Low Frequency-Noise Random Fiber Laser With Bidirectional SBS and Rayleigh Feedback

Frequency and intensity noise are characterized for a bidirectionally pumped Brillouin random fiber laser. This novel laser incorporates the complementary effects of two counter-propagating stimulated Brillouin scattering gain profiles and the intrinsic Rayleigh distributed feedback present in ultralong optical fibers. The lasing mechanism as well as the contributing factors for the frequency and intensity noise has been discussed. This random laser exhibits a frequency noise level of <;1 Hz
²
/Hz at 2 kHz, which is lower than what is found in conventional narrow-linewidth erbium-doped fiber (EDF) fiber laser and a custom EDF-Rayleigh random laser by a factor of 200 and 2, respectively.