The principles and characteristics of a novel fiber loop mirror (FLM), which is composed of polarization controller (PC) and an over-coupler whose coupling ratio is sensitive to wavelength are investigated. The notch depths and positions of loops′ reflection spectrum can be changed by adjusting the PC in the loops. The linear cavity of the L-band variable wavelength fiber laser consists of high-birefringence fiber loops and the over-coupler fiber loops. The reflectivity of various wavelengthes and the laser gain are controlled by changing the states of the polarization controllers in the cavity. In the experiment, the stable output wavelength can be changed from 1564 nm to 1592 nm, over 28 nm tuning range. Within this range, the 3 dB line-width is less than 0.2 nm and the side mode suppression ratio (SMSR) is more than 40 dB.