This Applications Engineering Note (AEN 135) explains and recommends standard measurement methods for characterizing optical fiber system performance. 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. As the components like fiber, connectors, splices, LED or laser sources, detectors and receivers are being developed, testing confirms their performance specifications and helps. ANSI/TIA‑568. 3‑E “Optical Fiber Cabling and Components Standard” was developed by the TIA TR‑42. In addition, the fiber does not conduct electricity and is pract lighter and smaller than copper cable. They describe how to set a '0 dB' reference, control mode power distribution, and use proper wavelengths.