An Effective Integration Solution for 100 Gb/s DP-QPSK Coherent Receiver With a Small Skew

We propose and develop a simple hybrid integration solution for a 100 Gb/s dual polarization quadrature phase shift keying coherent receiver. The cost-effective, precise, and passive alignment technique can be used to couple four output waveguides of planar lightwave circuits (PLCs) based 90 ° optical hybrid (OH) with a 1 × 4 photodiode (PD) array directly, adopting an infrared charge-coupled device camera to monitor the light spots, a beam of infrared light to illuminate the light spots and the active areas of PD array, and an epoxy glue to adhere the PLC-based 90 ° OH to the heat sink. Based on this proposed coupling scheme, the responsivity variation for the coherent receiver is less than ±0.18 dB for all PD channels in an environment temperature range of -5°C-80 °C and the skew of this coherent receiver is only 1.96 ps.