Gain clamped and gain flattened L-band EDFA design based on lasing cavity controlled structure using FBGs

Erbium doped fiber amplifiers (EDFAs) plays an important role in the optical communication systems. However, the operating bandwidth of EDFAs needs to be extended from conventional-band (C-Band) to the long-wavelength band (L-Band) to satisfy the requirements for high-capacity information transmission in DWDM (dense wavelength division multiplexing) systems. In the DWDM systems, the power of the output channels may change when the optical channels are added or dropped. If any control mechanism is not used in EDFA, this will degrade the overall performance of the transmission system. For this reason, wideband EDFAs exhibiting gain clamping and gain flattening features should be used in DWDM systems to overcome with the instability problems for varying input channel power/wavelength or the number of channels to be amplified. In this study, gain clamping and gain spectrum flattening performance in L-band EDFAs based on a lasing cavity controlled structure using a symmetrical FBG couple at C-band is theoretically and experimentally analyzed and compared with a single-stage bidirectionally pumped conventional L-band EDFA design. By optimizing the Bragg reflection wavelength of the FBG which is used for gain clamped and flattened operation in L-Band EDFA, a wide gain-clamped dynamic range (~33 dB) and a wide flattened gain spectrum (~35 nm) was obtained with an average gain of 19.70 dB. The experimental results obtained in this study are highly matched with the theoretical analysis results. It has been understood that gain clamped and gain flattened L-Band amplification with high dynamic range and bandwidth performance which required in wideband multichannel fiber optical communication systems, can be realized using the proposed L-band EDFA design.