This paper demonstrates a multiwavelength fiber laser (MWFL) with erbiumdoped fiber amplifier (EDFA) as gain  medium and Sagnac loop mirror interferometer as filter. Stable and flat lasing spectrum was achieved when highly  nonlinear fiber (HNLF) was inserted into the laser cavity. The number of lasing lines and extinction ratio (ER) was directly influenced by EDFA gain where at maximum setting, 14 lasing lines with ER of 19 dB were generated. The  stable and flat spectrum achieved spanned about 1.6 nm. This is due to the induced intensity dependent loss  mechanism in the cavity by adjusting the half-wave plate of the polarization controller in combination with the  HNLF. The MWFL output showed peak power variation of about 2.1 dB within 100 minutes of observation time.