A shaft (20), comprising: an elongated outer sheath (28)； at least one rotatable drive shaft (30,32) disposed within the outer sheath (28)； two tabs (20801, 20802) extend from a quadrature ring (2080) mounted on each of the at least one rotatable shaft, the two tabs extending radially from and configured to rotate with the at least one rotatable drive shaft； and two light sources (217) mounted within the outer sheath at a distal end of the shaft arranged approximately 90 degrees from each other relative to an axis of the at least one rotatable drive shaft wherein, upon rotation of the at least one rotatable drive shaft, the two tabs alternately block and allow light from each of the light sources； wherein, based on receipt by a remote power console (12) of the light emitted from the respective light sources, the angular position within one-quarter revolution increments and the rotational direction of the at least one rotatable drive shaft is determined； and wherein the quadrature ring (2080) is disposed within a coupling (26) detachably attached to a surgical attachment having an anvil and a staple driver/cutter； and wherein a controller (122), by tracking the angular position and rotational direction of the rotational drive shaft based on the output signal from the quadrature ring, can determine a relative displacement of the anvil with respect to the staple/driver cutter.
