Fiber Optic Adapters in the Data Center

Fiber optic couplers (also referred to as “adapters”) are an often overlooked part of the fiber optic cabling infrastructure in the data center. To the untrained eye, they all seem to look the same – but there are some very critical differences in adapter quality that can drastically affect data center performance.

These adapters play the critical role of aligning the individual fibers in a cable to the fibers in another cable. If fibers are not properly aligned, then loss is incurred at that mating point. If too much loss is incurred, downtime is a distinct possibility.

What should a data center technician look for in quality adapters?

Data center technicians should look at the materials used to manufacture couplers.

Some manufacturers may opt to use a metal, sometimes referred to as Phosphor Bronze (PB, Phos-Bronze and/or Phoz-Bronze). This alloy is noted for its strength and rigidity for large boat propellers, springs and bolts. However, ceramic materials are ideal for manufacturing couplers. Ceramics are non metallic, inorganic and crystalline in structure. The crystalline structure of ceramic allows for a very rigid surface that will not deform.

Why does this matter? As we discussed, alignment is critical. A softer metal like Phosphor Bronze will deform over time, especially with repeated plug-ins. Ceramic will hold its original shape for much longer. This makes a coupler that has ceramic alignment sleeves far superior to Phosphor Bronze.

Insertion loss is the amount of light lost (measured in dB) from the origination of a signal to the reception of that same signal.

What happens if insertion loss is too high?

Too high of an insertion loss will lead to what is know as “channel errors” that can cause equipment to go down and possibly cause data center downtime.

Why is knowing insertion loss important?

It is important to know the insertion loss of the products you are using or considering purchasing. Be sure to ask for insertion loss specifications before purchasing cables. Pay attention to words like “typical” versus “maximum” insertion loss.

Some manufacturers will supply statistics in typical readings or averages. This should not be considered a number to use – you may end up getting cables that are well above the average.

Instead, you should look for the “maximum” insertion loss of a product. This allows you to know the highest possible loss amounts that you will incur.

Have you ever lain awake at night pondering the difference between rails with M6 and rails with 10/32 tapped holes? What does a tapped hole even mean? And what is a cage nut?

I’ve looked to Great Lakes Case and Cabinet for the answers. Great Lakes has standardized on the M6 for its rails (although 10/32 tapped holes rails are available upon request). The M6 has a 3/8” square opening/hole that accepts metric 6mm hardware, Rapid Rail mounting, and cage nuts.

The 10/32 tapped holes accept screws that have 32 threads per inch. Basically, a tapped hole is a hole that contains internal threads. This is the original standard for 19” rack mount holes. It is not as common now, due to the possibility of the threads being stripped or damaged, or a bolt breaking off, thus making the mounting hole unusable.

Nowadays most server racks have square holes. Rapid Rails can automatically latch into the square holes, allowing boltless mounting and making easy installation and removal of hardware. Older equipment meant for racks with tapped holes can still be used if you use a cage nut. A cage nut is a square nut that has threaded holes wrapped in a cage like enclosure. Cage nuts can be snapped into the square hole and be converted to a threaded hole.

So there you have it: the difference between M6 and 10/32 tapped holes. Now you can sleep.

You’ve heard of “dust caps” used to protect the end-faces of network cabling (see the image to the left). But did you know that it’s actually a misnomer?

In fact, dust caps, or protective end caps, do very little to protect the fiber optic end-face from dust contamination.

Why? Because dust particles are very small – they will already be on the inside of the cap when the cap inserted on the cable at the factory. While most manufacturers do their best to maintain clean end-faces during the manufacturing process, there is no guarantee that there is not dust inside the cap when it goes on. When the cap has been put on, that dust can very easily migrate to the cable end-face and cause major issues.

End-face contamination can bring an entire network down. A word to the wise: inspect, clean and inspect again to make sure your cable end-faces aren’t contaminated. Learn more about fiber optic cable end-face cleaning.

Okay, it might be an exaggeration to say our cables are bullet-proof, but did you know that our fiber trunks contain Kevlar®? Check out the picture to the left – you can see the yellow fibers within a deconstructed cable.

Yes, the same material that can be found in an officer’s body armor to protect his or her life can be found in fiber trunk cables. Kevlar® is an exceptionally strong material that looks like horse hair or a tightly spun web. The weave of the Kevlar® is made so strong it’s literally unbreakable by the human hand.

Since it’s so flexible, the Kevlar® material makes for a perfect guardian around delicate fibers, yet making the trunk itself very durable. Also, the Kevlar® keeps everything on the inside in its place, but allows for flexibility when routing cables around bends inside of a data center. The fibers inside of the jacket can take on several stresses by outside forces, so when Kevlar® is utilized, it will ensure peak performance of the fiber trunk itself.