An Erbium-Doped Fiber Amplifier With Tunable Gain-Clamping in the Extended L-Band

To overcome the gain instability induced by the variations in the number of optical multiplexing channels, an improved configuration for an extended L-band gain-clamping erbium-doped fiber amplifier (EDFA) is proposed. Here, a broadband linear resonant cavity is formed by a pair of fiber reflective mirrors, and a variable optical attenuator (VOA) is used to tune resonant cavity loss. The broadband reflection characteristics of fiber reflective mirrors introduce laser mode competition, resulting in the winning laser consuming more population inversion and significantly compressing the signal gain. The VOA can make a trade-off between dynamic range and gain to meet different application scenarios, greatly simplifying the design of gain-clamping EDFAs. Experiments show that the proposed EDFA achieves a maximum gain of 30.5 dB and a minimum noise figure of 4.8 dB at 1605 nm with a wide dynamic range of 30 dB, and the instability is only 0.1 dB. The maximum wavelength for 20 dB gain is extended to 1624 nm.