The RS820-2101 from Oelabs is a Optical Time Domain Reflectometer (OTDR) with Event Dead Zone 2 m, Attenuation Dead Zone 10 m, Optical Wavelength 1310 to 1550 nm, Dynamic Range 40 to 42 dB, Pulse Width 5 to 20480 ns. More details for RS820-2101 can be seen below.