Ultracompact 100 Gbps coherent receiver monolithically integrated on silicon

This work describes an ultracompact coherent receiver monolithically integrated on silicon. The coherent receiver integrates one 1D grating coupler, one 2D grating coupler, two 90° hybrids, and eight Ge photodetectors in an area of only 1.3 × 1.4 mm2, which is about half the size of the smallest previously reported receiver. The design and performances of the components and the integrated coherent receiver are presented. The receiving of 100 Gbps polarization-division-multiplexed quadrature phase-shift keying (PDM-QPSK) signals is also successfully demonstrated.