Effects of acoustic reflection on the performance of a cladding-etched all-fiber acoustooptic variable optical attenuator

We analyzed the effects of acoustic reflection on the performance of an acoustooptic variable optical attenuator on a cladding-etched single-mode fiber. It is shown that the acoustic reflection will generate time-dependent modulation on the output optical signal and reduce the maximum achievable attenuation of the device. By employing a tapered fiber structure and using vacuum grease as the acoustic absorber, we showed that the acoustic reflectance can be reduced by two orders and the maximum attenuation of the device is increased from -10 to -29 dB.