This bubble resulted from dirt on the fiber end surface. Proper care should be taken care of during cleaning process of fiber optics by using appropriate cleaning device such as isoprophyl alcohol. Intrinsic factors, such as the refractive index of the fiber, are those that are inherent to the fiber itself. Are you splicing multi-mode fiber? If not put it on splicing mode auto Fusing power calibration should only be done with SM fiber, even if you're splicing MM. These splicers are a nightmare for throwing this error up ! As the previous. Whether supporting 5G deployments, delivering fiber to the home services, or keeping large data centers running efficiently, optical fiber splicing plays a central role in maintaining stable, high-performance communication. Precise optical fiber splicing reduces signal loss, improves network. Optical fibers can be joined together, such that light is efficiently transferred from one fiber to another.