Modular architecture for fully non-blocking silicon photonic switch fabric

Abstract

Integrated photonics offers the possibility of compact, low energy, bandwidth-dense interconnects for large port count spatial optical switches, facilitating flexible and energy efficient data movement in future data communications systems. To achieve widespread adoption, intimate integration with electronics has to be possible, requiring switch design using standard microelectronic foundry processes and available devices. We report on the feasibility of a switch fabric comprised of ubiquitous silicon photonic building blocks, opening the possibility to combine technologies, and materials towards a new path for switch fabric design. Rather than focus on integrating all devices on a single silicon chip die to achieve large port count optical switching, this work shifts the focus towards innovative packaging and integration schemes. In this work, we demonstrate 1 × 8 and 8 × 1 microring-based silicon photonic switch building blocks with software control, providing the feasibility of a full 8 × 8 architecture composed of silicon photonic building blocks. The proposed switch is fully non-blocking, has path-independent insertion loss, low crosstalk, and is straightforward to control. We further analyze this architecture and compare it with other common switching architectures for varying underlying technologies and radices, showing that the proposed architecture favorably scales to very large port counts when considering both crosstalk and architectural footprint. Separating a switch fabric into functional building blocks via multiple photonic integrated circuits offers the advantage of piece-wise manufacturing, packaging, and assembly, potentially reducing the number of optical I/O and electrical contacts on a single die.

Photoconductive heaters enable control of large-scale silicon photonic ring resonator circuits

“…The miniature size of silicon ring resonators make them attractive candidates for large-scale photonic systems as they can be densely integrated on-chip for lowering size, power-consumption, and cost [1][2][3]. As a result, numerous solutions based on ring resonators have been proposed for applications in communications systems [2,[4][5][6], signal processing [1,7], quantum computing [8], sensing [9], and machine learning [10]. A key requirement for the practical use of these systems is the ability to precisely control the resonance conditions of their ring resonators, which allows to 1) correct for fabrication errors, 2) adapt the system in real-time to account for temperature variations or laser wavelength fluctuations, and 3) reprogram the system altogether for implementing various transfer functions and different functionalities.…”

Photonic switching in high performance datacenters [Invited]

“…Recently, we proposed a modular switch-and-select topology by assembling 1 × N/N × 1 ring-based spatial (de-)multiplexers with low-loss fibers or 2D optical interposer (Fig. 6c) [76]. Each (de-)multiplexer comprises N ring resonators coupled to a bus waveguide to add or drop optical signals.…”

“…This design only allows second-order crosstalk and maintains the number of drop-rings per path at two, while further scale-up only adds bypassing rings through the bus. A proof-of-principle demonstration of an 8 × 8 switch-and-select MRR switch was performed with excellent results [76]. However, it scales with regard to the number of MRRs as 2N 2 and for monolithic integration, managing waveguide crossings at the central shuffle network becomes more and more difficult at high numbers.…”

On-chip wavelength locking for photonic switches

“…Multiple variants of fat pipe switches have been demonstrated in silicon photonics in [2][3][4]. Ring-resonatorbased wavelength-selective switches have been demonstrated by different groups [5,6], and provide the advantage of fine granularity wavelength switches which better fit the traffic patterns in datacenters.…”