Eng Tin Aw

Scalable optical switches for computing applications [Invited]

A scalable photonic interconnection network architecture is proposed whereby a Clos network is populated with broadcast-and-select stages. This enables the efficient exploitation of an emerging class of photonic integrated switch fabric. A low distortion space switch technology based on recently demonstrated quantum-dot semiconductor optical amplifier technology, which can be operated uncooled, is used as the base switch element. The viability of these switches in cascaded networks is reviewed, and predictions are made through detailed physical layer simulation to explore the potential for larger-scale network connectivity. Optical signal degradation is estimated as a function of data capacity and network size. Power efficiency and physical layer complexity are addressed for high end-to-end bandwidth, nanosecond-reconfigurable switch fabrics, to highlight the potential for scaling to several tens of connections. The proposed architecture is envisaged to facilitate high-capacity, low-latency switching suited to computing systems, backplanes, and data networks. Broadband operation through wavelength division multiplexing is studied to identify practical interconnection networks scalable to 100 Gbits/s per path and a power consumption of the order of 20 mW/(Gbits/s) for a 64×64 size interconnection network.

Control architecture for high capacity multistage photonic switch circuits

Feature Issue on Nanoscale Integrated Photonics for Optical Networks A layered, digital control architecture is proposed and demonstrated for relaxed-tolerance multistage photonic circuits. Preallocated optical paths and precalibrated switches are used in a hierarchical control scheme to anticipate and equalize power fluctuations from multiple input paths. Fast reconfigurability is facilitated, which ensures predefined optical powers at the switch stage outputs without incurring excess time delay or power transients. Experimental validation has led to the development of a dual stage switch router with three input nodes each transmitting four 10Gbit/s wavelength multiplexed payloads. Low penalty power equalization is observed after both a first and a second stage switch and is extendable to 10×10Gbit/s operation. We show that the output power is indeed set to within 0.5dB at 0dBm for an input power dynamic range of more than 20dB. The combination of self-calibration and modular control demonstrated in a two stage switch topology is believed to be scalable to more sophisticated multistage networks. As the concept does not require delay lines, it is believed that it will have advantages in facilitating the integration of controlled photonic circuits.

Temperature Independent Optical Amplification in Uncooled Quantum Dot Optical Amplifiers

1.3 μm QD SOAs are shown to provide 19 dB optical gain at temperatures up to 70 °C, allowing <; 0.1 dB system penalty at 10 Gb/s. The gain is constant to within ± 3.5 dB from 20°C-70°C for 10 nm spectral bandwidth.

High capacity demonstration of a compact regrowth-free integrated 4 × 4 quantum well semiconductor optical amplifier based switch

A fibre-to-fibre lossless integrated 4times4 SOA switch achieves an IPDR ~6 dB at <2 dB penalty for 8lambdatimes10 Gb/s. 10 Gb/s cascaded operation of two 4times4 switches is demonstrated.

Lossless multistage SOA switch fabric using high capacity monolithic 4×4 SOA circuits

The first high data-capacity routing in a 3-stage switch using integrated 4×4 QW-SOA circuits is reported. The feasibility of a proof-of-principle 16×16 routing switch is demonstrated for 8λ×10Gb/s operation, with an IPDR of 6dB.

Ultrafast FWM Self Routing between 10 Ports of Spectral Amplitude Coded 10 Gb/s Packets set on a 25 GHz Grid with Unequally Spaced Bins

A novel ultrafast self routing system is demonstrated using four-wave-mixing of 10 Gb/s packets spectrally-encoded in 25 GHz grid bins which are unequally spaced. Codes with a maximum separation of 1.6 nm enable routing to 10 different ports.

Demonstration of an SOA Efficient 32×32 Optical Switch for Radio Over Fiber Distribution Systems

A 32x32 optical RoF switch is demonstrated. A 13 dB input dynamic range with acceptable EVM and, using open loop control, an input dynamic range of 10 dB with 1 dB variation in output RF power is achieved.

Uncooled 2x2 quantum dot semiconductor optical amplifier based switch

This paper highlights the potential of an integrated 2times2 quantum dot switch for uncooled switching applications. High gain of 11.6 dB and <0.6 dB power penalty over lldB dynamic range is demonstrated at temperatures up to 70degC.

Multi-Stage SOA Switch Fabrics: 4×40Gb/s Packet Switching and Fault Tolerance

Performance of packet switching at 4x40Gb/s through a multi-stage SOA is evaluated. Fault identification and rerouting in the multi-stage switch is demonstrated.

High Capacity Optically Switched Interconnects for Computer Network Applications

Abstract: We summarize the commercial needs for development of high capacity interconnects, specifically for short reach (backplane, board to board) applications and review the research challenges to be addressed for optically switched interconnects. We present recent work on our near term solution, SWIFT, for centrally controlled, single switch fabric, short link applications not requiring wavelength routing, optical buffering or optical delay lines.