What Is Fibre Optic Splicing and When Do You Need It?

What splicing actually is

An optical fibre is a strand of glass about 125 microns across, thinner than a human hair, that carries your broadband as pulses of light. When a cable is cut, extended or terminated, the two glass ends have to be joined so precisely that the light barely notices the join. That is splicing.

There are two methods. Fusion splicing uses a machine that aligns the two fibre ends under magnification and welds them together with an electric arc, typically losing less than 0.05 dB of signal. Mechanical splicing holds the fibres together in a small alignment sleeve with index matching gel. Fusion is stronger, lower loss and the standard for permanent work; mechanical splices are quicker but tend to be used as a temporary fix or where a fusion splicer cannot be brought in.

When you actually need a splice

Most people first hear the word after something has gone wrong. But splicing also crops up in perfectly routine work, so it is worth knowing the common scenarios before you assume the worst.

• A cable has been damaged, often by a digger, a fence post, gardening work or rodents chewing through ducting
• Your fibre broadband lead-in needs extending, for example to reach an outbuilding, garden office or a different room
• A new full fibre (FTTP) installation needs the drop cable joined to the network and terminated at the wall box
• You are connecting two buildings on one site, such as a house and a converted steading, common on rural properties across the Lothians and Borders
• A connector has failed and needs a new pigtail spliced on rather than the whole cable replaced

Why you cannot just tape it back together

Copper cable is forgiving; twist the cores together and something will usually work. Glass is not. The fibre ends must be cleaved flat, cleaned to a laboratory standard and aligned to within a fraction of a micron. A poor join scatters or reflects the light, and even a join that looks fine can add enough loss to drop your connection entirely or cause intermittent faults that are miserable to diagnose.

A proper engineer will strip and cleave the fibre, fuse it, protect the joint with a heat shrink sleeve, then test the link with an optical power meter or an OTDR, which measures loss along the whole cable and pinpoints any weak spots. You should be shown or given those readings; a splice without a test result is a guess.

What it costs and who is responsible

Costs depend on access more than the splice itself. A straightforward repair to an accessible cable in Edinburgh or the surrounding area typically runs to a call out charge plus an hour or two of labour, often somewhere in the region of £150 to £400. If the damage is underground and ducting has collapsed, or a long section needs replacing, the excavation is usually the expensive part, not the fibre work.

Who pays matters too. If the damaged cable belongs to Openreach or CityFibre, on their side of the boundary, report it to your internet provider and their engineers will repair it, usually at no cost unless you caused the damage. Private cabling on your property, such as a run to a garden office or between farm buildings, is your responsibility, and that is where an independent fibre engineer comes in. If a builder or contractor cut the line, their insurance normally covers the repair, so photograph the damage before anyone touches it.

Questions worth asking before you book

Fibre splicing is skilled work with expensive kit; a fusion splicer alone costs several thousand pounds, so not every electrician or aerial installer offers it. A few quick questions will sort out who is properly equipped.

• Do you fusion splice, or only fit mechanical connectors?
• Will you test the finished joint and provide the loss readings?
• Can you match my fibre type, typically single mode for broadband and most site links?
• Is the visit priced as a fixed call out or by the hour, and does that include materials such as sleeves and pigtails?