Architecture for low-cost and highly flexible metro-access networks using SOA-based OADM nodes and digital subcarrier multiplexing with power loading.

Metro-access networks exploiting wavelength division multiplexing (WDM) to cope with the ever-growing bandwidth demands are sensitive to cost and need to be fast-configurable to meet the requirements of many new network services. Optical add-drop multiplexers (OADMs) are a key component in enabling fast dynamic wavelength allocation and optimization. In this Letter, we propose and demonstrate, to our knowledge, a novel architecture for high-performance metro-access networks that utilizes semiconductor optical amplifier (SOA)-based OADM nodes, digital subcarrier multiplexing (DSCM), low-cost direct detection receivers, and power loading techniques, which makes the designed metro-access network cost-effective, fast reconfigurable, and flexible for bandwidth allocation on demand. Through a proof-of-concept experiment, we have successfully demonstrated a prototype horseshoe optical network consisting of up to four SOA-based OADM nodes at 40 Gb/s per wavelength channel by leveraging the proposed scheme. The flexible bandwidth allocation and dynamic add and drop operations have also been achieved in an emulated WDM optical network. All results indicate the great scalability and flexibility of the proposed architecture.

Polarization-insensitive 40-channel 100-GHz spacing fold-back planar echelle grating Mux/Demux for photonic integrated wavelength-selective switches.

We present and numerically demonstrate a novel polarization-insensitive (PI) 40-channel 100-GHz spacing fold-back planar echelle grating (PEG) multiplexer/demultiplexer (Mux/Demux) to realize the compact 1 × 2 crossing-less photonic integrated wavelength-selective switch (PIC-WSS). The PI operation is achieved by a polarization splitter to feed the TE and TM mode into the PEG via two waveguides with different incidental angles so that the two diffracted modes combine at the same output waveguide. By optimizing the design of different input/output angle combinations and sharing the same blazed angle, a single compact PI PEG with fold-back configuration can simultaneously work as twice the Demux and Mux required. The footprint of the single fold-back PI PEG is only ∼40 mm2. The numerical results show that the 40-channel 100-GHz spaced PI fold-back PEG has < 2.4 dB insertion loss, < -60 dB cross talk, zero polarization-dependent wavelength shift (PDWS), 0.3 dB polarization-dependent loss (PDL), < 0.5 dB loss variation and < 0.01 nm wavelength shift between Mux and Demux.

Nanosecond optical switching and control system for data center networks.

Electrical switching based data center networks have an intrinsic bandwidth bottleneck and, require inefficient and power-consuming multi-tier switching layers to cope with the rapid growing traffic in data centers. With the benefits of ultra-large bandwidth, high-efficient cost and power consumption, switching traffic in the optical domain has been investigated to replace the electrical switches inside data center networks. However, the deployment of nanosecond optical switches remains a challenge due to the lack of corresponding nanosecond switch control, the lack of optical buffers for packet contention, and the requirement of nanosecond clock and data recovery. In this work, a nanosecond optical switching and control system has been experimentally demonstrated to enable an optically switched data center network with 43.4 nanosecond switching and control capability and with packet contention resolution as well as 3.1 nanosecond clock and data recovery.

Ultra-wide band (O to L) photonic integrated polymer cross-bar switch matrix.

We present an ultra-wide band photonic integrated 4×4 polymer cross-bar switch matrix based on total internal reflection and the thermo-optic effect. The photonic integrated polymer switch owns low insertion loss, low power consumption, wavelength, and polarization-independent operation for all switching paths. The experimental results show ultra-wide band (O- to L-band) operation with fiber-to-fiber insertion losses ranging from -3.7 to -6.5dB, 0.1 to 0.6 dB polarization-dependent losses, switching the on-off ratio above 36 dB on average, and 25 mW power consumption per path. Error-free operation with a power penalty <0.2dB at 1 E-9 bit error rate (BER) for ultra-wide band non-return-to-zero on-off keying (NRZ-OOK) wavelength-division multiplexing (WDM) switched signals at 10, 25, 40, and 50 Gbit/s, and 510 Gbps dual polarization 64-QAM switched data with a negligible penalty were measured.

SDN enabled flexible optical data center network with dynamic bandwidth allocation based on photonic integrated wavelength selective switch.

