An OM4 MPO to LC breakout cable has one 12-fibre MPO connector at one end and six duplex LC connectors at the other, with each fibre pair on its own leg. It takes a Base-12 OM4 trunk or panel straight to duplex ports. Order it by MPO gender, fibre map, leg lengths and stagger, polarity and jacket.
What a 12-fibre MPO to 6 duplex LC breakout does
An OM4 MPO to LC breakout cable has a single 12-fibre MPO or MTP connector at one end and six duplex LC connectors at the other. The 12 fibres divide into six pairs, and each pair ends on its own LC duplex leg with its own jacket. It is the usual way to take a Base-12 multimode trunk or panel straight to duplex ports without a cassette in between.
An mpo to lc breakout cable in OM4 is normally ordered for one of these jobs:
- Landing a 12-fibre OM4 trunk on a block of six duplex LC ports on a switch or panel.
- Replacing a cassette and the LC cords that plug into it. The cassette's LC adapter and the cord go, which takes one mated pair out of each channel.
- Feeding six duplex server or storage ports from one MPO port on a Base-12 patch panel.
- Building test leads that turn a multi-fibre cable into duplex connections for an LC-based tester.
The wider family is on the MPO breakout cables and harnesses page, and the cable that usually feeds a breakout is described under MPO trunk cables.
What OM4 changes compared with OM3
OM4 and OM3 are both 50/125 micron laser-optimised multimode fibre. OM4 has a higher effective modal bandwidth, which is what buys the extra reach on shortwave optics. The legs of a breakout are short, so the grade matters less inside the breakout than across the whole channel behind it.
| Property | OM3 | OM4 |
|---|---|---|
| Effective modal bandwidth at 850 nm | 2000 MHz.km | 4700 MHz.km |
| 10GBASE-SR channel reach (IEEE 802.3) | 300 m | 400 m |
| 25GBASE-SR channel reach (IEEE 802.3) | 70 m | 100 m |
| Usual jacket colour | Aqua | Aqua, or violet where a site separates OM4 from OM3 |
The reaches apply to the whole channel and assume it stays inside its loss budget. If a channel mixes grades, treat it as the lower grade, so an OM3 breakout on an OM4 trunk gives OM3 reach. The OM3 vs OM4 vs OM5 guide sets out when the extra grade is worth specifying.
Fibre map: how 12 fibres reach six LC legs
The usual Base-12 arrangement pairs neighbouring positions, so each duplex leg carries two adjacent fibres of the MPO-12.
| Leg | MPO-12 positions | LC duplex content |
|---|---|---|
| 1 | 1 and 2 | One A fibre and one B fibre |
| 2 | 3 and 4 | One A fibre and one B fibre |
| 3 | 5 and 6 | One A fibre and one B fibre |
| 4 | 7 and 8 | One A fibre and one B fibre |
| 5 | 9 and 10 | One A fibre and one B fibre |
| 6 | 11 and 12 | One A fibre and one B fibre |
This is the layout used by most Base-12 duplex cassettes, but it is a convention, not a rule, so the drawing should carry the map. Which fibre of each pair sits in LC position A or B depends on the polarity method of the channel.
A six-leg cable built this way does not suit a 40G or 100G SR4 port. An SR4 optic transmits on positions 1 to 4 and receives on positions 9 to 12, so paired neighbours would put two transmit fibres on one duplex leg. For an SR4 port, order a four-leg breakout with its own map, as described on the general breakout page above.
Leg length, staggering and furcation
Leg length is where most breakout orders go wrong, because the six legs have to reach six ports of different distances from one fixed split point.
- Overall length and furcation position: give the distance from the MPO connector to the furcation, and the leg length beyond it. State where each length is measured to, such as the tip of the LC connector or the end of the boot, since the two differ by a few centimetres.
- Staggering: legs of equal length end in six connectors at one distance, which bunches the bulk at the ports. Stepped lengths let each LC duplex reach its port in sequence. Give the length of each leg, or the step between legs, on the drawing.
