An MPO trunk cable is a multi-fibre MPO to MPO cable installed as the permanent backbone between patch panels or cassettes. Radix Fibrotech builds MTP and MPO trunks in 12 to 48 fibres or more, in OM3, OM4, OM5 or OS2, with the polarity, gender, breakout stagger, jacket and pulling grip specified on the buyer's drawing.
What an MPO trunk cable does
An MPO trunk cable is the fixed part of a structured fibre channel. It runs from one patch field to another, usually between a main distribution area and the equipment rows, and is terminated at both ends in MTP or MPO connectors. Because the ends are factory terminated and tested, the trunk is pulled in, plugged into cassettes or adapter panels, and the channel is live without field splicing.
Buyers also search for an mtp trunk cable or an mpo to mpo cable. The terms describe the same thing: a multi-unit cable with MPO-type connectors on each end. Patch cords and breakouts then connect the trunk to equipment, as described on the MTP MPO cable assemblies page.
Trunk configurations
| Configuration | Construction | When it is chosen |
|---|---|---|
| Single-unit trunk | One 12, 16 or 24-fibre cable, one MPO each end | Point-to-point parallel link or one cassette per end |
| Multi-unit trunk | Several sub-units in one outer jacket, an MPO on each sub-unit | Feeding several cassettes from one pull, for example 48 or 96 fibres as 12-fibre legs |
| MPO to duplex trunk | MPO at one end, LC or SC legs at the other | Equipment with duplex ports at one end only; see breakouts |
| Armoured trunk | Metallic or dielectric armour over the cable core | Underfloor, inter-building or rodent-exposed routes |
Multi-unit trunks are normally specified with a staggered breakout so the connectors do not stack at one point, and with a pulling grip that protects the connectors during installation. State the stagger and the length of each leg on the drawing.
Fibre type and reach
Trunk length is fixed by the building, so the fibre must support the longest channel the optics will see. IEEE 802.3 publishes the following maximum reaches for common parallel multimode optics:
| Optic | Fibres used | OM3 reach | OM4 reach |
|---|---|---|---|
| 40GBASE-SR4 | 8 (MPO-12) | 100 m | 150 m |
| 100GBASE-SR4 | 8 (MPO-12) | 70 m | 100 m |
| 400GBASE-SR8 | 16 (MPO-16) | 70 m | 100 m |
Those reaches assume the channel stays within its loss budget, which includes every mated connector pair in the run. A trunk that lands on cassettes adds two more mated pairs than a direct MPO path. Use the fibre loss budget calculator to check the channel before fixing the design. Single-mode OS2 trunks with angled MPO connectors carry DR and FR optics over longer distances, and are the usual choice where future 800G single-mode optics are planned. The 400G and 800G cabling guide sets out the options.
Polarity, gender and end face
Specify the polarity type (A, B or C) to match the method used in the rest of the channel. The trunk, the cassettes or breakouts at each end, and the patch cords must agree, and a wrong trunk is expensive to replace once it is pulled in. The MPO polarity guide shows each method end to end.
Gender follows the hardware. Most cassettes and many adapter panels present pinned connectors at the rear, so trunks are commonly ordered unpinned at both ends; confirm this against the cassette datasheet. Multimode trunks are polished flat. Single-mode trunks are polished at an angle (APC).
Jacket and construction
- LSZH for occupied buildings where low smoke and zero halogen are specified.
- Plenum or riser rated jackets where the installation follows North American fire codes.
- Armoured construction for routes where crush or rodents are a concern.
- Jacket colour to the fibre type convention (aqua for OM3 and OM4, lime green for OM5, yellow for OS2) or to the site's own colour scheme.
Give the cable outer diameter limit if the trunk must pass through existing containment, and the minimum bend radius the route imposes.
Installation and acceptance testing
Most trunk damage happens during the pull. A pulling grip carries the load on the cable strength members instead of the connectors, and the connectors stay capped until they reach the panel. Keep within the cable's rated pulling tension and minimum bend radius, which the quote can state for the construction chosen.
Before the trunk is accepted, every end face should be inspected and, if needed, cleaned; the inspection criteria most buyers cite are those in IEC 61300-3-35. The installed channel is then tested for loss, either with MPO test equipment or through breakouts to a duplex test set. Compare the result with the per-channel factory report that ships with the trunk. A large difference points to contamination or a damaged connector introduced during installation, not to the cable.
Record the polarity type and leg labels in the site documentation so later moves follow the same method.
Specifying an MPO trunk cable
- Fibre count, number of legs and connectors per end.
- Fibre type and connector type (MTP or MPO).
- Gender at each end and end-face polish.
- Polarity type.
- Measured route length plus slack, and the tolerance.
- Breakout length and stagger at each end.
- Jacket rating, colour and any armour.
- Pulling grip at one or both ends.
- Label text at each leg and the cable marking.
- Required test data and maximum insertion loss per mated pair.
Radix reports insertion loss and return loss per channel. Send the route drawing or the list above through the quote request form.
Questions buyers ask
What is the difference between an MPO trunk cable and an MPO patch cord?
A trunk is the permanent backbone, usually longer, often multi-unit, and installed in containment. A patch cord is a short, single-unit cable that connects equipment to a panel and is expected to be moved. The connectors are the same family.
Should an MPO trunk be pinned or unpinned?
Match the hardware it plugs into. Two mating MPO connectors need one pinned and one unpinned. Many cassettes have pinned rear ports, so trunks are often unpinned at both ends, but check the cassette and panel datasheets.
How do I measure the length of an MPO trunk?
Measure the route through the containment, not the straight-line distance, and add slack for dressing at each rack. Then add the breakout length at each end. Trunks cannot be shortened on site without re-termination, so measure twice.
Can a trunk be built with different connectors at each end?
Yes. A trunk can carry MPO at one end and LC or SC legs at the other, or a different MPO fibre count at each end. Show both ends on the drawing with the fibre-to-position mapping.
Is OM4 or OS2 better for a new trunk?
OM4 suits short multimode runs at 100G and 400G within the reaches IEEE 802.3 publishes. OS2 suits longer runs and single-mode DR or FR optics. Choose by the optics you plan to use over the trunk's service life.