For fiber optic splicing in critical setups—e., a hospital's 5 km backbone—fusion's durability cuts maintenance—e., lasting 20+ years vs. In this comprehensive guide. A fiber optic cable splice is the process of permanently joining two fiber optic cables to create a continuous light path—vital when cables are cut, damaged, or need extending. 1. Over the years, optical fiber fusion splicing technology has been making steady progress with the advancement of optical fiber production technology and the development of new jointing methods. But what happens when you need to join two cables to extend a network or repair a break? You can't just twist them together.