  Rapid and large scanning of a dissipative Kerr-microresonator soliton comb
with the characterization of all comb modes along with the separation of the
comb modes is imperative for the emerging applications of the frequency-scanned
soliton combs. However, the scan speed is limited by the gain of feedback
systems and the measurement of the frequency shift of all comb modes has not
been demonstrated. To overcome the limitation of the feedback, we incorporate
the feedback with the feedforward. With the additional gain of > 40 dB by a
feedforward signal, a dissipative Kerr-microresonator soliton comb is scanned
by 70 GHz in 500 $\mu$s, 50 GHz in 125 $\mu$s, and 25 GHz in 50 $\mu$s (= 500
THz/s). Furthermore, we propose and demonstrate a method to measure the
frequency shift of all comb modes, in which an imbalanced Mach-Zehnder
interferometer with two outputs with different wavelengths is used. Because of
the two degrees of freedom of optical frequency combs, the measurement at the
two different wavelengths enables the estimation of the frequency shift of all
comb modes.
