Fiber-optic modulation and switching based on the Raman effect

This paper discusses optically controlled pulsed switching and modulation of high-power radiation in optical fibers, based on induced Raman scattering. It presents the transfer function of an optical switch based on a fiber-optic Sagnac interferometer and the characteristics of a Raman modulator for high-power ytterbium fiber lasers as a function of the laser power and the germanium concentration in the fiber. Spectral-selective optical switching with contrast greater than 18 dB is experimentally demonstrated. The optimum GeO2 concentration for increasing the efficiency of a modulator based on the Raman effect is determined. Induced losses of less than 1 dB are expected at optical powers of 5-100 W. (C) 2002 Optical Society of America.