A tunable erbium-doped fiber laser based on an MZ interferometer and a birefringence fiber filter

A tunable erbium-doped fiber laser (TEDFL) is proposed and demonstrated by using a MachZehnder interferometer (MZI) and a birefringence fiber filter (BFF) incorporating 6cm high birefringence (Hi-Bi) fiber. Theoretical analysis of the filtering function based on the Jones matrix has been performed. In this laser system, a section of 9m erbium doped fiber (EDF) serves as the gain medium. With the MZI defining the tuning step, the lasing wavelength can be discretely tuned by modifying the filtering characteristics of the BFF with the polarization controllers (PCs). The tuning range achieves 30nm with a power uniformity of less than 2dB, and a side-mode suppression ratio (SMSR) of 40dB. The power fluctuation and wavelength variation at 1556.26nm are observed to be less than 0.5dB and 0.04nm, respectively.