The OTDR "dead zone" is a topic of much interest to users. Dead zone is classified in two ways. Firstly, an "Event Dead Zone" is related to a reflective discrete optical event. In this situation, the measured dead zone will depend on a combination of the pulse length (see table), and the size of the reflection. Secondly, an "Attenuation Dead Zone" is related to a non-reflective event. In this situation, the measured dead zone will depend on a combination of the pulse length (see table).
A long signal integration time effectively increases OTDR manufacturer sensitivity by averaging the receiver output. The sensitivity increases with the square root of the integration time. So if the integration time is increased by 16 times, the sensitivity increases by a factor of 4. This imposes a sensitivity practical limit, with integration times of seconds to a few minutes.
The dynamic range of an fusion splicer is usually specified as the attenuation level where the measured signal gets lost in the detection noise level, for a particular combination of pulse length and signal integration time. This number is easy to deduce by inspection of the output trace, and is useful for comparison, but is not very useful in practice, since at this point the measured values are random. So the practical measuring range is be a smaller, depending on required attenuation measurement resolution.