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White Paper

100G & Beyond: Preparing for the

Terabit Era

Prepared by

Sterling Perrin

Senior Analyst, Heavy Reading

www.heavyreading.com

on behalf of

alcatel-lucent.com

huawei.com infinera.com

February 2013

http://www.heavyreading.com/

http://alcatel-lucent.com/

http://www.huawei.com/

http://www.infinera.com/

HEAVY READING | FEBRUARY 2013 | WHITE PAPER | 100G & BEYOND: PREPARING FOR THE TERABIT ERA 2

Introduction 100G transport is a great industry success story, and one that Light Reading and

Heavy Reading have been tracking since the technology's inception. In our

January 2012 100G Industry Initiative white paper "Deploying 100G Transport

Networks Today," we made the case that, following years of development and

trial activity, 100G had "arrived" and the stage was set for wide-scale adoption to

begin. Looking back on last year, we can say that our assessment was on the

mark and that commercial adoption is actually exceeding our expectations.

There are well over 170 commercial 100G wins to date, all over the world.

This year's 100G Industry Initiative white paper continues to track the 100G story

while also looking ahead to what lies beyond 100G. The paper starts by providing

a status update on 100G, including key drivers, a commercial round-up, and

Heavy Reading's forecast for 100G adoption through 2015.

The next section discusses key technology enablers, for 100G and beyond,

including: 1) super channels; 2) photonic integration; 3) flexible OTN containers;

and 4) flexible ROADMs. We then take a detailed look at adding control plane

intelligence for next-gen transport networks – including drivers, evolution and the

connections between optical transport and software-defined networking (SDN).

The final section addresses the evolution beyond 100G. Here, we focus on the

standards progress to date, from the IEEE and the ITU-T, and then outline technol-

ogy and market challenges that must be addressed in order to move forward.


Status of 100G Today

Drivers

When we ask operators what's driving their need for 100G and beyond, the

explanation is not that complicated. The simple explanation is continued growth in

network data traffic. Still, there are details beneath what drives that traffic growth.

The IEEE convened a working group to evaluate bandwidth needs, to help inform

their decision process on the next Ethernet bit rate beyond 100 GigE. In July 2012,

they published a study, "IEEE 802.3 Industry Connections Ethernet Bandwidth

Assessment." Figure 1 is a summary of the various traffic growth forecasts that the

group referenced in order to make their recommendations. The relative traffic

increase was normalized to 2010, which is the year that 802.3ba was approved.

Some key data points are summarized below:

The most aggressive growth rates are anticipated in the financial sector

and data-intensive science (a 95% CAGR and a 70% CAGR, respectively);

Slower growth rates (relative to the rest of the applications) are expected

for server input/output capacity and for IP traffic (a 36% CAGR and a 32%

CAGR, respectively);

Peering growth is forecast to be in the middle of the pack (64% CAGR);

Figure 1: Relative Traffic Increase Normalized to 2010

Source: Source: IEEE 802.3 Industry Connections Bandwidth Assessment, July 2012

http://www.ieee802.org/3/ad_hoc/bwa/BWA_Report.pdf

http://www.ieee802.org/3/ad_hoc/bwa/BWA_Report.pdf


The dotted red line showing the rate of increase of core networking as-

sumed by the 2007 IEEE 802.3 HSSG (58% CAGR) also appears in the mid-

dle of the group, suggesting to the report authors that their original as-

sumption back in 2007 is still reasonable and justified.

Global Deployments Overview

Heavy Reading and Light Reading have been researching and writing about

100G for many years. In fact, 100G has been an important topic at our optical

events and in our webinars since as far back as 2007. For most of that time, we

have focused on work that needs to be done to bring 100G to a commercial

reality, including standards development, technical innovations and emerging

applications (such as cloud services delivery).

The focus on 100G changed dramatically in 2012 as 100G ramped up commer-

cially. By the end of the third quarter of 2012, we had tallied more than 170

commercial 100G wins. This is a big change from the single-digit commercial win

tally at the end of 2010. After a long time coming, the uptake has been swifter

than even many 100G optimists (including Heavy Reading) had predicted.

Figure 2 shows a broad sampling of 100G customers that have been announced

globally. This figure does not provide an exhaustive list of 100G deployments (note

that many 100G deployments remain unannounced) but shows the geographic

breadth of 100G adoption, even at this early stage of commercial rollouts.

Figure 2: Sampling of 100G Commercial Deployments to Date


Heavy Reading 100G Forecast

Figure 3 shows Heavy Reading's forecast for long-haul DWDM capacity shipped

through 2015. Starting from virtually nothing in 2010, 100G is forecast to rise to the

largest share of long-haul capacity shipped by 2015, exceeding both the incum-

bent 10G technology and the high-speed challenger 40G.

