Multiwavelength Erbium-doped Fiber Laser Based On Phase Modulation And Polarization Hole Burning

Fiber lasers that oscillate simultaneously at multiple wavelengths with an accurate wavelength spacing are of great interest for many applications such as dense wavelength-division multiplexed (DWDM) communications, fiber-optic sensors, optical instrumentation, and microwave photonic systems. But erbium-doped fiber (EDF) is a homogeneous gain medium at room temperature, which lead to strong mode competition and unstable lasing. So it is different to obtain simultaneous multiwavelength lasing in erbium-doped fiber lasers. For realizing a stable multiwavelength erbium-doped fiber laser at room temperature, sinusoidal phase modulation and polarization hole burning are introduced in the laser cavity to suppress the mode competition.A semiconductor optical waveguide is driven by a sinusoidal signal in the laser cavity. It can be classified here as two optical devices: a sinusoidal phase modulator and a nonlinear phase retarder. The sinusoidal phase modulator produces frequency shift for the fiber laser, and the nonlinear phase retarder introduces polarization hole burning in the erbium-doped fiber. Stable lasing with multiple wavelengths up to 10 and wavelength spacing of 0.32nm was demonstrated at room temperature. The power fluctuation was less than 5dB. It indicated that the phase modulation and polarization hole burning are propitious to suppress the mode competition owing to the homogeneous broaden line.The numerical model is simulated in Matlab language in our study. Follows are the main points: the transmission characteristics of Sagnac loop mirror based on high-birefringence fiber are deduced. It can be see that the loop can be considered as a comb filter with an accurate wavelength spacing. Based on the analysis of phase shift in the semiconductor optical waveguide, it shows that the semiconductor optical waveguide works as a sinusoidal phase modulator and a nonlinear phase retarder. With the introduction of erbium ion dependencies, a Mueller matrix form of the erbium ion rate equations is presented to propagate powers and polarization states in the EDF.