US Patent 7421156 Methods to reduce polarization dependent loss in planar lightwave circuits

Polarization dependent loss may be reduced by providing at least one dummy waveguide or at least one dummy metal structure. Polarization dependent loss may also be reduced by imposing a mechanical force on the OIC to exert mechanical stress thereby changing at least one of the birefringence and the optical axes of at least one waveguide. And polarization dependent loss may be reduced by forming a metal heater using a first set of metal deposition parameters; forming a conductive metal structure contacting the metal heater using a second set of metal deposition parameters; and selecting the first set of metal deposition parameters and the second set of metal deposition parameters to reduce stress.