Abstract

Modulational instability (MI) in the normal group velocity dispersion (GVD) regime of an optical fiber may result from coupling between two pump waves with different wavelengths¹ or polarization·^2,3 In this work, we predict that MI may occur in the normal GVD regime with a single pump wave whenever the fiber is placed in a ring cavity. This new effect has many applications because it may lead to ultrashort pulse train generation at THz high-repetition rates at any wavelength. The physical mechanism leading to the amplification of a weak modulation with normal GVD is the interference effect occurring at each round trip between the synchronous input pulses and the cavity running pulse. This is analog to the bright-pulse compression phenomenon in lasers with additive pulse mode-lockmg.⁴

© 1992 Optical Society of America