June 6, 2019
The University of L’Aquila
Sumitomo Electric Industries, Ltd.
Optoscribe Ltd.

The World’s First Field Deployed Multi-Core Fiber
Testbed for Optical Communications Installed inL’Aquila, Italy
The University of L’Aquila, Sumitomo Electric Industries, Ltd. and Optoscribe Ltd.
have jointly deployed the world’s first testbed for multi-core fiber communications
in a field deployed environment in the city of L’Aquila, in Italy.

The University of L’Aquila, Sumitomo Electric, and Optoscribe have jointly deployed theworld’s first multi-core fiber (MCF) testbed for space-division multiplexed*1 (SDM) fiberoptic communications in a real-field environment in the city of L’Aquila, as part ofINCIPICT project.[1,2] An MCF is an optical fiber with multiple cores in a glass cladding
and is considered one of the most promising SDM transmission technologies toovercome the limitations of conventional single-core fiber communication systems. ForINCIPICT, Sumitomo Electric fabricated two types*2 [3–5] of uncoupled MCFs and one
type*3 of coupled MCFs with a standard glass diameter of 125 µm*4 (details in Table 1).
The standard glass diameter enabled the use of conventional optical fiber cable andconnector technologies. The MCFs were cabled into conventional loose-tube jelly-filledcables (Fig. 1) widely used in Europe. Optoscribe manufactured fan-in/fan-out (FIFO)
devices*5 3D OptoFanTM[6] for the conversion between MCFs and multiple standard
single-mode fibers (SMFs). The MCF cable was installed in a microduct placed on
INCIPICT’s rack in the walkable multi-service underground tunnel sketched in Fig. 1.
Figure 2 shows the experimental fiber-optic network of INCIPICT, in the city of L’Aquila.
The MCF testbed was installed as a part of it. The total length of the installed MCF cable
is 6.3 km, of which 5.6 km in the tunnel and 0.7 km in the laboratory that gives access tothe fibers. The optical properties of the MCFs were evaluatedbefore and after the installation, and no significant degradations
due to the installation were observed.

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Table 1: MCFs installed in the testbed
(a)

(b)

(c)

Uncoupled

Uncoupled

Coupled# of coresin a fiber844# of fibers
in a cable24

12

O bandO, C, L bands

1260 to 1625 nm

1530 to 1625 nm[3,4][5]n/aType

Fibercross section

Transmission
suitable
wavelengthband
Reference

1260 to 1360 nm

C, L band

Anti-rodent
microduct

Rack ofINCIPICT

Jelly

……

……

Racks
for otherservices

Inner
tube

LSZH
jacketMCFs

Strengthmember(FRP)

Pipes/ducts
for otherservices

Aramid yarns

Figure 1: Schematics of the walkable underground tunnel with INCIPICT’s rack (left),
and the installed MCF cable in a microduct (right)*The images are shown for illustrative purposes, and rack/pipe/duct counts/positions
may differ from the actual ones.

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Figure 2: L’Aquila city and the tunnel where MCF cable was installed[Future prospect]
The MCF testbed will be used to host various R&D activities in fiber optic communications,and specifically in the area of SDM transmission over MCFs. These include device testing,transmissions and software-defined networking, also in conjunction with the ongoing 5G
trial (L’Aquila is one of the five Italian sites selected for trialing 5G technologies). The
testbed will serve to assess problems and requirements for deployed MCFs, thereby
contributing to the development of SDM transmission systems. The testbed will beavailable to the international research community under the jurisdiction of the Universityof L’Aquila.

[Acknowledgements]
The MCFs fabricated by Sumitomo Electric for INCIPICT was cabled by Opticable S.A.,a joint venture of Nexans S.A. and Sumitomo Electric, in Belgium.

[About the city of L’Aquila, and INCIPICT Project]
The city of L’Aquila, the regional capital of Abruzzo, is located in central Italy. The city
was struck by a high-magnitude earthquake on April 6, 2009,
which destroyed most of the city center. Since the beginning ofthe reconstruction process, the city has been open to various

3/5experimental projects based on a green-field approach, to which a fraction of thereconstruction funds has been dedicated. One of these projects is INCIPICT (Innovating
City Planning through Information and Communications Technologies), proposed and ledby the University of L’Aquila and funded by the Italian Government, in the spirit of
supporting production and research activities in L’Aquila. Inspired by the concept of aliving-lab, this project includes various research activities that ultimately rely on the fiberoptic infrastructure. Details can be found in [1,2].

*1 Space-division multiplexed transmission
A transmission method for multiplexing signals using multiple spatial channels in opticalfiber. Various fiber structures have been proposed to this end, including MCFs, wherethe fiber cores are used as spatial channels, and few mode fibers, where the fiber modes
are used as spatial channels.

*2 Uncoupled multi-core fiber
An MCF designed so as to suppress crosstalk (XT) between cores, so that an MCF withN cores is equivalent to N isolated single-core fibers with higher spatial density of cores.

*3 Coupled multi-core fiber
An MCF with smaller core-to-core pitch than uncoupled MCFs, intentionally designed tohave random coupling between cores. Although multiple-input-multiple-output (MIMO)
digital signal processing is necessary for extracting the signals transmitted in the variouscores, random coupling reduces the accumulation of nonlinear propagation effects andmodal dispersion (which has a considerable impact on the MIMO complexity). Theseadvantages are significant in long-haul point-to-point links, such as submarinetransmission systems.

*4 Standard glass diameter
The cladding diameter of a fiber is defined to be 125 ± 0.7 µm and the coating diameterto be 235-265 µm by international standards.

*5 Fan-in/fan-out device

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A device that connects individual conventional SMFs to the cores of an MCF.

[References][1] http://incipict.univaq.it[2] C. Antonelli et al., “The City of L’Aquila as a Living Lab: the INCIPICT Project and the5G Trial,” in 2018 IEEE 5G World Forum (5GWF), 2018, pp. 410–415.
[3] T. Hayashi et al., in Opt. Fiber Commun. Conf. (OFC), Los Angeles, 2015, paper
Th5C.6.
[4] T. Hayashi et al., in Int. Wire Cable Symp. (IWCS), Providence, 2018, paper P-6.
[5] T. Matsui et al., in Eur. Conf. Opt. Commun. (ECOC), Valencia, 2015, paper We.1.4.5.
[6] http://www.optoscribe.com/products/fiber-to-fiber-interconnects/[Contact Information]

University of L’Aquila
Ufficio comunicazione web, network e social
Tel. +39 320 43 99496
E-mail: com@strutture.univaq.it

Sumitomo Electric
Public Relations Department
Reika Nishihira
Tel: +81-3-6406-2701
E-mail: web@info.sei.co.jp
Sumitomo Electric's Website：https://sumitomoelectric.com/
Optoscribe
Derek Milne
Communications Manager
Tel: +44 7734 137555
Email: d.milne@optoscribe.com

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