Optical switch based on stimulated Raman scattering

We investigate optical switching based on stimulated Raman scattering. The circuit consists of two fiber stages connected in series through a bandpass filter. When the pump and signal are launched to the input, the pump is saturated because of the signal amplification in the first stage; the amplified signal is rejected by the filter, so that only low-power pump enters the second stage; and no signal pulses appear at the output. The second stage is fed by 1 mW power at signal wavelength. When the pump only enters at the input, it passes through the first stage without saturation, enters the second stage, and amplifies the signal entering this stage; strong signal pulses appear at the output. We use 2-ns pump pulses at 1528 nm and cw signal at 1620 nm. In the first stage, we use both fibers with normal and anomalous dispersion. In fibers with anomalous dispersion, pump saturation is affected by modulation instability. We find that the contrast may be improved using fibers with normal and anomalous dispersion connected in series in the first stage, provided there is appropriate selection of their lengths. The best contrast we achieve is 15 dB at 6 W pump peak power. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3558851]