What's OTDR launch cable box / OTDR Dead Zone Eliminator used for? An OTDR (Optical Time Domain Reflectometer) launch cable box, also known as an OTDR Dead Zone Eliminator, is used in fiber optic testing and troubleshooting. In fiber optic testing, the OTDR is used to measure the characteristics of an optical fiber, such as loss, length, and quality. However, OTDRs have a limitation called the "de...