The impact of mixing fiber types in a digital connection

Written by Erik den Breejen, Senior Account Manager International Sales

As a veteran in digital infrastructure, I’ve seen firsthand how reliability, performance, and future scalability are critical in fiber optic networks. Whether you’re supporting carriers, data centers, or digital platforms, the physical path of your connection matters more than you might think. A common yet often underestimated issue is mixing different fiber types within one connection. In this blog, I’ll share my perspective on why this can be a serious risk, what technical consequences it brings, and how to avoid it through smarter design. Not all fiber types are created equal.

In the field, I frequently encounter connections where various fiber types - G.652.D, G.655, older legacy fibers, or even so-called Ultra fibers - are used in combination. It may seem harmless, but technically it can result in real trouble. Each type of fiber has unique properties when it comes to:

• Attenuation (signal loss)
• Dispersion, especially: Chromatic Dispersion (CD) – caused by slight differences in how various light wavelengths travel through the fiber, leading to stretched or overlapping pulses at high speeds. Polarization Mode Dispersion (PMD) – caused by asymmetries or stress in the fiber, where light traveling in different polarizations arrives at slightly different times, potentially distorting the signal.
• Back reflection and bend sensitivity

These physical properties affect signal quality, particularly in high-speed or long-distance connections. In WDM systems or latency-sensitive applications, even small differences in dispersion or attenuation can result in performance degradation, reduced capacity, or instability.

More splices = more signal loss

Another key factor is the number of splices in a route. Even with excellent fusion splicing, each splice introduces a small amount of attenuation. Accumulate enough of them, and the impact becomes measurable - and in high-performance environments, every dB counts.

This is especially relevant in dark fiber deployments, where customers operate directly on Layer 1 and require optimal optical performance.

My approach to fiber design

When designing (or reviewing) fiber routes, I work closely with my network engineer and solution architect as a team to ensure every design is technically and future-ready. Together, we focus on consistency and efficiency. Our principles are simple:

Use single, uniform fiber type across the entire route
Minimize the number of splices to reduce cumulative attenuation
Validate unknown or undocumented fiber sections before integrating them

This approach ensures a connection that performs predictably under current loads and scales reliably for future growth - without surprise degradation or compatibility issues.

Why it matters?

If you’re using dark fiber, WDM systems, or running low-latency traffic, your fiber’s physical characteristics are just as important as your active equipment. Even a small variation in attenuation or dispersion can have a big impact on system performance and cost-efficiency.

Digital infrastructure starts at the core - deep beneath the surface. That’s where the quality decisions are made.

Let’s talk

Are you planning a new fiber build? Or do you want to optimize your current infrastructure? Me and my technical team will be happy to exchange ideas, share insights, or offer a second opinion. Feel free to contact me. More info: https://www.eurofiber.com/solutions/connectivity