Low Frequency-Noise Ring Random Fiber Laser With a Dual-Cavity FBG Fabry-Perot Filter

A low frequency-noise ring random fiber laser (RFL) based on random Bragg grating array (RBGA) feedback is proposed. A dual-cavity fiber Bragg grating Fabry-Perot (FBG-FP) filter, which matches the wavelength of RBGA, is specially designed. Due to the narrower bandwidth, flatter response and steeper rolloff, the dual-cavity FBG-FP filter can significantly suppress the competition-induced frequency jitter and undesired residual random lasing modes, and contribute to establish stable lasing and further reduce frequency noise of RFL. The frequency noise of the proposed RFL is ∼3 Hz/√Hz above 1 kHz, and the frequency jitter is ∼3.11 × 10⁻¹¹ over 10 s. The 3-dB linewidth is ∼490 Hz with a ∼40 dB of optical signal-to-noise ratio.