Wideband wavelength tunable fiber ring laser with flattened output power spectrum

A wavelength tunable erbium-doped fiber ring laser with flattened output power spectrum over a broadband is proposed and demonstrated. The power flattening is achieved using a high-birefringence fiber loop mirror, in which a number of high-birefringence fiber sections and polarization controllers are used to get a reflection spectrum that can compensate for the output power spectrum. The wavelength tuning is realized by compressing or stretching the FBGs in the laser cavity. A 1×3 switchable fiber Bragg grating array is incorporated into the fiber ring to get a wideband tuning range of 38 nm, from 1527 to 1565 nm. Within this range, the output power uniformity is controlled within ±0.8 dB. The total output power is about 4 dBm, the 3-dB linewidth is 0.01 nm, and the side mode suppression ratio is more than 48 dB.