The ornamental design for an opticaltime-domain reflectometer, as shown and described.
FIG. 1 is a front view of an optical time-domain reflectometer, showing my new design;
FIG. 2 is a rear view thereof;
FIG. 3 is a left view thereof;
FIG. 4 is a right view thereof;
FIG. 5 is a top view thereof;
FIG. 6 is a bottom view thereof; and,
FIG. 7 is a perspective view thereof.
The broken lines present in the drawings are included for the purpose of illustrating portions of the article which form no part of the claimed design.