针对数据中心互连用波分复用芯片需求，采用折射率差为1.5%的硅基二氧化硅光波导，设计并制备了应用于数据中心发射端的同侧、小型化、低损耗4通道粗波分复用芯片，尺寸为6.6 mm×2.2 mm，最小插入损耗小于2.33 dB，1 dB带宽大于11.35 nm，偏振相关损耗小于0.14 dB，波长精准度偏差小于0.38 nm。完全满足数据中心光互连波分复用芯片商用指标要求。

Quantum key distribution (QKD) provides a solution for communication of unconditional security. However, the quantum channel disturbance in the field severely increases the quantum bit-error rate, degrading the performance of a QKD system. Here we present a setup comprising silica planar light wave circuits (PLCs), which is robust against the channel polarization disturbance. Our PLCs are based on the asymmetric Mach–Zehnder interferometer (AMZI), integrated with a tunable power splitter and thermo-optic phase modulators. The polarization characteristics of the AMZI PLC are investigated by a novel pulse self-interfering method to determine the operation temperature of implementing polarization insensitivity. Over a 20 km fiber channel with 30 Hz polarization scrambling, our time-bin phase-encoding QKD setup is characterized with an interference fringe visibility of 98.72%. The extinction ratio for the phase states is kept between 18 and 21 dB for 6 h without active phase correction.

A high-performance monolithic integrated wavelength division multiplexing silicon (Si) photonics receiver chip is fabricated on a silicon-on-insulator platform. The receiver chip has a 25-channel Si nanowire-arrayed waveguide grating, and each channel is integrated with a high-speed waveguide Ge-on-Si photodetector. The central wavelength, optical insertion loss, and cross talk of the array waveguide grating are 1550.6?nm, 5–8?dB, and ?12–?15??dB, respectively. The photodetectors show low dark current density of 16.9??mA/cm2 at ?1??V and a high responsivity of 0.82?A/W at 1550?nm. High bandwidths of 23 and 29?GHz are achieved at 0 and ?1??V, respectively. Each channel can operate at 50?Gbps with low input optical power even under zero bias, which realizes an aggregate data rate of 1.25?Tbps.

Both the 4×20 GHz coarse wavelength division multiplexing and LAN-WDM receiver optical sub-assemblies (ROSAs) were developed. The ROSA package was hybrid integrated with a planar lightwave circuit arrayed waveguide grating (AWG) with 2% refractive index difference and a four-channel top-illuminated positive-intrinsic-negative photodetector (PD) array. The output waveguides of the AWG were designed in a multimode structure to provide flat-top optical spectra, and their end facet was angle-polished to form a total internal reflection interface to realize vertical coupling with a PD array. The maximum responsivity of ROSA was about 0.4 A/W, and its 3 dB bandwidth of frequency response was up to 20 GHz for each transmission lane. The hybrid integrated ROSA would be a cost-effective and easy-assembling solution for 100 GbE data center interconnections.