Fusibility means the ability to fuse. Single mode fibers are jointed to make network link in the deployment field. Single mode fibers shall be able to fuse when heated using an electric arc in order to make joints or splicing. Arc fusion is used in fusion splicing technique to joint two single mode fibers.
When two single mode fiber ends are brought nearby to make fusion splicing and apply electric arc, they should melt and join together. The joint portion shall have uniform diameter almost equal to the typical cladding diameter of single mode fiber. Primary arcylate coating of singlemode fibers would be stripped off prior to the splicing operation. The stripped fibers are then cleaved to make sure flat surface before they are placed in the splicing machine.
Fusibility can be measured by the splice loss that is obtained after splicing operation. The splicing machine will report the splice loss, based on the geometrical calculation. Alternatively an OTDR can be used to measure the optical signal loss at the spliced point. Singlemode optical fibers shall have good fusibility in order to ensure faster and low-loss joints. Typical splice losses acceptable in the field are less than or equal to 0.05 dB.