Feedback controlled variable optical attenuatorfor channel power regulation in WDM systems

A variable optical attenuator is described which uses an asymmetric polymeric Y-branch waveguide. It incorporates an optical monitoring tap to regulate the optical output regardless of variations in input light power and polarisation. The dynamic attenuation range was > 18 dB at 1.55 µm. The attenuator was successfully used to regulate channel powers within 0.5 dB in a WDM system.