Multiple wavelength operation of distributed feedback fiber lasers

Summary form only given. Multiple wavelength distributed feedback (DFB) fiber lasers are attractive for a range of applications in optical communications, including soliton and microwave generation. Although such lasers have been demonstrated experimentally, it is not obvious how several laser modes can coexist in a homogeneously broadened gain medium. We propose that the coexistence of two or more fundamental modes of the same polarization can be attributed to the effect of dynamic gain gratings set up by the standing waves of different laser modes. A gain grating is in anti-phase with the standing wave pattern that created it, and therefore its presence is destructive for the corresponding laser mode. On the other hand, its interaction with other laser modes is small because of the frequency mismatch. Thus, the effect of the gain gratings is a reduction of the power of the dominant mode and an increase of the available gain for the other modes, resulting in a stable multiple wavelength operation of the laser.