IP67 and IP68 fibre connectors explained

What the two ratings say

IP67 and IP68 come from IEC 60529, the standard that defines Ingress Protection codes for enclosures. The code has two digits. The first digit is protection against solid objects and dust, and the second is protection against water. In both IP67 and IP68 the first digit is 6, which means dust-tight: no dust gets in during the test. The difference is in the second digit.

IP67 means the product survives temporary immersion. The test in the standard puts the sample under water with its lowest point 1 m below the surface, for 30 minutes. IP68 means continuous immersion beyond those conditions, but the standard does not fix the depth or the time. The maker and the user agree them, and the maker states them. An IP68 label without a depth and a duration next to it is therefore incomplete, and a fibre connector page that says only "IP68" has not told you what you need to know.

A fibre connector or cable assembly with one of these ratings is a fibre connector inside a sealed housing, with seals at the coupling and at the cable entry. This guide is about reading those ratings correctly for fibre links, for example on the outdoor end of a camera link, a sensor head, or a cable run through a wet duct. For the physical-contact and expanded-beam choices that sit behind most sealed fibre connectors, see our expanded beam connectors guide.

IP67 and IP68 side by side

The last row catches buyers out. Some IP68 products are rated for 1.5 m for one hour. Some IP67 products are used to deeper conditions than the label suggests because the maker never ran the extra test. Compare the stated test, not the number.

What the rating covers on a connector

The rating belongs to a condition, and for a connector there are three conditions.

• Mated. Plug and receptacle (or plug and plug through a sealed coupler) are fully engaged and the coupling is locked. Most connector IP ratings apply here and only here.
• Unmated with a cap. A sealing cap is fitted on the plug or on the receptacle. Some series carry the full rating with a cap and some carry a lower one.
• Unmated and uncapped. The ferrule face is open to the air. No IP claim applies, and the end face is exposed to dirt and water.

A rating also covers the connector body and its seals, not the whole link. The cable gland, the cable jacket, a panel gasket and the device housing each have their own sealing. A sealed connector on a cable that wicks water along its inside is a sealed connector with a wet fibre route behind it. The same applies to a panel receptacle fitted to a cabinet without its mounting gasket.

Also note what the rating does not say: it says nothing about optical loss, about salt fog, about ultraviolet ageing, about chemicals, or about pressure cycling. Those need their own lines in the specification. For wet and corrosive offshore conditions, read our offshore and subsea fibre connector guide next.

Where water actually gets in

Most field failures on sealed fibre connectors are not a failed IP test. They are one of the routes below.

The cable construction is a large part of this. Armoured and outdoor cables have jackets chosen for crush, ultraviolet and water exposure. The cable choices are laid out in our guide to outdoor fibre patch cords, UV and water and in the wider armoured fibre optic cables section.

Coupling styles on sealed fibre connectors

The way a sealed connector locks decides how easy it is to seat the seals properly in the field, and how it behaves under vibration or with gloves.

Many industrial LC sealed series use a push-pull or bayonet outer shell around a standard LC duplex, so a standard LC patch cord can still be used on the inside of the cabinet. Our guide to the industrial LC connector style and the ODC connector describes two sealed families. The Radix product range also lists ODC 2 to 4 channel connectors and expanded beam connectors, which are drawn from the same sealed-connector world.

Optical side: wet ports and clean ports

An IP rating protects the inside of a mated connector, and it does not make the end face immune to what happens when it is opened. The risk comes at the moment of mating and unmating, in the rain, in mud, or under spray.

• Physical contact (PC) connectors need two clean ferrule faces. A grain of grit between ferrules scratches the glass and raises loss. A film of water is less harmful than grit, but it leaves residue when it dries. Clean with the method in IEC 61300-3-35 for inspection, and with a proper dry or wet-dry cleaner. Our end-face cleaning and inspection guide sets out the steps.
• Expanded beam connectors spread the light across a lens, so a speck of dirt blocks a small part of a much wider beam. The loss is more tolerant of dirt, and the lens can be wiped in the field. They are common where a connector is mated in the open in bad conditions, as in the comparison of expanded beam and physical contact.
• APC or UPC polish is a separate choice, set by the transmitter. Do not mix the two by accident at the sealed interface. See connector polish types.

In short, a sealed connector gives a dry, sealed chamber in the mated state. A clean end face is still your job at every mating.

Worked example 1: water pressure and the seal

This example uses assumed values to show why IP68 needs a stated depth. Take a sealed LC connector with a circular mating seal of 20 mm diameter, fitted in a pit that floods to 10 m of fresh water.

