Acoustooptic Coherent Mode Coupling in Polarization-Maintaining Fiber and Its Application as a Variable-Polarization-Dependent Loss Element

In this letter, we investigate coherent acoustooptic coherent mode coupling from the LP
₀₁
core mode to LP
_1m
cladding mode of a polarization-maintaining fiber (PMF) induced by two acoustic gratings. We show narrowband variable attenuation along either birefringent axis of the PMF by varying the relative phase between the two acoustic gratings. By launching two acoustic gratings at different frequencies, variable attenuation and low crosstalk along either birefringent axis within the acoustooptic coupling bandwidth are demonstrated