On 11/26/24 06:00, John Stitt wrote:
From what I’ve found and what I’m hearing, I think everyone is correct that much like 40Gb, there just hasn’t been as much call for 25Gb handoff at customer demarc outside of the datacenter instead of jumping up to 100Gb ports. Before this search I hadn’t looked hard at 25Gb for anything other than in our datacenter, so I didn’t realize that also like 40Gb, ZR options in 25Gb were relatively new and still not common.
I think the issue here is maximizing the fibre expense, especially if it's 10km or longer. If the cost of 25G, 40G and 100G is all within the same ballpark, 100G will make the most sense. But getting 100G beyond 10km without amplification and dispersion compensation means you will need to go coherent. NRZ-based 100G-ZR4 says it will do 80km, but real life has shown things can be vastly different, primarily due to generally poor fibre characteristics.
Looking at higher speed PON options is an interesting thought, but I imagine it’d be a hard sell for this current use case as they expect dedicated fiber, not that we couldn’t use PON with each site being a home run back to the aggregation site, but that just feels wrong even if it would technically work, haha. I may look into that route a bit more just to see how it might stack up cost and feature wise, and it may be that we decide to roll out higher speed PON for other endeavors from that research.
In reality, if you are an operator that builds both Active-E and GPON, your sales people will slowly push you toward selling FTTB services over GPON, because you get to pass more buildings faster and cheaper. Watch out for that if you are not keen on "just closing sales" :-). That said, you might find OpenXR's latest work exciting for GPON. That group has put out a 400G coherent plug that uses digital subcarriers (wavelengths nested within a wavelength) to deliver 16x 25G channels in a p2mp topology, right in the plug itself. It can run both in normal or BiDi mode, and certainly makes future GPON and Active-E p2mp architectures very interesting. Infinera are the leading OEM that have put product out, but expect Acacia, Coherent and others to do the same soon: https://www.infinera.com/products/ice-x-400g-xr/ Mark.