Fiber Ring Lasers employed for generation of the multi-wavelength laser with so narrow bandwidth. In this research, the setup of multi-wavelength fiber ring laser source is demonstrated as well as eight figure cavity that by using a piece of Polarization Maintaining Fiber (PMF) in Sagnac filter achieved four stable and constant amplitude wavelengths with same spacing at room temperature. Also, we observed more than 250 narrow line width modes by using the 23 km length of Single Mode Fiber (SMF-28) at C and L communication windows which the stability of modes because of increasing the length was more less in compare to PMF Sagnac. Manuscript profile