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Dual-comb generation with bidirectional fiber ring laser is highly prospective for its compactness and coherency. In this paper, we propose a dual-ring hybrid mode-locked fiber laser for dual-comb generation. The dual-ring laser contains elements of hybrid mode-locking for each sub-ring individually, while sharing the bidirectionally pumped erbium-doped fiber (EDF). The hybrid mode-locking is realized by transmission semiconductor saturable absorber (SESA) and nonlinear polarization evolution (NPE). With the help of two three-port optical circulators, non-ideal reflection of two SESAs are eliminated. Accordingly, two series of short pules are generated in each sub-ring with different direction individually. Experimental observations and analyses demonstrate that dual comb of about 300 kHz difference in repetition rates are generated by inserting a 10 cm cavity length difference between the two sub-rings. With the help of hybrid mode-locking and large power bidirectional pumping, the mode-locking of dual combs are stable and self-starting.
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