By nature fiber cables are very strong. Not saying that I would use a fiber cable to tightrope across the Grand Canyon…but strong nonetheless.  Kevlar® is used as a strength member in fiber optics.  Since cables are most often pulled into place it is critical that they are strong.

With that being said…how can you know you have a strong and quality cable? Reliability is a starting point. Does your cable meet the industry standards for dB loss? Are you within your loss budgets? You must consider these factors when installing your cabling. You need to have reliable cables, that work every time!

What is the dB loss of the cable? Why does this make a difference? Loss occurs over cabling distance and at mating points where connections are made. Connections contribute to increased dB loss. You need cabling products with low optical loss rates to ensure your cabling environment is running at its peak. When comparing dB loss rates you want to look for “maximum” not “typical” loss rates. You want to know the maximum possible loss of each connection, so you don’t exceed your loss budgets.

So, I tell you that our maximum loss is 0.15 for LC connectors. Why should you believe me? Well…we send our test results with every Skinny-Trunk fiber cable.

This is a picture of an LC/LC Uniboot cable, just out of the bag.

Do you know the dB loss of your cables? Demand Documentation!

Are you familiar with common units of measurement used when referring to data center cabling? Understanding these terms will help you effectively communicate with your team or a vendor, particularly useful when ordering or installing new cable.

Common Units of Measurement for Data Center Cabling:

Meter – measures length; one meter equals 3.2808 feet

Kilometer – measures very long distances; one kilometer equals 1000 meters, 3,281 feet or 0.62 miles

Micrometer (µm) or micron – measures very short lengths; one micrometer equals 1 millionth of a meter. It is used to express the diameter of fibers. For example, the diameter of the core of an OM3 standard fiber cable is 50 µm or 50 microns, and the diameter of the cladding is 125 microns. This is the most common term in the measurement of fiber. See diagram below for example.

Nanometer (nm) – measures extremely short lengths; one nanometer equals 1 billionth of a meter. This measurement is used when talking about the wavelength of light. The period at the end of this sentence is 1,000,000 nanometers wide.

Decibel, or dB, is the unit for measuring the relative differences in the strength of light signals. It is a common measurement used to determine loss or gain in a system.

Today we’ll look at the construction of fiber optic cables.

An optical cable contains one or more fibers.

The core, cladding, Kevlar®, ferrule, and polishing are all involved in the construction of a fiber optic cable.

The core is the center part of the fiber cable through which light is transmitted; it is made up of a continuous strand of glass.

The fiber consists of a core surrounded by a cladding layer. The cladding surrounds and reflects light back into the core.  The diameter of the cladding is usually 125 microns.

Kevlar® is the registered trademark for the strong synthetic fiber or “yellow hair” used as a protective outer sheath for fiber optic cables. Its strength protects the cable from damage and kinking.

The ferrule is the protruding portion of a fiber connector. It is the ceramic, plastic or stainless steel part of a fiber-optic connector that holds the end of the fiber and precisely aligns it.

The fiber is inserted into the ferrule and cemented with an epoxy or adhesive. This gives it long-term mechanical strength and prevents contamination.

The ferrule is the most important and costly part of a fiber connector. If its length, hole centering, and inside and outside diameters are not exact, a poor connection will result.

The fiber at the end of the ferrule is then polished to create a flat even surface and to allow two cables to be mated to transfer a signal. Higher grades of polish give less insertion loss and lower back reflection.

More on insertion loss and back reflection to come!

There are a myriad of terms you may come across when talking about fiber jumpers or fiber cabling. Knowing the definition of singlemode and multimode fiber cables and how they apply to your network cabling will help you get the most out of your infrastructure.

Let’s start with the basic question:

What is the difference between Multimode and Singlemode Fiber Cables?

A standard multimode fiber cable has a core of either 50 or 62.5 microns and a cladding of 125. The light source used for multimode fiber is LED. The light goes through the core using several paths.

Watch this Cable Talk video to learn more.

The data in a singlemode fiber is transmitted in straight line down the center of the core. The light source is transmitted by laser. This increases the speed and distance that the data can be transmitted. The core of a Singlemode fiber cable is 9 microns and the cladding is 125.

The diagram below shows the difference of how light is transmitted between multimode and singlemode fiber cables:

Now that we’ve covered the difference between multimode and singlemode fiber cables, next week I’ll post a little bit about the construction of a fiber cable.

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.