An All-Optically Gain-Controlled Two-Stage Amplifier Using Two Independent Feedback Loops

We propose and demonstrate the scheme to combine a two-staged amplifier with a fixed gain flattening filter and two parallel optical feedback loops. This amplifier all-optically controls constant signal gain and gain level through all C-band with a dynamic input power range of up to -1 dBm while input signals are dynamically changed between one channel and 40 wavelength-division-multiplexing channels. The transient effects of each channel and their wavelength dependency are investigated. It is shown that the amplifier can be used in real field applications through transmission experiments, in which the amplifier performance is kept unchanged under wide dynamic traffic variance.