Notes From an Autodidact: What I'm Learning About Fiber Optics Now

0719 Fiber Optics Image Credit: iStock / MediaProduction
Image Credit: iStock / MediaProduction

Last month, I wrote about how a newcomer could get started in fiber optics and learn the basics. What if you are already experienced in fiber optics and want to keep up with new technology? I can empathize with you. I have been in this industry a long time and have seen many changes. I learn new things often. To continue writing about fiber optics and creating technical references for others, I have to work hard to keep up.

Over the last few years, I have learned about wireless technology, the electrical grid, autonomous vehicles, smart cities and other subjects that involve fiber optic infrastructure. I’ve also learned about new fiber optic technology and gotten my hands on equipment and supplies to learn and understand new fiber tech such as fusion splice-on connectors and understand how to effectively use video fiber optic connection microscopes and new connector cleaning processes. I have visited companies and work sites to see many interesting applications and processes, including new techniques for fiber-to-the-home (FTTH) installation and robots that can install fiber optic cables in sewers.

Thankfully, I have many industry contacts who introduce me to their products and teach me how to use them.

So, what am I trying to learn now?

At a fiber optic conference three years ago, an acquaintance who works for a cable company showed me a new type of fiber optic cable. It was about 1 inch in diameter and filled with many fibers. I guessed how many fibers were in the cable, but I was far too low. It had 1,728 fibers, the equivalent of a dozen 144 fiber cables, but in a bundle only about twice the diameter of just one 144-fiber cable. Since then, cables with two and four times that many fibers—3,456 and 6,912—have been introduced.

I was curious why one would want a cable with so many fibers. I learned there were two specific uses: FTTH networks in dense urban areas and data centers. FTTH networks can serve thousands of users in relatively small areas, such as urban centers. Data centers, especially the hyperscale data centers run by companies such as Google, Facebook and Amazon, can have hundreds of thousands of connections. Stuffing all those fibers into one cable simplifies installation and often saves conduit or overhead cable tray space.

Designing and manufacturing these cables is not simple. The fibers themselves usually have a smaller buffer coating—200 instead of 250 microns—and while fibers are organized in ribbons to speed up splicing, they are often using flexible ribbons with the fibers connected in spots so they can be flexed easily and even rolled up to maximize the number of fibers in a cable instead of being glued into hard ribbons.

This sounds like a great idea until you begin thinking about how you handle one cable with so many fibers. A cable with 1,728 fibers organized into ribbons has 144 12-fiber ribbons. That means you have to make 144 ribbon splices with an expensive mass fusion-splicing machine. You will be working in a very crowded splice closure or cabinet.

You have to figure out how to make the right connections. If you are splicing one big cable to several smaller ones, organizing the fiber ribbons, even identifying them, is going to take patience. They are color-coded in each ribbon; each ribbon has a new type of identifying marking a bit like Morse code, and colored binding tape bundles the ribbon.

If the cable uses the flexible ribbons, we are told it will take more time to splice than regular hard ribbons, maybe twice as long to ensure the fibers stay in the proper alignment. If you are splicing a cable with 200-micron buffer fibers to regular 250-micron fibers, you need special fixturing and procedures, something I hear not all splicing machine manufacturers have available yet.

You are going to especially need a lot of patience. Splicing 1,728 fibers one at a time would take about 120 hours of work, three or four weeks full time. Regular ribbons might take only about 20 hours, probably three days, but the flexible ribbons may need more time.

So my project right now is to learn how this is done and do some of the work myself. Only then will I have the answers to the questions raised above so I can share them with you.

About the Author

Jim Hayes

Fiber Optics Columnist and Contributing Editor

Jim Hayes is a VDV writer and trainer and the president of The Fiber Optic Association. Find him at www.JimHayes.com.

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