An arbitrarily switchable multi wavelength Yb doped fiber laser (YDFL) based on a phase shifted long period fiber grating (PS LPFG) is proposed and demonstrated. The PS LPFG, which was fabricated by a CO 2 laser under asymmetric exposure, acts as a spectral filter with anisotropic transmission spectrum at different states of polarization. The capability of arbitrary wavelength switching can be attributed to the com bination of the polarization dependent loss (PDL) of the PS LPFG and the nonlinear polarization rotation (NPR) effect. The method suggests a new possibility to achieve even more wavelengths output with an all fiber format, arbitrarily switchable and tunable capability in the Yb doped fiber laser system in a simple, sta ble and well controlled manner.

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