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On the base of the phase shifted fiber Bragg grating of 4 cm length written in the active non-PM Yb-doped fiber, a resonator with distributed feedback (DFB) has been formed. The single frequency single polarization unidirectional generation with the output power up to 4.5 mW has been obtained. The spectral and energy performances of the single frequency DFB fiber laser depending on the pump laser parameters and ways of pump wave coupling have been investigated. The competition between orthogonal polarization states has been also studied, and the single polarization regime of 0.5 mW power has been achieved.

The output characteristics of the conventional one-stage Raman fiber laser (RFL) are described in an optical wave turbulence formalism. Simple analytical expressions describing RFL output power and its spectral shape are presented, and square-root law for the output spectrum broadening law has been discovered. The indications of the turbulent-like spectral broadening in other types of cw fiber lasers and propagation phenomena in fibers are also discussed.

We present an analytical theory based on wave kinetic equations that describes a Raman fiber laser (RFL) generation spectrum. It is shown both theoretically and experimentally that the quasi-degenerate four-wave mixing between different longitudinal modes is the main broadening mechanism in the one-stage RFL at high powers. The shape and power dependence of the intracavity Stokes wave spectrum are in excellent quantitative agreement with predictions of the theory.