Ultra fabrication-tolerant fully packaged micro-optical polarization diversity hybrid

We report on a novel fully packaged micro-optical polarization diversity hybrid, which shows excellent performance in combination with large fabrication and assembly tolerances. Our novel design employs highly parallel glass plates, which results in parallel and equidistant input and output beams. Critical fabrication and alignment procedures are thus avoided. At the target wavelength of 1.55 μm, typical fiber-to-fiber insertion loss is 0.7 dB, balancing is 50±3%, polarization extinction ratios are better than 25 dB, and measured optical back reflection is smaller than -58 dB. Wavelength insensitive behavior has been observed, resulting in a wide usable spectral operating range in excess of 90 nm. The micro-optical hybrid has been successfully tested in a dual-balanced polarization-diversity coherent CPFSK transmission experiment at 2.5 Gbt/s