[SCI] Inherent Enhancement of Gain Flatness and Achievement of Broad Gain Bandwidth in Erbium-doped Silica Fiber Amplifiers
작성일 : 2021-02-22
작성자 : 김종오
We report new methods to inherently increase the
flatness and bandwidth of erbium-doped silica fiber amplifiers
from three perspectives: fiber design, pump-signal WDM coupler
optimization, and amplifier structure. First, to achieve inherent
control of the gain spectrum, a new type of composite fiber
structure with an Er-doped core and a Sm-doped cladding ring
is proposed and experimentally demonstrated. Interaction of the
optical field with the Sm-doped cladding to produce evanescent
wave filtering is modeled, which provides an in-line control of gain
fluctuation in the erbium-doped fiber amplifier (EDFA) C band,
1530–1560 nm. Second, the effect of the spectral characteristics
of WDM couplers over the L band of an EDFA is explored. A
fused taper fiber coupler for a 1480-nm pump is optimized for
signals in the wavelength range of 1570–1610 nm by measuring the
small-signal gain, gain tilt, and noise figure in an L-band EDFA.
Finally, a new all-fiber structure for a wide-band EDFA, where
the L and C bands were coupled serially, is demonstrated with
optimized pump-signal couplers. Further optimization of the new
composite fiber structure and the transient effects in the serially
coupled EDFAs are also discussed.