13. Perspectivas Futuras Das Redes Opticas (Artigo)

8/3/2019 13. Perspectivas Futuras Das Redes Opticas (Artigo)

1/13

4684 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 24, NO. 12, DECEMBER 2006

Future Optical NetworksMichael J. OMahony, Senior Member, IEEE, Christina Politi, Student Member, IEEE,

Dimitrios Klonidis, Member, IEEE, Reza Nejabati, Member, IEEE, andDimitra Simeonidou, Member, IEEE

Invited Paper

AbstractThis paper presents views on the future of optical net-working. A historical look at the emergence of optical networkingis first taken, followed by a discussion on the drivers pushing for anew and pervasive network, which is based on photonics and cansatisfy the needs of a broadening base of residential, business, andscientific users. Regional plans and targets for optical networkingare reviewed to understand which current approaches are judgedimportant. Today, two thrusts are driving separate optical networkinfrastructure models, namely 1) the need by nations to provide

a ubiquitous network infrastructure to support all the futureservices and telecommunication needs of residential and businessusers and 2) increasing demands by the scientific community fornetworks to support their requirements with respect to large-scaledata transport and processing. This paper discusses these networkmodels together with the key enabling technologies currently beingconsidered for future implementation, including optical circuit,burst and packet switching, and optical code-division multiplex-ing. Critical subsystem functionalities are also reviewed. The dis-cussion considers how these separate models might eventuallymerge to form a global optical network infrastructure.

Index TermsOptical communications, optical networks.

I. INTRODUCTIONEMERGENCE OF

OPTICAL NETWORKING

THE INVENTION of the laser by Schawlow and Townes

in 1958, followed by the work of Kao and Hockham

on optical fibers in 1965, and the subsequent demonstration

of optical fiber as a practical communication medium by

Maurer et al. in 1970 brought into being a technology plat-

form capable of supporting national and global communication

requirements for the 21st century and beyond. In the late

1970s, fiber began to replace coaxial cable as the transmission

medium in the trunk systems of telecommunication networks,

bringing many advantages both technical and economic. The

creation of the Internet (with Transmission Control Protocol

(TCP)/IP) in 1983 and subsequently the World Wide Web in1993 sparked the growth of data traffic on the network, and

Manuscript received April 19, 2006; revised September 20, 2006.M. J. OMahony, R. Nejabati, and D. Simeonidou are with the Photonic Net-

works Research Laboratory, University of Essex, CO4 3SQ Colchester, U.K.(e-mail: [email protected]; [email protected]; [email protected]).

C. Politi was with the Photonic Networks Research Laboratory, Universityof Essex, CO4 3SQ Colchester, U.K. She is now with the National TechnicalUniversity of Athens, 10682 Athens, Greece (e-mail: [email protected]).

D. Klonidis was with the Photonic Networks Research Laboratory, Uni-versity of Essex, CO4 3SQ Colchester, U.K. He is now with the AthensInformation Technology Centre, 19002 Athens, Greece (e-mail: [email protected]).

Color versions of Figs. 25 are available online at http://ieeexplore.ieee.org.Digital Object Identifier 10.1109/JLT.2006.885765

Fig. 1. Evolution of transport and service bit rates.

in 2002, or thereabouts, the amount of network data traffic

exceeded that of voice traffic. In the decade from 1985 to

1995, four significant events heralded the possibility of optical

networking, where both transmission and switching might be

based on optics. These were 1) the realization of optical am-

plifiers allowing 2) the economic deployment of wavelength

division multiplexing (WDM), 3) the demonstration of an

optical cross-connect (OXC) enabling the rapid reconfigura-

tion of lightpaths based on wavelength channels, and 4) the

convergence of service and transport transmission rate.

Early visions of optical networking considered, for example,

the deployment of OXCs to form an extension to the exist-

ing synchronous digital hierarchy/synchronous optical network

(SDH/SONET) network layersthe optical layer. In this paper,

an OXC is defined as a general wavelength switch that can be

realized in an all-optical (transparent) manner [optical input,

optical switch fabric, optical output (OOO)] or in an opaque

manner [optical input, electrical switch fabric, optical output

(OEO)] through choice of technologies. The optical layer wouldenable long-haul transit traffic to bypass the main switch nodes

and hence reduce the size and cost of the digital cross-connects

(DXCs). Demonstrations of such reconfigurable networks were

carried out in Europe and the United States in 1994 [1], [2].

The convergence of service and transport wavelength bit

rates around the year 2000 (Fig. 1), at a bit rate of 10 Gb/s,opened the possibility of direct interfacing between, for exam-

ple, an IP network and an optical transport network employing

WDM and OXCs, where the granularity of the network directly

matched the router interface rate. The figure also shows that

convergence at 40 Gb/s occurred in 2005 with the availability of

40-Gb/s routers and engineered 40-Gb/s dense WDM (DWDM)

0733-8724/$20.00 2006 IEEE


2/13

OMAHONY et al.: FUTURE OPTICAL NETWORKS 4685

Fig. 2. Schematic of telecommunications network.

transmission systems [3]. Each wavelength, of course, supports

many traffic streams.

Fig. 2 shows a schematic of the possible future telecommuni-

cations network showing core, metro, and access layers, which

builds on earlier concepts and will be used to discuss views

of future optical networks. The core cloud represents an opti-

cal network comprising a number of nodes interconnected by

amplified fiber links employing DWDM. The nodes comprise

an OXC in conjunction with a network service element (SE).

The OXC supports the bypass function and allows specific

wavelength channels to be dropped to the SE, which, for exam-

ple, could be an IP/multiprotocol label switching (IP/MPLS)

router, an SDH/SONET DXC, or an optical burst, packet,

or Ethernet switch, as discussed later. At the network edge,

traffic is mapped onto the network services via an edge inter-

face/router, which can perform either user network interface

(UNI) or network node interface (NNI) functionality as definedby the optical internetworking forum [4], depending on what is

connected to the core. A control plane is required to establish

paths across the data plane as requested at the network edge,

mapping, for example, an IP/MPLS stream from the metropoli-

tan area network onto a specific wavelength; path establishment

can be done in a centralized or distributed manner.

Fig. 2, however, shows only one of a number of network

models, based on optical technology, currently being developed

to satisfy an increasing diversity of users with greatly differing

service requirements; networks to support scientific users are

another example and are discussed below. Currently, operator

business models do not encourage the development of a ho-mogeneous network, and so, interoperability issues are arising

between these different (heterogeneous) networks. This paper

addresses two developing optical network models, representing

residential/business (telco) and scientific users, to understand

their requirements and evolution paths. The key (optical layer)

functionalities required in these networks are considered (rather

than the detail of all the technology issues that inevitably are

part of any evolution) with a view to understanding how a

future interoperable global heterogeneous optical network with

end-to-end connectivity and possibly eventually transparent

(homogeneous) networking might be achieved. It is recognized

that a number of functions, for example, dispersion compen-

sation, are currently migrating to the electronic domain, butthese topics are not considered here. As discussed earlier,

TABLE IRESIDENTIAL SERVICE REQUIREMENTS

optical networking includes the concept of OXCs (wavelength

switches) using either an OEO switching or OOO approach; the

latter is currently a more futuristic approach supporting network

transparency, which may well solve many problems including

cost issues related to the reduction in the required number ofOEO interfaces. However, recent approaches by Infinera [5],

where all the interfaces are integrated on a chip, challenge this

simple viewpoint.

In this paper, Section II looks at applications and their

requirements, Section III considers the importance of future

networks together with regional plans for optical infrastruc-

tures, Sections IV and V look at two emerging network models

as represented by national telecommunication networks and na-

tional research and educational networks (NRENs), Sections VI

and VII consider key networking approaches and technologies,

Section VII looks at a possible future global heterogeneous

optical network serving all users, and Section VIII summa-rizes. Here, it should be noted that the views in this paper

are essentially research led, and the adoption of many of the

approaches and technologies highlighted are, as always, subject

to commercial considerations that can change rapidly, as seen

in the year 2000.

II. 21ST CENTURY: EDGE OF THE DATA TSUNAMI

Between the years 2000 and 2003, the volume of data grew

from 3 billion to 24 billion gigabytes, with 93% of all data

being born digitally [6]. This highlights the start of a huge wave

of data to be expected over the next five to ten years as many

traditional services and industries move from analog to digital

(e.g., TV broadcasting and movie making), and the spread

and development of e-services across government, health, and

security become more available and acceptable. In addition

to the increased expectations from residential and business

users, new requirements from scientific users are driving the

deployment of high-performance optical networking. Examples

of these drivers are as follows.