Heavy Reading has long predicted that the advent of commercial 100G would

lead to the decline of the 40G opportunity. Based on the 100G uptake we have

seen in 2012 and operator plans for 2013, we believe that the rise of 100G, at the

expense of 40G, could be more rapid than previously predicted.

Figure 3: Worldwide Long-Haul DWDM Share of Line-Side Capacity by Speed


Technology Enablers for 100G & Beyond In this section we focus on four technology enablers that are setting the stage for

the terabit era. Some of these enablers – specifically, photonic integration and

flexible OTN – have contributed greatly to the success of 100G as well.

Super Channels

Perhaps the most significant technology change in moving from 100G (and lower

line rates) to beyond 100G is the super channel. A super channel is an evolution in

DWDM in which several optical carriers (or lasers) are combined to create a

composite signal of the desired capacity. A super channel differs from simply

sending multiple wavelengths down a fiber in two key ways:

The spacing of optical carriers within a super channel can be packed

tighter than the ITU-T WDM grid, thus enabling higher spectral efficiency, a

key driver for using super channels;

Super channels behave as a single unit of bandwidth, are brought into

service in a single operational cycle, and therefore allow service providers

to scale operations without scaling costs.

Greater spectral efficiency is achieved primarily because super channels use

coherent detection, but also via tighter spacing between sub-carriers. For exam-

ple, while today's long-haul DWDM systems are based on 50GHz channel spacing,

super channel implementations will remove the guard band between carriers

currently defined by ITU-T wavelength grids, enabling tighter spacing of carriers

and higher spectral efficiency. The combination of greater channel rates and

tighter spacing yields more bit/s per Hz, meaning more bit/s per fiber.

Significantly, super channels also occupy the same amount of spectrum as a

single laser being used for a given transmission rate and the same modulation

technique (e.g., 10 DP-QPSK sub-channels at 100G each, versus a single DP-QPSK

channel at 1 Tbit/s).

Beyond greater spectral efficiency, there is another critical advantage of super

channels versus traditional single-carrier transmission. Super channels enable the

industry to get to higher bit rates five or even 10 years sooner than would be

possible with single-channel technology. The reason is that optical transmission is

far ahead of electronic processing. Today, while 100G transport is moving into the

mainstream, the state of the art in electronic analog-to-digital conversion is only at

32 GBaud. Terabit-speed processing is more than a decade away.

Furthermore, even on the optics side there are time-to-market and economics

advantages in using super channels. There are no commercial modulators today

that operate at 1Tbit/s rates, yet 1Tbit/s super channels can be created using

multiple sub-carriers. Even when 1Tbit/s modulators do come to market, they will

be far more expensive than 100G optics.

A final significant point about super channels is applicable to long-haul DWDM

transmission. Suppliers building super channels from multiple DP-QPSK modulated

sub-carriers can achieve distances beyond 2,000 km. By contrast, using higher-

order modulation alone (for example 16 QAM) yields high data rates at the

expense of distance. A 16QAM modulated signal will be limited to regional

distances (around 600 km).


Photonic Integration

We have seen an increasing role for photonic integration in optical transport over

the past decade. The most significant case of photonic integration to date has

been Infinera's use of large-scale photonic integrated circuits (PICs) as the basis of

its widely deployed DTN DWDM systems. These systems have been deployed

commercially since 2004.

Beyond Infinera, small-scale PICs have also become widely deployed with JDSU's

integrated laser Mach-Zehnder, for example. This JDSU chip monolithically inte-

grates five optical functions in indium phosphide. As another example, for the 168-

pin 100G LH DWDM Multi-Source Agreement (MSA), the OIF specifies photonic

integration. Such integration is needed to achieve the specified footprint and

power consumption.

Heavy Reading believes that the optical industry will enter a new phase of

photonic integration as it moves beyond 100G and to the era of super channels,

as described earlier in this paper. Significantly, the large-scale PIC, by its design, fits

nicely into a super channel model that requires multiple carriers/lasers. To create a

1Tbit/s super channel composed of 10 channels, for example, a module requires

roughly 10x the number of optical components that a single-channel (non-super

channel) module would require. Therefore, photonic integration becomes

essential in reducing module costs, footprint and power consumption.

We expect that super channels will steer industry PIC implementation away from

single-channel design (known as serial integration) and toward multi-laser/multi-

channel PICs (known as parallel integration). We don't expect that there will be a

"magic number" for how many channels must reside on a single PIC.

