How do you measure attenuation in fiber? You can check attenuation with an OTDR or a power meter. The OTDR sends a light pulse and shows where the loss is. Understanding it is crucial for anyone involved in data centers, telecommunications, or enterprise networking. This guide will demystify signal loss, explore its causes, and show you how. 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. Fiber optic testing of a newly installed system not only verifies that the system meets its design requirements, but also creates a performance baseline for all future testing and troubleshooting of t at system. Key tests include: Effective.