We report the theoretical and experimental performance of new, linearly Ž . polarized superfluorescent fiber sources SFS . Internal polarization is produced either by splicing a fiber polarizer at an optimum location along a standard Er-doped SFS or by using a single-polarization Er-doped fiber. Numerical simulations predict that when operated in the backward, forward, or double-pass configuration, these SFSs produce nearly twice the power in the desired linear polarization as a standard, unpolarized SFS. This efficiency figure depends weakly on the polarizer location and extinction ratio, but Ž . requires a low polarizer insertion loss -0.5 dB . Laboratory prototypes of a backward and a forward polarized SFS are presented that exhibit a power output in the desired linear polarization about 1.75 times larger than that of an unpolarized SFS, and an extinction ratio in excess of 17.5 dB. ᮊ 1998 Academic Press