Runxiang Yu

Rapid and complete hitless defragmentation method using a coherent RX LO with fast wavelength tracking in elastic optical networks

This paper demonstrates a rapid and full hitless defragmentation method in elastic optical networks exploiting a new technique for fast wavelength tracking in coherent receivers. This technique can be applied to a single-carrier connection or each of the subcarriers forming a super-channel. A proof-of-concept demonstration shows hitless defragmentation of a 10 Gb/s QPSK single-carrier connection from 1547.75 nm to 1550.1 nm in less than 1 µs. This was obtained using a small (0.625 kB) link-layer transmitter buffer without the need for any additional transponder. We also demonstrated that the proposed defragmentation technique is capable of hopping over an existing connection, i.e. 10 Gb/s OOK at 1548.5 nm, without causing any degradation of its real-time Bit Error Rate (BER) value. The proposed scheme gives advantages in terms of overall network blocking probability reduction up to a factor of 40.

A scalable silicon photonic chip-scale optical switch for high performance computing systems

This paper discusses the architecture and provides performance studies of a silicon photonic chip-scale optical switch for scalable interconnect network in high performance computing systems. The proposed switch exploits optical wavelength parallelism and wavelength routing characteristics of an Arrayed Waveguide Grating Router (AWGR) to allow contention resolution in the wavelength domain. Simulation results from a cycle-accurate network simulator indicate that, even with only two transmitter/receiver pairs per node, the switch exhibits lower end-to-end latency and higher throughput at high (>90%) input loads compared with electronic switches. On the device integration level, we propose to integrate all the components (ring modulators, photodetectors and AWGR) on a CMOS-compatible silicon photonic platform to ensure a compact, energy efficient and cost-effective device. We successfully demonstrate proof-of-concept routing functions on an 8 × 8 prototype fabricated using foundry services provided by OpSIS-IME.

All-Optical Physical Layer NACK in AWGR-Based Optical Interconnects

This letter, proposes and experimentally demonstrates an all-optical physical layer negative acknowledgment (AO-NACK) technique to handle contention in array waveguide grating router (AWGR)-based optical interconnects. By using back-propagation in AWGR, the packets experiencing contention are reflected back to the senders in the optical domain to serve as a physical layer negative acknowledgement to trigger the retransmission. A host-switch distance of ≈ 20 m and a packet length of 204.8 ns are used in this proof-of-principle demonstration. Notification of AO-NACKs messages and successful packet retransmission and switching is demonstrated with error-free operation at 10 and 40 Gb/s.

A Theoretical and Experimental Study on Modulation-Format-Independent Wavelength Conversion

Modern optical networks are adopting advanced modulation formats. Future dynamic optical networks will benefit from all-optical wavelength conversion and signal regeneration techniques in support of multiple modulation formats. This paper presents a concept for a modulation-format-independent wavelength conversion technique based on an optical hybrid and an in-phase/quadrature (IQ) wavelength converter. This technique has the potential for wavelength conversion and signal regeneration of multiple modulation formats. This paper also discusses the signal distortions and noises in the semiconductor optical amplifier based IQ wavelength converter. A proof-of-principle experiment shows the wavelength conversion results of multiple modulation formats. Further, this paper presents the signal regeneration of a return-to-zero quadrature-phase-shifted-keying signal through simulation.

Scalable Optical Interconnect Architecture Using AWGR-Based TONAK LION Switch With Limited Number of Wavelengths

This paper analyzes the scalability in arrayed waveguide grating router (AWGR)-based interconnect architectures and demonstrates active AWGR-based switching using a distributed control plane. First, the paper analyses an all-to-all single AWGR passive interconnection with N nodes and proposes a new architecture that overcomes the scalability limitation given by wavelength registration and crosstalk, by introducing multiples of smaller AWGRs (W × W) operating on a fewer number of wavelengths . Second, this paper demonstrates active AWGR switching with a distributed control plane, to be used when the size of the interconnection network makes the all-to-all approach using passive AWGRs impractical. In particular, an active AWGR-based TONAK switch is introduced. TONAK combines an all-optical NACK technique, which removes the need for electrical buffers at the switch input/output ports, and a TOKEN technique, which enables a distributed all-optical arbiter to handle packet contention. The experimental validation and performance study of the AWGR-based TONAK switch is presented, demonstrating the feasibility of the TONAK solution and the high throughput and low average packet latency for an up to 75% offered load.

An All-Optical Token Technique Enabling a Fully-Distributed Control Plane in AWGR-Based Optical Interconnects

This paper proposes and experimentally demonstrates a fully-distributed All-Optical TOKEN (AO-TOKEN) contention resolution technique for AWGR-based optical interconnects. The AO-TOKEN technique is implemented by exploiting the saturation effect in SOAs placed at the AWGR outputs. A polarization-diversity scheme allows thoe data and control planes to share the same physical link. The AO-TOKEN is more scalable than alternative electrical/optical solutions since it eliminates the need for a centralized electrical control plane. Our experimental results show that the technique can work over a wavelength-range of ≈ 23 nm using off-the-shelf components. We also successfully demonstrate all-optical contention resolution, packet transmission, and switching with error-free operation at 10 Gb/s.

Scalable and Distributed Contention Resolution in AWGR-Based Data Center Switches Using RSOA-Based Optical Mutual Exclusion

We describe a mutual exclusion element using a reflective semiconductor optical amplifier (RSOA) and a simple scheme for contention resolution in arrayed waveguide grating router (AWGR)-based optical switches in data centers. We describe a hardware demonstration and detailed performance analysis of an AWGR-based optical switch based on the proposed concept. We show that the proposed RSOA-based contention resolution significantly reduces latency compared to existing methods and that it does not require any global or centralized coordination, which makes it inherently scalable and suitable for emerging data center networks.

40 Gb/s 8×8 low-latency optical switch for data centers

This paper reports on a 40 Gb/s 8×8 optical switch for data centers. Experiments demonstrate error-free operation with 118.2 ns switching latency in contention-less architecture. Simulations show 150 ns latency for consolidated architectures.

10-Gb/s BM-CDR Circuit With Synchronous Data Output for Optical Networks

This letter presents a 10-Gb/s burst-mode clock and data recovery (BM-CDR) circuit based on an analog phase-picking method. The experiment demonstrates that the proposed BM-CDR circuit is able to align the BM data to a local clock with a phase alignment accuracy of ±π/4, a 25-ns latency and zero bit loss. The circuit further resamples the aligned data using the local clock for jitter reduction. The experiment shows error-free operation of the BM-CDR circuit for burst-mode data packets with various phase delays.

Demonstration of multi-channel hitless defragmentation with fast auto-tracking coherent RX LOs

This paper demonstrates simultaneous defragmentation of two channels without causing errors (BER <; 10-11) on other connections lying in the middle. The technique exploits fast tunable lasers and burst-mode coherent receivers with fast wavelength auto-tracking.