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Fiber Pair Calculator

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

Inputs

links
fibres
%

Duplex Pairs

256pairs

Fibre Strands in Service

512strands

Strands to Provision

589strands

Trunk Cables Needed

25trunks

Trunk Fill

98.17%

Step by step

  1. Values used

    Links to build = 64 links; Optic type = 40G/100G SR4 — MPO-8, 8 fibres; Fibres per trunk cable = 24 fibres; Spare strand allowance = 15 %

  2. Fiber Pair

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

  3. Duplex Pairs

    = 256 pairs

  4. Fibre Strands in Service

    = 512 strands

  5. Strands to Provision

    = 589 strands

  6. Trunk Cables Needed

    = 25 trunks

  7. Trunk Fill

    = 98.17

How it works

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

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.

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