Silicon Photonic Subsystems for Inter-Chip Optical Networks

The continuous growth of electronic compute and memory nodes in terms of the number of I/O pins, bandwidth, and areal throughput poses major integration and packaging challenges associated with offloading multi-Tbit/s data rates within the few pJ/bit targets. While integrated photonics are already deployed in long and short distances such as inter and intra data centers communications, the promising characteristics of the silicon photonic platform set it as the future technology for optical interconnects in ultra short inter-chip distances. The high index contrast between the waveguide and the cladding together with strong thermo-optic and carrier effects in silicon allows developing a wide range of micro-scale and low power optical devices compatible with the CMOS fabrication processes. Furthermore, the availability of photonic foundries and new electrical and optical co-packaging techniques further pushes this platform for the next steps of commercial deployment. The work in this dissertation presents the current trends in high-performance memory and processor nodes and gives motivation for disaggregated and reconfigurable inter-chip network enabled with the silicon photonic layer. A dense WDM transceiver and broadband switch architectures are discussed to support a bi-directional network of ten hybrid-memory cubes (HMC) interconnected to ten processor nodes with an overall aggregated bandwidth of 9.6Tbit/s. Latency and energy consumption are key performance parameters in a processor to primary memory nodes connectivity. The transceiver design is based on energy-efficient micro-ring resonators, and the broadband switch is constructed with 2x2 Mach-Zehnder elements for nano-second reconfiguration. Each transceiver is based on hundreds of micro-rings to convert the native HMC electrical protocol to the optical domain and the switch is based on tens of hundreds of 2x2 elements to achieve non-blocking all-to-all connectivity. The next chapters focus on developing methods for controlling and monitoring such complex and highly integrated silicon photonic subsystems. The thermo-optic effect is characterized and we show experimentally that the phase of the optical carrier can be reliably controlled with pulse-width modulation (PWM) signal, ultimately relaxing the need for hundreds of digital to analog converters (DACs). We further show that doped waveguide heaters can be utilized as \textit{in-line} optical power monitors by measuring photo-conductance current, which is an alternative for the conventional tapping and integration of photo-diodes. The next part concerned with a common cascaded micro-ring resonator in a WDM transceiver design. We develop on an FPGA control algorithm that abstracts the physical layer and takes user-defined inputs to set the resonances to the desired wavelength in a unicast and multicast transmission modes. The associated sensitivities of these silicon ring resonators are presented and addressed with three closed-loop solutions. We first show a closed-loop operation based on tapping the error signal from the drop port of the micro-ring. The second solution presents a resonance wavelength locking with a single digital I/O for control and feedback signals. Lastly, we leverage the photo-conductance effect and demonstrate the locking procedure using only the doped heater for both control and feedback purposes. To achieve the inter-chip reconfigurability we discuss recent advances of high-port-count SiP broadband switches for reconfigurable inter-chip networks. To ensure optimal operation in terms of low insertion loss, low cross-talk and high signal integrity per routing path, hundreds of 2x2 Mach-Zehnder elements need to be biased precisely for the cross and bar states. We address this challenge with a tapless and a design agnostic calibration approach based on the photo-conductance effect. The automated algorithm returns a look-up table for all for each 2x2 element and the associated calibrated biases. Each routing scenario is then tested for insertion loss, crosstalk and bit-error rate of 25Gbit/s 4-level pulse amplitude modulation signals. The last part utilizes the Mach-Zehnder interferometers in WDM transceiver applications. We demonstrate a polarization insensitive four-channel WDM receiver with 40Gbit/s per channel and a transmitter design generating 8-level pulse amplitude modulation signals at 30Gbit/s

Teaching Emotion Regulation to Kindergarten Students: Teachers' Perspectives and Pracctices

