Patent ID: 8305228

Claim:
An apparatus for determining the location and/or displacement of a dynamic object in a wellbore, comprising: a reel of wound optic fiber line fixed to the dynamic object, the reel having a radius between 20 mm and 50 mm; and a light transmitter/receiver device able to generate a signal through the optic fiber line and to measure a change of said signal as the dynamic object moves through the wellbore, wherein the device is an apparatus in the family of optical time domain reflectometers; wherein the optic fiber line is fixed on a first position to a reference point linked to the light transmitter/receiver device and the optic fiber line is unwound from the reel on a second position; wherein the light transmitter/receiver device operates at two light-pulse wavelengths, and is able to measure the change of said signal when occurring at the second position.