A. Residential Users

The bandwidth requirements for fixed home users have been

estimated at 100 Mb/s (downstream) in the near future, asshown in Table I [7], the main demand arising from Triple


3/13


Play services (already launched in a number of EU countries)

that include voice data and video, and mobile users will also

require high bandwidth access, estimated as 30 Mb/s in this

model. These figures would be greatly increased if, as ex-

pected in Japan, superhigh-definition TV would also become a

broadcast service, moving access speed requirements into the

gigabits per second regime.

B. Large Business/Enterprise Users

Large business/enterprise users require access to high sym-

metric bandwidths (e.g., up to 10 Gb/s) for virtual private

networks, disaster recovery, storage, etc.

C. Scientific Users (Currently Served by NRENs)

Application examples include the following.

1) High-Energy Particle Physics: The next generation of

experiments at the Large Hadron Collider in CERN will pro-

duce data sets measured in tens of petabytes per year that canonly be processed and analyzed by globally distributed com-

puting resources. Experiments require deterministic transport

of 10- to 100-TB data sets, and a 100-TB data set requires a

throughput of 10 Gb/s for delivery within 24 h. Thus, optical

network services will be crucial to this discipline where dedi-

cated and guaranteed bandwidth is required for periods of days.

2) Very Long Baseline Interferometry (VLBI): VLBI is used

by radio astronomers to obtain detailed images of cosmic radio

sources, where the combination of signals from two or more

widely separated radio telescopes can effectively create an

instrument with a resolving power proportional to their spatial

separation. e-VLBI [8] will use high-speed networks to transfer

telescope data to a correlator, and the availability of opticalnetwork services at multi-gigabits per second (1040 Gb/s)

throughput will greatly increase the capability.

3) e-Health: Remote mammography poses challenges for

the deployment of supporting IT systems due to both the size

and the quantity of images, with networks required to transport

1.2 GB of data every 30 s. The availability of optical network

services offering real-time guarantees is important in this field.

All these applications, whether residential, scientific, or

business related, look for high bit rate access, wavelength

and subwavelength granularity, and quality-of-service (QoS)

guarantees; these qualities can be delivered through optical

networking.

III. MOVE TOWARD PERVASIVE AND UBIQUITOUS

NETWORKSR EGIONAL PLANS

In the face of this wave of new data-oriented services, the tra-

ditional telecommunications network is seen as transforming to

a generic and data-centric communications network optimized

for data. Most regions of the world have a vision of moving to

a situation that in Japan is called ubiquitous network society

and in Europe is called ambient intelligence. By this is meant

an environment (comprising wired and wireless network) where

one can communicate effortlessly and access key information

resources in a straightforward manner. To achieve these ideals,the ultimate network will have as its main building blocks

a fixed optical network platform accessed through wireless

(Wi-Fi, WiMax, UMTS) and wired infrastructures, such as fiber

to the premises (FTTP). Moving to such an all-pervasive net-

worked society, however, puts increased demands on network

reliability and security; it must be there when it is needed and

have the ability and flexibility to interface and integrate multiple

technologies and service requirements.The importance of future national network infrastructures is

mirrored in the ongoing discussions on how a new Internet

might be realized. It has been commented [9] that the Inter-

net is expanding from an information service to a critical

infrastructure for all aspects of society, and so, new network

architectures must evolve to overcome many of the problems

inherent in the current Internet. NRENs and experimental net-

work testbeds are currently being used (in part) to understand

how a new Internet might be constructed. The inference is

that at all levels, communication networks are no longer just

desirable but critical for a nations development and security.

Regional views on expected growth in capacity demands,

traffic profiles of new services, and the need to move to data-

centric networking are reflected in the scope of the major

research programs and their associated projects funded by

regional governments.

In Europe, the European Commission (EC) periodically re-

leases tranches of funding for R&D. Currently, there are no

overarching roadmaps for future networks, but a number of very

large integrated projects identify their own vision of the

future. The NOBEL project [10], for example, studies the

evolution of core and metropolitan optical transport networks,

supporting end-to-end QoS, with intelligent data-centric solu-

tions based on automatic switched optical network (ASON)

and generalized MPLS (GMPLS) [3] together with optical burstswitching (OBS) and optical packet switching (OPS).

The investigation of OPS has had long-term support within

EU and national programs with projects such as ATMOS,

KEOPS, DAVID [11], and OPSNET/OPORON [12], [13]

developing the technology and its application over a period of

about 15 years; however, it is still seen as a very future tech-

nology. On the other hand, OBS and GMPLS approaches are

viewed as realistic possibilities for more near-term deployment,

and research in these areas is also echoed in national funding in

many countries.

Recently, BT (U.K.) has committed itself to moving to a

converged national network solution (BT 21CN Network) withan IP/MPLS core [14]. This change is also under way in other

countries (Netherlands and Australia) and is significant in that

the architecture opens the path to a full optical transport net-

work at some point in the future, with the possible replacement

of OEO switches and regenerators with OOO technologies.

Europe is also characterized by a large number of NRENs

that exist in most member countries. These networks are na-

tionally funded and commonly used for research into scientific

applications (of the type discussed above). The EC funds an

overlay network GEANT [15] that provides interconnections

between these national networks and provides international

connections, for example, to the United States. These networks

look to lambda networking based on scheduled or dynamicprovision of lightpaths.


4/13


The Pacific Rim countries of Japan and Korea are well known

for their ambitious plans in relation to broadband deployment

and enhanced network infrastructures.

Japan has well-defined R&D programs; some are initiated

by the Japanese government with a view to evolving a legacy

telecommunications network to an IP over WDM network.

Such programs move in tandem with operator plans; forexample, NTT plans to migrate 30 million customers to FTTP

and IP telephony by 2010. The most recent program focused on

developing an all-optical transport network with terabit capa-

bility [16]. This paper comprised the study and development

of photonic nodes such as fast OXC based on microelectro-

mechanical system (MEMS) together with control plane (such

as GMPLS), OBS, and high-bit-rate ultralong transmission

based on DWDM (up to 1000 channels) and optical time

division multiplexing (OTDM). For photonic routing, targets

are related to the feasibility of 100-Tb/s routers and network

architectures appropriate to a terabit-class wavelength-routed

optical network. The current program seeks to understand how

this optical platform can support new bandwidth demanding

applications such as grid computing and real-time applications

like video, digital cinema, and network storage. It is anticipated

that broadcasting and streaming of high-quality video using

high- or superhigh-definition TV (4.5 Gb/s) together with grid

computing and e-science applications may need to be sup-

ported, many of these on FTTP. Key targets include 160-Gb/s

multilevel transmission systems using differential quadrature

phase shift keying/quadratic-amplitude modulation, etc., aim-

ing at bandwidth utilization of more than 2 bits/Hz by 2010.

Ultrafast signal processing functions such as optical gating,

optical-3R, OTDM, optical multiplexing/demultiplexing, and

optical wavelength conversion are seen as important.South Korea is known to (currently) have the worlds highest

(> 60%) penetration of broadband (> 4 Mb/s) Internet access.

The broadband convergence network (BcG) is the Korean

vision of the ITU-T next-generation (NG) network defining

future transport and access architectures and is expected to sup-

port 20 million users by the year 2010. In the access network,

technologies will be FTTP with E-passive optical network

(E-PON) and WDM-PON. The BcG transport network will be

a managed optical network with support for end-to-end QoS

provisioning. BcG is seen as a ubiquitous network that will also

support grid applications.

China has a number of optical network testbeds for ASONand OBS, which investigate the support of future IP-based

services. Moreover, there is a strong interest in optical grid

networking with associated research into architectures, control

plane functions, and interfaces [21].

In the USA, funding for research (nonindustrial) is through

the National Science Foundation and for large projects often

through DARPA. Current major photonic activities include

studies on optical code-division multiplexing (OCDM) and

terabit router technology; the latter represented by projects

IRIS [17] and LASOR [18] whose goal is to realize 100-Tb/s

routers. Both projects take the route of OPS, which offers

attractions in terms of footprint and power requirements.

The strong interest in optical networking in the USA isreflected in the existence of a number of national testbeds,

Fig. 3. Network evolution.

which enable the interconnection of scientific users and sup-port research into future networks. For example, the National

Lambda Rail (NLR) [19] is a high-speed national computer

network that is also used as a network testbed for experimen-

tation with NG large-scale networks. Links in the network

use DWDM at 10-Gb/s/channel. NLRs services are already

in use by many network research projects, for example, the

NSF OptIPuter project and Internet 2s Hybrid Optical Packet

Infrastructure (HOPI) project, which looks at a future in-

frastructure comprising an IP core network together with an

optically switched wavelength set, for the dynamic provisioning

of high-capacity paths. Currently being proposed is a new na-

tional facility GENI [20], which includes a global experimental

facility designed to explore new network architectures with

the broad scope of understanding new paradigms for Internet-

type networks.

