Published: May 2026 | Updated: May 2026 | Reading time: 8 minutes
Leasing 24 optical fibers over a distance of 20 km in the USA costs over $133,000 per month. By deploying DWDM with coherent modules on four fibers, our client now pays $22,000 per month for the same 4.8 Tb/s throughput and the ability to scale to 9.6 Tb/s without adding new fiber routes. Savings: $111,000 per month, over $1.3 million per year.
This is not the result of negotiating with the carrier. It is the result of choosing the right network architecture.
The Client and Their Requirements
The client operates in an industry requiring continuous data availability and extremely low latency. Their AI-based systems handle real-time processes across multiple international markets — any downtime or link degradation translates directly into business results.
The company maintained two independent data centres in the United States, approximately 20 kilometres apart. Between them, full backups of production environments had to be maintained, with every operation replicated in real time to the second location, with no acceptable downtime window.
Required throughput: 4.8 Tb/s. Required availability: continuous, no maintenance windows.
This was the third deployment we carried out for this client. Previous projects gave us an in-depth understanding of their environment and business requirements, which directly translated into the quality of the design and the speed of commissioning.
Two Scenarios
Before selecting a solution, we compared two architectural approaches.
Classic scenario: 400G links on separate fibers.
A throughput of 4.8 Tb/s using 400G modules requires 12 link pairs, meaning 24 fibers. Leasing 24 fibers over 12.4 miles at an average rate of $450 per mile per month generates a cost of over $133,000 per month. Every additional 400G of bandwidth means another fiber pair and another fixed operational cost. Scaling is expensive and linear.
DWDM scenario: multiple channels on four fibers.
DWDM allows multiple independent data streams to be transmitted over a single fiber, differentiated by wavelength. Instead of 24 fibers — 4 fibers with a DWDM layer. Leasing 4 fibers: just over $22,000 per month. Same throughput. Same reliability. Completely different numbers.
Monthly difference: $111,000. Annual difference: over $1.3 million.
Classic architecture
24 fibers × 400G
$133,920
per month
24 fibers × 12.4 miles × $450/mile $1,607,040 per year
DWDM architecture
4 fibers + DWDM layer
$22,320
per month
4 fibers × 12.4 miles × $450/mile $267,840 per year
Monthly saving
$111,600
83% cost reduction
Annual saving
$1,339,200
same 4.8 Tb/s throughput
What Did We Deploy?
The solution was built on four leased optical fibers, on which we deployed a DWDM layer using GBC Photonics coherent modules and PacketLight transponders.
On day one after commissioning, the system reached the target throughput of 4.8 Tb/s. No phased ramp-up, no weeks of calibration — full throughput from the start.
We designed the system with headroom: the architecture supports scaling to 9.6 Tb/s without adding new fiber routes. When the client needs twice the bandwidth, we activate DWDM channels — not new fibers. The lease cost remains unchanged.
The Numbers for the CFO
Item
Classic (24 fibers)
DWDM (4 fibers)
Number of fibers
24 fibers
4 fibers
Throughput
4.8 Tb/s
4.8 Tb/s
Scalability
New fibers = new cost
Up to 9.6 Tb/s without new routes
Monthly cost
$133,920
$22,320
Annual cost
$1,607,040
$267,840
CAPEX payback
—
A few months
5-year difference
$8,035,200classic architecture
$1,339,200annual saving
What Else Did the Client Gain Beyond the Savings?
💰
Operational saving
Reduction in fiber lease cost at the same 4.8 Tb/s throughput.
83%
⚡
Scalability without new routes
Growth to 9.6 Tb/s by activating DWDM channels — no new fibers, no negotiations, no maintenance window.
2×
🛡️
Higher operational resilience
Redundant optical paths with automatic traffic failover on failure — without operator intervention.
📅
Full throughput from day 1
4.8 Tb/s from the first day after commissioning. No phased ramp-up, no weeks of calibration.
The DCI scenario with expensive fiber leasing, as in this project, is not unique. A similar dynamic applies to connections between data centres in Polish cities and on routes across the CEE region. Every new fiber is a fixed monthly cost. DWDM lets you extract far more from what you are already leasing.
Before every project we carry out a technical analysis: optical budget for your routes, DWDM vs classic architecture cost comparison, hardware recommendation with a 5-year TCO estimate.
If you have two or more data centres and need a high-throughput connection, it is worth talking to us before you sign another fiber contract. Fill in the form and find out how we can help!
FAQ — DCI and DWDM
In the described case: 83% reduction in the operational cost of fiber leasing — from $133,920 to $22,320 per month, at the same 4.8 Tb/s throughput. Annual saving: over $1.3 million. The scale of savings depends on the distance, the number of fibers required, and the lease rates at your carrier. The more fibers you lease today, the greater the savings potential when moving to DWDM.
In the described project: 4 fibers instead of 24 — for the same 4.8 Tb/s throughput. DWDM allows multiple independent data streams to be transmitted over a single fiber, differentiated by wavelength. Instead of one fiber per 400G link, a single fiber carries multiple channels simultaneously. The specific number of fibers depends on the required throughput, the DWDM hardware selected, and the optical path parameters — we calculate this during a free technical analysis.
With savings of $111,600 per month — as in the described case — the CAPEX on DWDM hardware pays back within a few months. Every subsequent month is pure operational profit. The exact payback period depends on the hardware cost and the scale of fiber lease savings. Before every project we prepare a 5-year TCO calculator with a concrete payback period for your specific parameters.
In a DWDM architecture, bandwidth growth means activating new channels — not building new routes. In the described project the system was designed with headroom for 9.6 Tb/s without adding new fibers and without changes to the lease agreement. In the classic architecture, every additional 400G means another fiber pair and another fixed monthly cost. That is a fundamental difference in the cost scaling model.
Yes — four fibers with a DWDM layer and redundant paths provide higher fault resilience than 24 fibers without an optical management layer. Traffic failover on failure is automatic, without operator involvement. The DWDM management layer provides full real-time visibility of the state of every optical channel — something classic point-to-point links do not offer.
Yes. The DCI scenario with expensive fiber leasing is not unique to the US market — a similar dynamic applies to connections between data centres in Polish cities and on routes across the CEE region. Every new fiber is a fixed monthly cost. DWDM lets you extract far more from what you are already leasing — without renegotiating carrier contracts and without physical work on the cable infrastructure.
Start with three pieces of information: (1) How many fibers are you currently leasing between your locations and at what cost per month? (2) What is the distance between your data centres? (3) What throughput do you need today and what do you expect in 3 years? With this information we can prepare a free technical analysis: optical budget for your routes, DWDM vs classic architecture cost comparison, and a hardware recommendation with a 5-year TCO estimate. Contact us — we will tell you straight whether DWDM makes sense for you and when it pays back.
Reservation systems, operational planning, fleet telemetry, passenger handling — all of this generates massive data streams transmitted in real time. A network failure here has direct operational consequences.
