A fiber optic tracking system for tracking a substantially rigid object, the system comprising: a light source adapted to provide optical signals; an optical fiber having a sensing component configured to receive and modify the optical signals from the light source, wherein the modified optical signals correspond to a strain in the optical fiber, the optical fiber being configured to attach to the substantially rigid object, the sensing component having sensing points along the optical fiber, wherein the sensing component includes at least a first set of optical elements at a first sensing point and a second set of optical elements at a second sensing point, wherein the sensing points are separated at a distance along the optical fiber and the optical fiber is in a fixed geometry between the first and second sensing points and wherein each set of optical elements comprises a plurality of optical elements; a detection unit connected to the optical fiber to receive the modified optical signals from the sensing component; and a computer-based calculation unit connected to the detection unit and configured to determine a pose of the substantially rigid object in six degrees of freedom based on the received modified optical signals; Characterised In That; when the optical fiber is attached to the substantially rigid object, the first and second sensing points are fixed relative to the substantially rigid object and the fiber orientation for the at least two sensing points is non-collinear; the computer-based calculation unit is further configured to determine a local fiber bend at the first and second sensing points based on a frequency distribution of the modified optical signals, to determine the position coordinates of the first and second sensing points and the fiber orientation at the at least two sensing points, and to determine the pose of the substantially rigid object based on the position coordinates of the first and second sensing points and the fiber orientation at the at least two sensing points, and the optical fiber is constrained such that a pose of the first set of optical elements is different from a pose of the second set of optical elements. a light source adapted to provide optical signals; an optical fiber having a sensing component configured to receive and modify the optical signals from the light source, wherein the modified optical signals correspond to a strain in the optical fiber, the optical fiber being configured to attach to the substantially rigid object, the sensing component having sensing points along the optical fiber, wherein the sensing component includes at least a first set of optical elements at a first sensing point and a second set of optical elements at a second sensing point, wherein the sensing points are separated at a distance along the optical fiber and the optical fiber is in a fixed geometry between the first and second sensing points and wherein each set of optical elements comprises a plurality of optical elements; a detection unit connected to the optical fiber to receive the modified optical signals from the sensing component; and a computer-based calculation unit connected to the detection unit and configured to determine a pose of the substantially rigid object in six degrees of freedom based on the received modified optical signals; Characterised In That; when the optical fiber is attached to the substantially rigid object, the first and second sensing points are fixed relative to the substantially rigid object and the fiber orientation for the at least two sensing points is non-collinear; the computer-based calculation unit is further configured to determine a local fiber bend at the first and second sensing points based on a frequency distribution of the modified optical signals, to determine the position coordinates of the first and second sensing points and the fiber orientation at the at least two sensing points, and to determine the pose of the substantially rigid object based on the position coordinates of the first and second sensing points and the fiber orientation at the at least two sensing points, and the optical fiber is constrained such that a pose of the first set of optical elements is different from a pose of the second set of optical elements. when the optical fiber is attached to the substantially rigid object, the first and second sensing points are fixed relative to the substantially rigid object and the fiber orientation for the at least two sensing points is non-collinear; the computer-based calculation unit is further configured to determine a local fiber bend at the first and second sensing points based on a frequency distribution of the modified optical signals, to determine the position coordinates of the first and second sensing points and the fiber orientation at the at least two sensing points, and to determine the pose of the substantially rigid object based on the position coordinates of the first and second sensing points and the fiber orientation at the at least two sensing points, and the optical fiber is constrained such that a pose of the first set of optical elements is different from a pose of the second set of optical elements.