1. Water pressure at depth: P = ρ × g × h = 1000 kg/m³ × 9.81 m/s² × 10 m = 98,100 Pa, about 98 kPa above atmospheric. That is close to one extra atmosphere.
2. Seal area: A = π × (0.010 m)² = 3.14 × 10⁻⁴ m², or 314 mm².
3. Force on that area: F = P × A = 98,100 × 3.14 × 10⁻⁴ ≈ 31 N.

About 31 N, roughly the weight of a 3 kg object, presses water against the seal for as long as the pit stays flooded. At the IP67 test depth of 1 m the same calculation gives about 3 N. So the seal that works at 1 m for 30 minutes has been tested at a tenth of the load, and for a far shorter time. This is why a continuous-immersion application needs a rating with the actual depth and duration written out, and why the seal compound and the coupling lock matter as much as the number.

Salt water adds density (about 1,025 kg/m³ for seawater), and long exposure adds corrosion on metal shells. Ask for the shell material and plating if the connector will sit in salt water for months.

Worked example 2: loss budget through two sealed interfaces

A sealed connector is still a connector, and each mated pair spends part of your loss budget. This example uses assumed values; the real figures come from the data sheet of the series you select.

If the transceiver pair offers a 5 dB budget, the link has about 2.2 dB to spare on these assumptions. Swap in a sealed series that is rated at 1.0 dB per pair, and the total moves to 3.84 dB with only about 1.2 dB left. Replace the connector without checking and a link that was fine at install can sit near its limit. The method for working out budgets is in the fibre loss budget guide, and you can run numbers in the fibre loss budget calculator.

How to read a sealed-connector data sheet

Look for these items, in this order.

1. Rating with conditions. IP67 or IP68, mated or capped, and for IP68 the depth in metres and the time.
2. Test standard. IEC 60529 for the IP code. Some data sheets also list vibration, shock, salt mist or temperature cycling standards. If they do not, ask which tests were run.
3. Temperature range. Operating and storage. Seals harden in cold and soften in heat.
4. Mating cycles. The count for which the rating holds, because seals wear.
5. Cable range. The outside diameter the gland accepts, and the jacket types.
6. Optical limits. Typical and maximum insertion loss and return loss per mated pair, for the fibre type you will use.
7. Materials. Shell metal and plating, seal compound, and whether the plastics are rated for ultraviolet.
8. Panel details. Cut-out, thickness range, gasket and nut torque for receptacles.

If a data sheet leaves out the test conditions, ask for them before you design the link around the rating.

Buyer checklist before you order

1. Name the water condition in plain words: splash, jetting, rain, short flood, or continuous submersion. Add the depth and duration for submersion.
2. Name the fluid: fresh water, salt water, oil, wash-down chemicals.
3. State whether the connector will be mated all the time, or opened regularly. Frequent opening favours expanded beam or a lanyard-fitted cap.
4. Pick the fibre type and count, the optical connector inside the shell, and the polish.
5. Choose the cable: jacket, armour, water-blocking, and the minimum bend radius for the route. Read armoured vs unarmoured fibre cable if you have not decided.
6. Write the cable length from connector to connector, the receptacle or plug at each end, and the panel details.
7. Ask the supplier which tests back the stated IP rating, and for a drawing that shows the seal positions.
8. Plan the cleaning kit, spare seals and caps for the site, and decide who owns them.

Common mistakes and when IP67 or IP68 is not the right question

• Treating IP68 as better than IP67 without reading the depth. A 1 m, 1 hour IP68 and a 1 m, 30 minute IP67 are close to the same product.
• Forgetting the cable. A sealed connector on an open-ended, non-water-blocked cable can fill with water from the other end.
• Leaving receptacles uncapped. Rain on an open receptacle fouls the end face, and the IP rating then covers nothing.
• Specifying IP68 for a place that is only damp. It adds cost and a bulkier shell where a gasketed IP65 enclosure and ordinary connectors would do. IP65 and IP66 refer to jets of water and are a different test.
• Ignoring pressure and temperature cycles. Hot equipment that cools in a flooded pit draws water past imperfect seals. If your device heats and cools, say so in the enquiry.
• Using IP rating for corrosion. Salt, acid and solvents need material choices, not a code digit.

Sometimes the better answer is to keep the connection out of the wet. A patch panel inside a dry enclosure with armoured fibre running to it can be simpler to maintain than a sealed connector in a pit. Weigh both before committing.

Request a quote

Radix Fibrotech makes fibre optic assemblies to the customer's drawing in Pune. If you need a sealed or outdoor assembly, send the drawing or a clear description: the water condition with depth and duration, the connector series you have chosen, fibre type and count, cable construction, length and the drawing of the receptacle or panel. Send it through the request a quote page, by phone or by WhatsApp, and ask the quote to state the connector series, the rating with its test conditions, and the cable outside diameter, so that you can check them against your design.