Rather, component and systems suppliers will seek the greatest balance between

high levels of integration and high yields – something that will likely vary from

supplier to supplier.

While reducing costs, footprint and power, PICs that combine multiple lasers on a

chip also play into the "fluid bandwidth" proposition of super channels. With super

channels, operators will be able to throttle bandwidth up and down, as needed,

by adding and subtracting carriers, as well as by tuning into different modulation

formats that trade-off between capacity and reach.

Flexible OTN Containers

While early-generation optical crossconnect elements were based on Sonet/SDH

switching, a new generation of elements based on OTN has emerged as the

bandwidth management and grooming technology of choice for the next

generation of core transport networks. ITU-T standard OTN is an ideal transition

technology as it handles legacy TDM traffic better than Ethernet in its current form,

and it is also better suited than Sonet/SDH for transporting and switching the data

traffic that is driving traffic and operator revenue growth. Standards advances

such as ODU0 (for Gigabit Ethernet) and ODUflex have further adapted OTN for

the packet transport and switching role.

Heavy Reading sees a tight coupling of OTN and 100G, and many network

operators are upgrading their networks to both technologies in tandem. The

reason for this coupling is that the move to line-side 100G transport is creating a

large mismatch between the line side (100G) and the client side (primarily 10G

and below) that requires traffic grooming in between.


For example, even as client-side interfaces move up to 10G, there is still a 10x

mismatch between the line side and client side on a 100G network. While opera-

tors worldwide are eager to enjoy the capex and opex benefits of 100G transport,

those benefits will be more than offset by the bandwidth-wasting disadvantages

of the point-to-point muxponder-based network architecture of the past.

Furthermore, market research shows that the mismatch between client rates and

line-side rates is here to stay for the foreseeable future (see Figure 4). Operators

view OTN as the Layer 1 grooming technology of choice for efficiently packing

100G waves.

The role of switched OTN is set to continue beyond 100G as: 1) the Sonet/SDH

hierarchy ends at 40G and 2) the mismatch between the line rate and the client

rate is expected to continue. Future developments will likely focus on increasing

the flexibility/adaptability of OTN containers for high-order bit rates. There is strong

industry interest in expanding the low-order flexibility of ODUflex to wavelength-

level rates.

We discuss flexible/adaptable OTN standards development further in the State of

"Beyond 100G" section of this paper.

Flexible ROADM

The last technology innovation we discuss in this paper is ROADMs that support

flexible spectrum. This is another technology trend that is tightly coupled with the

transport migration beyond 100G.

For speeds beyond 100G – i.e., 400G, 1 Tbit/s or anything in between – more than

50 GHz of spectrum will be required. Most network operators would like to be able

to accommodate those future speeds on the same networks that are also

transporting 40G and 100G wavelengths.

The proposed solution is a more granular version of the ITU grid that breaks

spectrum down to 25GHz granularities, or some other increment. ROADM nodes

Figure 4: Projected Core Network Client-Side Interface Share, 2015

Source: Heavy Reading, 2012


supporting a flexible grid could operate at any speed that is based on increments

of 25GHz spacing, such as 75GHz spacing or 125GHz spacing, etc. (see Figure 5).

While wide-scale deployments of 100G+ line rates are still years away, operator

interest in flexible ROADMs that support these 100G+ line rates is far more immedi-

ate. Network operators are demanding that their 100G systems are 100G+ ready,

meaning that they contain flexible ROADM hardware, even if they have no near-

term plans to "turn on" the function. This future-proofing move is designed to save

operators from having to do another major network upgrade when the 100G+

time comes. Heavy Reading research shows that many operators are even willing

to pay a (small) premium for this flexible ROADM piece of mind.

Figure 5: Illustration of Flexible Spectrum Architecture

Source: Huawei


Adding Control Plane Intelligence There is no question that the telecom industry is in the midst of a monumental shift

from the hardware focus of the past to a new era focused on software. SDN

embodies this shift, and it is shaking up nearly every facet of the telecom industry.

Optical transport is not excluded from the push to SDN. At the same time, software

control in optical networks is not entirely new. This section discusses the values and

benefits of software control, looking at the past, present and future, and then

places optical control within the newer context of SDN.

Drivers & Benefits

Optical control plane intelligence has been used in commercial networks for more

than a decade, since the introduction of Sonet/SDH-based optical crossconnect

elements in 2000. The value of the optical control plane comes from replacing

functions that are done manually with network automation. Automation translates

into operational savings, reducing the amount of time that workers must be paid

to perform the functions. A second benefit of automation is faster time to perform

functions (and with fewer errors), which speeds revenue recognition for bandwidth

provisioning and, therefore, contributes to operators' bottom lines. A third benefit is

greater efficiency and simplicity in organizing the storage and updating of

network data.

