Stuttgart 2012 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 66: Photonik 4

Q 66.2: Vortrag

Freitag, 16. März 2012, 14:15–14:30, V38.01

Brillouin Gain Bandwidth Reduction down to 3 MHz in Standard Single Mode Fibers — •Andrzej Wiatrek, Stefan Preussler, Kambiz Jamshidi, and Thomas Schneider — Institut für Hochfrequenztechnik, Hochschule für Telekommunikation Leipzig, Gustav-Freytag-Str. 43-45, D-04277 Leipzig, Germany

Due to its very low threshold, the nonlinear optical effect of stimulated Brillouin scattering (SBS) is the dominant effect in optical fibers. A strong pump wave induces a frequency downshifted narrow-band gain for counter-propagating signals. The energy transfer between the pump and the signal wave is mediated by an acoustical phonon wave inside the SBS medium. The linewidth of the SBS resonance is a product of the intrinsic attenuation of the phonons and the speed of sound in the medium. Both values are constant for certain environmental and medium specific parameters, such as temperature, strain and possible dopants. Since the effective SBS gain bandwidth is a convolution of the pump power spectrum and the natural SBS linewidth, the natural linewidth determines the smallest possible gain bandwidth. At room temperature this natural gain bandwidth is about 10 to 60 MHz in standard single mode fibers. A significant reduction of this value requires a cooling of the fiber down to cryogenic temperatures. In our contribution we propose a novel method to reduce the SBS gain bandwidth at room temperature. In the presented approach the spectrum of interest is superposed with a spectral aperture to exploit the saturation characteristics of the SBS. Based on our proof of concept experiment we report a gain bandwidth reduction by one order of magnitude.