Acoustooptic characterization of a birefringent two-mode photonic crystal fiber

The effect of axial variations in acoustooptic phase-mismatch coefficient of a two-mode birefringent photonic crystal fiber (PCF) is studied experimentally using two different methods. The first method is to determine axial non-uniformities directly from the transmission spectrum, while the second method is to use acoustic pulses. Both methods are seen to be in good agreement. It is found that axial non-uniformities increase the coupling bandwidth significantly as compared to an axially uniform fiber. The effect of acoustic birefringence is also considered.