Reference level free multichannel gain equalization and transient gain suppression of EDFA with differential ASE power monitoring

We demonstrate a novel means of gain flatness monitoring and control of a multichannel gain flattened erbium-doped fiber amplifier (EDFA), which does not require a gain dependent reference level for the feedback loop. Using the difference of amplified spontaneous emission/probe powers extracted from the edges of the gain-flattened bandwidth, gain flatness monitoring, equalization, and transient gain suppression can be achieved regardless of the steady-state gain value of an EDFA, This approach eliminates the need of elaborate measurements for the determination of control parameters for each application, making it possible to use the same circuitry for different amplifiers. Measurements show flatness control within 0.03 dB/10 nm, at the same time the suppression of time-dependent gain excursion to below 0.2 dB.