A bidirectional add/drop optical amplifier used in wavelength division multiplexing (WDM) optical networks to suppress the power change resulting from the adding and dropping of optical signals using an all optical gain control includes two fiber Bragg gratings (FBGs) and a bidirectional add/drop optical amplifier module composed of an Arrayed Waveguide Grating (AWG) and two bidirectional optical amplifiers. The filtered amplified spontaneous emission (ASE) lights are lased with the two FBGs and then used to adjust the gain of the bidirectional amplifiers.