Product design issues relating to rare-earth doped fiber ring lasers and superfluorescence sources

The high gain offered by Erbium doped fiber amplifiers has, since its first demonstration, been explored in lasers and super fluorescence sources. Although such devices have been the topic for numerous scientific publications only a few configurations have resulted in commercial products. We have identified the principal reasons for this to be the difficulty in obtaining single longitudinal mode laser operation in the inherently long laser cavities and the tendency of superfluorescence fiber sources (SFS) to show spurious lasing in high power operation. In this manuscript we show some results of our effort to deal with these obstacles. A technique based on a saturable absorber (SA) grating filter is shown to assure stable single longitudinal mode lasing even when the laser cavity is subject to temperature variations. The saturable absorber filter has a narrow passband and dynamically tracks the lasing mode. An all-polarization maintaining (PM) fiber ring cavity in combination with a saturable absorber filter provides a solution for stable single mode, single polarization laser operation. Progress on amplified spontaneous emission (ASE) superfluorescence sources is fueled by improvements in available pump power ratings. However spurious lasing is limiting the spectral power density of the broadband emission. We present techniques based on tailored optical feedback using filtered ASE seeding or Faraday rotator (FR) mirror which increases lasing threshold and thus the achievable output power. These advances have allowed the manufacture of fiber optic sources which maintain their performance parameters over time even when subject to temperature and vibration perturbations found in real applications.