Optical frequency tripling method by use of selective amplification of stimulated Brillouin scattering and Brillouin re-injection

A simple optical method of frequency tripling is proposed and experimentally demonstrated. The proposed method is based on Brillouin selective amplification characteristic of stimulated Brillouin scattering and Brillouin re-injection using a single optical source in an optical fiber. The first sideband optically generated by a r-f signal is selectively amplified by stimulated Brillouin scattering and reused for the generation of the second Stokes wave to selectively amplify the second side band. In a same manner, the third sideband is selectively amplified and other sidebands are suppressed. Finally, copropagating sideband and optical carrier generate a frequency-tripled signal. The experimental results show that the r-f signal of 32.493 GHz can be obtained from the modulation frequency of 10.831 GHz with an 8 GHz optical modulator. Also, the linewidth is the same as that of the modulation signal. The frequency-tripled signal was amplified by 20 dB and the fundamental r-f signal was suppressed by 25 dB.