Continued expansion in fibre optic communications has resulted in a growing number of applications and deployment environments for optical cables. Telco backhaul, access networks, fibre to the home, LAN, sensing and submarine installations all present unique challenges – both optically and environmentally – to network operators and installers alike.
Fusion splicing is the process where two optical fibres are joined together to create one continuous optical path. Fibres are fused together using a series of electrical arcs that clean the fibres and then heat the two fibre surfaces. Once heated, the two fibres are pushed together to create a continuous optical path. The aim is to fuse the fibres together while maintaining the lowest optical loss performance. Prior to splicing, the fibres are cleaved. Cleaving is the process by which the bare fibres are scored and snapped using a precision blade to expose a clean fibre end face, perpendicular to the fibre. The cable jacket, protective materials and water-blocking gels are removed and the primary coating is stripped to expose the bare fibre. The fibres are now ready for cleaving.
Splicing methods
Core alignment fusion splicing is the most commonly used fusion-splicing technology. A system of cameras, lenses, light sources and motors work together to optimise the fibres core location and alignment. Fibres are located in v-grooves that allow them to move in all three axis, which provides core-core alignment optimisation. The ability to control core location on each fibre results in improved splice performance as the splicer can compensate against influences, such as fibre offset due to contamination or core-cladding concentricity mismatches.
Cladding alignment splicing
In cladding alignment fusion splicing, a fixed v-groove alignment method is used to align the claddings of the two fibres. Fibres are moved inwards and outwards only. In addition to cleave quality, the alignment and subsequent splice performance is influenced by fibre position, core-cladding concentricity and mode field diameter (MFD). Fibre location is influenced by contamination on the fibre or v-grooves, and can be controlled by the operator. Maintaining clean fibre and v-grooves will ensure the fibres are seated in their optimum position. Splice performance is also influenced by core-cladding concentricity and MFD. However, these are fibre manufacture parameters and cannot be controlled by the operator. These factors typically come into consideration when splicing new to old fibres and also dissimilar fibres such as single-mode G652.D to G657.A.
After splicing
Once the fibres have been fused together, the splicer will provide a loss estimate and perform a proof test. The proof test applies a force to the fibre in opposing directions to check the mechanical integrity of the splice joint. A splice protector sleeve is placed over the joint and with heat applied, shrunk down over the fibre to provide additional mechanical protection.