Analysis of narrow linewidth fiber laser using double subring resonators

In this paper, a narrow linewidth fiber laser based on subring resonators is proposed using two different lengths of coupled subring resonators and a fiber Bragg grating. The laser physical operation is modeled using rate equations, considering the optical signal spectrum and the effect of subring resonators on the laser output linewidth. To verify the model, the proposed fiber laser is implemented, and its measured results are compared with the model results. For the implemented single-mode laser, a laser linewidth less than 10 KHz with a 60 dB optical signal-to-noise ratio was achieved. Moreover, output powers up to 25 mW at 1550 nm were obtained for 300 mW pumped power at 980 nm.