Optical switching techniques featuring the fast and large capacity have the potential to enable low latency and high throughput optical data center networks (DCN) to afford the rapid increasing of traffic-boosted applications. Flexibility of the DCN is of key importance to provide adaptive and dynamic bandwidth to handle the variable traffic patterns generated by the heterogeneous applications while optimizing the network resources. Aiming at providing the flexible bandwidth for optical DCNs, we propose and experimentally investigate a software-defined networking (SDN) enabled reconfigurable optical DCN architecture based on novel optical top of rack (OToR) switch exploiting photonic-integrated wavelength selective switch. Experimental results show that the optical bandwidth per link can be automatically reallocated under the management of the deployed SDN control plane according to the variable traffic patterns. With respect to the network with inflexible interconnections, the average packet loss of the reconfigurable DCN decreases 1 order of magnitude and the server-to-server latency performance improves of 42.2%. Scalability investigation illustrates limited (11.7%) performance degradation as the reconfigurable network scale from 2560 to 40960 servers. Both the numerical and experimental assessments validate the proposed DCN with reconfigurable bandwidth feature and lower latency variations with respect to the inflexible DCNs.

40 Gb/s all-optical unicast and multicast wavelength converter array on an InP monolithically integrated chip fabricated by MPW technology.

We present an InP monolithically integrated all-optical wavelength converter array chip and experimentally validate its performance for unicast (single output wavelength) and multicast (multiple output wavelengths) wavelength conversion. The monolithically integrated chip includes four semiconductor optical amplifiers with an arrayed-waveguide grating and two delayed interferometers. The chip is fabricated on a multi-project wafer (MPW) platform, which allows multiple designers to share space on the same wafer exploiting a generic integration platform. We demonstrate error-free non-return-to-zero (NRZ) unicast wavelength conversions using 231-1 pseudorandom bit sequence data at 10 Gb/s, 20 Gb/s and 40 Gb/s with a 25-nm conversion range. Power penalties as low as 2.3 dB and 2.7 dB for NRZ and return-to-zero (RZ) unicast wavelength conversion at 40 Gb/s are obtained, respectively. Additionally, power penalties of 2.5 dB for NRZ and 3.2 dB for RZ signals at 40 Gb/s 1 × 2 multicast wavelength conversions are also achieved.

Multiport InP monolithically integrated all-optical wavelength router.

An indium phosphide-based monolithically integrated wavelength router is demonstrated in this Letter. The wavelength router has four input ports and four output ports, which integrate four wavelength converters and a 4×4 arrayed-waveguide grating router. Each wavelength converter is achieved based on cross-gain modulation and cross-phase modulation effects in a semiconductor optical amplifier. Error-free wavelength switching for a non-return-to-zero 231-1 ps eudorandom binary sequence at 40 Gb/s data rate is performed. Both 1×4 and 3×1 all-optical routing functions of this chip are demonstrated for the first time with power penalties as low as 3.2 dB.

Novel flat datacenter network architecture based on scalable and flow-controlled optical switch system.

We propose and demonstrate an optical flat datacenter network based on scalable optical switch system with optical flow control. Modular structure with distributed control results in port-count independent optical switch reconfiguration time. RF tone in-band labeling technique allowing parallel processing of the label bits ensures the low latency operation regardless of the switch port-count. Hardware flow control is conducted at optical level by re-using the label wavelength without occupying extra bandwidth, space, and network resources which further improves the performance of latency within a simple structure. Dynamic switching including multicasting operation is validated for a 4 x 4 system. Error free operation of 40 Gb/s data packets has been achieved with only 1 dB penalty. The system could handle an input load up to 0.5 providing a packet loss lower that 10(-5) and an average latency less that 500 ns when a buffer size of 16 packets is employed. Investigation on scalability also indicates that the proposed system could potentially scale up to large port count with limited power penalty.

Low latency and efficient optical flow control for intra data center networks.

We experimentally demonstrate a highly spectral efficient optical flow control technique for intra data center networks. A bi-directional system is implemented for generating flow control signal by reusing label wavelength and the transmission link within the same WDM channel. Dynamic operation shows high-quality flow control signal with 265 ns latency including 220 ns propagation delay and 500 mV amplitude with low input power and low bias current. Error free operation with 0.5 dB penalty for 40 Gb/s payload indicates that no distortion has been caused due the transmission of label and flow control signal.

320 Gb/s all-optical clock recovery and time de-multiplexing after transmission enabled by single quantum dash mode-locked laser.

We report, to the best of our knowledge, the first demonstration of 320 Gb/s all-optical clock recovery and all-optical time de-multiplexing after 51 km transmission by exploiting single-quantum dash mode-locked laser diode (QD-MLLD). Based on injection locking of the QD-MLLD, the 40 GHz synchronized optical clock pulses were recovered from the 320 Gb/s with a pulse width of 1.9 ps and timing jitter of 135 fs, which allowed directly time de-multiplexing of 320-40 Gb/s without additional complex optoelectronic circuitry. The 320-40 Gb/s all-optical de-multiplexing was achieved with averaging a power penalty of 4.5 dB at BER of 1E-6.

