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First Demonstration of Dynamically Controlled Multicore Fiber Network

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October 10, 2013

The National Institute of Information and Communications Technology (NICT, President: Dr. Masao Sakauchi) in collaboration with the University of Bristol of United Kingdom has demonstrated successfully for the first time a dynamically controlled multicore fiber based network. The research relies on Space Division Multiplexing (SDM) provided by the multicore fibers and on Software Defined Networking (SDN) control, which are considered promising solutions to fulfill and control the ever-increasing demand for data consumption in communication networks.
While multicore fibers and associated optical components have been intensively investigated as key components for SDM in recent years, only little effort has been put so far into addressing challenges that arise when controlling optical networks composed of multicore fibers. This work represents the first successful demonstration of a fully functional multicore fiber network taking advantage of the flexibility and intelligence that SDN can offer in order to provide services to emerging Internet applications. As such, the implemented OpenFlow interface dynamically configures the node in a way that the network can deal more effectively with specific traffic requirements such as bandwidth and QoT (Quality of Transport). With the growing popularity of OpenFlow, this demonstration is believed to bring multicore fiber networks one big step closer to their practical realization. The results of the demonstration were selected for presentation as a prestigious post-deadline paper at the European Conference and Exhibition on Optical Communication (ECOC) 2013 in London on September 26, 2013.


As today’s optical fiber networks are steadily approaching their theoretical capacity limits, Space Division Multiplexing (SDM) technologies such as multicore fibers have been at the focus of worldwide research to overcome this physical barrier. Although most on-going research efforts have been concentrating solely on the improvement of data throughput and transmission distance of point-to-point links, it is becoming apparent that the success of SDM will also be strongly governed by its applicability to optical networks together with an adequate control of all required switching functions in the network nodes.
From the viewpoint of network control, Software Defined Networking (SDN) has been recently gaining increasingly attention as a technology that enables network operators to adapt easily the network infrastructure to quickly changing user or application requirements and thus improve network efficiency. To date, however, SDN has been applied only to optical networks based on single-core fibers and therefore restricted to the capacity bottlenecks of the current fiber infrastructure.

Demonstration of Multicore Fiber Network
Demonstration of Multicore Fiber Network

In this work, NICT and the University of Bristol have joined forces to demonstrate the first successful operation of an SDN controlled SDM network. NICT contributed with two multicore fibers (MCFs) and a new transmission technique based on self-homodyne detection (SHD). The University of Bristol developed the SDN control based on extensions of the OpenFlow protocol and provided the novel network node equipment. As shown in Fig. 1 in the appendix, the network for this demonstration consists of three nodes connected by a 19-core MCF, a 7-core MCF and single-core fibers. The SDN controller translates connectivity requirements such as source, destination, bandwidth and Quality of Transport (QoT), into physical layer requirements such as number of cores, wavelength, data rate and the modulation format. Each data signal can be assigned to either a single core or a group of cores (4, 6 or 8 in this case) to demonstrate flexible bandwidth provisioning from 40 to 512 Gbps in conjunction with different QoT requirements. In addition, SHD significantly relaxed the signal processing requirements in the receiver.
Spatial multiplexing will give networks more flexibility in allocating optical paths to a growing number of applications in the future. In combination with the popular OpenFlow protocol we expect that this demonstration will encourage the use of SDM and multicore fibers in future optical networks.

Future Prospects

NICT and the University of Bristol hope to further improve their network technologies on both the software and hardware side and promote together the practical realization of multicore fiber networks.


Fig.1 Example of network control and data transmission in SDN-controlled SDM networks
SHD: Self-homodyne Detection,
QAM: Quadrature Amplitude Modulation,
QPSK: Quadrature Phase Shift Keying,
BPSK: Binary Phase Shift Keying,
MCF: Multicore Fiber,
SMF: single-mode / single-core fiber


SDN (Software Defined Networking)

A generic name of technologies which makes the network control method programmable from software outside from the network equipment, unlike the traditional method that is implemented in the same unit. SDN is marked as a method which makes it possible to provide customized network control for each service, or totally new networking methods.


One of SDN technologies of which the Open Networking Foundation (ONF) is currently working toward standardization in the industry. A lot of adopted equipment is already released. The network control in OpenFlow is done by an external controller that sends information called ‘flow entry’ to the switches. Each switch decides the packet processing based on this information.


The European Conference and Exhibition on Optical Communication (ECOC) is the largest optical communication event in Europe and provides a forum for new results and developments. The 39th ECOC Conference was held in London from September 22 - 26, 2013.

Self-homodyne Detection (SHD)

In optical transmission system data signals get distorted by noise, and error-free detection requires powerful signal processing in the receiver. The self-homodyne detection technique in combination with multicore fibers utilizes an additional signal called the pilot tone which is generated from the same source as the data signal but sent through a different core of the fiber. By combining optically the data signal and pilot tone in the receiver much noise can be removed already in the optical regime and thus relax the requirements of the signal processing in the electric regime, which in turn reduces the overall power consumption of the receiver.

Technical Contact

Naoya Wada
Photonic Network System Laboratory
Photonic Network Research Institute
Tel: +81-42-327-6371 

Hiroaki Harai
Network Architecture Laboratory
Photonic Network Research Institute
Tel: +81-42-327-5418 

Media Contact

Sachiko Hirota
Public Relations Department
Tel: +81-42-327-6923