What is the fibre colour sequence?

Blue, orange, green, brown, slate, white, red, black, yellow, violet, rose, aqua. The same twelve are used for tubes and for the fibres inside them, and both restart after twelve. Cable built to other conventions exists, so the cable's own datasheet is the only authority.

Why can a colour pair be ambiguous?

Because tube colours repeat once the convention runs out. On a 288-fibre cable the blue tube appears twice, so “blue tube, green fibre” matches both fibre 3 and fibre 147. Above the convention's tube count, a colour pair narrows things down without settling them.

What identifies a tube when the colours repeat?

The binder — a coloured thread bundling groups of tubes, following its own colour sequence — or the tube's physical position in the cable. The binder colour is also the detail most often missing from the drawing, so it is worth establishing before the closure is open rather than while holding two identical blue tubes.

How are 24-fibre tubes numbered?

Usually by repeating the same twelve colours with a black tracer stripe or ring for fibres 13 to 24. That convention is available here, and like the rest it should be confirmed against the cable's datasheet.

Does this work for ribbon cable?

Not directly. In ribbon cable the ribbon carries the identity — usually printed — and the fibres within it follow the colour sequence in physical order from the marked edge. The lookup here follows loose-tube convention.

Does the colour tell me whether a fibre is in service?

No. Colour identifies which fibre, not what it is doing. Whether it is live is a question for the records and then for a light source, in that order.

Fibre Optic Colour Code Lookup

Q: Which fibre is number 87?

On a cable with twelve fibres to a tube, fibre 87 is in tube 8 — black — and is the third fibre in it, which is green. The tool works it out for any tube size, and in reverse.

Which fibre is number 87, and what colour is it? Both directions, for cables up to 1728 fibres — plus a printable map of the whole cable.

Colour conventions are not universal This uses the twelve-colour sequence most commonly encountered, and cable built to other conventions exists. Before cutting anything, check the datasheet for the specific cable in front of you. A tool cannot know which convention a drum was manufactured to, and getting it wrong on a live cable is expensive.

The sequence

The same twelve colours are used for tubes and for the fibres inside them. Both restart after twelve, which is why a colour pair alone is ambiguous on a large cable.

Find a fibre

I have a number I have the colours

Convention

Fibres per tube

Fibre number

The whole cable

Fibre count

Why a colour pair is not an address

On a 96-fibre cable with twelve fibres per tube there are eight tubes, and the twelve colours cover them comfortably. Fibre 15 is the green fibre in the orange tube, and nothing else is.

Go past 144 fibres and the tube colours run out and start again. On a 288-fibre cable the blue tube appears twice — tubes 1 and 13 — so “blue tube, green fibre” matches both fibre 3 and fibre 147. At that point the tube's position in the cable, or a binder-group colour, is what actually identifies it.

This tool says so rather than picking the lower number and hoping. On any cable above the convention's tube count, a colour pair narrows things down and does not settle them.

Binders, and the layer nobody documents

Large cables group tubes into binders — bundles held together with coloured thread, themselves following a colour sequence. A 432-fibre cable might be six binders of six tubes of twelve fibres.

The binder colour is what disambiguates the repeated tube colours, and it is also the thing most likely to be missing from the drawing you were given. If you are working on a cable large enough for tube colours to repeat, establish how the binders are identified before the closure is open, not while holding two identical blue tubes.

Ribbon cable counts differently

In ribbon cable the fibres are bonded side by side in a flat array, and it is the ribbon that carries an identity — usually printed — while the fibres within it run through the standard colour sequence in physical order.

The lookup here follows loose-tube convention. For ribbon, the ribbon number replaces the tube colour and the fibre position within the ribbon is read left to right from the marked edge.

Before you cut

Three things are worth confirming, and none of them takes long compared with what a wrong cut costs:

The cable's own datasheet. It states the convention. Nothing else is authoritative.
The count direction. Whether fibre 1 is at the marked end, and which end is marked.
What is live. Colour tells you which fibre, not whether it is carrying traffic. That is a question for the records and for a light source, in that order.