Dual-comb fiber laser for stable frequency distribution

A passive dual-comb laser can generate two optical frequency combs with different repetition frequencies. These repetition differences have high relative stability and mutual coherence through passive common-mode noise suppression without complex tight phase locking from a single-laser cavity. The comb-based frequency distribution requires the dual-comb laser to have a high repetition frequency difference. This paper presents a high repetition frequency difference bidirectional dual-comb fiber laser based on an all-polarization-maintaining cavity configuration and a semiconductor saturable absorption mirror with single polarization output. The proposed comb laser has a standard deviation of 69 Hz and an Allan deviation of 1.17 × 10-7 at τ = 1 s under different repetition frequencies of 12.815 MHz. Moreover, a transmission experiment has been conducted. Owing to the passive common-mode noise rejection capability of dual-comb laser, after passing an 84 km fiber link, the frequency stability of the repetition frequency difference signal is improved by two orders of magnitude than the repetition frequency signal at the receiver side.