The three standard methods for testing fiber optic cabling are a visible light source, power meter and light source, and optical time domain reflectometer (OTDR). While there are many different fiber optic cable tests, the most common version is an insertion loss test, also known as an attenuation, jumper, or connectivity test. Why Does Fiber Optic Testing Matter? Fiber internet offers better speed and performance than copper options, but the cables are very sensitive to bending, contamination, and physical. While specialized testers are commonly used for this purpose, there are ways to test fiber optic cables without a tester. Version 1: Visual. Over the years, I've used a few main tests to check fiber optic cables. Each one tells you something different. I grab a flashlight and a magnifying glass and.