In a multi-client study on core packet optical networks, we asked network opera-

tors to select the single biggest driver for implementing optical control planes in

their optical networks. Figure 6 shows the results from 89 network operator re-

spondents globally.

Figure 6: Most Important Driver for GMPLS/ASON Control Plane

Source: Operator Plans for Core Packet-Optical Transport: A Heavy Reading Multi-Client

Study, December 2010; n=89


Evolution

Software control of optical networks has existed for a long time already, so when

we talk about the development of SDN for the optical transport layers, the starting

point is different than it is for some other parts of the network – where the concept

itself is new.

Relevant standards for the software control plane come from the IETF (GMPLS), the

ITU (ASON) and the OIF. GMPLS and ASON standards actually have been in place

since the early 2000s, and mesh optical networks (controlled by software) have

been in existence since the first optical crossconnect deployments in 2000. AT&T's

optical mesh network has more than 500 nodes and is, we believe, the world's

largest optical mesh network.

Yet, while standards were supposed to make vendor interoperability a reality (and,

by extension, network operator interoperability), after more than a decade, this

has not happened. Despite completion of many standards and large public

interoperability demonstrations organized by the OIF over the years, implementa-

tions are single vendor, typically single domain, and proprietary in nature.

SDN & the Future of the Optical Control Plane

This is where SDN – and OpenFlow as an open, SDN protocol – enter the debate.

Early OpenFlow proponents envisioned the protocol as a replacement for the

existing IETF and OIF standards work. They argued that GMPLS failed in its mission to

promote interoperability between suppliers and domains and to unify packet and

circuit layers – arguments that do have merit.

However, Heavy Reading does not believe in a simple "swap and replace" model

for transport SDN. The key arguments against such an approach are described

below:

OpenFlow was created specifically for the campus environment. Efforts to

adapt OpenFlow to the network operator environment are very new (i.e.,

the ONF was formed in 2011). If OpenFlow is to be used in transport, exten-

sions will be required. The ONF's new Transport Working Group will look at

such extensions.

Google's OpenFlow SDN application focused on packet in a relatively

simple network and may not translate well to a complex network operator

environment. Re-building OpenFlow for transport networks runs the risk of

simply adding back all the complexity that OpenFlow was supposed to

eliminate in the first place.

Some transport functions can be centralized, but others should remain

decentralized. Network optimization functions such as path computation

for primary and backup paths benefit from centralization, since centraliza-

tion allows the network to be viewed holistically. But other functions – such

as real-time recovery, for example – benefit from localization/distribution,

since reaction times are quickest when control is closest to the point of

failure.

Operators have invested billions of dollars globally in transport elements

that cannot be swapped out for new OpenFlow switches. Furthermore,

with many SDN concepts already part of transport standards, it does

make sense to completely reinvent the wheel for transport SDN.


Future Direction: A Hybrid World

We know what is absolutely necessary at this point is to accelerate work to

achieve the following three goals:

Multi-vendor interoperability (allowing control plane functionality to work

across different vendor's transport equipment;

Multi-domain interoperability (allowing control plane functionality to con-

nect different domains, such as a long-haul network and a metro net-

work); and

Multi-layer interoperability (allowing control plane functionality to work

across different layers of the OSI stack, including Layer 0, 1, 2 and 3.

In our discussions with network operators, these control plane interoperability

requirements have moved from "nice to have" functions (which often don't get

funded due to competing priorities) to "must have" functions that are central in

network planning discussions. Clearly, operator focus on cloud applications and

services more generally is driving optical control plane interoperability up the

priority list, and network equipment suppliers are obligated to act.

Heavy Reading believes that the likely scenario moving forward is a hybrid that

combines distributed control with centralized control; existing standards (including

IETF GMPLS and OIF work) with new technologies, such as OpenFlow; additional

IETF work such as Path Computation Element (PCE) and Application Layer

Transport Optimization (ALTO); and work by other groups that is still to be defined.


The State of "Beyond 100G" With 100G standardization complete and with commercial deployments ramping

up, now is the time for the industry to turn its attention to the next bit rate beyond

100G. If we accept the IEEE Bandwidth ad hoc findings as reasonable (Figure 1),

then the time will come when 100G is no longer the most efficient container for

networks. Some service providers (including Google) see some terabit require-

ments even today.

