We present preliminary experimental studies of a novel polarization-maintaining (PM) ytterbium (Yb)-doped photonic crystal fiber (PCF) possessing a three-segment transverse acoustic profile and a mode field diameter (MFD) of approximately 30 μm. The concentrations of the dopants (fluorine, aluminum, and germanium) in the three segments were selected such that the corresponding Brillouin shifts were sufficiently separated to allow for the introduction of a large thermal gradient for further stimulated Brillouin scattering (SBS) suppression. A pump-probe experiment was conducted in order to characterize the Brillouin gain spectrum (BGS) and to confirm the existence of three narrow Brillouin gain peaks. Individual peak separation was > 220 MHz and the bandwidth of each peak was estimated to be 50 MHz. The fiber was implemented in a counter-pumped single-frequency amplifier configuration.
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