An MPO-24 trunk cable carries 24 fibres in a two-row MPO connector at each end, so one cable does the work of two 12-fibre trunks. It is built in OM4 multimode or OS2 single-mode, with Type A, B or C polarity and pinned or unpinned ends. Radix Fibrotech makes MPO-24 and MTP-24 trunks to the length and drawing the buyer supplies.
What an MPO-24 trunk cable is
An MPO-24 connector holds 24 fibres in two rows of 12 in one rectangular ferrule. A trunk with this connector at both ends links two patch fields with a single plug at each side. The fibres are numbered 1 to 24 across the two rows, and the numbering matters because polarity and breakouts are defined by position.
A 24-fibre connector and a 12-fibre connector do not form a working pair. The change from one to the other is made inside a cassette or through a conversion harness. MTP-24 is the brand name for the enhanced version and mates with standard MPO-24 parts. The general rules for backbone cabling are on the MPO trunk cables page; this page covers what is specific to 24 fibres.
Where 24-fibre trunks are used
| Use | How the 24 fibres are used | Why it is chosen |
|---|---|---|
| Two 12-fibre cassette channels | 12 + 12, split in the cassette | One pull and one plug per end instead of two |
| Three parallel SR4 links (40G or 100G) | 3 x 8 fibres, through a 24-fibre to three-module cassette | All 24 fibres carry traffic, where a 12-fibre trunk leaves four dark per link |
| Up to twelve duplex links (10G or 25G) | 12 x 2 fibres, through LC cassettes | Highest duplex count per connector in the backbone |
| 100GBASE-SR10 (an early 100G standard) | 20 of 24, ten each way | Found in older CFP and CXP equipment |
Most new parallel optics use 8 or 16 fibres, so a 24-fibre trunk is usually a cabling choice made for density and fibre use, not a requirement of the optic. It suits main distribution areas where panel space and containment fill are the limits.
MPO-24 or two MPO-12 trunks
| Factor | One MPO-24 trunk | Two MPO-12 trunks |
|---|---|---|
| Connectors per end | 1 | 2 |
| Pulls through containment | 1 | 2, or one multi-unit cable |
| Fibres on one dirty or damaged connector | 24 | 12 |
| Fibre use with 8-fibre parallel optics | Full, at 3 links of 8 | 8 of 12, four idle per link |
| Cassette and panel choice | 24-fibre parts only | The wider 12-fibre range |
| Mid-life change to 12-fibre hardware | Needs a conversion harness | Direct |
Choose the 24-fibre trunk when the panels and cassettes at both ends are already 24-fibre or are being bought with the trunk. Choose two 12-fibre trunks when the plant is mostly 12-fibre, or when losing 24 fibres to one damaged connector is a risk you do not accept.
Polarity on a 24-fibre trunk
The three array methods carry over to 24 fibres. Type A is straight through, with position 1 landing on position 1 and 24 on 24, and the key up at one end and down at the other. Type B is reversed, with position 1 landing on 24, and the key up at both ends. Type C flips each adjacent pair, so 1 goes to 2 and 2 to 1. The MPO polarity guide shows the 12-fibre case, and the logic is the same.
Two points are particular to 24 fibres. First, state which row is which on the drawing if the trunk splits into legs, since a 24-fibre trunk is often built as two or three legs of 12 or 8 fibres. Second, check the cassette vendor's fibre map, because the order in which cassettes number the two rows is not the same everywhere.
OM4 and OS2 versions
| Grade | Fibre | End face | Used with | Jacket colour |
|---|---|---|---|---|
| OM4 | 50/125 µm multimode | Flat (PC or UPC) | 850 nm SR optics and duplex SR through cassettes | Aqua |
| OS2 | 9/125 µm single-mode | Angled (APC), 8 degrees | Parallel and duplex single-mode optics through cassettes | Yellow |
Never mate an angled connector with a flat one. The end faces do not meet, loss rises, and the ferrules can be damaged. Single-mode MPO assemblies are APC, and the connector body is often green to show it.
OM4 suits runs inside a building within the reach of the optic. OS2 suits longer runs, campus links and plant that must outlast several optic generations, since single-mode fibre has no modal bandwidth limit. The OM3 vs OM4 vs OM5 guide covers the multimode grades.
What to send us for a quote
- Fibre count (24), number of trunks and any leg split, such as 2 x 12 or 3 x 8.
- Grade: OM4 or OS2, with bend-insensitive fibre if wanted.
- Connectors: MTP or MPO, female or male at each end, and the end-face polish.
- Polarity: Type A, B or C, with the fibre map for the cassettes.
- Length for each line, tolerance, and breakout length and stagger at each end.
- Jacket: LSZH, riser, plenum or armoured, with colour and outer diameter limit.
- Quantity, and pulling grip at one or both ends.
- Marking: leg labels and cable print, plus test report format.
Use the quote request form, or email sales@radixfibrotech.com with a sketch. Radix builds to your drawing and bill of materials.
Installing and testing a 24-fibre trunk
The wide ferrule has two rows, so inspect both rows of end faces and clean with a tool sized for a 24-fibre ferrule. Keep the dust caps on until the connector reaches the panel, and keep to the minimum bend radius of the cable. Testing is done fibre by fibre, either with 24-fibre test leads or through a breakout to a duplex tester. Ask in the quote for the loss data you expect, since a per-fibre report makes later fault finding quicker.
Questions buyers ask
What is the difference between MPO-24 and MTP-24?
MPO is the generic connector type. MTP is a branded, enhanced version with a floating ferrule and tighter tolerances. The two mate with each other, so a drawing that says MPO-24 can usually be built with MTP-24 connectors.
Is one MPO-24 trunk better than two MPO-12 trunks?
It is better for density, pulls and fibre use when the hardware at both ends is 24-fibre. It is worse if the plant is mostly 12-fibre, because converting needs a harness, and one damaged connector affects 24 fibres instead of 12.
Can an MPO-24 trunk connect to MPO-12 equipment?
Not directly. Use a 24-fibre to 12-fibre cassette, or a harness with an MPO-24 on one end and two MPO-12 on the other. State the fibre mapping on the drawing.
Which MPO-24 polarity should I choose?
Follow the method used by the cassettes and cords in the channel. Type B is common for direct parallel links and Type A or C appear in cassette methods. If the channel is not yet designed, send what you have and we will help match the type to it.
Does MPO-24 work for OS2 single-mode?
Yes. Single-mode MPO-24 trunks use angled APC polish and carry duplex or parallel single-mode optics through cassettes. Both ends of every mated pair must be APC.
What length tolerance should I ask for?
Give the tolerance your route allows. Trunks cannot be shortened after termination, so most buyers add slack at each rack and state a small plus tolerance. Measure the route through the containment, not in a straight line.