FO Tech Tutorial

What is a fiber optic continuity tester?

Fiber continuity tester is also called fiber optic continuity checker. It is the simplest visual test of a fiber optic cable link.

To function properly, a fiber optic cable link must be "continuous", meaning no breakage, either within the fiber cable or in the fiber connectors, should exist. The simplest and least expensive way to check is to inject some visual light into one fiber end and check the light coming out from the other end.

To perform this task, two types of fiber testers are available: a fiber optic continuity tester or a laser visual fault locator.

Differences between a fiber continuity tester and a laser visual fault locator

The most important difference is their light source. A fiber continuity tester typically uses a red or green color high intensity LED while a laser visual fault locator uses red color semiconductor laser.

Visible lasers produce a more powerful light and can provide more information to the technician than a LED light. By coupling the fiber link to a visible laser, problems with connectors, breaks in the fiber near connectors or splices, and some bend radius violations can be located.

On the other hand, LED powered fiber continuity tester can only verify that light can travel through the fiber link and no more information is obtained. Fiber continuity tester simply yields a "no go" result. If the light isn't visible at the other end of the fiber link, then the fiber is unusable in its present state and requires further testing and repair.

Applications of a fiber continuity tester

Its best application is testing fiber on a reel before you pull it to make sure it hasn't been damaged during shipment. Look for visible signs of damage (like cracked or broken reels, kinks in the cable, etc.)

The other good application is to check fiber patch cables at patch panels. When connecting fiber cables at patch panels, use the fiber optic continuity tester to make sure each connection is the right two fibers!

And to make certain the proper fibers are connected to the transmitter and receiver, use the continuity tester in place of the transmitter and your eye instead of the receiver.

Understanding the features of a fiber continuity tester

1. Fiber mode compatibility 
   Some fiber continuity testers only support multimode fibers while the others support both single mode fibers and multimode fibers. So it's best to check the spec sheet from manufacturers to choose the type you need.
2. Fiber connectors supported 
   Most fiber continuity testers have adapters available for testing 2.5mm ferrule connectors such as ST, SC and FC, 1.25mm ferrule connectors such as LC, MU and special types such as SMA connectors.
3. Fiber distance 
   Most fiber continuity testers have enough light power to support 2km on multimode fibers.

The fiber optic continuity tester makes it easy to trace fiber optic cable runs.

Compared to laser and incandescent light source testers, this low-cost unit is safer to use and easier for the eye to locate.

This unit has bright red light source which is focused into the fiber optic cable. A multi-use coupler enables connection to ST, SC, FC, RSD and FSD without additional adapters or cables.

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