24-line multiwavelength operation of erbium-doped fiber-ring laser

Simultaneous lasing at up to 24 wavelengths is demonstrated in an erbium-doped fiber-ring laser using a simple design. This result is achieved using a low-loss cavity, controlled polarization evolution and liquid nitrogen cooling to enhance spectral hole-burning, polarization hole-burning, and polarization selectivity. The design does not include any wavelength-selective components; instead, it utilizes wavelength selectivity provided by polarization evolution in the cavity. The amplitude variation between emission peaks is less than 3 dB over a 17-nm spectral range. A narrow linewidth of 0.15 nm, dense line spacing of 1.1 nm, and a good signal-to-noise ratio of more than 30 dB are achieved over most of the erbium bandwidth. The comb spectrum location and width are adjustable by changing and adjusting cavity components.