A robotic medical instrument system, comprising: a controller configured to control actuation of at least one servo motor; a plurality of elongate instruments , each elongate instrument configured to move in response to actuation of the at least one servo motor and comprising: a Bragg sensor optical fiber having a distal portion coupled to a distal portion of the respective elongate instrument ; and a detector operatively coupled to proximal ends of the Bragg sensor optical fibers of the elongate instruments and configured to detect respective light signals of the Bragg sensor optical fibers , the system being characterized by an imaging device such as a fluoroscopic system to image each elongate instrument or a portion thereof in two dimensions of the coordinate system of the imaging device; wherein the controller is configured to determine the three-dimensional location of each elongate instrument based on signals received from the respective Bragg sensor optical fibers in the coordinate system of the Bragg sensor optical fibers and the location of each elongate instrument in the two dimensions of the coordinate system of imaging device, and to register the respective locations of each of the elongate instruments in a single reference coordinate system, the respective Bragg sensor optical fibers providing the third dimensional location of the distal portion of the respective elongate instrument in the coordinate system of the imaging device, said third dimensional location being the depth dimension. a controller configured to control actuation of at least one servo motor; a plurality of elongate instruments , each elongate instrument configured to move in response to actuation of the at least one servo motor and comprising: a Bragg sensor optical fiber having a distal portion coupled to a distal portion of the respective elongate instrument ; and a detector operatively coupled to proximal ends of the Bragg sensor optical fibers of the elongate instruments and configured to detect respective light signals of the Bragg sensor optical fibers , a Bragg sensor optical fiber having a distal portion coupled to a distal portion of the respective elongate instrument ; and a detector operatively coupled to proximal ends of the Bragg sensor optical fibers of the elongate instruments and configured to detect respective light signals of the Bragg sensor optical fibers , the system being characterized by an imaging device such as a fluoroscopic system to image each elongate instrument or a portion thereof in two dimensions of the coordinate system of the imaging device; wherein the controller is configured to determine the three-dimensional location of each elongate instrument based on signals received from the respective Bragg sensor optical fibers in the coordinate system of the Bragg sensor optical fibers and the location of each elongate instrument in the two dimensions of the coordinate system of imaging device, and to register the respective locations of each of the elongate instruments in a single reference coordinate system, the respective Bragg sensor optical fibers providing the third dimensional location of the distal portion of the respective elongate instrument in the coordinate system of the imaging device, said third dimensional location being the depth dimension. <EOS>