This section outlines the key standards work and timelines for defining the next-

generation transport bit rate.

Standards Progress Update & Timeline

Two standards bodies are responsible for defining the next transport rate beyond

100G. These two bodies are the IEEE, which is responsible for Ethernet applications

and the ITU-T, which is responsible for OTN. The IEEE will define the Ethernet inter-

face for the next Ethernet bit rate and the ITU-T will define the standardized OTN

container for this Ethernet rate. In terms of flow, the ITU-T needs to understand the

IEEE Ethernet roadmap to define an OTN container that efficiently transports that

rate. Thus, the two groups must work together closely.

The following section discusses the IEEE and ITU-T Beyond 100G work and

roadmaps in more detail.

IEEE Client Side

The next Ethernet bit-rate beyond 100GE is not yet defined, which is why we must

speak vaguely in terms of "beyond 100G" when discussing the evolution. On the

table for the client side is a 4x jump from 100GE to 400GE or a 10x jump to 1Tbit/s

Ethernet. The IEEE 802.3 Industry Connections Higher Speed Ethernet Consensus

Group was formed in August 2012 to build consensus on the next bit rate questions

and is preparing a Call for Interest on 400GE, which is slated for March 2013. Given

the activities of this ad hoc group to date, 400GE appears the likely winner, but

nothing is certain until the vote is completed and the official study group is formed

to define the standard. Current expectations are for a completed standard in

2016 or 2017.

ITU-T Line Side

The ITU-T Study Group 15 began discussions of the next-gen transport rate at its

Plenary Meeting in Geneva, held in September 2012. On the line side, no decisions

have been made, and there are currently three options on the table:

400 Gbit/s

1 Tbit/s

A flexible line rate decoupled from the client rate and is built from stand-

ardized building blocks

The current goal is to complete the standard in the 2014 to 2016 timeframe,

though the IEEE Ethernet rate is an important input into the ITU-T decision process

and could impact the line-side timetable if there were unforeseen delays in

reaching a client-side consensus.


We believe that a flexible and adaptive line-side rate has strong merits and has

the most momentum. Called "OTUadapt" in one proposal, though the official

name may ultimately change, the flexible channel rate option has been added to

the living list of beyond 100G proposal options – along with the 400G and 1Tbit/s

fixed-rate options.

The concept is that larger OTN containers can be created dynamically by adding

or subtracting standardized building blocks, such as 25 Gbit/s or some other

increment that is decided by the standard. One of the key advantages of this

approach is that it mitigates the need to convene a standards body every time a

new line rate is required, meaning that line rate innovation would occur more

quickly than ever before. The approach also enables a decoupling of the line side

and the client side, since the line-side containers would be assembled to hold

whatever client rate is presented.

As a final and important point, multi sub-carrier super channels fit well with a

flexible line rate standard as the sub-carriers could be added and subtracted from

the line to provide the right amount of capacity required for the container. The

use of sub-carriers means that capacity is not wasted when channel capacity

requirements are low. Idle sub-carriers are available to be used for other wave-

lengths. This would not be the case for ultra-high-capacity, single-carrier wave-

lengths (such as with a single-carrier 1Tbit/s channel, for example).

Technology & Market Challenges

With nearly a decade of hard work in the rear view mirror, the optical industry is

well-positioned for the migration to 100G transport, which is occurring right now,

and the migration beyond 100G that will occur late in this decade. Still, there is

work to be done to meet the stringent requirements set by network operators.

Cost: First and foremost is the pricing challenge. Reducing cost per bit re-

mains the fundamental goal of optical transport. The next-generation bit

rate will have to prove in economically to be adopted. For every new bit

rate that hits the market, operators always have the option of maintaining

the status quo (in this case 100G) until the cost benefits swing in favor of

migrating. For super channels in particular, the challenges will be combin-

ing multiple carriers into small form factors, at low costs, and with low

overall power consumption.

Standards: The 100G success story proves the benefits of industry collabo-

ration and stands in stark contrast to the fragmented, and ultimately not

very successful, approach to 40G. With a decision to be made on wheth-

er to move to 400GE or 1Tbit/s Ethernet, there is potential for delays (and

fragmentation) if consensus cannot be reached. There are also multiple

proposals being considered on the line side. Lack of consensus could

cause delays here as well.

Still, the good news is that the beyond 100G question is already being tackled by

all major industry players and standards groups. At this early stage, we believe that

pieces are in being put in place for all challenges to be met, and we remain fully

confident that the terabit era will arrive sooner, rather than later.


