Conducting a visual inspection test involves using a fiber scope or microscope to examine the endfaces of connectors for dirt, scratches, or cracks. Always inspect before you connect. Cable contamination can also damage your equipment, turning a preventive measure into an expensive. Fiber optic cable is a type of cabling that contains one or more optical fibers for transmitting data at high speeds and/or over long distances using light. These fibers are most commonly made of glass and are very thin, typically less than a tenth of the width of a human hair. Before diving into the testing process, it's crucial to understand why testing is necessary. Cable contamination can also.