A first link and a second link are articulated relative to each other via a joint coupled between the first and second links. A shape-sensing optical fiber is used to sense a position of the first link and the second link relative to each other. The fiber passes through a channel having an opening defining a lip and extending from the first link toward the joint. The lip has a curved surface that begins substantially tangent to a wall of the channel, and during bending of the optical fiber, the optical fiber is positioned tangent to the curved surface of the lip.