Alcatel-Lucent Perspective

Not Just Faster, but Smarter

As network speeds (or more accurately, capacities) increase, it is critical to

harness that tremendous increase in capacity by implementing it more intelligent-

ly. Until recently, the demand for greater automation and programmability was

met by adding control planes for each layer of the network. Time to revenue

improved and operations became less labor intensive and more automated.

However, disparate operational models for each layer of the network are not

optimal and can benefit from tighter integration.

The latest innovations in optical networking, such as photonic OAM and embed-

ded analytics, hold the promise for even more automated and more program-

mable networks. A multilayer control plane with per-flow performance control and

multilayer network management can lead to a more common operational model

across network layers and offers the possibility of the lowest total cost of ownership

and fastest time to revenue.

The following concepts enable increased optical network intelligence and

optimized 100G+ network efficiency and costs.

Multilayer Network Design Optimization

Routing & Wavelength Assignment algorithms and "Optical Feasibility" algorithms

are capable of multilayer design optimization. The algorithms ensure traffic is

photonically bypassed when it is more economical to do so, while at the same

time maximizing bandwidth efficiency.

When it comes to network resiliency and high network utilization, dimensioning

algorithms optimize the minimal amount of equipment required, and associated

cost, to meet network resiliency specifications. Network assets are essentially

dimensioned in a manner that optimizes the sharing of common assets by multiple

services that are not impacted by the same failures in a restoration scenario. This

helps reduce capex and extend the network's lifespan.

Automatic Commissioning & Provisioning

Automatic commissioning and provisioning ensures all Layer 0 and Layer 1

commissioning parameters are automatically loaded for ROADMs, amplifiers,

transponders, etc. instead of manually. This dramatically reduces the time required

for service activation. This also reduces the number of site visits required and

minimizes the potential for human error associated with the manual configuration

of cross-layer, end-to-end paths. Overall, it helps evolve to a services-oriented

network with faster time to revenue.

Accurate, Continuous, Autonomous, Ubiquitous Monitoring

Smarter 100G networking hinges on measurement and analytics to better under-

stand the network. Photonic OAM includes measuring characteristics such as

power, signal noise and latency. Power measurement is used for continuous,

autonomous and automatic power balancing of individual wavelengths and

groups of wavelengths along multiple touch points in the network for an end-to-


end service. Finally, photonic monitoring helps avoid misconnections and wave-

length collisions even under circumstances that require recoloring of a wave-

length as it traverses across a network.

Layer 1 and Layer 2 service monitoring consists of measuring and reporting

characteristics such as bit error rate, frame loss and latency. These type measure-

ments are targeted around monitoring services whether that service is a 100G

Ethernet service or a 1G Ethernet service. These services are routed through the

network based on defined SLA parameters and can be monitored. The control

plane can be configured to react automatically to failure or degradation in the

network without human intervention. Conversely, it can be configured for manual

intervention should a situation occur that degrades a particular service, whether it

is caused by a network failure or for some other reason.

Scheduled Offline Maintenance Activities

There are cases where scheduled maintenance activities are beneficial. For

example, after the network automatically restores in response to a network event

or failure it can be configured to revert back to its original state.

In other circumstances, offline simulations may be required to analyze a network

problem. For example, if threshold alarms indicate an amplifier site has degraded

in performance, but without any traffic loss or outage, simulations – based on

actual ODU SLAs – can be run to assess the impact of rerouting the affected

wavelengths and ODU service demands onto alternative routes. As the amplifier

issue is being rectified, the control plane automatically recalculates the restoration

paths of all the affected services based on the operator's SLA objectives.

Regular network audits can detect when the network veers from its optimal state.

For example, an audit can detect when services are routed along non-optimal

paths or when a possible failure will result in long switch times, broken SLA guaran-

tees or other non-optimal circumstances. Scheduled maintenance activities can

re-optimize multilayer routing and bandwidth usage over the network's lifespan.

Similarly, regular network audits can detect when wavelengths have been lit in a

non-optimal fashion based on somewhat random service demands. Again,

regularly scheduled maintenance activities can re-optimize defragmented

wavelengths to minimize the recoloring or tuning of wavelengths for future services

or for restoration purposes thus minimizing restoration times.

Real-Time Network Monitoring & Control

In contrast to scheduled maintenance activities, if the network is running a mix of

traffic speeds (not just 100G) an intelligent network automatically intervenes in times

of a network failure. In fact, it can do so such that SLA guarantees are taken into

consideration and lower-priority traffic is preempted in favor of higher-priority traffic.

Finally, a smarter 100G network enables differentiated services with support for

enhanced SLAs. Service restoration is coordinated between electrical and

photonic layers so that restoration is achieved at the most economical layer while

still respecting target SLA guarantees.


