Several years ago, when the Fiber Optic Association (FOA) began online certification testing using a service called ClassMarker, we began getting better data on the results of the exams. That allowed us to evaluate our testing to see what questions were most often missed and update the tests and training curriculum to better cover those topics.

But some of the results puzzled us. We could understand techs missing questions on complicated topics such as testing, but why did 25% of the test-takers miss a simple question such as, “What do you strip when you strip fiber for splicing or termination?” Instead of answering “the buffer coating,” the correct answer, 25% of the test-takers answered that you strip the cladding. Even some instructors on their instructor certification exams answered that question incorrectly.

Where did they get that idea? I decided to ask some of them, and they thought the fiber’s core and cladding were separate and the cladding could be stripped. Why did they think the core and cladding were separate if the optical fiber was a 125-micron (0.125 mm or 0.005 inch) glass fiber the size of a human hair? Quite a few mentioned that diagrams of fiber always show the core sticking out of the cladding and those two sticking out of the plastic buffer coating.

We started looking on the web, and here is a sampling of what we found:

Almost every drawing of an optical fiber on the internet looks like this, with the core sticking out of the cladding. Then it made sense that people looking at drawings like this would think the core and cladding of the fiber were separate and the cladding could be stripped off, leaving only the core.

It turns out, only the FOA consistently shows fiber with the core and cladding as one solid piece of glass, such as this:

Our dilemma was how to convince people that when you strip a fiber, all you remove is the plastic coating, called the buffer or primary buffer coating, from the solid glass fiber. So, we have tried a couple of different ways.

Techs often inspect connectors with a microscope to check cleanliness, and this is what they see (actual photo with annotation):

The connector ferrule is molded ceramic with a 125-micron hole, which is the size of the outside diameter of the cladding of the fiber. If a finished connector shows the cladding, it certainly was not stripped off when preparing the fiber for termination.

Another way to see this is in the display of a fusion splicer like this:

The display on a fusion splicer clearly shows the fiber core and cladding as the fibers are being aligned and spliced. The cladding has certainly not been stripped.

While we have proof that you don’t strip the cladding on optical fiber to prepare it for termination or splicing, how do we overcome the hundreds or thousands of images online that indicate otherwise? Maybe our readers can help. If you see an image like the examples above on a company website, just tell them it’s inaccurate and confuses everybody.