IV. EVOLUTION TOWARD NATIONAL OPTICALTELECOMMUNICATION NETWORKS

Fig. 3 outlines a possible evolution route for the network

structures and technologies that may appear in the future op-

tical (transport) network; a version of many such diagrams

have been presented over the years. Progress toward optical

networking has been much slower than envisaged in the late

1990s, and currently, the first real steps toward networkingare seen in the deployment of reconfigurable optical adddrop

multiplexers (ROADMs), in particular those based on a mul-

tiport wavelength selective switch (WSS) [22]. These devices

have the functionality of OXCsan exciting development. In

the following discussion, the evolution is examined from three

viewpoints.

A. Transmission Speed

Current networks employ amplified DWDM systems with

individual channel bit rates up to 10 Gb/s to connect main

switching centers, and the industry is on the verge of deploying

40-Gb/s systems. There are many reasons for believing that bitrates will increase beyond 10 Gb/s and perhaps even to 160 Gb/s


5/13


(Fig. 3). For example, 1) in the past, it has always been

advantageous to move to high bit rates from a cost viewpoint;

2) although optical amplifiers are reasonably bit rate agnostic,

most of the more advanced functions currently considered for

future networks such as all-optical regeneration, wavelength

conversion, dispersion compensators, etc., can only operate on

a single wavelength; and 3) when future OOO switches aredeployed, then increasing the bit rate can help in reducing the

port count required of the switch fabrics [23], as large OOO

switch fabrics are difficult to realize, for example, in the case

of an OPS where it is difficult to scale fabrics; for wavelength

switching, waveband approaches [24] can be used to mitigate

these technological issues. Increasing the bit rate, however,

leads to a more demanding requirement for system design to

minimize the effects of dispersion (chromatic and polarization)

and nonlinear effects; thus, there is the increasing interest in

modulation techniques such as differential phase-shift keying

(DPSK), which is more robust to transmission impairments than

intensity modulation.

B. Network Switching

Much research has focused on moving from the traditional

circuit-based switching to a more dynamic and data-centric

network enabling rapid lightpath reconfiguration and providing

subwavelength granularity, as needed by the new applications

discussed above. In its present form, the network has a complex

layering to allow the simultaneous support of data and voice

services; in this mode, data (IP) may be encapsulated into

asynchronous transfer mode (ATM) cells (or SDH/SONET

frames) for transmission across the point-to-point connections

between DXCs. Currently, the network is changing to a moredata-oriented version of SDH/SONET (NG SDH/SONET).

Fig. 3 illustrates the possible further stages in the network

switching evolution. Fig. 3(a) represents the move to a more

data-centric and dynamic switching model using an ASON

[4] architecture, which would allow automated lighpath pro-

visioning and supports NG-SDH/SONET with DXC or OXC

(OEO) switching in the data plane. Fig. 3(a) also shows that

a move to IP/MPLS (i.e., IP routers) or GMPLS (with OEO

or OOO wavelength switches) architectures is foreseen, which

provides an enhanced dynamic capability GMPLS to allow all

transport modes, circuits, burst, and packets to be supported and

can be deployed in either a centralized or a distributed mode.This represents one of the options to build a converged net-

work, where the backbone is a multitechnology IP/GMPLS/

OEO/OOO network supporting all services (voice, data, video),

which may overtake the ASON architecture. It is also the

case that in recent times carrier Ethernet [25] (based on native

Ethernet or MPLS) looks increasingly attractive across all

layers of the network. Indeed, within the U.K., some (small)

network providers already operate national converged networks

with Ethernet switching elements. The move toward 100 GbE

standards illustrates the importance of this technology and

hints of future major roles in NG networks. Fig. 3(b) rep-

resents a move to a user-centric design based on OBS with

GMPLS (OBS/GMPLS); this technology provides subwave-length granularity and is also of interest to future optical grid

networks [26]. Finally, Fig. 3(c) represents the move to an

OPS network, where MPLS provides a common (across elec-

trical/optical domains) control plane. OPS offers the finest

granularity and is still seen as the ultimate switching technique,

but its success will depend on many technological advances;

these options are discussed in more detail in Section VI.

The metro/aggregation network (Fig. 2) delivers data fromthe access to the edge device for processing and will likely use

DWDM supporting, for example, carrier Ethernet, but it is the

access network that provides the key to the future, in particular,

the move toward FTTP.

C. Access PONs

FTTP supports the PON concept, which has been studied

for over 20 years but now increasingly deployed. PONs offer

multiservice (voice, data, video, and telemetry) and multiproto-

col (IP, TDM, and ATM) support and thus are a very flexible

infrastructure. A number of possibilities have been studied,

which exploit the basic PON concept but with a view to reduce

costs. Two examples follow.

Long-Reach PONs: Some operators [27] see the possibility

of merging metro and access in a long-reach (amplified) PON.

Optical amplification is included to boost the power budget and

increase bandwidth, range, and number of splits. Long reach is

used to bypass the metro network and terminate at a core edge

node; this enables the removal of the local exchange or remote

concentrator site. In the U.K., this would require 100 of these

core edge nodes with long reach spans of 100 km and bit rates

of at least 10 Gb/s.

CWDM/OCDMA PONs: Coarse WDM (CWDM) allows

low-cost WDM to be deployed (as device cooling is not re-quired), and CWDM uses a channel spacing of 20 nm, so only

eight or so channels can normally be deployed. Optical code-

division multiple access (OCDMA) has been demonstrated

[28], [29] as a robust complementary technology that could

also be deployed in conjunction with CWDM to increase the

number of users. As with WDM, OCDMA offers the possibility

of translation from one channel to another (code translation),

opening many interesting possibilities.

V. EMERGENCE OF AN ALTERNATIVE NETWORK MODEL

Following the realization that a computer bus speed cannot

match a lambda-based optical network (at 10 Gb/s), it was

suggested that it should be possible to create a tightly integrated

cluster of computational, storage, visualization, and instrumen-

tation resources linked over parallel dedicated optical networks

across campus, metro, national, and international scales to sup-

port scientific tasks, and this concept is now being demonstrated

in network testbeds and NRENs. Scientific and grid applica-

tions have complex workflows, which will make extensive use

of an optical network, for example, to transfer huge amounts of

data between storage and computing or visualization resources.

In many ways, NRENs mirror the possible future requirements

on telecommunication networks and may evolve to use a similarset of optical technologies (e.g., OBS).


6/13


Fig. 4. NRENs.

NRENs have high-speed optical backbones and can already

offer dedicated channels (wavelengths) to individual research

users. Switching within these networks is, at present, generally

achieved through OEO switches, allowing wavelength rout-

ing. NRENs are seen as an important vehicle for advancing

innovation and discovery and as a platform for undertaking

network research. In Europe, GEANT connects 30 such NRENs

(with bit rates up to 10 Gb/s); in Japan, JGN2 provides an

research and development environment (at 10 Gb/s); Abiline in

the United States interconnects 50 states; Canada has CA,net;

and Chinas CERNET2 connects 20 cities (at 10 Gb/s). Global

Lambda Integrated Facility (GLIF) [30] is an international

virtual organisation whose members are NRENs and promotes

lambda networking for international collaboration and research.

In todays NRENs, resources are provided either exclusively

for an application or are shared on a best-effort base. Many

emerging applications demonstrate a dynamic nature and re-

quire connectivity, bandwidth, or QoS that may change with

time and/or user profile. The administrative and technical over-

head to provide such network services and the high associatedcosts currently inhibit a wider commercial adoption of such de-

manding applications. A short- to medium-term solution to the

above requirements is the ability to negotiate flexible service

level agreements between the application and the resource pro-

vided. This is a subject of current research and standardization

within the Global Grid Forum [31].

As a longer-term solution, a new network service model that

allows users or/and applications to adapt the network to their

applications is discussed here. This network model will require

the network topology to migrate from the traditional edge-core

telecom model (Fig. 2) to a more distributed model. In this type

of network, the user may have the ability to control routingin an end-to-end manner and set up and tear-down lightpaths

between routing domains. To facilitate this level of user control,

users or applications will be offered management/control of the

network resources (i.e., bandwidth allocation at the wavelength

and subwavelength level). These resources could be leased and

exchanged between users. Such new topological solutions will

have a direct impact on network management and control as

well as the network infrastructure, including network elements

and user interfaces to enable and support these functionalities.

An important step toward this is the ability to make dynamic

resource reservations immediately when needed or in advance

for a time period in the future. Dynamic optical networking

can satisfy the bandwidth and reconfiguration requirements ofthis model together with software tools and frameworks for

end-to-end on-demand provisioning of network services across

multiple administrative and network technology domains.

