George Papen

Integrating microsecond circuit switching into the data center

Recent proposals have employed optical circuit switching (OCS) to reduce the cost of data center networks. However, the relatively slow switching times (10--100 ms) assumed by these approaches, and the accompanying latencies of their control planes, has limited its use to only the largest data center networks with highly aggregated and constrained workloads. As faster switch technologies become available, designing a control plane capable of supporting them becomes a key challenge. In this paper, we design and implement an OCS prototype capable of switching in 11.5 us, and we use this prototype to expose a set of challenges that arise when supporting switching at microsecond time scales. In response, we propose a microsecond-latency control plane based on a circuit scheduling approach we call Traffic Matrix Scheduling (TMS) that proactively communicates circuit assignments to communicating entities so that circuit bandwidth can be used efficiently.

Optical fiber with an acoustic guiding layer for stimulated Brillouin scattering suppression

Experimental results are presented demonstrating significant suppression of stimulated Brillouin scattering (SBS) in a specially designed fiber structure. SBS suppression is achieved using an acoustic guiding layer surrounding an optical core.

Signal Statistics and Maximum Likelihood Sequence Estimation in Intensity Modulated Fiber Optic Links Containing a Single Optical Pre-amplifier.

Exact signal statistics for fiber-optic links containing a single optical pre-amplifier are calculated and applied to sequence estimation for electronic dispersion compensation. The performance is evaluated and compared with results based on the approximate chi-square statistics. We show that detection in existing systems based on exact statistics can be improved relative to using a chi-square distribution for realistic filter shapes. In contrast, for high-spectral efficiency systems the difference between the two approaches diminishes, and performance tends to be less dependent on the exact shape of the filter used.

A Multiport Microsecond Optical Circuit Switch for Data Center Networking

We experimentally evaluate the network-level switching time of a functional 23-host prototype hybrid optical circuit-switched/electrical packet-switched network for datacenters called Mordia (Microsecond Optical Research Datacenter Interconnect Architecture). This hybrid network uses a standard electrical packet switch and an optical circuit-switched architecture based on a wavelength-selective switch that has a measured mean port-to-port network reconfiguration time of 11.5

On the Multiuser Capacity of WDM in a Nonlinear Optical Fiber: Coherent Communication

\mu{\rm s}

Experimental demonstration of 10 Gb/s NRZ extended dispersion-limited reach over 600 km-SMF link without optical dispersion compensation

including the signal acquisition by the network interface card. Using multiple parallel rings, we show that this architecture can scale to support the large bisection bandwidth required for future datacenters.

Wideband silicon-photonic thermo-optic switch in a wavelength-division multiplexed ring network

Previous results suggest that the crosstalk produced by the fiber nonlinearity in a WDM system imposes a severe limit to the capacity of optical fiber channels, since the interference power increases faster than the signal power, thereby limiting the maximum achievable signal-to-interference-plus-noise ratio (SINR). We study this system in the weakly nonlinear regime as a multiple-access channel, and show that by optimally using the information from all the channels for detection, the change in the capacity region due to the nonlinear effect is minimal. On the other hand, if the receiver uses the output of only one wavelength channel, the capacity is significantly reduced due to the nonlinearity, and saturates as the interference power becomes comparable to the noise, which is consistent with earlier results. The results hold in channels with or without memory. Every point in the capacity region can be achieved without knowledge of the nonlinearity parameters at the transmitters. The structures of optimal/suboptimal receivers are briefly discussed

A demonstration of ultra-low-latency data center optical circuit switching

We demonstrate an extended dispersion-limited reach of 600 km at 10 Gb/s with a conventional NRZ transmitter in the absence of optical dispersion compensation. The novel approach combines a new type of spectral channel narrowing and electronic processing based on a reduced complexity Viterbi algorithm at the receiver.

A 10 µs hybrid optical-circuit/electrical-packet network for datacenters

Using a compact (0.03 mm(2)) silicon-photonic bias-free thermo-optic cross-bar switch, we demonstrate microsecond-scale switching of twenty wavelength channels of a C-band wavelength-division multiplexed optical ring network, each carrying 10 Gbit/second data concurrently, with 15 mW electrical power consumption (no temperature control required). A convenient pulsed driving scheme is demonstrated and eye patterns and bit-error rate measurements are shown. An algorithm is developed to measure the power-division ratio between the two output ports, the insertion and switching losses, and non-ideal phase deviations.

RotorNet: A Scalable, Low-complexity, Optical Datacenter Network

We designed and constructed a 24x24-port optical circuit switch (OCS) prototype with a programming time of 68.5 μs, a switching time of 2.8 μs, and a receiver electronics initialization time of 8.7 μs [1]. We demonstrate the operation of this prototype switch in a data center testbed under various workloads.