The effects of Lyot filter on the SNR of mode-locked fiber laser

Abstract Based on a transmittance model, we discovered that, by carefully changing the connection angle between the polarization-maintaining fibers in a laser cavity, the filtering effect effectively suppresses the Kelly sidebands caused by the strong nonlinear phase shift in a fiber mode-locked laser, thereby improving the signal-to-noise ratio of the mode-locked fiber laser. Compared with other spectral filtering approaches, the Lyot filter scheme, which has small insertion loss, simple structure, and adjustable modulation depth and transmission peak, can suppress the Kelly sidebands more effectively without affecting the shape of the mode-locked soliton. This was also verified experimentally. When the connection angle increases from 0° to 6°, the SNR of output pulses increases by 8 dB.