An MPO breakout cable splits one multi-fibre MPO connector into several duplex or simplex legs, most often LC, so a parallel-optic port or trunk can connect to duplex equipment. Radix Fibrotech builds MPO to LC breakouts, fan-outs and MPO conversion harnesses to drawing, with the fibre mapping, leg length, polarity, connector and jacket the buyer specifies.
What an MPO breakout cable does
An MPO breakout cable has one MPO or MTP connector at one end and several individual connectors at the other. The most common form is an mpo to lc cable: an MPO-12 or MPO-8 at the head, and four or six LC duplex legs at the tail. It joins equipment that speaks in parallel optics to equipment that speaks in duplex pairs.
Typical uses:
- Running a 40G or 100G SR4 port as four 10G or 25G duplex links to separate servers or switches.
- Landing an MPO trunk directly on duplex equipment without a cassette, which removes one mated pair from the loss budget.
- Connecting a parallel-optic patch field to legacy duplex panels during a migration.
The breakout is the transition point in the wider MTP MPO cable range.
Breakout, fan-out and harness: what differs
| Type | Head | Tail | Construction note |
|---|---|---|---|
| Breakout cable | MPO-8, 12, 16 or 24 | LC, SC, FC or ST legs | Legs leave a furcation point, each with its own sub-unit jacket |
| Fan-out | MPO | Short loose-tube legs | Compact transition, usually inside a panel or enclosure |
| Conversion harness | One MPO | Two or three MPO | Changes fibre count, for example one MPO-24 to two MPO-12 |
| Equipment harness | Any connector set | Any connector set | Multi-branch assembly built to a platform drawing |
Harnesses that go beyond MPO, with mixed connector types or several branches, are covered under harnesses and optical systems and on the custom fibre optic assemblies page.
Construction at the furcation
The furcation is where the multi-fibre cable divides into legs, and it is the point that takes the strain when legs are pulled or dressed. A breakout built for a rack is different from one built for a moving machine or a field enclosure, so state where it will be installed.
- Furcation housing: a rigid body anchors the cable strength members and the leg sub-units, so a pull on one leg is not transferred to the fibre.
- Leg construction: legs with their own aramid strength member and jacket survive handling better than bare buffered fibre, which belongs only inside an enclosure.
- Position: give the distance from the MPO head to the furcation, so the split falls where the cable management expects it.
- Bend radius: the legs and the main cable each have a minimum bend radius; dress them in trays or rings that respect it.
Fibre mapping and polarity
The fibre map is the most important line on a breakout drawing. It states which MPO position goes to which leg, and which fibre in each leg is transmit and which is receive. For an SR4 port on an MPO-12, positions 1 to 4 transmit and positions 9 to 12 receive, with the four centre positions unused; each LC duplex leg pairs one transmit fibre with one receive fibre.
The breakout's polarity must match the trunk and cords in the channel. If the map is wrong, the link fails with no physical fault to find. The MPO polarity guide shows the standard methods. If the equipment uses a non-standard map, put the map on the drawing as a table.
Single-mode breakouts
Single-mode parallel optics also break out. A 400G DR4 port, for example, can run as four 100G single-mode links, each on a duplex LC leg. The MPO head on these breakouts is normally angled (APC), while the polish on the LC legs follows the optic at the far end, which is often UPC. Check both datasheets and state the polish at each end separately on the drawing; a breakout with the wrong polish on either end will not perform.
Duplex connectors on the legs
LC is the usual choice for data centre equipment. SC, FC and ST legs are built for test equipment, industrial panels and older installations. The fibre connector types guide compares them. For each leg specify:
- Connector type and whether duplex clips or simplex connectors are wanted.
- Polish: UPC for most single-mode, APC where the system needs angled end faces, flat or PC for multimode.
- Leg length, and whether legs are equal or staggered.
- Leg diameter (for example 2.0 mm or 3.0 mm) and colour or numbering.
- Labels on each leg.
Specifying an MPO breakout cable
- MPO fibre count, gender and polish at the head.
- Fibre type: OM3, OM4, OM5 or OS2.
- Number of legs and connector type on each.
- Fibre-to-leg map with transmit and receive identified.
- Polarity method used in the channel.
- Overall length, furcation position and leg lengths.
- Jacket rating and colour.
- Labels, test data and maximum loss per mated pair.
Radix reports insertion loss and return loss per channel. Each leg is tested and reported against its position in the fibre map, which makes the report useful at commissioning. Send the drawing through the request a quote page.
Questions buyers ask
What is an MPO to LC breakout cable used for?
It connects a parallel-optic port or MPO trunk to duplex LC equipment. A common example is running one 100G SR4 port as four 25G duplex links, or landing a trunk directly on duplex switch ports.
How many LC legs does an MPO-12 breakout have?
Usually four duplex legs when the link uses 8 of the 12 fibres, as SR4 optics do, or six duplex legs when all 12 fibres are used. State which on the drawing.
Is a breakout better than a cassette?
A breakout removes one mated pair, which helps a tight loss budget, and suits fixed, known connections. A cassette suits patch fields that will be reconfigured. Many sites use both.
Can you build MPO conversion harnesses?
Yes. Harnesses that convert one MPO-24 to two MPO-12, or other fibre count changes, are built to drawing. The fibre map must be supplied so the polarity through the conversion is correct.
Can breakout legs be different lengths?
Yes. Legs can be equal or staggered, and each length is cut to the drawing. Staggered legs reduce bulk where connectors land on adjacent ports.