This paper proposes a routing and spectrum assignment algorithm for elastic optical networks. The algorithm achieves high utilization of spectrum resources by considering the consecutiveness of common available spectrum slots among relevant fibers.

Routing and spectrum assignment algorithm maximizes spectrum utilization in optical networks

Optical connections support virtual links in MPLS-over-optical multilayer networks and therefore, errors in the optical layer impact on the quality of the services deployed on such networks. Monitoring the performance of the physical layer allows verifying the proper operation of optical connections, as well as detecting bit error rate (BER) degradations and anticipating connection disruption. In addition, failure identification facilitates localizing the cause of the failure by providing a short list of potential failed elements and enables self-decision making to keep committed service level. In this paper, we analyze several failure causes affecting the quality of optical connections and propose two different algorithms: one focused on detecting significant BER changes in optical connections, named as BANDO, and the other focused on identifying the most probable failure pattern, named as LUCIDA. BANDO runs inside the network nodes to accelerate degradation detection and sends a notification to the LUCIDA algorithm running on the centralized controller. Experimental measures were carried out on two different setups to obtain values for BER and received power and used to generate synthetic data used in subsequent simulations. Results show significant improvement anticipating maximum BER violation with small failure identification errors.

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BER Degradation Detection and Failure Identification in Elastic Optical Networks

Next-generation ROADM networks are incorporating an extensive range of new features and capabilities including colorless, directionless, and contentionless multiplexing and demultiplexing, flexible spectrum channel definition, and higher-order modulation formats. To efficiently support these new features, both new ROADM node architectures along with complementary optical components and technologies are being synergistically designed. In this article, we describe these new architectures, components, and technologies, and how they work together to support these features in a compact and costefficient manner.

New devices enabling software-defined optical networks

The architecture of a single-chip dual-polarization QPSK/BPSK 50 Gigabits per second (Gb/s) DSP-based transceiver for coherent optical communications is presented. The receiver compensates the chromatic dispersion (CD) of more than 3,500 km of standard single-mode fiber using a frequency-domain equalizer. A time-domain four-dimensional MIMO transversal equalizer compensates up to 200 ps of differential group delay (DGD) and 8000 ps 2 of second-order polarization-mode dispersion (SOPMD). Other key DSP functions of the receiver include carrier and timing recovery, automatic gain control, channel diagnostics, etc. A novel low-latency parallel-processing carrier recovery implementation which is robust in the presence of laser phase noise and frequency jitter is proposed. The chip integrates the transmitter, receiver, framer and host interface functions and features a 4-channel 25 Gs/s 6-bit ADC with a figure of merit (FOM) of 0.4 pJ/conversion. Each ADC channel is based on an 8-way interleaved flash architecture. The DSP uses a 16-way parallel processing architecture. Extensive measurement results are presented which confirm the design targets. Measured optical signal-to-noise ratio (OSNR) penalty when compensating 200 ps DGD and 8000 ps 2 is 0.1 dB, while OSNR penalty when compensating 55 ns/nm CD (corresponding to 3,500 km of standard single-mode fiber) is 0.5 dB.

Architecture of a Single-Chip 50 Gb/s DP-QPSK/BPSK Transceiver With Electronic Dispersion Compensation for Coherent Optical Channels

We have developed an NxN cyclic-frequency router with improved performance by employing two types of modified configuration; a uniform-loss and cyclic-frequency (ULCF) arrayed-waveguide grating (AWG) and an interconnected multiple AWG. We have demonstrated a compact 50-GHz-spacing 64x64 ULCF-AWG router with low and uniform insertion losses of 5.4-6.8 dB and frequency deviations from the grid of less than plusmn8 GHz. We have also demonstrated a 100-GHz-spacing 8x8 interconnected multiple-AWG router with a practical configuration, very low and uniform insertion losses of 2.3-3.4 dB, and frequency deviations from the grid of less than plusmn6 GHz. We discuss the suitable or realizable scale N of the two types of routers by comparison with a conventional AWG router in terms of optical and dimensional performance and productivity.

$N \times N$ Cyclic-Frequency Router With Improved Performance Based on Arrayed-Waveguide Grating

https://www.jstage.jst.go.jp/article/comex/1/2/1_54/_pdf

Evaluation of optical filtering penalty in digital coherent detection system

We demonstrate hybrid 40-Gb/s and 100-Gb/s PDM-QPSK DWDM transmission using real-time DSP in 580-km DSF-installed field testbed. The nonlinear crosstalk penalty due to the hybrid transmission of less than 0.5 dB is confirmed.

Hybrid 40-Gb/s and 100-Gb/s PDM-QPSK DWDM transmission using real-time DSP in field testbed

We demonstrate a colourless, directionless, contentionless ROADM consisting of 1×43 WSSs and PLC-based transponder aggregators The experimental results show that the introduction of a C/D/C-less function causes no significant penalty for 127-Gbit/s DP-QPSK signal transmission

Experimental demonstration of colourless, directionless, contentionless ROADM using 1×43 WSS and PLC-based transponder aggregator for 127-Gbit/s DP-QPSK system

We demonstrate the feasibility of arrayed optical amplifiers sharing a single pump laser to realize full-add/drop C/D/C-less ROADM nodes. Experimental results show that the arrayed optical amplifiers corresponded properly to the wavelength path reconfigurations by adjusting the splitting ratio of the splitter between the pump laser and eight EDFAs.

Full-add/drop C/D/C-less ROADM achieved by developing arrayed optical amplifiers with a shared pump laser

PROBLEM TO BE SOLVED: To optimize a network accordingly from time to time over a plurality of layers without giving an impact to a service.SOLUTION: In two or more layers, each layer has an interface part and a cross-connect part, the interface part and the cross-connect part of each layer are connected to a device control part of the layer, the device control parts of the respective layers are connected to an integrated network control part, and information of the respective layers are integrally managed in the integrated network control part so that a network is optimized. In the integrated network control part, an object function corresponding to an optimization index is calculated using a prescribed algorithm on the basis of given conditions, whether or not the result is optimum is determined, and an interface is set on the basis of a calculation result determined as being optimum.

Takeshi Kawai

Papers

Evaluation of optical filtering penalty in digital coherent detection system

Hybrid 40-Gb/s and 100-Gb/s PDM-QPSK DWDM transmission using real-time DSP in field testbed

Experimental demonstration of colourless, directionless, contentionless ROADM using 1×43 WSS and PLC-based transponder aggregator for 127-Gbit/s DP-QPSK system

Full-add/drop C/D/C-less ROADM achieved by developing arrayed optical amplifiers with a shared pump laser

Multilayer integrated transmitter and optimization method