Huawei Perspective

Current 100G Technology

Huawei's experience in 100G commercial projects and feedback from operators

has shown that, to fully demonstrate advantages and create more benefits for

customers, 100G must keep evolving and interoperate with other technologies.

Second-Generation Soft-Decision Technology

FEC, QPSK, PDM and coherent detection are core technologies for 100G. Most of

these technologies are mature and will not undergo many changes. However,

FEC has experienced great changes, from early hard-decision FEC to first-

generation software-decision (SD) FEC, which then quickly evolved to second-

generation SD-FEC, providing significant improvements in performance. 100G

products that support second-gen SD-FEC have the following features:

Ultra-long transmission: Using the improved SD algorithm, second-gen FEC consid-

erably reduces back-to-back ROSNR with a higher net coding gain and better

tolerance to fiber nonlinearities, effectively extending the 100G transmission

distance. 100G systems that support second-gen SD-FEC are capable of unre-

peatered 100G transmission over ~4,000 km of terrestrial spans.

Low power consumption and high integration: In addition to the advanced SD-FEC

algorithm, 100G line cards that support second-gen FEC have also seen improve-

ments in chip technology, such as the use of 28-nm processing technology. The

new chip technology significantly reduces the power consumption of core chips

and allows 100G products to demonstrate much better performance while

consuming less power. This makes possible the commercial use of highly integrat-

ed products, helping operators to greatly reduce their TCO.

In the second quarter of 2013, Huawei will launch its first 100G product that

supports second-gen SD-FEC. This product will outperform any 100G product that

supports the first-gen SD-FEC, while consuming less power.

OTN – A Necessity for the 100G Era

Huawei's 100G shipment show 70% to 80% customers use OTN cross-connections,

with separated tributary and line access architecture. To resolve the disparity

between the client-side and line-side, OTN cross-connection technology is applied

to map lower-rate services into high-speed pipes, support transparent transmission

and protection of lower-rate services, and thus improve wavelength utilization via

more flexible service grooming. Traditional networks are based on the IP+WDM

model. In a traditional network, routers and WDM equipment are connected back

to back, Such a model is not the most efficient way for bandwidth management,

especially in 100G era. If a WDM network is constructed based on an OTN plat-

form, the router/OTN synergy will greatly reduce the need for router ports via IP-

offloading and thus less power consumption, leading to capex reduction by 30%.

Going Beyond 100G

As the telecom industry advances, future networks will experience enormous

changes. According to information from all sides, future optical network architec-

ture and key technologies will have the following features.


Future Optical Network Architecture

Optical transport network have changed from static to dynamic. For the coming

era of beyond 100G, the industry is seeking an optimal optical transport platform

to meet upcoming challenges. In general, the future network must have the

following features:

Unified platform and programmable functionality: Operators would be

able to select the most efficient BW-reach transport function through pro-

grammable settings;

Open interfaces and cloud resources: A third-party can program transport

resources through open interfaces.

Intelligent network and on-demand bandwidth: The network must be in-

telligent to provision services based on service demands.

Flexible Transceiver

In the beyond 100G era, transmitters will use a multi-carrier optical source. The

receiver will be adaptable to wavelengths and support any combination of sub-

carriers. In addition, the receiver will employ the Nyquist pulse shaping to further

improve spectrum utilization. Beyond 100G technologies will support adaptable

transmission distance and bandwidth based on channel conditions.

Huawei has rolled out the industry's first 2Tbit/s prototype, which has been tested

on one of Vodafone Germany's live networks. The trial demonstrated that the

adaption between the line bandwidth and transmission distance is possible. For

the trial, when the Nyquist-PDM-QPSK modulation format was used, the transmis-

sion distance reached 3,325 km and the C-band capacity was 12Tbit/s. When the

modulation format was changed to Nyquist-PDM-16QAM, the transmission

distance was 1,440 km and the C-band capacity increased to 21.3Tbit/s.

Flexible ROADM

Flexible ROADM is a key technology for 100G+ networks. As the line symbol rate

increases, the spectrum of an optical signal widens. To further improve spectrum

utilization, future DWDM networks are expected to dynamically allocate spectral

resources so that a high-speed signal can occupy multiple flexibly adjusted

spectral granularities via Flexible ROADM.