Fig. 4 illustrates the global interconnection of a number of

NRENs using interconnecting networks such as GEANT or

GLIF. Within each network, the choice of switching technol-

ogy and transport format is an important consideration that

influences the ability to deliver NG network services. As dis-cussed above, optical switching offers bandwidth manipulation

at the wavelength and subwavelength level (e.g., with optical

circuit/burst/packet switching) as well as the capability to ac-

commodate a wide variety of traffic characteristics and distri-

butions. The transport format determines how signaling and

control messages as well as data are sent from the user/client

to the optical network and depends on the form of switching.

Thus, for 1) circuit switching, signaling is sent in conjunction

with the data or over a dedicated wavelength or SDH/SONET

connection, and for 2) OBS/OPS, signaling is sent using a

signaling packet or control burst; hybrid approaches can also

be used.

The service model proposed here does not depend on

transport technology (i.e., CS, OBS, OPS). Actually, the first

implementation will address wavelength-switched optical in-

frastructures. However, subwavelength granularity will enable

the offering of dynamic network services to a wider range of

users and applications.

The choice of transport format is mainly driven by an un-

derstanding of the traffic characteristics generated by users and

their applications. For example, wavelength switching may be

the preferred solution for moving terabytes of data from A to B

but is inappropriate for video games applications.

The diagram also shows other important elements of this

global network. Each NREN has an associated network re-sources provisioning system (NRPS) currently being devel-

oped and deployed around the world by different international

organizations. These systems are based on the abstraction of

network resources. For instance, the user-controlled lightpath

provisioning system (UCLP) can be thought of as a configu-

ration and partition manager that exposes each lightpath in a

physical network and each network element associated with a

lightpath as an object or service that can be put under the

control of different network users to create their own IP network

topologies. UCLP, as proposed by CANARIE, is an NRPS that

deals with the abstraction of network resources as objects to

allow end users to manage them in order to build reconfigurablediscipline or application-specific networks. More specifically,

UCLP [32] is a set of distributed services that are used to es-

tablish and tear down end-to-end connections across an optical

network.

The service plane mainly involves application-level middle-

ware and Application Programming Interfaces (APIs). The

service middleware in this architecture will provide a unified

application execution environment relying on a high-bandwidth

QoS-enabled network infrastructure of global scale. The mid-

dleware could implement service abstractions exposing net-

work resources (end-to-end QoS management). Hence, it will

be possible for an application to request network constraints

(e.g., guaranteed bandwidth or latency among computationalnodes).


7/13


VI. KEY NETWORK TECHNOLOGIES

Research on advanced switching and networking technolo-

gies is mainly determined by the needs identified in the core

of the network, where large amounts of data with different

characteristics (generated by different services) require efficient

switching in terms of bandwidth utilization, resource manage-

ment, and performance. Following the switching technologyevolution plan presented earlier (Fig. 3), research in the area

of optical networking can be categorized in a) the near termas automatically reconfigurable circuit-switching solutions,

b) near to long term as OBS solutions, and c) long term as OPS

solutions. The feasibility of implementing these solutions is

reflected in the results of research studies and demonstrations;

these are briefly discussed here to understand feasibility.

A. Optical Circuit Switching

The widely deployed circuit-switching technology is cur-

rently moving toward the deployment of fast and automatically

reconfigurable nodes with switching granularity at the wave-length level. This is now represented in standards by the ASON

architecture [4]. To enable dynamic networking, the provi-

sioning of lightpaths is automated. This is achieved with an

advanced control plane, which provides the necessary signaling

capabilities. The user can request, through the UNI, a new

lightpath, and the controllers in the network nodes exchange,

through NNIs, the necessary information for the lightpath setup

(allocation of wavelengths, etc.).

Research in this area is at the level of final product develop-

ment and is carried out by a number of leading companies pre-

senting applicable solutions for a) node design like ROADMs

based on WSSs and for b) control planes for dynamic network-ing, channel provisioning, and management based on IP/MPLS

solutions. Demonstrations of these can both be represented as

that in Fig. 2, where for IP/MPLS the core has an MPLS router

as the SE together with an optical switch (initially OEO, but

with possible upgrading to OOO) at the nodes. For the ASON

network, the SE represents an OXC controller, and lightpaths

are being set up by the control layer.

As currently viewed, the ASON network, which is based on

SDH/SONET, has advantages in terms of QoS, management,

and security, and is able to reduce the load taken from the

IP/MPLS network. However, due to the domination of IP-

centric traffic, future solutions are focusing on bursty net-

working models able to handle dynamic segments instead ofcontinuous data.

B. OBS

Segmented data transmission has been derived by the In-

ternet paradigm in order to mainly offer increased bandwidth

utilization and reduced overhead. One idea is to set-up and tear

down a path dynamically (similar to circuit switching) but for

a much shorter duration, equal only to the duration required

to transmit a complete set of data, a data burst. This is the

fundamental premise of OBS, which is based on the separation

of the control and data planes, and the segregation of func-

tionality within the appropriate domain (electronic or optical).Prior to data burst transmission, a burst control packet (BCP)

is created and sent toward the destination by an OBS ingress

node (edge router). The BCP is typically sent out-of-band over

a separate signaling wavelength and processed at intermediate

OBS routers. It informs each node of the impending data

burst and sets up an optical path for its corresponding data

burst. Data bursts remain in the optical plane end-to-end and

are typically not buffered as they transit the network core.The bursts content, protocol, bit rate, modulation format, and

encoding are completely transparent to the intermediate routers.

The main advantages of the OBS in comparison to the other

optical networking schemes are that unlike optical wavelength-

switched networks, the optical bandwidth is reserved only for

the duration of the burst, and that unlike the OPS network, it can

be bufferless, but it also needs a switch reconfiguration speed in

the order of microseconds.

Due to these implementation issues (easier processing,

bufferless operation, and slow switching requirements), OBS

is seen as a practical solution and is considered as the next

evolution step in future optical networking. The feasibility of

OBS technology can be identified by a number of reportedresults from field trials and testbeds. The most complete demon-

strator was set up in Japan under the OBS network project

and accommodated six nodes with MEMS-based switches,

achieving switching times of 1 ms for bursts with a minimum

size of 100 ms [33]. In China, a collaborative work between two

universities under the TBOBS project resulted in an OBS field

experiment that comprises three edges and one core node [34].

In this demonstrator, switching is achieved in nanosecond times

utilizing a tunable WSS based on semiconductor optical am-

plifiers (SOAs). Additionally, high-speed electronics are used

for the header control mechanism. The fast switching time

allows routing of relatively small packets, 720 s, transmittedat 1.25 Gb/s.

OBS makes an attractive proposition for deployment in

metro/wide area networks. Until now, the only way to build net-

works with more than 10 Gb of bandwidth has required the use

of DWDM technology to create point-to-point circuits for every

path across a network. This has proven to be both expensive and

cumbersome to manage. OBS offers a new alternative by using

burst transponders that can communicate directly with multiple

destinations across a network. This means no circuit needs to

be preprovisioned, and high-speed transponders need not be

dedicated for every single communication path. This frees up

capital, simplifies network design, and enables the creation of

packet metro aggregation networks where bandwidth shifts inreal time to where it is needed in the network.

A new generation of startup companies [35] is appearing and,

for the first time, delivering commercial equipment merging

the best of both worldsthe efficiencies of Ethernet packet

switching with the bandwidth of DWDM optical technology.

OBS has also been identified as a compatible solution for

the physical layer infrastructure in grid computing applications

with possible realization on NRENs [36].

C. OPS

OPS is a purely connectionless networking solution thatis fully compatible with IP-centric data traffic and offers the


8/13


finest network granularity and optimum bandwidth utilization.

In OPS networking, incoming IP packets are assembled at

the network edge to form the payload of an optical packet,

which has a leading optical header. At the switch node, the

header is interrogated and used to configure the associated

optical switch for forwarding of the payload. OPS requires the

use of more demanding subsystems (than OBS) with intrinsicintelligence to realize adequate packet processing and routing

on the fly. The main challenges in OPS are the implementation

of the optical header processing mechanism, the development

of an intelligent switch controller, the realization of ultrafast

switching in nanosecond timescale, and the exploitation of

buffering mechanisms to reduce packet blocking.

