Using the nonlinear polarization rotation technique and an Er<sup>3+</sup>/Yb<sup>3+</sup> co-doped fiber amplifier, we have
experimentally obtained high output power wavelength continuously tunable laser and high output power passively
mode-locked pulse in an erbium-doped fiber ring laser.
By using the nonlinear polarization rotation (NPR), we demonstrated a novel wavelength-tunable narrow linewidth
erbium-doped fiber ring laser (EDFL) with a maximum tuning rang up to 25 nm (from 1532.0 nm to 1557.2 nm). The
NPR effect effectively induced intensity- and wavelength-dependent loss to alleviate mode competition caused by
homogenous gain broadening in erbium-doped fibers. By adjusting the polarization controllers in the cavity, the laser has
a power-equalized output, and the output power fluctuation between different wavelengths is smaller than 0.2dB, the
line-width of each light laser is 0.06 nm by 3 dB.