Wenjia Zhang

40-Gb/s DPSK Data Transmission Through a Silicon Microring Switch

We experimentally demonstrate switching of a 40-Gb/s differential-phase-shift-keyed (DPSK) signal through a coupled silicon photonic microring switch. By simultaneously electro-optically biasing both microring cavities, we achieve 14-dB extinction ratio for signals egressing from both output ports of the switch. Packetized transmission of the 40-Gb/s DPSK signal is achieved with power penalties of 0.6 and 2.4 dB for through port and drop port signals, respectively. The effects of a coupled silicon microring are investigated, showing a broad bandwidth and a linear phase response for the drop port are necessary characteristics for routing 40-Gb/s data through the switch for photonic interconnection networks.

A hybrid optical packet and wavelength selective switching platform for high-performance data center networks

We propose and experimentally demonstrate for the first time a hybrid optical packet and wavelength selective switching platform for high-performance data center networks. This architecture based on cascaded silicon microrings and semiconductor optical amplifiers (SOAs) supports wavelength reconfigurable packet and circuit switching, and is highly scalable, energy efficient and potentially integratable. By combining the wavelength-selective behavior of the microring and the broadband behavior of the SOA switch, we are able to achieve fast switching transitions, high extinction ratios, and low driving voltages, which are all requirements for future optical high-performance data center networks. Routing correctness and error-free operation (<10(-12)) are verified for both 10-Gb/s and 40-Gb/s packets and streaming data with format transparency.

Broadband Silicon Photonic Packet-Switching Node for Large-Scale Computing Systems

We present a broadband packet-switching node that utilizes silicon photonic technology. The node design uses a silicon microring for switching functionality, leverages in-flight header processing for arbitration, and has a tunable driving circuit for thermal-effect mitigation. Moreover, these integrated microring switches are capable of scaling to tremendously high port counts in a compact area, which are attractive for data-center networks. We experimentally characterize the extinction ratio of the switch for varying packet durations, interarrival times, and driving voltages and demonstrate an error-free routing of 10-Gb/s wavelength-striped packets with lengths of up to 1536 ns. We further study the resonance thermal drifting for long- hold-time packet switching through carrier injection and show thermal-effect mitigation using a pre-emphasized gating signal.

Highly sensitive and reconfigurable fiber optic current sensor by optical recirculating in a fiber loop

An advanced fiber optic current sensor (FOCS) is proposed based on recirculating fiber loop architecture for significantly enhancing the current sensitivity. The recirculating loop is constructed by a 2X2 optical switch and the standard single mode fiber (SSMF) is used as the sensing head. The proposed FOCS is coupler-free with low insertion loss which results in a significantly improved current sensitivity. We experimentally obtained a sensitivity of 11.5 degrees/A for 1-Km SSMF FOCS and a sensitivity of 21.2 degrees/A for 500-m SSMF FOCS, both of which have been enhanced by more than ten times. The flexible switch control of recirculating can support the FOCS to work for different current scenarios with the same system and thus reconfigurable operation of the FOCS has been achieved. The significantly enhanced high sensitivity with reconfigurable operation capability makes the proposed FOCS a promising method for practical applications.

First Demonstration of a Cross-Layer Enabled Network Node

Exploding traffic demands and increasing energy consumptions facing todays networks are driving the designs of next-generation networking technologies. Cross-layer enabled approaches will allow for the packet-level control of the optical layer, to enable dynamic resource allocation and traffic engineering at the physical layer. We demonstrate an intelligent cross-layer enabled network node that can support high-bandwidth, all-optically routed packets, using emerging photonic technologies including optical packet switched fabrics and packet-scale performance monitoring. Using a cross-layer control and management plane, the node can dynamically optimize optical switching based on higher-layer constraints such as quality-of-service and energy consumption, as well as quality-of-transmission metrics such as link integrity and bit-error rates. We demonstrate a first-generation prototype of the cross-layer node, outlining its architecture and major implemented subsystems. The packet-rate physical-layer reconfiguration of the nodes fabric is shown using an implemented performance monitor and control plane. The realized node supports 8 40-Gb/s wavelength-striped optical packets with pseudorandom data with error-free transmission (bit-error rates less than ), in conjunction with the heterogeneous transmission of video traffic using 10-Gigabit Ethernet optical network interface cards based on field-programmable gate arrays.

Experimental demonstration of wavelength-reconfigurable optical packet- and circuit-switched platform for data center networks

We demonstrate a wavelength-reconfigurable optical packet- and circuit-switched platform for data center networks based on a modular optical switch fabric prototyping system.

Experimental demonstration of 10 gigabit ethernet-based optical interconnection network interface for large-scale computing systems

A novel 10GE-based optical network interface card is proposed to connect high performance processors and an optical interconnection network. We demonstrate end-to-end link setup, and TCP and HD video streaming utilizing 4×3.125Gb/s wavelength-striped WDM payloads.

Nonlinear Distortion Mitigation by Machine Learning of SVM Classification for PAM-4 and PAM-8 Modulated Optical Interconnection

We  demonstrated  a support  vector machine (SVM) based machine learning method to mitigate modulation nonlinearity distortion for PAM-4 and PAM-8 vertical cavity surface emitter laser multi-mode fiber (VCSEL-MMF) optical link. Simulations at 100 Gb/s data rate and experimental work at 60 Gb/s data rate were carried out. We achieved a significant improvement in bit error rate (BER) when complete binary tree SVMs (CBT-SVMs) are applied for both PAM-4 and PAM-8 signals. Quantitative analysis of the sensitivity gain versus modulation nonlinearity distortion is presented with experimentally verification. The results indicate that CBT-SVMs have better performance for PAM-8 compared to PAM-4. The sensitivity gain increases almost linearly with the increase of eye-linearity (increase of modulation nonlinearity distortion). Up to 2.5-dB sensitivity improvement is achieved by the proposed CBT-SVMs at eye-linearity of 1.72 for PAM-4.

Fabrication and performance analysis of polymer waveguides for optical interconnects

We designed and fabricated low loss polymer waveguides (<;0.05 dB/cm at 850 nm) using a lithography method. We experimentally investigated their insertion loss and numerically analyzed their mode power distribution and differential mode delay dependence on the launch condition for high speed optical interconnects.

Experimental Demonstration of 100-Gbps Optical PAM-4 Transmission over 4-km SSMF Using Wiener Filter

We experimentally demonstrate a 100-Gbps optically-uncompensated PAM-4 transmission over 4-km SSMF at 1.55-um by using Wiener filter. The performance of the adaptive filters, including LMS and Wiener filter, are both analysed and compared.