In contrast to OBS, complete OPS demonstrators are mainly

restricted to the development of fully functional but small

switching elements that simply show the feasibility of fast

packet switching on the physical layer with some extensions to

the link layer. In the OPSnet project [12], dynamic switching of

asynchronous optical packets at 40 Gb/s has been demonstrated

in a fully controllable set up able to identify and process the

header and route the payload accordingly. In [37], contention

resolution on the wavelength level is also considered on a

10-Gb/s packet switching node. Newly developed schemes [38]

are based on the same concept and use more advanced elec-

tronics for faster clock extraction and processing, while the

integration capabilities with the WSS are investigated. A more

feasible approach toward the implementation of OPS considers

the use of synchronously (slotted) transmitted packets with

fixed lengths, but in this case, the hardware overhead is on

the implementation of the packet synchronizer at the input.

However, slotted solutions are attractive for other applications

like computer interconnects.Despite their feasibility limitations, OPS demonstrators

assisted the development of numerous ultrafast switching and

processing techniques regarding wavelength conversion, header

encoding/decoding and processing, label swapping, fast clock

extraction, regeneration, and optical contention resolution.

Additionally, various switch architectural designs and control

protocols have been proposed, which in combination with the

significant technological advances over the last years indicated

the possible deployment of OPS in the future. However, its

future relies on advances in photonic integration that will enable

cost-effective subsystems to be constructed.

D. OCDMA

OCDMA has been studied as an alternative networking

solution able to increase passively the number of users per

wavelength. The other solution is OTDM, but this requires ac-

tive processing. The advantages of OCDMA have been evident

for some time through its successful use in wireless networks.

For optical networking, its potential for enhanced security,

decentralized control, and flexibility in bandwidth granularity

provides interesting possibilities to solve these well-known

issues in the development of future networks. Additionally, the

feasibility of OCDMA has been assisted by newly developedcomponents able to provide simple ways of coding and decod-

ing signals in a passive manner, which is a particularly attractive

and cost-effective feature.

The principle of OCDMA relies on applying unique or-

thogonal codes to each user while they share the same band-

width (wavelength). User codes are multiplexed on to the fiber

channel and are matched at the receiver against copies of the

codes through an autocorrelation process. The code length ischosen to try and maximize discrimination in the detection

process, where multiple access interference (MAI) is a key

problem. OCDMA must support many users, and hence, the

codes chosen must satisfy certain correlation conditions. Both

the time-shifted autocorrelation function of each code and the

cross-correlation function between codes must be low when

compared to the peak autocorrelation value. The recent devel-

opment of coherent OCDMA en/decoders allowed the efficient

separation of a large number of simultaneously transmitted

users providing a feasible solution for low-cost applications

in multiuser LAN environments. Also, the combination of

OCDMA with CWDM technology can boost the total number

of supported users, showing compatibility with PON architec-

tures for FTTP solutions.

The combination of OCDMA and WDM technology in

a LAN/access environment has been recently demonstrated

in [28]. The paper reported the field trial of a 3-WDM

10-OCDMA 10.71-Gb/s system over a 111-km field trial.

Key aspects of the approach were 1) the use of a multiport

encoder/decoder in the central office, which can give multiple

optical codes in multiple-wavelength bands (this device gives

good correlation properties to suppress MAI and beat noise),

and 2) the use of a super structured fiber Bragg grating (SSFBG)

(or tunable transversal filter) at the optical network unit (ONU).

The use of DPSKOCDMA with balanced detection is seen asa key enabler over conventional ON/OFF-keying OCDMA with

superior noise performance.

In recent times, other interesting possibilities for OCDMA

have been considered. One such is the concept of code trans-

lation, where, analogous to wavelength conversion, codes can

be transformed to match users in other subnets (i.e., provide

routing). Experiments [29] have also shown how a narrowband

spectral-phase-encoded (NB-SPE) OCDMA compatible with

existing WDM networks can be used with passive code transla-

tion to play a role in ring- and star-based network architectures.

Finally, the use of optical codes under a different concept has

shown the feasibility to implement an OPS node [39]. Here, op-tical codes are used as labels in order to distinguish the different

headers of the transmitted packets. After header matching, the

autocorrelation peak triggers an electronic controller that shows

the output port where the packet should be routed.

VII. KEY SUBSYSTEMS AND TECHNOLOGIES

The roadmap in Fig. 3 and the above discussion broadly out-

line a much argued route forward to the future with switching or

transmission aspects relevant to a future global heterogeneous

optical network. Generally, the picture is that transmission

speeds are still predicted to increase as before (e.g., to 160 Gb/s

probably using DPSK), within the context of a more dynamicand granular network, supported by appropriate control plane


9/13


(e.g., GMPLS with extensions). Many of the key functional

subsystems needed for this future flexible network have al-

ready been described with experimental demonstrations (e.g.,

all-optical regeneration at 40 Gb/s has been widely reported

[40], as has wavelength conversion, fast tunable lasers, tunable

dispersion compensators, MEMS-based switch fabrics, etc.).

Others are still gleams in the eye of the network designerwith, as yet, no sure route for realization, for example, optical

memory and multiwavelength optical regeneration.

However, what has become well recognized is that the

future of realizing the full potential of optical networks, at

affordable cost, lies in the ability to perform good levels of

photonic integration. This has not been an easy route to date,

but some interesting examples of future approaches are starting

to appear. Generally, the integration of photonic components

is not straightforward as the substrate technology for various

components differs (e.g., lasers are grown on InP, whereas

filters benefit from silicon technology). Existing photonic in-

tegration approaches are based on hybrid integration, where

individual components are laid down and interconnected on a

suitable substrate (e.g., silicon); hybrid integration offers full

functionality, lower cost, and shorter development times; or

on monolithic integration, where a limited set of functions,

realizable on a common material, is combined.

Recent advances in the integration of MachZehnder inter-

ferometers (MZI) illustrate the potential benefits of integration.

In a typical device, a pump signal is split between two inter-

ferometer arms, and the phase difference between arms is con-

trolled by the optical signal operating on a nonlinear element,

typically an SOA. Integrated MZIs can be used for a variety of

functions needed in future systems and cannot be realized by

assembling discrete components; current commercial devicescan operate at 40 Gb/s and have been extensively used for

wavelength conversion at 10 and 40 Gb/s with regenerative

capabilities [41]. To maximize speed, pushpull configurations

have been suggested where, by applying phase changes in

both arms, performance can be significantly enhanced, with

up to 160-Gb/s operation reported [42]. This configuration has

been used in a number of different signal processing appli-

cations such as regeneration, add-drop multiplexing, time slot

interchange switching [43] format, and wavelength conversion,

and other optical processing functions. 3R regeneration can be

achieved by using the input signal to gate-extracted optical-

clock pulses in a pushpull configuration. The ability to inte-grate many interferometers in one substrate makes the device

very interesting and versatile, for example, to realize logic

functions and bursty receivers [44].

Recently, novel approaches based on silicon photonic inte-

gration (Silicon Photonics) have been reported by Intel [45].

Silicon is a well-understood material and the basis of low-

cost electronics. It is transparent at infrared wavelengths and

so can be used to guide light but cannot emit light. Intel is

pioneering a process whereby a laser chip mounted in a silicon

external cavity forms a tunable laser, which together with

silicon modulators (realized by MZI configurations) and photo-

detectors (with Ge doping) shows promise as a future low-cost

integration strategy. The current performance is at 1 Gb/s, but1040 Gb/s is predicted.

There are a number of key functions necessary, at a link and

network level, to enable efficient operation of the future optical

network. Examples are as follows.

A. Optical Switching

To fully advance to transparent networking, OOO switches

are required at microsecond (for OBS), millisecond (for OXCs),

and nanosecond (for OPS) reconfiguration times. 3-D MEMS

switches (ms reconfiguration) are now available with port

counts to 160 160 [46], and the recent interest in the de-

ployment of ROADMs means that the functionality of OOO

switches is now available. Fast (in nanoseconds) switch fab-

rics (of high dimension) are realized through the combination

of tunable lasers/wavelength converters together with arrayed

waveguides; it is hard to see this situation changing. Neverthe-

less, low-dimension nanosecond switch modules are available

[47]. An example based on the total internal reflection in a

compound semiconductor power line carrier [48] forms the core

of a commercially deployed OPS system.Recent advances in fabrication have made it possible to

fabricate compact microring resonators with radii as small as

2.5 m and quality factors as high as 10 000 by tightly confining

semiconductor waveguides [49]. The large field-enhancement

factors obtained in these microcavities can result in three to four

orders of magnitude reduction in the required switching powers,

while the small dimension of the devices helps reduce the cavity

lifetime, and hence the switching times, down to the picosec-

onds regime. With the microring arranged in either the single-

coupler (all-pass) or double-coupler (adddrop) configuration,

the device can be used to perform efficient switching, pulse

routing, wavelength conversion using four-wave mixing, aswell as logic functions; further research is needed to understand

the potential of this approach.

