An EDFA-Gain Equalizer Based On a Sagnac Loop With an Unpumped Erbium-Doped Fiber

Saturable absorption and its consequent effects in bistable erbium-doped fiber ring laser

“…Therefore, the presence of the filter leads to a narrowlinewidth signal of higher power in the cavity which can act as a pump at a narrow band for the EDF if it lies within the 4 I 13/2 level. It is known from earlier work [2,28] and shown from our experimental results in section 2, that an unpumped section of an EDF can act as a saturable absorber. When the narrowlinewidth signal reaches the end section of a long length EDF, where the main pump at 980 nm is negligible, it can bleach the entire absorption spectrum of EDF, with the depth of bleaching in EDF dependent on the pump power and wavelength [13].…”

“…Pumping can be at 980 nm, corresponding to the 4 I 15/2 to 4 I 11/2 transition, or at 1480 nm, applicable to the 4 I 15/2 to 4 I 13/2 transition. Emission between the Stark-split levels of 4 I 13/2 and 4 I 15/2 can span the entire C-and L-bands of fiber-optic communication, making it the popular choice in commercial applications [2]. Inside the cavity of an EDFRL, the spontaneous emission from the EDF makes multiple passes in time, gets amplified by the gain of EDF under optimum conditions of the pump, and evolves into stimulated emission when the conditions at the chosen wavelength are conducive for the process.…”

“…Erbium-doped fiber (EDF) is a well-studied system for laser action. It is an excellent gain medium [1,2] which gives tunable laser output over the C-and L-bands of fiber-optic communication under suitable conditions [3][4][5]. Understanding the process of absorption in EDF is critical for comprehending various processes that contribute to the optical amplification in erbium-doped fiber amplifiers (EDFA) and in laser action.…”