Photonic Integrated Self-Coherent Homodyne Receiver Without Optical Polarization Control for Polarization-Multiplexing Short-Reach Optical Interconnects

Standard coherent communication technology is being introduced to short-reach optical communications to further scale the link throughput by leveraging more degrees of freedom of an optical channel. However, the cost, footprint, and power consumption of the coherent transceivers may impede its application to short-reach optical interconnects. Silicon photonics technology has realized the monolithic integration of various optoelectronic components for coherent transceivers on a single chip to lower the cost but except for a silicon laser. Heterogeneous integration has been developed to realize distributed feedback (DFB) laser sources, which are not well suited for standard coherent communication. Therefore, there is a trade-off between the receiver complexity and the cost of laser sources. Self-coherent homodyne detection as a compromising solution of coherent detection for short-reach applications has been studied to utilize the un-cooled DFB lasers. In this paper, as one realization of self-coherent homodyne detection without optical polarization control, the first integrated complementary polarization-diversity coherent receiver (C-PDCR) chip for addressing the complexity issue has been successfully demonstrated with rapid polarization tracking of remotely delivered local oscillator (LO). To the best of our knowledge, the fastest reported polarization tracking speed is achieved and reaches 9 Mrad/s with negligible performance degradation based on electronic MIMO DSP given the system symbol rate and MIMO coefficients updating conditions/algorithms for a 70-Gbaud dual-polarization (DP) PCS-64QAM signal with 630-Gb/s line rate (net rate 485 Gb/s). The maximal transmission capacity of this on-chip C-PDCR can reach 714 Gb/s (net rate 540 Gb/s over 35 GHz electrical bandwidth).