  In this paper we consider light-cone fluctuations arising as a consequence of
the nontrivial topology of the locally flat cosmic string spacetime. By setting
the light-cone along the z-direction we are able to develop a full analysis to
calculate the renormalized graviton two-point function, as well as the mean
square fluctuation in the geodesic interval function and the time delay (or
advance) in the propagation of a light-pulse. We found that all these
expressions depend upon the parameter characterizing the conical topology of
the cosmic string spacetime and vanish in the absence of it. We also point out
that at large distances from the cosmic string the mean square fluctuation in
the geodesic interval function is extremely small while in the opposite limit
it logarithmically increases, improving the signal and thus, making possible
the detection of such quantity.
