1e-12 Bit Error Rate (BER) is one bit error
every 10 seconds. This is simply unacceptable for most applications. Also
we're in the analog domain, so BER can go up as things start aging, but still
"work".
I think RAS gave a talk about this at the last NANOG.
> https://www.youtube.com/watch?v=4CfneOR3XqI
Here's the fun thing about the 100g standards, IEEE made -DR (500m), then the
100gLambda trade group made the -FR (2km) and -LR (10km) standards. DR and FR
is exactly the same in terms of link budget, so DR is FR and FR is DR. From
FR to LR is 2.3 dB difference; there's no optic-electronic component
(Laser/PIN Diode/etc) that has such a small delta. This means the DR and FR
are built with the same underlying parts, and DR will have no issues pushing
10km.
https://100glambda.com/specifications/send/2-specifications/9-100g-fr-and-100g-lr-technical-specs-rev2-0
If you look at the 2.1.3 table, you'll see how much signal loss is given to
cable, connector, and splice losses. In most cases, this is 5-7 times more
than what is achievable in the real world. Unless you have a circuit going
through 10 patch panels with saggy fiber, it's a non issue. This does mean
you should demand each cross connect is scoped and cleaned with wet/dry
process if needed.
tl;dr - Use 100g-DR for everything and monitor your pre-FEC error rates.
--
Bryan Fields
727-409-1194 - Voice
http://bryanfields.net
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