You have a DCI network or you are planning one. Below you will find a TCO calculator, a checklist, and a clear recommendation - no theory, just numbers and specifics.
Decision in 60 Seconds
Before we get into the details, a quick matrix for those who already know what they are looking for.
New DCI 2026, distance below 120 km
Choose 800G modules in the 800ZR standard
Interoperability confirmed by OIF, lead time 40 weeks, prices ~$10,000 in Q1 2026
Existing 400ZR infrastructure
Leave it alone. Replacement ROI is negative for smoothly running infrastructure
Plan a natural migration at end-of-life
Metro or regional network 100–2,000 km
400G modules in the OpenZR+ standard in ZR+ mode
Multi-vendor standard verified by OIF — at the OIF plugfest February 2024, 14 different OpenZR+ modules were tested. Ensure both ends of the link operate with the same FEC and modulation settings
AI clusters between locations 50–1,000 km
800G modules in IP-over-DWDM architecture without transponders
Adoption growing 10x year-over-year per Dell’Oro
Infrastructure with a 5+ year horizon
Choose ROADM with flex-grid and C+L band readiness
1600ZR standard enters production in 2027–2028
TCO Calculator: Two Scenarios for 800 Gb/s
The only meaningful economic comparison is the same throughput, not cost per module. 400G and 800G modules have twice the difference in throughput and comparing their prices or power consumption directly makes no sense. We always calculate per Gbps and per task: delivering 800 Gb/s on a single DCI link over 5 years. Energy calculated at PUE 1.4 and €0.50 per kWh.
Scenario A
Two 400ZR modules
CAPEX (2 × €6,500)€13,000
Power draw2 × 18 W = 36 W
Energy per year~€220
Energy 5 years€1,100
Ports occupied2
5-year TCO€14,100
Scenario B — Recommended
One 800ZR module
CAPEX€10,000
Power draw~25 W
Energy per year€153
Energy 5 years€765
Ports occupied1
5-year TCO€10,765
Saving per link (5 years)
€6,670
modules + energy
Across 100 DCI links
~€667,000
plus recovered ports
Recovered port per link
1 port
option to double throughput without switch replacement
If you want to calculate your own scenario: take the number of planned links, multiply by €6,670, and you get the lower bound of savings. The upper bound depends on the value of recovered ports in your infrastructure.
Infrastructure Requirements - What to Check Before Ordering?
DWDM Grid
400G modules operate on a grid of at least 75 GHz. 800G modules in basic mode require a wider channel — 150 GHz. If your ROADM and amplifiers were designed for a 50 GHz grid, you must verify support for the wider grid before ordering.
Critical
OSNR link budget
For 800G modules in DP-16QAM mode you need approximately 27 dB OSNR on the path. In QPSK modes the requirement drops to 16–17 dB. Calculate the link budget for every planned link before deployment — do not assume it works until you have calculated it.
Critical
IP-over-DWDM
If you are considering an IPoDWDM architecture — coherent module directly in the router port without a transponder — the module must transmit at 0 dBm. Most DWDM systems are calibrated to this value at the multiplexer input. Modules transmitting at –10 dBm require an additional amplifier and have worse transmitter OSNR. IPoDWDM done properly delivers CAPEX savings of around 65% on backbone networks and power consumption reduction of 70–90%.
Verify specification
Purchase Checklist - 5 Questions Before Signing the Order
01
What is the link distance?
Below 120 km — 800G modules in the 800ZR standard without reservation. 120–1,000 km — 800G modules in ZR+ mode, check the DSP capabilities of the chosen vendor. Above 1,000 km — 400G modules in the OpenZR+ standard or embedded transponder.
Key
02
Does your ROADM support a 150 GHz grid?
Required for 800G modules at 118 Gbaud. Older ROADMs may need an update. Check before ordering.
Critical
03
What switch or router?
Ensure the software version you are using supports coherent modules.
04
Open Line System or proprietary?
Ensure your optical system supports foreign lambda handling — this is essential for coherent modules to operate correctly in an IP-over-DWDM architecture.
05
Does the contract include an interop guarantee with other vendors’ equipment?
OIF compliance should be stated explicitly. Ask for the results of the specific module from OIF plugfests.
Verify in writing
Final Recommendation - 2026
New DCI below 120 km
800G modules in the OIF 800ZR standard. Best economics per Gbps, lowest power draw per gigabit transmitted, full interoperability confirmed at OIF plugfests with dozens of participating companies.
Recommended
Metro and regional networks above 120 km
400G modules in the OpenZR+ standard with adaptive modes. Multi-vendor standard with active interoperability verification by OIF. Choose the operating mode appropriate for your distance and verify that your network delivers the correct OSNR.
Metro and backbone
Existing 400ZR infrastructure
Do not replace without a concrete TCO justification. Run the calculator from section two at your scale.
No migration pressure
Next Step
Our engineers will prepare an offer tailored to your infrastructure. They will guide you through the process from assumption verification, through PoC, to deployment.
Send an enquiry → technical recommendation and module offer within 24 hours.
.avif)
