Upcoming generations of coherent intra/inter data center interconnects currently lack a clear path toward a reduction of cost and power consumption, which are the driving factors for these data links. In this work, the tradeoffs associated with a transition from coherent C-band to O-band silicon photonics are addressed and evaluated. The discussion includes the fundamental components of coherent data links, namely the optical components, fiber link and transceivers. As a major component of these links, a monolithic silicon photonic BiCMOS O-band coherent receiver is evaluated for its potential performance and compared to an analogous C-band device.

We investigate numerically and experimentally sheared 2D grating couplers in a photonic BiCMOS technology with a focus on their splitting behavior. Two realization forms of a waveguide-to-grating shear angle are considered. The cross-polarization used as a figure-of-merit is shown to be strongly dependent on the grating perturbation strength and is a crucial limitation not only for the grating splitting performance, but also for its coupling efficiency.

Multiband coherent communication is being handled as a promising candidate to address the increasing demand for higher data rates and capacity. At the same time, coherent communication is expected to enter the data center domain in the near future. With coherent data links in both, data-and telecom, spanning multiple optical bands, novel approaches to coherent transceiver design and traffic engineering will become a necessity. In this work, we present a monolithically integrated silicon photonic coherent receiver for O-and C-band. The receiver features a 2 × 2 multi-mode interference coupler network as 90 • hybrid optimized for 1430 nm (E-band). The total power consumption is 460 mW at a footprint of approximately 6 mm 2 , and an opto-electrical bandwidth of 33 GHz. 64 GBd operation is demonstrated in O-and C-band, which is competitive to the state-of-the-art for silicon photonic coherent receiver in the Cband, and the highest symbol rate to date for O-band coherent communication.

We investigate fundamental properties of polarization-splitting/combining 2D grating couplers for silicon photonic coherent transceivers. Linear cross-polarization related polarization crosstalk causes signal non-orthogonality. The relevance of these effects is illustrated in a 16-QAM experiment.

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