Optical Fiber Cable attenuation new metric
Over the years, single core fiber attenuation in the largest fiber optic cable has become the industry standard for fiber attenuation performance. This ensures that the system designer can consider the worst-case attenuation of the link design. With the most advanced fiber and cable manufacturing technologies available today, the frequency of the largest fiber attenuation events in these cables is becoming more and more frequent, and second, more representative attenuation specifications are necessary. This proposed indicator, link design degradation (based on typical attenuation), defines a more practical attenuation value for fiber optic cable performance analysis and system design.
Link design attenuation
To determine how this new metric is specified, the fiber attenuation distribution in an actual fiber optic cable is the average attenuation value produced by random sampling spanning from two to twenty lengths of fiber. The resulting graph, shown in Figures 1A and 1B, was used to connect up to 20 fiber optic cables and then analyzed to determine that the required span was near steady state. The number of links at which the span has reached a steady state represents the minimum required to produce a technically credible average attenuation. Figures 1A and 1B clearly show that only eight optical fibers are attenuated in series after being connected in series. Other methods can be used to achieve the same result.
In order to properly generate the proposed specifications, additional statistical processing is required. At the steady-state point, the limit of link design attenuation can be drawn, which is evidenced by eight tandem links. In FIGS. 2A and 2B, the proposed link design attenuation is represented by the green line, which represents a 99.9% confidence threshold based on the specifications of the eight connection links. This result supports the concept of using link design attenuation to optimize network design and maintain a reasonable guard band.
The industry has established a precedent (IEC 60794-3) for the definitive application of statistical processing of PMDs in link design. To maintain consistency with existing standards, twenty spans can be used to determine link design attenuation values. Monte Carlo simulations show that as long as eight spans are sufficient to achieve a steady performance of link design degradation. The use of extra spans does not result in a significant increase in capacity. In addition, the smaller number of spans helps to better align the specification with the access network. Table 1 provides an example of how link design degradation benefits customers by ensuring higher levels of performance.
Several benefits of using this link design attenuation instead of the maximum fiber attenuation become apparent. Long distance transmission lines can reach longer distances. FTTH can serve a larger area by increasing the radial distance between the optical line terminal (OLT) at the center office and the optical network terminal (ONT) at the premises. This ensures high-performance fiber contained in a high-quality fiber optic cable, the best design capabilities available today, and the amount of space available for implementation.