The flatness of distributed Raman amplifier’s （DRA） gain profile is a key parame-ter. This paper verified the great influence of pumping configuration and signals power ongain profile by experiment. The WDM signals of 20 channels （ranging from 1 537. 377 to1 560. 605 nm） on the ITU-T grid were used as the incident signals of DRA. Each channelwas modu1ated externally by a electro--absorption （EA） modulator using a 2. 5 Gbit/s non-return--to zero （NRZ） format

with a 2

7

-- 1 long pseudo-random bit sequence （PRBS） sig-nal. The experimental results have referential value for optimizing the flatness of DRA.