An MPO cable is a fibre optic assembly terminated with MPO (multi-fibre push-on) connectors, which hold 8, 12, 16, 24 or more fibres in one rectangular MT ferrule. MPO cables are used as trunks, patch cords and breakouts in data centres, where they save panel space and installation time and carry parallel optics such as 40G, 100G and 400G short-reach links.
How an MPO connector works
An MPO cable is any fibre assembly that ends in an MPO connector. MPO stands for multi-fibre push-on, and the connector interface is defined internationally in IEC 61754-7 and in North America in TIA-604-5 (FOCIS 5). At its centre is an MT (mechanical transfer) ferrule: a moulded rectangular block with the fibres laid side by side in one or more rows at a 250 micron pitch.
Alignment does not come from a round sleeve, as it does with LC or SC connectors. Two steel guide pins on one connector enter two precision holes on the other, and that pin-and-hole fit lines up every fibre in the array at once. A spring pushes the two ferrule faces together so the fibres make physical contact.
The housing latches with a push-pull action, much like an SC connector. A raised key on one side of the housing fixes the orientation, so fibre position 1 always sits at a known place. The key and the guide pins drive most of the decisions a buyer makes when ordering MPO cable: gender, adapter type and polarity.
MPO fibre counts
The fibre count is set by the ferrule. Most data centre cabling uses 12-fibre and 24-fibre ferrules, and 16-fibre ferrules are now common because 400G and 800G optics use eight lanes.
| Connector | Ferrule layout | Typical use |
|---|---|---|
| MPO-8 | 12-position ferrule with 8 fibres fitted (positions 1 to 4 and 9 to 12) | Four-lane parallel optics such as 40GBASE-SR4, 100GBASE-SR4 and 400GBASE-DR4 |
| MPO-12 | One row of 12 fibres | General trunking; four-lane parallel optics with the middle four positions unused |
| MPO-16 | One row of 16 fibres | Eight-lane parallel optics such as 400GBASE-SR8 and 800G DR8 modules |
| MPO-24 | Two rows of 12 fibres | High-density trunks; the older 100GBASE-SR10 interface |
| MPO-32 | Two rows of 16 fibres | High-density trunking in 16-fibre systems |
MPO-16 and MPO-32 connectors use an offset key, so they do not mate with 12-fibre and 24-fibre connectors. A link that mixes the two families needs a conversion cord or a conversion module. Higher fibre counts are built by grouping several MPO legs in one cable, for example a 48-fibre trunk with four MPO-12 connectors at each end.
Pin gender and keying
Every mated MPO pair is one pinned (male) connector against one unpinned (female) connector. Two pinned connectors will not seat. Two unpinned connectors can be pushed together, but the fibres are not aligned and the loss is high, so this is a fault, not an option.
Parallel optic transceivers such as QSFP SR4 and DR4 modules have pinned ports, so the cord that plugs into them must be unpinned. In structured cabling, trunks are commonly unpinned at both ends and plug into pinned ports on cassettes or fan-out modules. The reverse arrangement also works if it is drawn and ordered consistently across the site.
Adapters come in two forms. A key-up to key-down adapter (Type A) joins two connectors with their keys on opposite sides. A key-up to key-up adapter (Type B) joins them with keys on the same side, which reverses the fibre order. The adapter type, the trunk type and the patch cords together set the polarity of the link, which our guide to MPO polarity methods A, B and C explains with fibre maps.
Polish and fibre type
Multimode MPO connectors (OM3, OM4 and OM5) are normally polished flat for physical contact. Single-mode MPO connectors used for parallel optics such as 400GBASE-DR4 are usually angle polished (APC) at 8 degrees to cut back reflection. An angled connector must only mate with another angled connector. Mating APC with a flat polish leaves an air gap at the fibre cores and causes high loss.
Housing colour helps on site. Industry practice uses green housings for single-mode APC, and aqua, violet or lime green housings for multimode, broadly following the jacket colours for each fibre grade. Colour is a convention only, so the label and the drawing should still state the fibre type and polish.
Types of MPO cable assembly
- Trunk cables run between panels or cassettes as the permanent link, often with 12 to 144 fibres and MPO connectors at both ends. See MTP/MPO trunk cables.
- Patch cords are short MPO-to-MPO jumpers that connect transceivers to panels or cross-connect two panels. Radix makes MTP OM4 patch cords as well as OM3 versions.
