Multi-wavelength fiber lasers have wide applications in the wavelength-division Multiplexed (WDM) communication systems, optical signal processing and fiber sensing. Because of such potential applications, they have aroused great attention in the decades. One remaining challenge for achieving erbium-doped fiber laser with stable multi-wavelength lasing at room temperature is to suppress the homogeneous line broadening and the cross gain saturation. In this thesis, we propose a new type linear cavity multi-wavelength erbium-doped fiber laser based on intensity-dependent loss assistance of nonlinear polarization rotation (NPR) in nonlinear optical loop mirror (NOLM). And we experimentally achieve stable and tunable room-temperature multi-wavelength operations.Firstly, the working principle of multi-wavelength fiber laser and the level energy model of Er3+are discussed. We then establish a theoretical model of the NOLM whose switching is based on the NPR effect. The NOLM transmission is derived by means of Johns matrix. Accordingly, we analyze the influence of polarization state on the NOLM transmission and determine the polarization condition for power-independent output. We then study the influence of the pump power, input polarization and the length of the single mode fiber on output wavelength by experiment. It is shown that the number of output wavelength can be easily controlled by adjusting the pump power. Up to 20-wavelength lasing operation in 3 dB bandwidth has been achieved.Furthermore, based on the linear cavity multi-wavelength erbium-doped fiber laser, a new type multi-wavelength erbium-doped fiber laser with ultra-narrow wavelength spacing is proposed. The tunable parameters of our laser system, such as the length of single mode fiber, the pump power and so on, are studied systematically. More than 30-line stable room-temperature multi-wavelength output with ultra-narrow wavelength spacing in 1nm is achieved.All these results show that our new type multi-wavelength laser can effectively suppress the homogeneous line broadening and the cross gain saturation in the Erbium-doped, and enable stable and tunable multi-wavelength operation at room tempreture. |