Fully packaged ultra-fabrication-tolerant micro-optical polarization-diversity hybrid

Polarization-diversity hybrids are key components for coherent optical receivers. Polarization-diversity networks that make use of fiber-based components,1 monolithic InP-based integration with balanced photodetectors,2 and micro-optical assembly techniques,3 have been reported. However, fiber-based hybrids may suffer from reliability problems, photonic integrated circuits show high losses and reflection problems, and micro-optical techniques pose stringent fabrication tolerances affecting cost and reliability. In introducing lightwave communication systems to the market, the availability of low-cost, compact, and highly reliable components is crucial. In this paper we show how a high-performance polarization-diversity hybrid has been manufactured by making the elimination of critica1 alignments the very starting point of the design.