Waveband-tunable multiwavelength erbium-doped fiber laser
A waveband-tunable multiwavelength erbium-doped fiber laser based on a novel integrated structure of nonlinear polarization rotation and an unbalanced in-line Sagnac interferometer is proposed and demonstrated. An ultrabroadband lasing spectrum with 140 wavelength lasing peaks periodically distributed from 1563 to 1612.5 nm accompanied by a lasing linewidth of 0.112 nm, a free spectral range (FSR) of 0.32 nm, and a signal-to-noise ratio (SNR) of 20 dB has been achieved. A laser with high-wavelength lasing and waveband tunability was also achieved by merely adjusting the polarization controllers. The wavebands can be tuned from 1567 to 1606 nm continuously. Thirty-one lasing wavelengths in a 3 dB flattened spectrum has been achieved with a SNR of 48 dB, a linewidth of 0.03 nm, and a FSR of 0.32 nm. Good stability of the laser operating at room temperature has been verified by using an optical spectrum analyzer to measure every 2 min for a half-hour.