A tool may comprise an optical fiber including a proximal end, a distal end, an intermediate portion between the proximal end and the distal end, and an adjustable bend between the proximal end and the intermediate portion. Motion of the intermediate portion may be constrained to translational motion substantially along an axis defined by the optical fiber at the intermediate portion. The tool may also comprise a cylindrical passage through which the intermediate portion of the optical fiber extends and a housing enclosing the adjustable bend and the cylindrical passage. The cylindrical passage may extend through a cylindrical member that includes an outer wall surrounding the cylindrical passage. The housing encloses the outer wall of the cylindrical member.