Fig. 1. Principle of fiber nutation tracking system based on direct detection.

Fig. 2. Principle of “four-point scanning algorithm”. The area in the black circle is the spot mode field at the focal plane, the blue circle is the nutation trail, and the area in the brown circle is the scanning range of fiber nutation. The red, green, yellow, and purple circles represent the positions of the end face of the SMF when nutation trail coincides with the coordinate axis, respectively.

Fig. 3. Loss of coupling efficiency as a function of nutation radius.

Fig. 4. (a) and (b) are the coupling efficiency and the calculated boresight error as a function of the real boresight error under the simplified model and real model.

Fig. 5. Calculation error as a function of the relative nutation rate with different jitter amplitudes.

Fig. 6. Calculation error as a function of θA/θv and β.