Before the optical fibers can be successfully fusion-spliced, they need to be carefully stripped of their outer jackets and polymer coating, thoroughly cleaned, and then precisely cleaved to form smooth, perpendicular end faces. Once all of these completed, each fiber is placed into a holder in the fusion splicer’s enclosure. From this point on, the fiber optic fusion splicer takes over the rest of the process, which involves 3 steps:

Alignment

Using small, precise motors, the fusion splicer makes minute adjustments to the fibers’ positions until they’re properly aligned, so the finished splice will be as seamless and attenuation-free as possible. During the alignment process, the fiber optic technician is able to view the fiber alignment, thanks to magnification by optical power meter, video camera, or viewing scope.

Impurity Burn-Off

Since the slightest trace of dust or other impurities can wreak havoc on a splice’s ability to transmit optical signals, you can never be too clean when it comes to fusion splicing. Even though fibers are hand-cleaned before being inserted into the splicing device, many fusion splicers incorporate an extra precautionary cleaning step into the process: prior to fusing, they generate a small spark between the fiber ends to burn off any remaining dust or moisture.

Fusion

After the fibers have been properly positioned and any remaining moisture and dust have been burned off, it’s time to fuse the fibers ends together to form a permanent splice. The fiber splicer emits a second, larger spark that melts the optical fiber end faces without causing the fibers’ cladding and molten glass core to run together (keeping the cladding and core separate is vital for a good splice – it minimizes optical loss). The melted fiber tips are then joined together, forming the final fusion splice. Estimated splice-loss tests are then performed, with most fiber fusion splices showing a typical optical loss of 0.1 dB or less.