B. Optical Monitoring

As the network performance increases, it is crucial to un-

derstand the state of the physical layer so that appropriate

routing and remedial actions can be taken. For example, within

a network, a variety of bit rates from 10 to 160 Gb/s may exist,

with some routes more appropriate to one bit rate than another

from the point of view of optical signal-to-noise ratio, residual

dispersion channel power, etc. Information should be available

through optical monitoring to inform routing decisions at net-work nodes; this trend now appears in the area of cross-layer

routing and is an important one for research.

C. Optical Encryption

Security will always be of great importance in networks, and

it proves difficult to perform electronic encryption at speeds

beyond 10 Gb/s. Thus, there is a strong interest in the inves-

tigation of encryption possibilities in the optical medium. Two

main techniques have been investigated based on 1) quantum

cryptography and 2) chaos cryptography. The first is based on

secure key distribution, in which the key can then be used to

transmit information securely by the conventional algorithm-based encryption. Quantum cryptography guarantees secure


10/13


communications by harnessing the quantum nature of photons

sent between users. Any attempt to intercept the photons will

disturb their quantum state, and as this quantum quality is an

integral part of key generation, the disturbance will be detected.

Several experiments have extended the key distribution over an

ordinary 100-km fiber [50]; however, the technique is sensitive

to noise.Chaos-based encryption has the advantage of allowing

very high encryption speeds (> 10 Gb/s). It relies on the

synchronization of chaotic systems, for example, a pair of

unidirectionally coupled single-mode semiconductor lasers

subjected to coherent optical feedback or injection. Synchro-

nization means that the chaotic output of the emitter device

can be reproduced by the receiver. Once the two lasers have

synchronized, the output light of the emitter can be used to en-

code a message. An experiment over a commercially installed

fiber (2.5 Gb/s) showed the possibility of recovering chaotic

transmission after 120 km [51].

D. All-Optical Wavelength Conversion and Regeneration

All-optical wavelength conversion and regeneration are de-

sirable (including from a power and footprint viewpoint) for

networks operating at speeds of> 40 Gb/s. To achieve conver-

sion, the physical properties of a nonlinear element are used

to perform a logic function between the input signal and a

pump. The main nonlinear elements used are SOA, an electro-

absorption modulator (EAM), fiber, a photonic crystal, and

periodically poled LiNbO3 waveguides (PPLNs). SOA-based

devices, especially quantum dot, and EAMs have the added

advantages of compactness and low-energy requirements to

trigger nonlinearities. Fibers have an instantaneous response to

pulses but, on the other hand, have limited nonlinearity, even in

specially designed photonic crystal fibers; hence, long lengths

are required. PPLNs require intermediate lengths, and very fast

conversion (40160 Gb/s) has been demonstrated.

Considerable research has been done in the area of single-

wavelength subsystems. For example, advanced all-optical

regenerative schemes at bit rates beyond 100 Gb/s have been

recently proposed in [52] as well as well reported demonstra-

tions at 40 Gb/s [53]. Multiwavelength all-optical regeneration,

if feasible, will dramatically decrease the cost of DWDM

transmission links. A number of techniques are currently being

considered, for example, 1) through the mechanism of self-phase modulation, which in principle enables operation at

speeds of> 160 Gb/s, and 2) based on the inhomogeneously

broadened gain of self-assembled quantum dots in quantum dot

SOAs [54].

E. Optical Memory

All-optical buffering through fiber delay lines is an approach

that requires complex control, and packets are delayed rather

than stored. Recently, in the framework of LASOR [18], inte-

grated delay lines have been developed as it has been shown

[55] that a small number of low-depth buffers are sufficient foran OPS network.

Nevertheless, recent research has established that it is possi-

ble to exercise control of the velocity of light pulses propagating

through a material. Light propagation with a very low group

velocity (slow light) has been observed in atomic vapors and

solid-state crystal via electromagnetically induced transparency

and coherent population oscillation. Recently, direct time-

domain measurements in SOA quantum wells showed control-lable delay up to 1 ns; this results in a direct measurement

of group velocity of < 200 m/s, giving a slow down factor

of up to 1.5 106 [56]. Various other methods have been

proposed and demonstrated, and the area is still one of strong

research. Critics of this technique have concluded that there is a

delaybandwidth product that inevitably limits the achievement

of reasonable delays at high bit rates.

VIII. FUTURE GLOBAL HETEROGENEOUS

OPTICAL NETWORK

In the above discussions, it has been shown that there are

ever-growing demands on future networks from a number of

directions. The historic telecommunications network is seen as

evolving to a fully pervasive or ubiquitous network supporting

a wide variety of users. Key to this goal is the evolution

to a multiservice platform comprising (eventually) an optical

core with wavelength and subwavelength granularities together

with an advanced control plane such as GMPLS. The core

data plane will support electrical circuit switching (e.g., with

DXCs), electronic packet switching using IP/MPLS routers,

OBS using microsecond optical switches with appropriate edge

interfaces to set incoming data on to specific wavelengths, and

finally, possibly OPS using nanosecond optical switches and

appropriate edge interfaces.The optical transport core will be accessible to the user via

fixed and wireless access networks, providing high bandwidth

availability. Single-channel transmission speeds will increase in

the very near future to 40 Gb/s (matching router interface rates),

and it is likely that development will continue to move to higher

rates such as 160 Gb/s, perhaps using DPSK, and via OTDM.

Continued development in photonic integration will enable

appropriate optical processing subsystems, for example, all-

optical regeneration, to be realized supporting these changes.

From the scientific user direction, it was shown that dedicated

optical networks, for example, NRENs, based on dark fiber and

readily available optical technology are already being put inplace to satisfy the requirements of these users for a dynamic

network with specific requirements on bandwidth, latency, and

availability, to access global processing resources, transfer high

data volumes with QoS, and provide a secure infrastructure

for future high-end services. These networks, with their well-

defined requirements, will likely continue to rely on dynamic

circuit-based switching, but the advantages of OBS for grid

applications make it likely that this technology will move to

these networks as well.

Fig. 5 shows how these separate networks might eventually

coexist to form a global heterogeneous optical network, increas-

ingly supported by advanced optical technology. The figure

shows how a core telecommunications network can providea platform for both residential users through the metro/access


11/13


Fig. 5. Global heterogeneous optical network.

route or for scientific communities through the interconnection

with NRENs.

This solution is one that allows telecom operators to build

a ubiquitous network, which also supports the flexible services

needed by high-end researchers. The future vision here is of op-

erators providing transport services to research users and legacy

ones (i.e., residential/business users), on different sections of

the same network infrastructure or sharing the same infrastruc-

ture, but under a single unified control and management plane.

It is necessary that this common control plane should interwork

with the existing NRPS used by NRENs in order to dynamicallyimplement worldwide optical transport services.

GMPLS has proved to be the most efficient telecom-oriented

solution for the fast and automated provisioning of connections

across multitechnology (IP/MPLS, Ethernet, SDH/SONET,

DWDM, OBS, etc.) and multidomain networks: GMPLS en-

ables advanced network functionalities for traffic engineering,

traffic resilience, automatic resource discovery, and manage-

ment. However, GMPLS is not natively designed to support the

flexible network services described above, and a major tech-

nical challenge rises from the interworking of the application

platforms and of their resource management systems with the

underlying NG optical networks powered with the GMPLScontrol plane.

This network vision needs to ensure a service boundary is

kept between the users and the network service provider but

also enable differentiated and configurable interfacing proce-

dures. According to this approach, the boundary of the network

will be transparent only for power users (i.e., scientific and

high-performance grid) who will

obtain network topology information to be used by re-

source brokering entities (i.e., NRPS);

request specific lightpaths by providing lightpath descrip-

tion;

communicate application layer information (e.g., CPU,storage, etc.) into the GMPLS control plane, which will

allow dissemination of this information within the same

virtual.

The proposed coordination between the telecom network

control plane, the NRPS, and the service plane on top of the

switched physical layer will enable end-to-end dynamic service

provisioning across a global heterogeneous optical network

infrastructure.In this scenario, therefore, it is likely that progress will

continue toward a common or shared optical infrastructure sup-

porting residential, business, and scientific users. All these users

require a more dynamic network with wavelength and subwave-

length access, which will likely eventually be supported, for

example, through OBS or indeed (in the far distance) OPS. The

common core network will continue to move to higher speeds

with an eventual move from OEO to OOO switching. Photonic

integration is seen as a key to enable high-performance optical

networking. For the global heterogeneous optical network,

however, there are many challenges on both physical and

network layers, requiring much cooperation among traditional

electronic engineers, computer scientists, and users.

