  Here, ultra-low relative phase jitters over a wide optical spectrum were
achieved for dual Ti:Sapphire optical frequency combs. The two optical
frequency combs were independently phase-locked to a Sr optical lattice clock
laser delivered through a commercial optical fiber network. We confirmed that
the relative phase jitters between the two combs integrated from 8.3 mHz to 200
kHz were below 1 rad, corresponding to a relative linewidth of below 8.3 mHz,
over the entire wavelength of the optical frequency combs ranging from 550 nm
to 1020 nm. Our work paves the way for ultrahigh-precision dual-comb
spectroscopy covering a wide optical spectral range with a simple setup, and
provides an absolute optical frequency reference with great stability over a
wide range of wavelengths.
