A fusion splicer not fusing properly is a problem that can often be resolved with a bit of troubleshooting. Even a minor error can lead to significant signal loss or faulty splices. Fiber contamination Alignment error messages. Fiber cables are made of glass, and even a tiny speck of dust can block the light or cause the fibers to misalign. Whether you're extending your route, adding a new customer, or repairing a cut, the quality of your splice directly affects your network's performance. But many cable operators still struggle with splice failures, leading to power loss, LOS.