IX. SUMMARY

This paper presented a story of the evolution of optical

networking from early concepts to its strong progression to

provide the main high-capacity and flexible platform necessary

to support the near and future requirements of a global network

supporting the communication requirements of a growing di-

versity of residential, enterprise, and scientific users. Many of

the switching and subsystem technology solutions necessary

to achieve these aims have already been glimpsed but need

considerable progress in integration techniques to overcomedeployment cost problems. There is also much research to be

done at the software level to ensure interoperability between

networks at a global level. Eventually, hardware and software

evolution may lead to increased levels of transparency in these

future optical networks.

REFERENCES

[1] J. Zhou, R. Cadeddu, E. Casaccia, C. Cavazzoni, and M. J. OMahony,Crosstalk in multiwavelength optical cross-connect networks, J. Lightw.Technol., vol. 14, no. 6, pp. 14231435, Jun. 1996.

[2] R. E. Wagner et al., Monet: Multiwavelength optical networking,J. Lightw. Technol., vol. 14, no. 6, pp. 13491355, Jun. 1996.

[3] T. Freeman, DWDM platform set for 40 G deployment, Fibre Syst.,

vol. 3, no. 1, p. 23, Jan./Feb. 2006.[4] N. Larkin, ASON & GMPLS; The Battle for the Optical Control Plane .

[Online]. Available: http://www.dataconnection.com/network/download/whitepapers/asongmpls.pdf

[5] R. Nagarajan, C. Joyner, and R. Schneider, Large-scale photonic inte-grated circuits, IEEE J. Sel. Topics Quantum Electron., vol. 11, no. 1,pp. 5065, Jan./Feb. 2005.

[6] J. S. da Silva, Broadband R&D in the context of convergence, pre-sented at the Broadband Europe Conf., Bordeaux, France, Dec. 2005,Paper M01.03.

[7] J. J. Lepley, The evolution of the access network: Options for fibre pen-etration into the access network, London, U.K.: MUSE Summer SchoolBroadband Access Technol., Jul. 45, 2005. [Online]. Available: http://www.istmuse.org/Documents/NOC2005/Summer_School/Jason_Lepley_Fibre_Penetration_in_XDSL_Networks.pdf

[8] [Online]. Available: http://www.jb.man.ac.uk/news/evlbi/

[9] B. St. Arnaud, Future internet issues, in Proc. OECD ICCP Work-shop, Paris, France, Mar. 2006. [Online]. Available: http://www.oecd.org/dataoecd/43/63/36274169.pdf


12/13


[10] C. Cavazzoni, D. Colle, A. Di Giglio, G. Edwall, G. Eilenberger,G. Ferraris, H. Haunstein, S. Herbst, M. Jaeger, G. Lehmann, J. F. Lobo,A. Manzalini, S. Santoni, and M. Schiano, Evolution of optical trans-port networks in Europe: The NOBEL project vision, presented at theBroadband Europe Conf., Bordeaux, France, Dec. 2005. Paper T04A.01.[Online]. Available: www.bbeurope.org

[11] A. Stavdas, S. Sygletos, M. O. Mahony, H. L. Lee, C. Matrakidis, andA. Dupas, IST-DAVID: Concept presentation and physical layer mod-

elling of the metropolitan area network, J. Lightw. Technol., vol. 21,no. 2, pp. 372384, Feb. 2003.[12] D. Klonidis, C. T. Politi, R. Nejabati, M. J. OMahony, and

D. Simeonidou, OPSnet: Design and demonstration of an asynchronoushigh speed optical packet switch, J. Lightw. Technol., vol. 23, no. 10,pp. 29142925, Oct. 2005.

[13] R. Nejabati, D. Klonidis, G. Zervas, D. Simeonidou, and M. O Mahony,Demonstration of a complete and fully functional end-to-end asynchro-nous optical packet switched network, presented at the Optical FiberCommun. Conf. (OFC), Anaheim, CA, Mar. 2006, Paper OWP5.

[14] J. Ryan, An outlook for optical executatives, OSA Executative Program,Mar. 2006, Anaheim, CA. [Online]. Available: www.osa.org/partner/network/program/Ryan%20John.ppt

[15] B. Fabianek, Optical networking testbeds in Europe, presented atthe Optical Fiber Commun. Conf. (OFC), Anaheim, CA, Mar. 2006,Paper OWU1.

[16] K. Kitayama, T. Miki, T. Morioka, H. Tsushima, M. Koga, K. Mori,

S. Araki, K. Sato, H. Onaka, S. Namiki, and T. Aoyama, Photonic net-work R&D activities in JapanCurrent activities and future prospects,

J. Lightw. Technol., vol. 23, no. 10, pp. 34043418, Oct. 2005.[17] D. T. Neilson, D. Stiliadis, and P. Bernasconi, Ultra-high capacity optical

IP routers for the networks of tomorrow: IRIS project, presented atthe Eur. Conf. Optical Commun. (ECOC), Glasgow, U.K., Sep. 2005,Paper We 1.1.4.

[18] D. J Blumenthal, LASOR (label switched optical router): Architectureand underlying integration technologies, in Proc. ECOC, Glasgow, U.K.,Sep. 2005, p. 49.

[19] [Online]. Available: http://www.nlr.net/ess/index.html[20] P. Freeman, (2006, Mar.)GENI: Global environment for networking in-

novations,Proc. Future InternetParis, France.OECD. [Online]. Available:http://www.oecd.org/dataoecd/43/63/36274169.pdf

[21] J. Lin and J. Wu, Optical networking testbeds in China, presentedat the Optical Fiber Commun. Conf. (OFC), Anaheim, CA, Mar. 2006,

Paper OWU2.[22] L. Zong, P. Ji, T. Wang, O. Matsuda, and M. Cvijetic, Study onwavelength cross-connect realised with wavelength selective switches,presented at the Optical Fiber Commun. Conf. (OFC), Anaheim, CA,Mar. 2006, Paper NThC3.

[23] E. Le Rouzic and S. Gosselin, 160 Gb/s optical networking: A prospec-tive techno-economic analysis, J. Lightw. Technol., vol. 23, no. 10,pp. 30243033, Oct. 2005.

[24] P. Torab, V. Hutcheon, and D. Walters, Waveband switching efficiency inWDM networks: Analysis and case study, presented at the Optical FiberCommun. Conf. (OFC), Anaheim, CA, Mar. 7, 2006, OTuG. [OpticalNetwork Architectures].

[25] E. Hernandez-Valencia and H. Menendez, Exploiting carrier Ethernet todeliver profitable new services, presented at the Optical Fiber Commun.Conf. (OFC), Anaheim, CA, Mar. 2006, Paper NTUD1.

[26] D. Simeonidou, R. Nejabati, B. St. Arnaud, M. Beck, P. Clarke, B. Hoang,D. Hutchison, G. Karmous-Edwards, T. Lavian, J. Leigh, J. Mambretti,

V. Sander, J. Strand, and F. Travostino, Optical Network Infrastructurefor Grid. [Online]. Available: http://www.ggf.org/gf/docs/?final

[27] D. Payne and R. Davey, Long reach access networksAvoiding thebandwidthprice dilemma, presented at the Broadband Europe Conf.,Bruges, Belgium, Dec. 2004, Paper T01A.02. GGF.

[28] K. Kitayama, X. Wang, and N. Wada, A solution path to gigabit-symmetric FTTH: OCDMA over WDM PON, presented at theBroadband Europe Conf., Bordeaux, France, Dec. 2005. paper T01A.02.[Online]. Available: http://www.bbeurope.org

[29] R. C. Mendez, P. Toliver, S. Galli, A. Agarwal, T. Banwell, J. Jackel,J. Young, and S. Etemad, Network applications of cascaded code trans-lation for WDM-compatible spectrally phase encoded optical CDMA,

J. Lightw. Technol., vol. 23, no. 10, pp. 31293231, Oct. 2006.[30] M. Brown, Blueprint for the future of high performance networking,

Commun. ACM (CACM), vol. 46, no. 11, pp. 3077, Nov. 2003. ASON.[31] [Online]. Available: http://www.gridforum.org/

[32] [Online]. Available: http://www.uclp.ca/[33] A. Sahara, R. Kasahara, E. Yamazaki, S. Aisawa, and M. Koga, Thedemonstration of congestion controlled optical burst switching network

utilizing two-way signaling field trial in JGN II testbed, presented atthe Optical Fiber Commun. Conf. (OFC), Anaheim, CA, Mar. 2005,Paper OFA7.

[34] H. Guo, Z. Lan, J. Wu, and J. Lin, A testbed for optical burst switch-ing network, presented at the Optical Fiber Commun. Conf. (OFC),Anaheim, CA, Mar. 2005, Paper OFA6.

