Optical polarization-diversity receiver integrated on titanium-diffused lithium niobate

The authors describe the design and measurement characteristics of a lithium niobate polarization-diversity chip, realized on an X-cut, Z-propagation substrate. The use of the electrooptic effect offers the potential advantage of tunability in a wide spectral range. This device can be used as part of a hybrid balance substrate. The receiver structure is shown. The optimal signals from the transmission fiber and the local oscillator are combined in a 3-dB directional coupler. The transverse-electric and transverse-magnetic polarized waves from the coupler´s output waveguides are then spatially separated using two polarization splitters. This design avoids the use of intersecting waveguides.<>