Photonic network-on-chip (PNoC) is a promising candidate to replace traditional electrical NoC in manycore systems that require substantial bandwidths. The photonic links in the PNoC comprise laser sources, optical ring resonators, passive waveguides, and photodetectors. Reliable link operation requires laser sources and ring resonators to have matching optical frequencies. However, inherent thermal sensitivity of photonic devices and manufacturing process variations can lead to a frequency mismatch. To avoid this mismatch, micro-heaters are used for thermal trimming and tuning, which can dissipate a significant amount of power. This paper proposes a novel FreqAlign workload allocation policy, accompanying an adaptive frequency tuning (AFT) policy, that is capable of reducing thermal tuning power of PNoC. FreqAlign uses thread allocation and thread migration to control temperature for matching the optical frequencies of ring resonators in each photonic link. The AFT policy reduces the remaining optical frequency difference among ring resonators and corresponding on-chip laser sources by hardware tuning methods. We use a full modeling stack of a PNoC that includes a performance simulator, a power simulator, and a thermal simulator with a temperature-dependent laser source power model to design and evaluate our proposed policies. Our experimental results demonstrate that FreqAlign reduces the resonant frequency gradient between ring resonators by 50%–60% when compared to existing workload allocation policies. Coupled with AFT, FreqAlign reduces localized thermal tuning power by 19.28 W on average, and is capable of saving up to 34.57 W when running realistic loads in a 256-core system without any performance degradation.

Many-core chip architectures are now feasible, but the power consumption of electrical networks-on-chip does not scale well. Silicon photonic NoCs (PNoCs) are more scalable and power efficient, but floorplan optimization is challenging. Prior work optimizes PNoC floorplans through simultaneous place and route, but does not address cross-layer effects that span optical and electrical boundaries, chip thermal profiles, or effects of job scheduling policies. This paper proposes a more comprehensive, cross-layer optimization of the silicon PNoC and core cluster floorplan. Our simultaneous placement (locations of router groups and core clusters) and routing (waveguide layout) considers scheduling policy, thermal tuning, and heterogeneity in chip power profiles. The core of our optimizer is a mixed-integer linear programming formulation that minimizes NoC power, including (1) laser source power due to propagation, bend and crossing losses; (2) electrical and electrical-optical-electrical conversion power; and (3) thermal tuning power. Our experiments vary numbers of cores, optical data rate per wavelength, number of waveguides and other parameters to investigate scalability and tradeoffs through a large design space. We demonstrate how the optimal floorplan changes with cross-layer awareness: metrics of interest such as optimal waveguide length or thermal tuning power change significantly (up to 4X) based on power and utilization levels of cores, chip and cluster aspect ratio, and laser source sharing mechanism. Exploration of a large solution space is achieved with reasonable runtimes, and is perfectly parallelizable. Our optimizer thus affords designers with more accurate, cross-layer chip planning decision support to accelerate adoption of PNoC-based solutions.

To demonstrate control over the quantum spectrum of light, we tune the joint spectral intensity of photon pairs generated at telecommunications wavelengths using a low-power diode-pumped compact CMOS-compatible silicon chip at room temperature.

Using a compact optically-pumped silicon nanophotonic chip consisting of coupled silicon microrings, we generate photon pairs in multiple pairs of wavelengths around 1.55 μm. The wavelengths are tunable over several nanometers, demonstrating the capability to generate wavelength division multiplexed photon pairs at freely-chosen telecommunications-band wavelengths.

Using a compact optically pumped silicon nanophotonic chip consisting of coupled silicon microrings, we generate photon pairs in multiple pairs of wavelengths around 1.55 μm. The wavelengths are tunable over several nanometers, demonstrating the capability to generate wavelength division multiplexed photon pairs at freely chosen telecommunications-band wavelengths.