Routed optical networks

Tue May 9 18:37:24 UTC 2023

From: Mark Tinka <mark at tinka.africa>
Date: Tuesday, May 9, 2023 at 2:03 AM
To: Phil Bedard <bedard.phil at gmail.com>, nanog at nanog.org <nanog at nanog.org>
Subject: Re: Routed optical networks
On 5/8/23 21:53, Phil Bedard wrote:

  There are quite a few QDD pluggables in production today capable of supporting 100G signals over 1000s of km or 400G near 1500km.

I think the more interesting QSPF-DD (or OSFP) development is OpenZR+, which is an MSA project to standardize 400ZR+. The plan is to be able to support 100Gbps up to 5,800km, and 400Gbps up to 480km (EDFA) or about 1,000km (EDFA + Raman). With a 4x 100Gbps mode supported on QSFP28 router ports, you can have one muxponder talking to 4x routers at 100Gbps each.

[phil] These are already available today and have been for some time and in use in production networks for over a year now.  This is with 400G links running up to 600km in routers with QDD ports.  400G-16QAM using 60Gbaud (the OpenZR+ standard) can reach around 1300km.   These optics are being used in both routers and xponders on the line side.

  Now that’s not what you can get out of some external transponders, so those will still have their place in high performance applications.   When you move to 800G, 1.2Tbps single channel they also have their own distance limitations.  So it really depends on the application and the network.

800Gbps and 1.2Tbps applications are really for long haul use-cases, especially if you used 400Gbps pluggables before and run out of distance (so less than 1,000km). They are also preferred for submarine use-cases.

[phil] 800Gbps and 1.2Tbps are not really positioned for long haul use cases yet.  It requires lowering the modulation to something like QPSK which at those speeds requires baud rates which are not yet commercially available.

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