Flexible OTN

The line rate evolution from 2.5G to 10G, to 40G, and then to 100G is based on

direct addition to the bandwidth of a single wavelength. However, for beyond

100G, the entire bandwidth will be adjusted in granularities of 100G or 200G. This is

to ensure that signals beyond 100G, such as 400G, 1Tbit/s and 2Tbit/s signals, will

be multiplexed and cross-connected with the highest efficiency to flexibly adapt

to future service development and network scalability requirements.

Flexible Controller

In the beyond 100G era, SDN technology will be at the core of transport network

management to uniformly coordinate all devices on a network. It will select the

best path based on service distance, rate, transmission latency and bandwidth to

provide efficient, flexible and open bandwidth management.


Infinera Perspective PIC-based coherent super channels are now the most popular way for service

providers to deploy long-haul optical capacity at 100G and beyond.

Photonic Integration Benefits

Parallel (i.e., multi-wavelength) PICs have three distinct benefits for super channel

implementation:

Approximately 50% electrical power saving because PICs virtually elimi-

nate optical chip to chip coupling losses.

Much smaller footprint because of the elimination of huge numbers of

optical components.

Economic enabler to using more carriers (i.e., wavelengths) in the super

channel.

The third bullet may be the most important, because using more optical carriers

for a given capacity of super channel means that the data rate of each carrier is

less. For example, a 500G single-carrier implementation would have this carrier

running at 500G. This performance of electronics may not be available for another

10 years. Moving to a 10-carrier super channel means that the electronics for each

carrier is running at only 50G, which is available now.

To a first approximation a parallel PIC chip costs about the same to produce

regardless of the number of carriers, so this gives the line card designer tremen-

dous flexibility to optimize the implementation of the super channel.

Fixed Grid to Flexible Grid Evolution

The result is that it becomes possible to deliver production 500G PM-QPSK super

channels, with ultra-long-haul reach, from mid-2012. These first-gen super channels

deliver most of the spectral efficiency gains, and all of the operational scalability

gains expected from super channels while retaining compatibility with fixed grid

DWDM line systems.

By moving to flexible grid, the second-gen super channel solution will enable a

further 20% gain in spectral efficiency (comparing like-for-like modulation tech-

niques).

Fluid Bandwidth Capability

Some observers have noted that 500G is a large amount of capacity for some

service providers to purchase on Day 1. While they may be experiencing expo-

nential increases in demand, it is also essential to help them control capex and

cash flow, so that there is the minimum delay between purchasing super channel

capacity and receiving revenue for the services using that capacity.

To address this issue Infinera has introduced a feature called Instant Bandwidth.

With Instant Bandwidth, a service provider can purchase capacity in 100G chunks,

but because the full 500G super channel is already deployed, then the additional

capacity becomes available for service provisioning "instantly" (in practice, it


requires a few seconds for the protocols to activate the additional capacity). This

is Infinera's version of the "fluid bandwidth" feature mentioned above. It is difficult

to imagine how this type of feature could be implemented without parallel

photonic integration.

Integrated OTN Switching

Service providers are already aware that integrated OTN switching allows DWDM

capacity to be used more efficiently (typically a 2x efficiency gain), and allows

intelligent control planes (such as GMPLS) to operate in a deterministic way.

Since a PIC-based super channel line card is so much smaller than the same

capacity implemented in separate transponders, and uses less power thanks to

lower on-board coupling losses, there can be more physical space, and sufficient

power and cooling budget to allow for the integration of OTN switching in the

same chassis.

Intelligent Network Control Planes

GMPLS is already deployed on all of Infinera's PIC-based transport platforms.

Service providers are already familiar with the ease-of-use benefits of GMPLS, and

these will become even more compelling with the advent of ITU G.SMP (shared

mesh protection), which will allow sub-50ms service protection using shared link

resources.

Infinera is a leading proponent of a transport-optimized version of the SDN

architecture. Infinera recently completed a demonstration of "Transport SDN" in

cooperation with ESnet, and it is working within the Open Networking Foundation

to standardize this architecture.

The End Result: Infinera DTN-X

Infinera designs and manufactures highly advanced, parallel PICs in its own

fabrication facility in Sunnyvale, California. However, it does not sell these PICs on

the open market; instead, it has developed a complete DWDM transmission and

switching platform based on this technology. This is the Infinera DTN-X, which offers

in a single rack:

500G super channel capacity per line card slot; the existing DTN-X slots are

designed to support 1Tbit/s super channel cards in the future

5 Tbit/s of total transmission capacity with 500G line cards (10 Tbit/s in the

future)

5 Tbit/s of non-blocking OTN switching capacity

Instant bandwidth capability

GMPLS control plane

This platform has been shipping commercially since mid-2012, and has already

leapt to the number one position in the 100G long-haul transport market.

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