Recently, I covered some ways for the fiber contractor and installer to become more productive, including components such as microcables and high fiber count cables, and installation practices such as microtrenching, blowing cables and ribbon splicing. This month, I’m going to discuss testing.
Visual fault locator
I started FOTEC, one of the first fiber optic test equipment companies, back in 1980. In the 20 years I ran it, we saw some interesting developments in fiber optic testing and created a few of them ourselves. My favorite was the visual fault locator (VFL), the red laser that helps trace fibers and find faults such as breaks or bends in fiber.
One of my customers used helium-neon (HeNe) red lasers in its R&D lab to trace fibers. I thought it was a great idea and would be useful in the field. The problem was, his laser was about a foot in diameter, 4 feet long and weighed over 100 pounds, so it was hardly portable.
After some searching, I found a small HeNe laser about 2 inches in diameter and a foot long, which had enough power to trace fibers. We managed to stuff the laser, its high-voltage power supply, a motorcycle battery and some optics into a small suitcase—and the portable VFL was born.
The first field trial was with a telco tech having trouble finding a fiber break in a splice closure. He had spliced it twice, but each time the loss was much too high. When we connected our VFL to the fiber, it showed a break in the fiber about 4 inches from the splice, where the fiber had been broken by closing the cover of the splice tray on the fiber. Problem solved. The telco was so impressed it bought hundreds of them, considering the $3,200 price a bargain because of its value in troubleshooting.
Today, you can buy a VFL the size of a laser pointer that uses a laser diode developed for CD and DVD players for less than $100. It’s considered an essential tool for fiber optic installation and tests. Every fiber tech should have one in their tool kit.
OTDRs to the rescue
Around the time we introduced the VFL, a portable optical time domain reflectometer (OTDR) was a large piece of equipment weighing about 40 pounds with a price tag of $15,000–$50,000. It was not affordable, and it took a week of training to understand how to use it. Its use was also limited because the design was optimized for long fiber optic links, not short cables used in buildings or campuses.
With the price and the need for an expert tech to use it, OTDRs were limited primarily to specialized techs troubleshooting outside plant cables.
Technology has done its thing, of course, so OTDRs today are about one-tenth the size and price of those early monsters. They look like a thick tablet computer with touchscreen controls. They can be used on very long cables and some also work on very short ones.
Should I upgrade?
Many contractors already own an OTDR, but if it’s more than about 5 years old, it’s probably time to upgrade. The big difference in the latest OTDRs is not the hardware—it’s the software. New operating modes using artificial intelligence (A.I.) can automatically make tests that are faster and more accurate than most techs.
Most OTDRs have had an “auto test” function for many years, but the early ones I’ve used were not very good. They often chose a test setup in the middle of the test range that was inappropriate for most conditions. It was always better to do the test parameter setup yourself.
Using A.I. and much faster processing speeds, modern OTDRs make several preliminary tests on a fiber to determine basic parameters such as length and loss, which allows optimizing the test setup for that particular fiber and every other one in the same cable. If you test multiple fibers in a single cable, which is the most common way OTDRs are used during installation tests, the known setup and faster processing speeds can reduce testing and documentation time considerably. That enhances productivity and can quickly pay back the cost of the instrument itself.
While A.I. can make the OTDR smarter than the average operator (as one manufacturer described its device), the user still needs to know how to recognize OTDR events such as gainers and ghosts and do some troubleshooting. That still takes some training and experience.