Fiber optic adapter reflection strength affects attenuation dead zone

Attenuation dead zone is a specification indicators, refers the desired distance of the OTDR signal fiber backscatter intensity returns to below 0.5 dB difference after the reflection point.The receiver electronic devices and the photodetector both lead to the recovery area after reflection.
OTDR Specifications from each manufacturers, attenuation dead zone performance usually masked by excellent reflection conditions(-45 dB, -55 DB or -65 dB, depending on the OTDR the manufacturer).As we all known, the reflective intensity level will directly affect OTDR dead zone, with the rise of the reflection intensity, the blind spot will become longer. This is because the reflection intensity of the fiber optic adapter may be many times magnitude higher than backscatter signal strength measured by OTDR.
Good UPC fiber optical adaptor reflection intensity is -55 dB, the produced signal peak may 100 times higher than 5 ns pulse red fiber backscatter (approximately -75 dB at 1550 nm. While bad UPC fiber optical adaptor (reflection strength is typically -45 to -25 dB) peak signal backscatter may be 1000 to
100,000 times than the fiber. Due to the ratio range of the reflection intensity vs backscatter is so large, it is evident that the attenuation blind height depend on the fiber optical adaptor reflection intensity.

Figure1. reflection intensity of -45 dB and -25 dB typical OTDR curve: reflection strength of -25 dB attenuation dead zone emergence of significant growth.