  THz oscillators generated via frequency-multiplication of microwaves are
facing difficulty in achieving low phase noise. Photonics-based techniques, in
which optical two tones are translated to a THz wave through opto-electronic
conversion, are promising if the relative phase noise between the two tones is
well suppressed. Here, a THz ($\approx$ 560 GHz) wave with a low phase noise is
provided by a frequency-stabilized, dissipative Kerr microresonator soliton
comb. The repetition frequency of the comb is stabilized to a long fiber in a
two-wavelength delayed self-heterodyne interferometer, significantly reducing
the phase noise of the THz wave. A measurement technique to characterize the
phase noise of the THz wave beyond the limit of a frequency-multiplied
microwave is also demonstrated, showing the superior phase noise of the THz
wave to any other photonic THz oscillators (> 300 GHz).
