Experimental study of Raman amplification on stimulated Brillouin scattering in the G652 fibers at 1520nm

Abstract

The forward and backward cascaded stimulated Brillouin scattering(SBS) in the backward pumped S band distributed G652 fiber Raman amplifier have been researched, pumped by the tunable power at 1428nm fiber Raman laser and signal source is a tunable power external cavity laser (ECL) with narrow spectral bandwidth (<100MHz). The threshold power of backward Stokes the first and second stimulated Brillouin scattering SB₁^- and SB₂^- in the backward pumped S band distributed fiber Raman amplifier is 5mW and 67.6mW, respectively. The Stokes stimulated Brillouin scattering lines is amplified by fiber Raman amplifier and fiber Brillouin amplifier. The total G_A is production of the gain of Raman G_R and the gain of Brillouin amplifier G_B. G_A=G_R×G_B. In experimental work, the saturation gain of SB₁^- and SB₂^- is about 50dB and 65dB respectively and the saturation gain of 25km G652 backward FRA is about 25dB, so the gain of backward fiber Brillouin amplifier SB₁^- and SB₂^- are about 25dB and 40dB, respectively. The forward SBS does not obey the common theory that only weakening backward-SBS lines existed, according to conservation of energy and momentum and wave vector selected rule. Because the wave-guide characters weaken the wave vector rule, but the forward transmit sound wave-guide forward Brillouin scattering lines are generated and amplified in S band G652 FRA. The stimulated threshold power of the forward first Stokes SBS (SB₁^- ) in the backward pumped FRA is 6.6mW. In experimental work, the saturation gain of SB₁^- is about 49dB and the saturation gain of 25km G652 backward FRA is about 10dB, so the gain of SB₁^- in the forward fiber Brillouin amplifier is about 39dB.