Fiber optic networks send data using light signals. As the light travels through the cable, some signal power becomes weaker. Because of this natural process, every cable and connection point reduces the signal strength. As a result, the signal cannot stay strong forever. The amount of power that disappears during transmission is called DB loss.
Since signal strength affects performance, it has a direct impact on network quality. If the loss becomes too high, the signal may not reach the endpoint clearly. For this reason, network operators must understand it before designing a system. With this knowledge, they can keep signals strong over long distances. At the same time, they can check cable quality, detect connection problems, and plan the correct power budget for stable transmission.
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What is DB loss?
DB loss (decibel loss) is the measurement of signal power reduction in fiber optic cables, and it is written in decibels or dB. As light moves through the cable, a small amount of power disappears naturally. Therefore, longer cables experience greater loss than shorter ones. In addition to cable length, connectors and splices also increase total loss.
Signal strength is written in -dBm, and the value usually ranges from 0 to -100. The closer the number is to 0, the stronger the signal becomes. For example, -41 dBm shows a stronger signal than -61 dBm. Because fiber systems require stable power levels, most of them operate best between -10 dBm and -25 dBm. However, the exact range depends on the network design. Meanwhile, the fiber industry continues working to reduce signal loss. In March 2024, Sumitomo Electric introduced ultra-low loss fiber at 0.1397 dB/km during an international conference.
Key causes of DB loss in fiber cables
DB loss happens because of two main types of causes: intrinsic losses and extrinsic losses.
Intrinsic losses
These losses happen naturally within the fiber material as light travels through it.
- Material absorption: The glass absorbs some light and turns it into heat.
- Scattering: Small defects in the glass scatter light away from the path.
- Dispersion: Light signals spread out over long distances and become weaker.
Extrinsic losses
On the other hand, these losses happen because of external factors such as handling and connections.
- Dirty connectors: Dust or oil blocks light and reduces signal quality.
- Cable bending: Sharp bends let light escape from the core.
- Connector and splice misalignment: Poor alignment causes signal loss.
- Return loss: Some light reflects back toward the source.
By understanding these causes, network teams can reduce signal loss and improve performance.
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How to calculate DB loss?
To understand total signal reduction, all loss components must be added. Therefore, network teams calculate total fiber loss using this formula:
| Total Fiber Loss (dB) = Fiber Attenuation (dB/km) × Fiber Length (km) + Connector Loss (dB) + Splice Loss (dB) |
Each part is calculated separately, and then the results are combined.
- Cable Attenuation = Attenuation per km × Length
- Splice Loss = Loss per Splice × Number of Splices
- Connector Loss = Loss per Connector × Number of Connector Pairs
For example, consider a 40 km single-mode link with 5 splices and 2 connector pairs at 1310 nm.
- Cable Attenuation: 40 km × 0.4 dB/km = 16 dB
- Splice Loss: 0.1 dB × 5 = 0.5 dB
- Connector Loss: 0.75 dB × 2 = 1.5 dB
- Safety Margin: 3 dB
Total Link Loss: 21 dB
This result shows the minimum power required for stable transmission. After installation, network teams should measure the actual link loss. By comparing measured values with calculated values, they can find possible issues early. In this way, they can maintain strong and reliable network performance over time.
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Building reliable fiber infrastructure
When organizations understand DB loss clearly, they can design stronger networks. With proper planning, they can select quality cables and install them correctly. As a result, the network becomes more stable and efficient. The fiber market is also growing rapidly. In 2024, MarketsandMarkets reported a global value of USD 3.2 billion, and it may reach USD 6.8 billion by 2029. This growth shows that demand for strong fiber infrastructure continues to rise. In this environment, dark fiber gives operators full control over signal quality. Because they manage their own equipment, they can monitor signal performance more closely.
ARNet provides dark fiber solutions across Southeast Asia. Through its networks in Malaysia, Indonesia, Singapore, and Thailand, the company supports major telecommunications providers and hyperscalers. In addition, it offers long haul, metro, and last mile fiber connections with stable DB loss characteristics.
For many organizations, this model removes the need to build infrastructure from the beginning. As such, they gain direct access to premium fiber networks without added complexity. At the same time, they receive full visibility into performance metrics, including DB loss measurements. Through this approach, ARNet supports businesses that require scalable and high-performance connectivity.