- Leg diameter: thinner legs route more easily on a dense panel, while thicker legs resist handling better. Say whether you want 2.0 mm or 3.0 mm.
- Duplex style: a standard duplex clip or uniboot on each leg, to suit the port spacing.
- Numbering: legs numbered 1 to 6 so the label matches the fibre map and the port record.
Measure the route through the cable manager rather than the straight distance between ports, and add only a small allowance for slack.
Gender, polarity and polish at the MPO head
The MPO head has to mate with whatever it plugs into. Every mated pair needs exactly one pinned connector, so the gender of the head is set by the other side.
| The MPO head plugs into | Head gender |
|---|---|
| An adapter whose other side is an unpinned trunk end or cord | Male (pinned) |
| A pinned port, such as a pinned cassette or module | Female (unpinned) |
Most trunks are built unpinned at both ends, so a breakout fed from a trunk usually has a pinned head. Check the real hardware rather than assuming.
Multimode OM4 heads are polished flat, and the polish must match the rest of the channel. Polarity decides how the fibres are assigned to the legs and whether the A and B fibres of each leg are swapped. Give the method used in the channel and ask for the map to be confirmed on the drawing before production. The MPO polarity guide covers the methods.
Breakout or cassette in a rack
A breakout suits a fixed connection where the legs can be routed to their ports and left alone. A cassette suits a patch field that will be reconfigured, because the LC front can be re-patched without touching the MPO side. Many sites use both: cassettes in the main distribution area and breakouts at the equipment row.
In the rack, set the furcation beside the cable manager so the six legs fan out along the route to the ports, and fit the first leg to the nearest port. Each breakout carries one MPO and twelve LC connectors, and every one needs a dust cap until the moment it is plugged in. Inspect and clean the MPO end face before mating, as set out in the MPO cleaning guide, because one dirty fibre fails one of the six duplex links.
What to send us for a quote
Send one line per configuration with:
- Fibre grade: OM4, with bend-insensitive fibre if wanted.
- MPO head: MPO or MTP, 12 fibres, gender and polish.
- Number of legs, LC duplex style and diameter of each leg.
- Fibre map from MPO position to leg, with A and B fibres identified.
- Polarity method used in the channel.
- Overall length, furcation position, leg lengths and stagger.
- Jacket rating and colour, such as LSZH, riser or plenum.
- Leg labels, test report format and the maximum insertion loss per mated pair.
- Quantity for each line.
Ask for the insertion loss and return loss figures you need in the quote, since the report becomes your baseline at commissioning. Attach a drawing if you have one when you use the request a quote page.
Questions buyers ask
How many LC connectors does a 12-fibre MPO breakout have?
Twelve LC connectors, arranged as six duplex legs. Each leg carries two adjacent fibres of the MPO-12 in the usual Base-12 layout. If you need four duplex legs instead, for an SR4 port, say so, because that uses a different fibre map.
Can an OM4 breakout be used on an OM3 trunk?
It will mate, because OM3 and OM4 share the same 50/125 micron size and connector. The channel reach, however, is that of the lower grade. If the trunk is OM3, an OM4 breakout does not extend the reach.
Can I use a six-leg breakout on a 40G or 100G SR4 port?
Not with the neighbour-pair map. SR4 transmits on positions 1 to 4 and receives on 9 to 12, so adjacent pairing would put two transmit fibres on one duplex leg. An SR4 port needs a breakout built to its own map.
Should the MPO head be male or female?
It must be the opposite of the connector it mates with, because only one side of a mated pair carries pins. A head that plugs into an unpinned trunk end is male. A head that plugs into a pinned cassette or port is female.
Do the six legs have to be the same length?
No. Legs can be equal or stepped, and each length follows the drawing. Stepped lengths help where the six connectors land on ports at different distances from the furcation.
When is a cassette a better choice than a breakout?
Choose a cassette where the patch field will be reconfigured, because the LC side can be re-patched without disturbing the MPO trunk. Choose a breakout for fixed connections, where removing one mated pair helps the loss budget.