AirMT Junior Connector

What the AirMT Junior connector is

The AirMT Junior connector is the compact, behind-the-wall member of the AirMT family. The manufacturer lists it as "behind-the-wall AirMT; 12/24F". That wording places it inside the enclosure, where it connects the fibres of the rear cable to the back of a panel or cassette adapter, and not on the patch cords that people unplug every day.

AirMT is the manufacturer’s non-contact MT ferrule technology, licensed from Sumitomo Electric Industries, with the trademark jointly owned by the manufacturer and Sumitomo. The ferrules in a mated pair do not touch. The manufacturer says insertion loss and return loss stay stable after many matings with minimal cleaning. You will find this connector under the AirMT connectors hub. Radix can supply it from loose or built into assemblies to your drawing.

How non-contact MT mating works

A conventional MPO presses two polished ferrules together under spring force, and the fibres are in physical contact. An AirMT pair is aligned by the body and pins, but the end faces stay a small, controlled distance apart. With no contact there is no scratching of the glass, and a small piece of dust is less likely to be trapped between two hard surfaces.

The trade is optical. A small gap needs an angled polish to control back reflection, and the manufacturer gives its AirMT figures for single-mode APC. The idea of angled polish is explained in the UPC vs APC guide. The gap also means the connector is springless, which the manufacturer lists, so mating force is lower than a typical MPO.

Facts

Typical loss is not a guarantee for a particular assembly. Use the maximum value when you build a link budget, and read insertion loss vs return loss for how the two figures behave.

Where a behind-the-wall connector sits

Inside a high-density cabinet there are two kinds of connection. The ones in front are touched all the time by technicians. The ones behind the panel are set once, and then left. For the rear side, what matters is small size, stable loss and low risk in installation. That is the niche for this part.

Compare the two options in the family: the AirMT connector has a push-pull tab for the front-of-panel side, and the Junior is meant for the inside. The stackable PCB version is the MBMC stackable connector. The adapter that holds the front connectors is the dust shutter adapter.

Compatibility with MPO and with other AirMT parts

AirMT is a different optical system from a standard MPO. Do not assume that an AirMT connector mates with an MPO. Ask in the quote which adapter and which mating partners are needed, and expect to buy AirMT parts as a set. Where a link must go from AirMT to MPO, use a cord with AirMT on one end and MPO on the other, so each end meets its own kind. Fibre count and polarity still need planning; see the MPO polarity guide for the logic that carries over.

Cleaning and inspection

• Minimal cleaning does not mean no cleaning. Inspect the end faces before the first mate.
• Use the cleaning tools and method named in the data sheet for AirMT.
• Keep dust caps on until the moment of mating.
• Test after install and keep the record; see end face cleaning and inspection.

Worked example: a cassette with 24 fibres behind the wall

Assume a patching area has cassettes where a 24-fibre trunk lands at the rear, and 12-fibre ports face the front. Assumed values: 10 cassettes, 2 trunks per cassette.

1. Rear connectors. 10 cassettes with 2 trunks each makes 20 rear connectors, plus 2 spares.
2. Loss budget. Using the manufacturer’s maximum of 0.50 dB per mated pair on the rear joint, 20 joints each take up to 0.50 dB.
3. Cleaning. The rear connectors are mated once and left, so the inspection routine happens at install.
4. Order. 20 AirMT Junior connectors built into trunks, fibre count 24, single-mode APC, with a pulling sleeve if the trunk is drawn through a duct.

The numbers are for method. Replace them with your cabinet counts.

Planning the rear side of a cabinet

Behind a panel the space is tight and access is poor. Sketch the rear of the cabinet before you choose the connector: how the trunk enters, where it is clamped, where the connector sits, and how much slack is stored. A behind-the-wall connector reduces the volume taken up, but the cable still needs its bend radius, which the bend radius calculator can check.

Strain relief matters more than usual. A connector that sits at the back of a cassette sees the weight of the trunk on every service visit. Clamp the trunk to the frame a short distance before the connector so that the pull never reaches it.

Why durability and cleaning affect cost over time

A rear connector should rarely be moved, so a high mating count is of little use there. What matters more is that the connector does not need to be opened and cleaned. The manufacturer’s statement that loss stays stable with minimal cleaning is the real saving. Every visit to a rear connector costs a technician's time, a risk of dislodging a neighbour, and a risk of contamination.

When you compare the Junior connector with a conventional MPO for the rear side, include the labour of future inspection in the comparison, and not just the price of the part.

Transport and installation of pre-terminated trunks

A trunk with factory-fitted connectors needs a protective sleeve for pulling, and a pulling grip that loads the cable and not the connector. Ask for the sleeve outside diameter, and compare it with the duct. Keep dust caps on until the connector is at its destination, and make the first mating the day the connector is inspected.

Questions to put to the data sheet

• What is the exact body size and the clearance needed around it?
• Which adapters and cassettes is it approved to mate with?
• What is the keying, and how is the fibre order marked?
• What pulling force can the connector body take during installation?
• What cleaning method and tools does the manufacturer name for AirMT?
• Is the 12 fibre or the 24 fibre version needed for your cassette?

Put the answers in the project file with the order. They will be asked for again when the cabinet is audited, and finding them takes less time at the start.

What to send Radix to quote it

• Quantity of connectors or assemblies, plus spares.
• Fibre count, 12 or 24, and single-mode APC confirmation.
• Cable type and outside diameter, and assembly length if built into a cord or trunk.
• Boot colour and any marking.
• Cassette or panel model that the connector will land in.
• Mating partners: AirMT, or a mixed AirMT to MPO cord.
• Any vibration or temperature conditions at the site.

Reviewing a quote for AirMT Junior parts

When the quote arrives, check that it states fibre count, fibre type and polish, cable outside diameter, length, boot colour and the mating partner for every line. Ask which data sheet applies and whether loss values are typical or maximum. If anything is left to assumption, say so in writing before you place the order, since a rear-of-cabinet connector is costly to change once the trunk is pulled.

Also confirm how the assemblies will be labelled at each end, because rear connectors are hard to identify later.

When this is not the right part

• The connector is on a patch cord that is plugged and unplugged all day. The push-pull AirMT suits that side.
• The other end is a standard MPO and you need to mate directly. Plan a mixed cord instead.
• You need a PCB-mounted part. See the MBMC stackable connector.
• Multimode is the target. The figures the manufacturer gives are for single-mode APC.
• The link is outdoors. Look at the IP series.

Browse the these connectors section, or send your layout with a quote request.