Abstract: A dual polarization quadrature modulator includes an input planar lightwave circuit (PLC) configured to deliver coherent light to a polymer-on substrate device including a plurality of electro-optic (E-O) polymer optical modulation waveguides configured to each phase modulate the coherent light, and the E-O polymer optical modulation waveguides output modulated coherent light to an output PLC configured to combine waveguide pairs of phase modulated light into Mach-Zehnder interferometric signals, combine pairs of Mach-Zehnder interferometric signals into quadrature modulated signals. A polarization rotator rotates modulated light from one of the quadrature modulated signals into an orthogonal polarization. The output PLC combines the quadrature-modulated and rotated quadrature modulated light to form a dual polarization, quadrature modulated light signal. The PLCs and the polymer-on-substrate device are integrated onto a single assembly substrate.