Dual-wavelength distributed feedback fiber laser based on double exposure and equivalent phase shift method

A special sampling structure based on double exposure technology is proposed to achieve dual-wavelength lasing in the distributed feedback fiber laser. This structure is composed of two grating pitches in one sampling period, which could be realized by changing the fiber's length in the fabrication. Through employing an equivalent phase shift, only a submicrometer-level precision is required for precise phase control. Then a stable dual-wavelength laser with the spacing of 400?pm is obtained in the experiment successfully. The output power is 30.46?μW and the sidemode suppression ratio is 46?dB under a pumped power of 146?mW.