A short length of fibre with a factory-terminated connector on one end and bare fibre on the other, for splicing into the plant.
What Is a Fiber Pigtail?
A pigtail is half a patch cord: a connector, a short length of fibre — usually one to three metres of 900 µm tight buffer — and a bare end. It exists so that the connector can be made and polished in a factory under controlled conditions, then joined to the installed cable by a fusion splice on site.
That division of labour is the entire point. Everything that determines connector quality — apex offset, fibre height, radius of curvature, cleanliness during polish — is done on a machine and measured on an interferometer, not in a riser cupboard with a headtorch.
The Loss Arithmetic
The installed cable is stripped and cleaved, the pigtail is cleaved, and a fusion splicer arc-welds the two together. The joint costs about 0.1 dB and often much less on single-mode. The factory connector contributes about 0.25 dB when mated, so the total from cable to patch panel is roughly 0.35 dB.
Field-terminated connectors — mechanical splice-on types, or epoxy-and-polish — typically land between 0.5 and 0.75 dB, with a spread several times wider. Across a 96-fibre distribution frame that difference is the margin that decides whether the channels close. Run it through the link budget calculator if the design is marginal.
Ribbon pigtails apply the same logic twelve fibres at a time: a mass-fusion splicer joins a whole ribbon in one arc, which is how a 288-fibre closure gets terminated in a shift rather than a week. Each joint is protected in a 40 or 60 mm heat-shrink sleeve and laid into a tray with enough slack that it can be re-worked later without disturbing its neighbours.
What Goes Wrong
Splice quality is not self-evident. A splicer's estimated loss is an image-processing guess from the arc, not a measurement, and it can be optimistic on a core-offset joint. Anything that matters gets verified with an OTDR from both ends, which is exactly what Tier 2 testing is for.
The other recurring problem is bend radius in the splice tray. Coiling excess pigtail too tightly against the tray wall adds macrobend loss that appears at 1550 nm and not at 1310, which is a very confusing symptom until you know to look for it — see G.657.
Where You Meet It
Every distribution frame, splice closure, terminal box and FTTH cabinet. Available in single-mode and multimode with any connector and polish: our LC/UPC pigtails and SC/UPC pigtails are the usual choices for terminating outdoor cable.
Fibre pigtail reference
| Construction | one factory-terminated connector, one bare fibre end |
|---|---|
| Typical length | 1 to 3 m |
| Buffer | 900 µm tight buffer, or 250 µm in ribbon form |
| Fusion splice loss | about 0.1 dB; often 0.02 to 0.05 dB on single-mode |
| Mated connector loss | about 0.25 dB standard, 0.12 dB low-loss grade |
| Connector plus splice | about 0.35 dB total |
| Field-terminated connector | typically 0.5 to 0.75 dB, and far more variable |
| Splice protection | 40 or 60 mm heat-shrink sleeve, coiled in a tray |
| Ribbon pigtails | 12 fibres mass-fusion spliced in one operation |
Related Terms
insertion loss, G.657, Tier 1 and Tier 2 testing, uniboot, APC vs UPC.