Multi‐wavelength L‐band gain‐clamped erbium‐doped fiber amplifier with high gain and flatness by using composite FBGS

ABSTRACTThe gain‐clamped erbium‐doped fiber amplifiers (EDFA) can efficiently stabilize the gain fluctuation of signals, but with the price of gain–loss and worsened flatness. In this paper, we theoretically study the relationships between clamping and loss and propose a novel linear‐cavity gain controller based on a pair of composite fiber Bragg gratings (FBGs) to balance gain and clamping, which consist of a uniform FBG with high‐reflectivity and a chirp‐FBG with low‐reflectivity. The comprehensive experiments and comparisons are then conducted in terms of gain, flatness and clamping capability. Under the optimized central wavelength and reflectivity of FBGs, the ±0.1 dB stability of multi‐wavelength signals is achieved in ∼30 dB dynamic range. Moreover, our designed amplifier simultaneously guarantees the high average gain (∼24 dB) and low un‐flatness (∼±0.8 dB) in the range of 1570–1610 nm. This is a very promising technology for practicality of L‐band gain‐clamped EDFAs due to its simple configuration and adjustment. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:691–695, 2017