We demonstrate the transmission of 10-Gb/s up-stream signals over 20-km fiber using a 1.3-GHz-bandwidth reflective semiconductor optical amplifier and a 40-ps delay interferometer (DI) in a loopback configured wavelength-division-multiplexed (WDM) passive optical network. We show that a single DI can be used in a set-and-forget mode to equalize 34 WDM channels anchored at the 100-GHz spaced ITU grid, without any help of postdetection electronic processing.