Integrated electroabsorption attenuator-photodetector for optical power control in WDM transmission systems

A new InP-based waveguide device capable of functioning simultaneously as an optical power monitor and variable optical attenuator is reported. It allows easy integration with passive InP-based lightwave components by using a new technique referred to as single-mode vertical integration. The device exhibits high on-chip responsivity of ∼0.93 A/W and attenuation values exceeding 25 dB. It is shown to effectively stabilize a time-varying input power signal by monitoring the input light level while simultaneously adjusting its internal attenuation. Integrated with planar (de)multiplexers, it enables very compact, monolithically integrated components for power controlling in WDM transmission systems to be realized.