How 100G Coherent DCO QSFP28 Conquered a 120km High-Attenuation Fiber Link

Introduction: The Unstable Link

For network operators, distance and signal degradation are constant adversaries. One of Mexico’s leading internet providers was facing this battle daily on a critical fiber link between Chalma and Ixtapan. Spanning over 100 kilometres, this route was essential for their operations but plagued by instability.

Their existing solution, conventional 10G ZR+ (120km) NRZ transceivers, was buckling under the pressure. The link suffered from continuous attenuation events, leading to frequent drops, unreliable service, and a constant stream of engineering headaches. A new approach was needed—one that could deliver rock-solid performance where standard technology had failed.

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Executive Summary

The provider's challenge was twofold: it was not just a technical failure but also an operational inefficiency. To achieve the required capacity across the problematic 120km route, they were forced to use four separate pairs of fiber, with each pair carrying an individual 10G link. This approach was not only complex but also operationally expensive, tying up valuable fiber assets and increasing the potential points of failure. Even with this multi-fiber setup, the core problem of signal attenuation remained, making all four links unreliable.

The Challenge: Pushing Past the Limits of 10G

The customer needed a solution that would not only solve the instability but also radically improve their infrastructure efficiency.

The goals were ambitious:

Achieve Stability: Conquer the extreme 30dB of attenuation that was causing constant link drops on their existing 10G ZR+ modules and establish a single, packet-loss-free connection.
Dramatically Improve Fiber Efficiency: Consolidate the traffic from four 10G links (and four fiber pairs) onto a single, powerful 100G link using just one fiber pair. This would immediately free up three pairs of fiber for future use.
Reduce Operational Costs: By decommissioning three active fiber links, the provider could significantly lower costs associated with fiber maintenance and repairs.
Create a Path for Future Growth: The freed-up fiber assets would provide a clear and immediate path to scale capacity to 400G or beyond without the need to lay new cables.
Ensure Seamless Integration: The new, advanced transceiver had to be fully compatible with their existing Huawei NetEngine 8000 M14 platform.

The EPS Global Solution: Power and Intelligence with Coherent Optics

EPS Global, in partnership with TelcoPhotonics, stepped in to diagnose the problem and propose a next-generation solution. We knew that simply trying another long-reach module wouldn't be enough. This level of attenuation called for the advanced capabilities of Coherent optics.

We selected the Coherent (Finisar) FTLC3353R3PL1, a 100G QSFP28 DCO (Digital Coherent Optics) transceiver. This wasn't just an incremental upgrade; it was a technological leap forward, featuring:

Steelerton™ DSP: The industry’s first purpose-built digital signal processor for 100G ZR applications. This powerful "brain" inside the module actively compensates for signal impairments, enabling performance that is impossible with older NRZ technology.
High Optical Output Power: With a transmit power greater than +0 dBm, this module has the "muscle" to push a strong, clean signal across extreme distances and high-loss fiber.
Integrated Tunable Optical Filter (TOF): This feature ensures out-of-band noise is suppressed, allowing the receiver to hear the signal clearly even when it's very faint, maximizing reach and performance.
Low Power Footprint: Despite its immense power, the module has a typical power consumption of less than 5W, making it a highly efficient solution for access networks and space-constrained deployments.

Field Test Results: The Moment of Truth

The true test of any network solution is its real-world performance. The EPS Global and TelcoPhotonics field teams travelled to the Chalma ↔ Ixtapan link to prove the power of the 100G DCO solution in the customer's live environment.

What made this test particularly impressive was its elegant simplicity. The connection was a direct, point-to-point link between two of the customer’s legacy Huawei NetEngine 8000 M14 switches.

Crucially, no external amplifiers, such as EDFAs, were required. The link was established using only the transceiver's internal power and intelligence, plugged directly into the existing switches. This demonstrates the sheer optical power and advanced signal processing capabilities built into the module, eliminating the cost and complexity of additional amplification hardware.

Test Snapshot:

Location: Chalma ↔ Ixtapan link (>100 km of fiber)
Setup: Direct point-to-point connection. No external amplifiers were used.
Hardware: 2x legacy Huawei NetEngine 8000 M14 Switches
Transmit Power: +1.5 dBm
Received Power: -28.54 dBm
Total Attenuation: ~30 dB

The Verdict: Success. The link was established immediately with 100% stability and zero packet loss.

The 100G DCO transceiver performed faultlessly, turning a problematic, unreliable connection into a robust and high-performance link. The customer could finally depend on the connectivity between these two critical sites.

Key Customer Benefits Delivered

This successful test delivered more than just a stable link; it provided tangible business value:

Reliable Long-Distance Connectivity: The provider can now offer dependable services over routes that were previously considered impossible with standard pluggable optics.
Superior Performance: The solution demonstrated exceptional resilience, maintaining a perfect connection even under extreme 30dB attenuation conditions.
Expert Partnership: The customer received direct, hands-on technical support and field assistance from both EPS Global and TelcoPhotonics, ensuring a smooth and successful deployment from start to finish.

More Than a Part: The EPS Global Advantage

This case study highlights a critical truth in modern networking: having the right component is only half the battle. Having the right supply chain partner to deliver it—when and how you need it—is what turns technology into a competitive advantage.

At EPS Global, we transform the supply chain from a constraint into a catalyst for growth. While legacy vendors quote 18-24 month lead times, our Global Inventory Buffer Strategy and 28 worldwide locations ensure you get critical infrastructure in days, not years. We provide:

Supply Chain Resilience: Our multi-vendor, multi-region approach acts as an "insurance policy" against disruptions, ensuring you're never dependent on a single source.
Plug-and-Play Simplicity: Through our SwitchLab Integration Services, we pre-configure, test, and validate complex solutions, so they arrive ready for zero-touch deployment.
Single Point of Accountability: We manage the entire ecosystem—hardware, software, optics, and support—under one roof, eliminating vendor complexity for you.

EPS Global ensures your network infrastructure is never the bottleneck to your business.

Facing a similar network challenge? Don't let distance or attenuation limit your growth. Contact the experts at EPS Global today to find out how we can design a resilient, high-performance solution for you.

How 100G Coherent DCO QSFP28 Conquered a 120km High-Attenuation Fiber Link

From Frequent Drops to Flawless Connectivity: Solving a Major ISP's Toughest Network Challenge in Mexico

Introduction: The Unstable Link

Executive Summary