A system for measuring a parameter within a well comprises a first and second apparatus. The first apparatus comprises a first reel of first wound optic fiber line (or fiber) able to be unwound from the first reel and at least a first sensor able to measure the parameter of the well, wherein information on the parameter can be transmitted through the first optic fiber. The second apparatus comprises a second reel of second wound optic fiber line able to be unwound from the second reel, an extremity of the second optic fiber being fixed to a reference point. A light transmitter or receiver device is linked to the reference point and able to generate or detect a light pulse through the second optic fiber line. Means to exchange the light pulse between first and second optic fiber line are also provided.