We report a self-starting gigantic pulse generation observed during steady state stimulated Raman scattering (SRS) process in 10 km long telecom fiber. In our rather specific experimental configuration, the fiber was pumped by radiation from a 2.4 W continuous wave (CW) fiber laser source operating at 1455 nm. This pump provided the generation of light at Raman shifted wavelength around 1555 nm. At pumping face, the fiber was spliced with a broadband fiber loop mirror that reflected ~80% of Stokes power back into the fiber. Reflection from the far fiber end face was strongly prevented by the use of an optical isolator. The configuration provided ~30% power conversion from pump to Stokes radiation. Pulsations were observed from both ends of the fiber and occurred in rather stochastic manner with repetition rates in the range from hundreds kilohertz to several megahertz. Gigantic pulses with duration down to ~1 ns and peak power estimated to be above ~1 kW were recorded from the far fiber end. Smaller pulses with duration down to ~50 ns were observed from the pumping side of the fiber. Using a digital oscilloscope we investigated the fine structures of the pulses and determined some consistent patterns of their mutual dynamics. The RF spectrum measurements highlighted the stimulated Brillouin scattering that is suspected to be a main dynamical mechanism initiating pulsations. We observed also other different nonlinear effects caused by propagation of the intensive pulses through the fiber. Corresponding optical spectra were recorded and interpreted. Reported experimental data indicate that Rayleigh, Brillouin and Raman scatterings are all involved in the process of gigantic pulse generation in the fiber.

Date Published: 3 May 2004
PDF: 9 pages
Proc. SPIE 5480, Laser Optics 2003: Diode Lasers and Telecommunication Systems, (3 May 2004); doi: 10.1117/12.558571

Published in SPIE Proceedings Vol. 5480:
Laser Optics 2003: Diode Lasers and Telecommunication Systems
Nikolay N. Rozanov; Sergey A. Gurevich, Editor(s)