In the change from glass to air, energy reflected back to the OTDR is of such intensity that the light pulse is reflected off of the connector at the OTDR and is again returned a second time. As the OTDR converts the travel time of the light pulse into distance, the reflective event is painted on the screen a second time—thus, a ghost. - Charles Lohrman
I have been in the field of fiber optics since early 1990s. I gained fiber optics skills and knowledge via my working experience as end-user, main contractor and sub-contractor and finally as an optical fiber enterpreneur.