  We improved a previously proposed method of using closed-orbit modulation for
linear optics correction. Instead of fitting individual closed orbits, the
improved method decomposes the orbit oscillation data into two orthogonal modes
and fits the amplitudes of the modes at all BPMs. While the original method is
limited to process around tens to a hundred orbits, the improved method can
process thousands of orbits, which are easily available when
alternating-current (AC) waveforms are applied to the two modulating
correctors. The method has been experimentally demonstrated on the National
Synchrotron Light Source (NSLS)-II storage ring.
