Multiwavelength erbium-doped fiber ring lasers with overlap-written fiber Bragg gratings

Eight-wavelength Er-doped fiber lasers with lasing wavelength separations of $\sim 1.6$ and $\sim 0.8 \mathrm{nm}$, respectively, have been achieved by use of overlap-written fiber Bragg gratings (OWFBG’s) in the fiber lasers and by cooling of the Er-doped fiber with liquid ${\mathrm{N}}_2$. Our experiment shows that by utilizing the OWFBG’s to select the lasing wavelengths one can achieve fiber lasers with lasing wavelengths and lasing wavelength separations that match the International Telecommunication Union channel-allocation grid well.