[35] [Online]. Available: http://www.matissenetworks.com/product.php[36] D. Simeonidou, R. Nejabati, G. Zervas, D. Klonidis, A. Tzanakaki, and

M. J. OMahony, Dynamic optical network architectures and technolo-gies for existing and emerging grid services, J. Lightw. Technol., vol. 23,no. 10, pp. 33473357, Oct. 2005.

[37] F. Xue, Z. Pan, H. Yang, J. Yang, J. Cao, K. Okamoto, S. Kamei, V. Akella,and S. J. B. Yoo, Design and experimental demonstration of a variable-length optical packet routing system with unified contention resolution,

J. Lightw. Technol., vol. 22, no. 11, pp. 25702581, Nov. 2004.[38] H. N. Poulsen, D. Wolfson, S. Rangarajan, and D. J. Blumenthal, Burst

mode 10 G optical header recovery and lookup processing for asyn-chronous variable length 40 G optical packet switching, presented atthe Optical Fiber Commun. Conf. (OFC), Anaheim, CA, Mar. 2006,Paper OFJ2.

[39] X. Wang and N. Wada, Demonstration of OCDMA traffic over opticalpacket switching networks with PLC and SSFBG en/decoders for timedomain OC processing, presented at the Eur. Conf. Optical Commun.(ECOC), Glasgow, U.K., Sep. 2005, PDL We1.4.5.

[40] K. Stubkjaer, Semiconductor optical amplifier-based all-optical gates for

high speed optical processing, IEEE J. Sel. Topics Quantum Electron.,vol. 6, no. 6, p. 1428, Nov. 2000.

[41] G. Maxwell, R. McDougall, R. Harmon, M. Neild, L. Rivers, andA. Poustie, WDM-enabled, 40 GB/s hybrid integrated all-optical regen-erator, presented at the Eur. Conf. Optical Commun. (ECOC), Glasgow,U.K., Sep. 2005, PDL 4.2.2.

[42] S. Nakamura, Y. Ueno, and K. Tajima, 168 Gb/s all-optical wavelengthconversion with a symmetric-MachZehnder-type switch, IEEE Photon.Technol. Lett., vol. 13, no. 10, p. 1091, Oct. 2001.

[43] S. Pau, Y. Jianjun, K. Kojima, N. Chand, and V. Swaminathan, 160-Gb/sall-optical MEMS time-slot switch for OTDM and WDM applica-tions, IEEE Photon. Technol. Lett., vol. 14, no. 10, pp. 14601462,Oct. 2002.

[44] D. Petrantonakis, G. T. Kanellos, P. Zakynthinos, N. Pleros,D. Apostolopoulos, and H. Avramopoulos, A 40 Gb/s 3R burst-modereceiver with 4 integrated MZI switches, presented at the Optical Fiber

Commun. Conf. (OFC), Anaheim, CA, Mar. 2006, Paper PDP 25.[45] P. Koonath, T. Indukuri, and B. Jalali, Monolithic 3-D Silicon Photon-ics, J. Lightw. Technol., vol. 24, no. 4, pp. 17961804, Apr. 2006.

[46] [Online]. Available: http://www.glimmerglass.com[47] R. Varrazza, I. B. Djordjevic, and Y. Siyuan, Active vertical-coupler-

based optical crosspoint switch matrix for optical packet-switchingapplications, J. Lightw. Technol., vol. 22, no. 9, pp. 20342042,Sep. 2004.

[48] [Online]. Available: http://www.yokogawa.com[49] V. Van, A. Ibrahin, P. P. Absil, F. G. Johnson, R. Grover, and

P. Ho, Optical signal processing using nonlinear semiconductor micro-ring resonators, IEEE J. Sel. Topics Quantum Electron., vol. 8, no. 3,pp. 705713, May 2002.

[50] C. Gobby, Z. L. Yuan, and A. J. Shields, Quantum key distribution over122 km of standard telecom fiber, Appl. Phys. Lett., vol. 84, no. 19,pp. 37623764, May 2004.

[51] A. Argyris, D. Syvridis, L. Larger, V. Annovazzi-Lodi, P. Colet,

I. Fischer, J. Garca-Ojalvo, C. R. Mirasso, L. Pesquera, and K. A. Shore,Chaos-based communications at high bit rates using commercial fibre-optic links, Nature, vol. 438, no. 7066, pp. 343346, Nov. 17, 2005.

[52] Y. Liu, E. Tangdiongga, Z. Li, H. de Waardt, A. M. J. Koonen, G. D. Khoe,H. J. S. Dorren, X. Shu, and I. Bennion, Error-free 320 Gb/s SOA-basedwavelength conversion using optical filtering, presented at the OpticalFiber Commun. Conf. (OFC), Anaheim, CA, Mar. 2006, Paper PDP 28.

[53] O. Lecrec et al., Optical regeneration at 40 Gb/s and beyond, J. Lightw.Technol., vol. 21, no. 11, pp. 27792790, Nov. 2003.

[54] T. Akiyama et al., Application of spectral-hole burning in the inhomo-geneously broadened gain of self-assembled quantum dots to a multi-channel nonlinear optical device, IEEE Photon. Technol. Lett., vol. 12,no. 10, pp. 13011303, Oct. 2000.

[55] N. Beheshti, Y. Ganjali, R. Rajaduray, D. Blumenthal, and N. McKeown,Buffer sizing in all-optical packet switches, presented at the OpticalFiber Commun. Conf. (OFC), Anaheim, CA, Mar. 2006, Paper OThF8.

[56] C. Chang-Hasnain, Controlling light speed in semiconductors, pre-sented at the Eur. Conf. Optical Commun. (ECOC), Glasgow, U.K.,Sep. 2005, Paper Mo3.1.3.


13/13


Michael J. OMahony (M91SM91) received thePh.D. degree in digital transmission systems from theUniversity of Essex, Colchester, U.K., in 1978.

In 1979, he was with the Optical System ResearchDivision, British Telecom, working on research intofiber-optic systems for undersea systems, in partic-ular, experimental and theoretical studies of receiverandtransmitter design. In 1991,he joinedthe Depart-

ment of Electronic Systems Engineering, Universityof Essex, as Professor of communication networksand was Head of the department from 1996 to 1999.

He is the Principal Investigator for grants supported by industry, nationalresearch councils, and the EU. He is the author of over 200 papers relatingto optical communications. His current research is related to the study of futurenetwork infrastructures and technologies.

Dr. OMahony is a member of the Institution of Electrical Engineers (IEE).

Christina Politi (S05) was born in Zografou,Greece, in 1975. She received the degree in physicsfrom the University of Athens, Athens, Greece,in 1998 and the M.Sc. degree in the physics oflaser communications from the University of Essex,Colchester, U.K., in 2000. She is currently workingtoward the Ph.D. degree on ultrafast wavelength con-version and optical processing for optical circuit andpacket-switched networks at the University of Essex.

She has been involved with the EuropeanIST-OPTIMIST and IST-BREAD projects.

Dimitrios Klonidis (M02) received the degree inelectrical and computer engineering from AristotleUniversity, Thessaloniki, Greece, in 1998 and theM.Sc. degree in telecommunication and informationsystems from the University of Essex, Colchester,U.K., in 2001. He is currently working toward thePh.D. degree in high-speed optical packet switchingat the University of Essex.

Since August 2004, he has worked for the EPSRCproject OPSnet. He is currently involved with a

number of research activities within the Universityof Essex. His main research topics are in the area of ultrafast optical communi-cation networks.

Reza Nejabati (M02) received the B.Sc. degree inelectrical engineering from Shahid Beheshti (Melli)University, Tehran, Iran, in 1997 and the M.Sc.degree (with distinction) in telecommunication andinformation systems from the University of Essex,Colchester, U.K., in 2001.

He is a Senior Research Officer with the PhotonicNetwork Research Group, University of Essex. His

main research interests are in the area of opticalsubwavelength switching and grid networking.

Dimitra Simeonidou (M95) received the B.Sc.and M.Sc. degrees from the Physics Department,Aristotle University, Thessaloniki, Greece, in 1987and 1989, respectively, and the Ph.D. degree fromthe University of Essex, Colchester, U.K., in 1994.

She has over ten years of experience in the fieldof optical transmission and optical networks. From1992 to 1994, she was a Senior Research Officerwith the University of Essex in association with theMWTN RACE project. In 1994, she was a PrincipleEngineer with Alcatel Submarine Networks and con-

tributed to the introduction of wavelength-division-multiplexing (WDM) tech-nologies in submerged photonic networks. She participated in standardizationcommittees and was an advising member of the Alcatel Submarine networkspatent committee. She is a currently a Professor with the University of Essex.She is the author over 120 papers and holds 11 patents relating to photonic tech-

nologies and networks. Her main research interests include optical wavelengthand packet-switched networks, network control and management, and GRIDnetworking.