Light source and an amplifier using the dispersion formula perform suppression spontaneous emission is amplified (ASE), the L-band thulium doped fiber and S-band erbium-doped fiber

摘要

Erbium doped fiber amplifier (EDFA), and the present invention is to provide a light source for generating light of a wavelength of the S-band by using the EDFA. W-shaped distribution fiber fiber amplifier Depuresuto cladding or (10), is a (12) core which is defined by the refractive index n ₀ and the core cross-section and are added (18) active substance there. Refractive index _n cladding ₂ of the secondary (16) is surrounded Depuresuto cladding (14) (14) and also has a surround (12) Depuresuto core-cladding refractive index of _{1 n.} This fiber amplifier, the active substance is subjected to excitation at the level of high relative inversion D is shown a high gain in the long-wavelength band and shows a positive gain in the short-wavelength band. In one embodiment, n ₂ and _0, n ₁ the refractive index n that the core cross-section, and Depuresuto cladding cross-section, is a longer wavelength than the cut-off wavelength λ _c over the entire length of the fiber amplifier (10) is selected dispersion formula ASE suppression is to ensure that done. In another embodiment, by such selection, roll-off loss curve is provided around the cut-off wavelength λ _c. This roll-off curve loss, loss at least comparable to the high gain in the long wavelength band, as well as produce a smaller loss substantially compared with a positive gain in the short-wavelength band. In order to obtain a roll-off loss curve of the desired refractive index n ₀ in the core, so that the effective refractive index n _eff obtained by confinement mode to maximize the roll-off slope of the roll-off loss curve in front of the cut-off wavelength and are selected on the.