Relative timing jitter in a counterpropagating all-normal dispersion dual-comb fiber laser

Counter-propagating all-normal dispersion (CANDi) fiber laser is an emerging high-energy single-cavity dual-comb source. Its relative timing jitter (RTJ), a critical parameter for precision and spectral resolution, has not been comprehensively investigated. In this paper, we enhance the state-of-the-art CANDi pulse energy from 1 nJ to 8 nJ. We then introduce novel reference-free RTJ characterization technique that provides shot-to-shot measurement capability at femtosecond first time. The noise floor reaches 1.6x10-7 fs2/Hz, corresponding integrated only 1.8 fs (1 kHz, 20 MHz). With new tool, are able study physical origin of laser's in detail. verify cavity length fluctuation does contribute RTJ. Then measure be 39 MHz) identify pump intensity (RIN) dominant factor responsible it. particular, RIN coupled through Gordon-Haus effect. Finally, solutions reduce free-running discussed. This work general guideline improve performance compact systems like benefitting various applications.