The purpose of this qualitative research project was to learn what perspectives a small sample of kindergarten teachers in Ontario hold in regards to teaching emotion regulation, a skill that is proven to be vital for students’ social-emotional development, and how these perspectives inform their practice. Data was collected through semi-structured interviews with two kindergarten teachers who work in publicly funded schools in Ontario. Interview transcripts were analysed and the emerged themes were organized into four main themes: the strategies used by the participants to teach their students to regulate their emotions; the outcomes they observed; the resources that helped to inform their practice; and the barriers and challenges they were facing in the area of teaching emotion regulation. Findings suggest that although teachers’ training programs were not identified as a main resource in this area, participants sought support from their colleagues to improve their practices and learn effective strategies to teach emotion regulation. Implications for the education community and personal practice are discussed, and recommendations are made for the Ontario College of Teachers and the faculties of education across Ontario to increase the emphasis being put on the social-emotional development of children in teachers’ preparation programs

High Performance MoxN Electrode Fabricated by Solution Precursor Plasma Spraying

Changing climate and decreasing availability of fossil fuels stimulate the use of alternative energy sources and energy storage devices such as electrochemical capacitors The current study investigates the implementation of SPPS (Solution Precursor Plasma Spraying) for the deposition of high surface area electrochemical capacitor electrodes. A high performance MoxN electrochemical capacitor electrode was produced by solution precursor plasma spraying for the first time. The best electrode exhibited an initial capacitance of 62.4 mF cm-2 at a scan rate of 100 mV sec-1. The capacitance decreased by 22% after the first 1000 cycles, but the performance then stabilized, decreasing by only 0.15% over cycles 4000 to 5000 and exhibiting a capacitance of 30mF cm-2 after 5000 cycles. SPPS is a novel deposition method, thus further understanding and optimization of the process is required to improve the performance and manufacturability, but a clear potential was proven.M.A.S

Arrhythmia of the Leasing Market

The article describes the impact of the current crisis on the lease industry in Russia and gives an estimation of lease market volatility. The lease effect on macroeconomic proportions is analyzed by calculating the lease capacity of investment and gross domestic product.

Leasing instruments of high-rise construction financing

The leasing sector of the business economics is expanding. Leasing instruments for high-rise construction financing allow to determine the best business behaviour in the leasing economy sector, not only in the sphere of transactions with equipment and vehicles. Investments in high-rise construction have a multiplicative effect. It initiates an active search and leasing instruments use in the economic behaviour of construction organizations. The study of the high-rise construction sector in the structure of the leasing market participants significantly expands the leasing system framework. The scheme of internal and external leasing process factors influence on the result formation in the leasing sector of economy is offered

Software-defined networking control plane for seamless integration of multiple silicon photonic switches in Datacom networks.

Silicon photonics based switches offer an effective option for the delivery of dynamic bandwidth for future large-scale Datacom systems while maintaining scalable energy efficiency. The integration of a silicon photonics-based optical switching fabric within electronic Datacom architectures requires novel network topologies and arbitration strategies to effectively manage the active elements in the network. We present a scalable software-defined networking control plane to integrate silicon photonic based switches with conventional Ethernet or InfiniBand networks. Our software-defined control plane manages both electronic packet switches and multiple silicon photonic switches for simultaneous packet and circuit switching. We built an experimental Dragonfly network testbed with 16 electronic packet switches and 2 silicon photonic switches to evaluate our control plane. Observed latencies occupied by each step of the switching procedure demonstrate a total of 344 µs control plane latency for data-center and high performance computing platforms

Thermal Rectification of Integrated Microheaters for Microring Resonators in Silicon Photonics Platform

Heating elements are used to tune the optical properties of silicon photonic devices, to stabilize operating temperatures, and to compensate for fabrication variations. In this paper, we characterize the transient thermal response and develop models for silicon photonic devices equipped with such heating mechanisms. To demonstrate the usefulness and practicality of the proposed models, we investigate pulse width modulation (PWM) drive scheme for microheaters and experimentally demonstrate its use in stabilizing microring resonators by digital driving signals (two-level voltage). Requirements on the drive frequency and duty cycle of the PWM signal to minimize optical power penalties owing to the undesired thermal ripples are discussed based on the accurately modeled thermal frequency response of the heater-ring system. It is shown that smaller duty cycles require higher drive frequencies and the maximum optical ripple for a microring resonator occurs at 65% duty cycle