What issue arises when the backscatter level shifts up instead of down between two spliced fibers?

When analyzing the issue that occurs when the backscatter level shifts up between two spliced fibers, the key concept involved is the presence of a "gainer." A gainer refers to a situation where there is an increase in signal strength or power resulting from the splice or connection between fibers.

In optical fiber systems, backscatter is the light that is reflected or scattered back into the fiber from various points along its length due to impurities or irregularities in the fiber. If the backscatter level increases, it indicates that there is more light being reflected back, which suggests that the splice may be causing some sort of gain in the signal rather than a loss.

A gainer can occur when the splice is effectively combining two fibers with differing characteristics, potentially taking advantage of the differences in refractive indices or the quality of the fibers to enhance the overall signal strength. This is a critical factor to identify during installations and troubleshooting, as it shows that the connection is not only maintaining the signal but potentially improving it.

Understanding this phenomenon is essential for installers and technicians, as any unexpected gain can affect system performance, lead to potential overload situations, or indicate underlying issues that may need to be addressed.