Cascaded microoptical waveguide on microactuating platform structure for high-power wideband variable optical attenuator applications

We present a novel cascaded two-stage microoptical waveguide (MOW) on microactuating platform (MAP) structure for applications in high-power ultrawideband variable optical attenuator (VOA). The device consists of a fused biconical taper (FBT) fiber coupler, which acts as a MOW, mounted on an electromechanical system MAP, where an axial stress over the waist of FBT coupler is precisely controlled by a piezoelectric transducer actuator. Cascaded two stages with complementary spectral responses were employed to enhance the spectral flatness and optical extinction ratio, which allowed the maximum attenuation over 60 dB at 1450 nm and a low spectral tilt of < 1 dB over 100 nm for 20-dB attenuation, as well as low polarization-dependent loss of < 0.07 dB. These VOA characteristics were maintained for optical power over 1 W.