- Breakout or harness cables fan one MPO out to duplex LC or other connectors, for example an MPO-8 to four LC duplex legs so that a 100G SR4 port can run as four 25G links. See MPO breakout cables.
- Conversion cords join different MPO families, such as a 24-fibre trunk to three 8-fibre ports, or MPO-12 to MPO-16.
Trunks are usually round indoor cables, with armoured or outdoor constructions where the route passes through ducts, risers or open trays that need them. Patch cords favour small, flexible jackets because they are handled often.
MPO assembly types at a glance
Four assembly types cover most orders. The last column is what to state when you ask for a quote.
| Assembly | Ends | What it connects | State when ordering |
|---|---|---|---|
| Trunk | MPO at both ends | The permanent link between panels or cassettes | Fibre count, length, polarity type, pinned or unpinned at each end |
| Patch cord | MPO at both ends | A transceiver to a panel, or one panel to another | Length, polarity type, gender. A cord that plugs into a transceiver is unpinned |
| Breakout or harness | MPO at one end, duplex LC or other connectors at the other | One multi-fibre port to several separate duplex ports | Fibre count, leg length, leg connector type |
| Conversion cord | Different MPO families at each end | Links that use different fibre counts, such as 24 fibres to three 8-fibre ports | Fibre count at each end and the fibre mapping |
Where MPO cables are used
MPO cabling is mainly a data centre and enterprise backbone product. Its value is density and speed of installation. A factory-terminated, tested trunk is pulled and plugged rather than spliced or terminated in the field, and an MPO adapter fits the same panel cut-out as an SC simplex or LC duplex adapter while carrying many more fibres.
- Backbone trunks between rows in spine-and-leaf networks.
- Direct connection of parallel optic transceivers at 40G, 100G, 400G and 800G.
- Pre-terminated links in colocation suites and enterprise server rooms, where installation windows are short.
- High-density fibre in broadcast facilities and test laboratories.
Because the connectors are factory made, the quality of the polish and the test report matter more than any field skill. Ask for insertion loss on every fibre and for end-face inspection results with each assembly.
How to specify an MPO cable
Most MPO ordering errors come from a missing detail rather than a wrong product. A complete request states:
- Fibre type: OS2, OM3, OM4 or OM5.
- Fibre count and connector: MPO-8, MPO-12, MPO-16 or MPO-24, and the number of legs at each end.
- Gender at each end: pinned or unpinned.
- Polarity: Type A, Type B or Type C.
- Polish: flat (PC or UPC) or angled (APC).
- Length measured connector to connector, and the tolerance you will accept.
- Jacket rating: LSZH, riser or plenum, as your building code requires.
- Loss grade: standard or low loss, with the maximum insertion loss per mated pair you need.
- Test report: insertion loss per fibre and end-face inspection results.
Send that list, with a drawing if you have one, through the request a quote page. Our guide on writing an RFQ for fibre assemblies has a checklist you can copy.
Questions buyers ask
What does MPO stand for?
MPO stands for multi-fibre push-on. It is the generic name for the multi-fibre connector defined in IEC 61754-7 and TIA-604-5. MTP is a brand of MPO-compatible connector with mechanical refinements, and the two intermate.
How many fibres are in an MPO cable?
A single MPO connector usually carries 8, 12, 16 or 24 fibres, and 32-fibre versions exist. A trunk cable carries more by grouping several MPO connectors at each end, for example 48, 96 or 144 fibres in one jacket.
Can I plug an MPO cable straight into a switch?
Yes, if the switch port holds a parallel optic transceiver with an MPO receptacle, such as a QSFP SR4 or DR4 module. These ports are pinned, so the cord needs unpinned connectors. For a direct transceiver-to-transceiver link the cord is normally Type B polarity.
What is the difference between an MPO trunk and an MPO patch cord?
A trunk is a longer, permanent link installed between panels or cassettes, often with more fibres and a heavier jacket. A patch cord is a short jumper that connects equipment to the panel and is expected to be unplugged and moved during the life of the network.
Is MPO used with single-mode fibre?
Yes. Single-mode MPO assemblies carry parallel single-mode optics such as 400GBASE-DR4 and dense backbone links. They are usually APC polished at 8 degrees and must only mate with other APC connectors.
What insertion loss should I expect from an MPO connection?
TIA-568 allows up to 0.75 dB per mated connector pair when building a loss budget, and that allowance applies to MPO connections too. Many suppliers offer low-loss MPO grades well inside that allowance. Ask for the maximum per mated pair in the quote and check it against your application's channel limit.