EFFICIENT CASCADED RAMAN GENERATION AND SIGNAL AMPLIFICATION AT 1.3 MU-M IN GEO2-DOPED SINGLE-MODE FIBER

We demonstrate a high-gain, cascaded fibre Raman amplifier, operating at 1.3 mu m. Raman generation and amplification are achieved in a ring resonator constructed solely from fused fibre WDM couplers with low-l oss GeO2-doped single mode fibre used as the active medium. The amplif ier is pumped by a Nd:YAG laser at 1.064 mu m. In our resonant cascade d geometry, this generates the third Stokes line at 1.24 mu m, which a cts as a pump for Raman amplification of signals around 1.3 mu m. A ga in of 28 dB is demonstrated with output signal powers of up to 20 dBm for 3.4 W of pump power. Our experiments also indicate the important r ole of filters to suppress feedback in the resonator, permitting high Raman gain and good signal quality. (C) 1997 Elsevier Science B.V.