Fibre colour codes

The TIA-598 fibre colour code

ANSI/TIA-598 sets a sequence of 12 colours for individual fibres, for buffer tubes and for units within a cable. Fibre 1 is always blue and fibre 12 is always aqua. When a single group holds more than 12 fibres, positions 13 to 24 repeat the same colours with a black stripe or dashed marking. Black, at position 20, takes a yellow stripe instead so it stays visible.

The same order is used for tight-buffered fibres in indoor cables, for coloured fibres inside loose tubes and for the legs of breakout assemblies. It is worth learning by heart: most splicing and termination errors start with a misread colour.

Tube and fibre colours above 12 fibres

Loose tube cables group fibres in coloured tubes, and the tubes follow the same 12-colour order. Tube 1 is blue, tube 2 orange, and so on. In a cable with 12 fibres per tube, the fibre number is found like this:

Fibre number = (tube number - 1) x 12 + fibre position in the tube

• Green tube (3), white fibre (6): (3 - 1) x 12 + 6 = fibre 30.
• Red tube (7), slate fibre (5): (7 - 1) x 12 + 5 = fibre 77.
• Brown tube (4), brown fibre (4): (4 - 1) x 12 + 4 = fibre 40.

Where a cable has 6, 8 or 24 fibres per tube, replace 12 with the tube count. Filler rods that keep the cable round are not counted. Cables with more than 12 tubes repeat the tube colours with stripes, or group tubes under coloured binder threads. Ribbon cables number each ribbon and keep the same colour order across the fibres in it.

TIA-598 is not the only sequence in use. Some operators and national standards outside North America use different colour orders, so confirm the code on the cable datasheet before splicing new cable to existing plant.

Jacket and connector colours by fibre type

TIA-598 also sets outer jacket colours for premises cable, so the fibre type can be read from across a room. Connector and adaptor body colours follow a parallel convention in ANSI/TIA-568.

Outdoor cable is usually black whatever fibre it holds, because black polyethylene resists ultraviolet light. Military and some industrial cables use their own jacket colours. In every case the printed legend on the jacket is the reliable record of fibre type and count. Our single-mode vs multimode guide explains the grades behind these colours.

MPO fibre position mapping

An MPO-12 connector holds one row of 12 fibres. Positions are numbered 1 to 12 and, by the usual TIA convention, position 1 is on the left when you look at the end face with the key up. In a standard assembly, position 1 carries the blue fibre and position 12 the aqua fibre, following the TIA-598 order. An MPO-24 adds a second row for positions 13 to 24, using the striped colours. Confirm the row and view orientation on the assembly drawing, since it is easy to mirror.

Parallel optics such as 40GBASE-SR4, 100GBASE-SR4 and 400GBASE-DR4 use only eight fibres: four to transmit on positions 1 to 4 and four to receive on positions 9 to 12. Positions 5 to 8 are dark, which is why 8-fibre MPO assemblies exist for these links.

Polarity decides which position at one end meets which at the other. Type A keeps position 1 at position 1, Type B reverses the row so 1 meets 12, and Type C swaps adjacent pairs. Our guide to MPO polarity types A, B and C covers how to keep transmit and receive matched end to end. In MPO breakout cables, the leg colours normally follow the same sequence, so a blue leg comes from position 1.

Colour codes on drawings and test reports

• State the colour code standard on the drawing, for example TIA-598, especially when the cable will be spliced to existing plant.
• Label each breakout leg with its fibre number as well as relying on its colour.
• Ask for test results reported by fibre number, so a failed fibre can be found by colour on site.
• For MPO assemblies, state the polarity type, pin gender at each end and the fibre count.

Radix builds custom fibre optic assemblies to the customer's drawing, including colour code, marking and labelling. Send your drawing through the quote form.