We investigate and compare the characteristics of erbium-doped superfluorescent fiber sources (SFS’s) obtained from the use of different flattening techniques in double-pass forward (DPF) and double-pass backward (DPB) configurations. The intrinsic flattening technique consists of optimizing the length of the erbium-doped fiber. The extrinsic flattening methods include the addition of a samarium-doped fiber (SDF) and a fiber-Bragg-grating (FBG) notched filter at the output end separately to shape the SFS spectrum. Although intrinsically flattened DPF and DPB SFS’s have a large output power of >34 mW, they are accompanied by an ~3-dB ripple. The FBG-flattened DPF and DPB SFS’s can achieve a wide linewidth of 35 nm with a small ripple of ~1.7 dB and better pump-power-dependent mean-wavelength stability; SDF-flattened DPF and DPB SFS’s are inferior because of the SDF’s lossy spectrum.
© 1999 Optical Society of America
Tsair-Chun Liang, Yun-Shi Lin, and Yung-Kuang Chen, "Comparison of the Characteristics of Double-Pass Erbium-Doped Superfluorescent Fiber Sources Obtained from Different Flattening Techniques," Appl. Opt. 38, 522-529 (1999)