Side mode suppression using a doped fiber in a long external-cavity semiconductor laser operating at 1490 nm

We report on the spectral analysis of the first 1490 nm external cavity laser with an intra-cavity erbium-doped fiber. Self-mode beating and heterodyne beating methods are employed to measure the side mode suppression ratios and to study the effect of the rare-earth doped fiber on the spectrum of the external-cavity laser. Experimental and simulated results show a substantial decrease in the number of the external-cavity modes and a side-mode suppression ratio of >15 dB.