Intro: This instructable will show you how to make a simple fiber optic cable tester for any LC style fiber. I work in the medical industry for a company that builds integrated OR’s (Operating Rooms). We supply images to flat panel displays for minimally invasive surgery that includes laparoscopic cameras, MRI’s, and live C-arm images. All of these are delivered via DVI over fiber optic cables. We have to use fiber because of the distance between the image source and the space limitations of flat panel arms. Our DVI signal is carried over four fibers, one each for the red, green, blue and clock signals. We use LC connectors which are standard for IT infrastructure too. Our installers pull the fiber through conduit during the installation of the OR and need a quick way to verify that the fiber is good. Most testers I found were very expensive and measured db loss through the fiber. We just needed to know if it was intact or broken. I came up with this idea after looking at an LC fiber coupler and shoving a 5mm LED into it and finding out it was a perfect press fit! This tester works great for finding a broken fiber or if you have multiple fibers in an IT closet that no one has labeled (like that would ever happen…) identifying them.