Theoretical model and experimental demonstration of frequency control in rare-earth-doped fiber lasers with a 3 × 3 nonplanar fused-fiber coupler

Abstract

We present a numerical analysis that illustrates the potential of 3×3 nonplanar fused-fiber couplers for inhibiting longitudinal mode hops in rare-earth-doped-fiber lasers. A unidirectional erbium-doped ring-fiber laser is configured that contains a single 3×3 fused-fiber coupler. Narrow linewidth operation without any evidence of longitudinal mode hops is observed. The oscillating linewidth is 14 kHz with a rms frequency jitter ∼2 kHz. The relative intensity noise is measured in both the frequency stabilized and the frequency unstabilized cases. An average 15-dB reduction in the relative intensity noise over the 0–200 Hz frequency range is observed when the laser is stabilized.