A two-color visible frequency comb system based on a 1.5-μm all-polarization-maintaining (PM) fiber femtosecond laser was developed. This configuration relies on the implementation of three amplifiers, seeded by a single master oscillator. With the repetition rate (f_r) of the oscillator locked to a reference frequency of 200 MHz, the output of the first amplifier was used to generate the feedback signal and achieve simultaneous phase lock of the carrier envelop offset frequency (f_(ceo)). The remaining two independently configurable amplifiers followed by highly nonlinear fibers and MgO-doped periodically poled lithium niobite crystals were used to produce visible comb lights at 543 and 633 nm (in air), respectively. By referencing to a hydrogen maser, the Allan deviations of f_r and f_(ceo) at a gate time of 1 s are 438 μHz and 63 mHz, respectively. The spectral bandwidths of the 543- and 633-nm comb lights are 0.157 and 0.174 nm, respectively, and the single-mode powers of these comb lights are higher than 1 μW. The multiple-branch all-PM fiber-based visible frequency comb system exhibiting a narrow spectrum and a high single-mode power will facilitate the development of optical clocks and wavelength standard calibrations.
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