Fiber Pair Calculator

Convert link count and optic type into fibre strands, duplex pairs and MPO trunk cables required.

About Fiber Pair Calculator

Serial optics use one transmit and one receive strand, while parallel optics such as SR4 and SR8 use a lane per direction and consume 8 or 16 strands per link. Dividing the provisioned strand count by trunk capacity gives the number of trunks to pull. Structured cabling is installed once and lives for a decade, so under-provisioning strands means opening the containment again when 400G parallel optics arrive.

Formula

Fiber Pair

strands = links × fibres per link; pairs = strands ÷ 2; trunks = ceil(strands with spares ÷ fibres per trunk).

fibres per link: 2 for duplex LC, 8 for SR4, 16 for 400G SR8, 20 for SR10
trunk: Pre-terminated multi-fibre cable, commonly 12, 24 or 144 strands

Worked example

With the default values below, Fiber Pair Calculator returns Duplex Pairs of 256. Change any input above and every figure here is recalculated in your browser.

Inputs used

Links to buildaccepts 1–20,000 links: 64 links
Optic typeone of Duplex LC — 2 fibres (1 pair), 40G/100G SR4 — MPO-8, 8 fibres, 400G SR8 — MPO-16, 16 fibres, 100G SR10 — MPO-24, 20 fibres: 40G/100G SR4 — MPO-8, 8 fibres
Fibres per trunk cableaccepts 2–864 fibres: 24 fibres
Spare strand allowanceaccepts 0–100 %: 15 %

Results

Duplex Pairs: 256 pairs
Fibre Strands in Service: 512 strands
Strands to Provision: 589 strands
Trunk Cables Needed: 25 trunks
Trunk Fill: 98.17%

Step by step

1Values used
2Fiber Pair
3Duplex Pairs= 256 pairs
4Fibre Strands in Service= 512 strands
5Strands to Provision= 589 strands
6Trunk Cables Needed= 25 trunks
7Trunk Fill= 98.17

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Fiber Pair calculated?

strands = links × fibres per link; pairs = strands ÷ 2; trunks = ceil(strands with spares ÷ fibres per trunk). Serial optics use one transmit and one receive strand, while parallel optics such as SR4 and SR8 use a lane per direction and consume 8 or 16 strands per link. Dividing the provisioned strand count by trunk capacity gives the number of trunks to pull.

Why does Fiber Pair matter?

Structured cabling is installed once and lives for a decade, so under-provisioning strands means opening the containment again when 400G parallel optics arrive.

What values do I need to enter?

This calculator takes 4 inputs: Links to build, Optic type, Fibres per trunk cable, Spare strand allowance. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.