Challenges with Deploying Coherent ZR Pluggables Over Existing Fiber I

[erica-dalton]

Hi everyone, We’re looking to upgrade our metro network using coherent ZR/ZR+ pluggables in existing single-mode fiber that was originally installed for 10 G services. Before making the leap, I’d like to ask: what are the common issues when deploying these coherent optics over older fiber spans (e.g., fiber routes with many bends, multiple splices, patch panels)? Has anyone dealt with unexpectedly high OSNR loss, dispersion or crosstalk impacting reach, and how did you mitigate them? Any design or testing guidelines you found essential would be really helpful.

[Enes Simnica]

gDay @erica-dalton For sure the biggest issues u’ll hit on older fiber are higher loss, low OSNR, and sometimes dispersion if the route’s long or full of splices/bends. Definitely run an OTDR and spectrum/OSNR test before turning up the ZR/ZR+ optics. Which means that cleaning connectors, replacing bad patch cords, and checking total loss budget usually fix most surprises......

also check this and hope it helps: https://www.ciscolive.com/c/dam/r/ciscolive/global-event/docs/2025/pdf/BRKOPT-2556.pdf

-Enes

[Enes Simnica]

@erica-dalton this one also: https://www.cisco.com/c/en/us/products/collateral/interfaces-modules/transceiver-modules/datasheet-c78-744377.html