Error-free 320-to-40-Gbit/s optical demultiplexing based on blueshift filtering in a quantum-dot semiconductor optical amplifier.

We present an ultrahigh-speed optical demultiplexing concept based on optical blue-shift filtering in a quantum-dot semiconductor optical amplifier (QD-SOA). Using a simple scheme, a QD-SOA and an optical bandpass filter, we have successfully achieved error-free operations at 40 Gbit/s on all the extracted tributaries from an aggregated traffic at 320 Gbit/s.

Scalable InP integrated wavelength selector based on binary search.

We present an InP monolithically integrated wavelength selector that implements a binary search for selecting one from N modulated wavelengths. The InP chip requires only log(2)N optical filters and log(2)N optical switches. Experimental results show nanosecond reconfiguration and error-free wavelength selection of four modulated wavelengths with 2 dB of power penalty.

320 Gbit/s wavelength conversion using four-wave mixing in quantum-dot semiconductor optical amplifiers.

In this study, we demonstrate error-free all-optical wavelength conversion of ultrahigh-speed intensity modulated signals by means of four-wave mixing in a quantum-dot semiconductor optical amplifier. Error-free performance at a bit rate of 320 Gbit/s is measured for the extracted 40 Gbit/s tributaries with a 3.4 dB average power penalty to the original signal.

InP monolithically integrated wavelength selector based on periodic optical filter and optical switch chain.

We present an InP monolithically integrated wavelength selector that implements a binary search for selecting N modulated wavelengths. The wavelength selector filter is realized using log(2)N an active Mach-Zehnder interferometer filter and broadband optical gating elements. Nanosecond reconfigurable operation with a spectral-alignment over 3.2 nm free spectral range is achieved with an extinction ratio exceeding 25 dB. Error-free operation of the wavelength selector for four modulated wavelengths with 2 dB of power penalty is demonstrated.

Ultrahigh-speed and widely tunable wavelength conversion based on cross-gain modulation in a quantum-dot semiconductor optical amplifier.

We present ultrahigh-speed and full C-band tunable wavelength conversions using cross-gain modulation in a quantum-dot semiconductor optical amplifier (QD-SOA). In this study, we successfully demonstrated error-free 320-Gbit/s operation of an all-optical wavelength converter (AOWC) using the QD-SOA for the first time. We also demonstrated full C-band tunable operation of the AOWC in the wavelength range between 1535 nm and 1565 nm at a bit rate of 160-Gbit/s.

Multichannel wavelength conversion of 50-Gbit/s NRZ-DQPSK signals using a quantum-dot semiconductor optical amplifier.

We demonstrate simultaneous four-channel wavelength conversion of 50-Gbit/s non-return-to-zero differential quadrature-shift-keying signals with a channel spacing of 100-GHz using a quantum-dot semiconductor optical amplifier. Error-free operations with low-power penalties are successfully achieved with various channel configurations.

Clock-distribution with instantaneous synchronization for 160 Gbit/s optical time-domain multiplexed systems packet transmission.

We demonstrate for the first time, to our knowledge, a clock-distribution method for ultra-high-speed optical time-domain multiplexed systems data packets that provides instantaneous synchronization, fast locking/unlocking times, and a highly stable bursty clock, enabling error-free operation of 160 to 10 Gbit/s time demultiplexing with a power penalty of 1.5 dB after 51 km transmission in standard single-mode fiber (ITU G.652).

Fast-synchronization and low-timing-jitter self-clocking concept for 160 Gbit/s optical time-division multiplexing transmissions.

We propose a self-clocking method based on in-band clock pilot insertion at the transmission data signal. The method can achieve clock recovery without the need for an ultrafast phase comparator and a phase-locked loop in the receiver. We demonstrate fast synchronization, low timing jitter, and a highly stable recovered clock from a 160 Gbit/s optical time-division multiplexing data signal after a 51 km fiber transmission. The recovered clock shows no patterning effect with a clock dynamic range of 10 dB for error-free operation of 160 to 40 Gbit/s demultiplexing with a power penalty of 1.1 dB.

Optical injection in semiconductor ring lasers: backfire dynamics.

We report on directional mode switching in semiconductor ring lasers through optical injection co-propagating with the lasing mode. The understanding of this novel feature in ring lasers is based on the particular structure of a two-dimensional asymptotic phase space. Our theoretical results are verified numerically and experimentally.