Waveguide-MEMS cascaded variable optical attenuator with enhanced performance

We present a novel micro optical waveguide (MOW) on micro actuating platform (MAP) structure that is used for a variable optical attenuator. The device is consists of a fused biconical taper (FBT) coupler mounted on an electromechanical system where an axial stress over the waist of FBT coupler is precisely controlled. Its operation is based on change of coupling constant by compressive stress induced photoelastic effects on the waist zone. We use two FBT couplers to implement an enhanced performance of variable optical attenuator. The couplers are made from a standard single mode fiber and have a circular cross-section in their waist with an enough heating temperature. Each FBT coupler is optimized at 1450nm where total insertion loss is 0.75dB. π phase shifts in the coupling constant have been observed at an axial displacement of 9.5μm. The spectral response between two output ports of the coupler is reciprocal. This allows the proposed device to achieve a high attenuation of >72dB and for 20dB attenuation a flat bandwidth of <1dB over 100nm. Both a low polarization dependent loss (PDL) of <0.07dB and a low operating voltage of 15.3V have been demonstrated with a micro-order actuation.