The Intel 50G Silicon Photonics Link

*B.Rajivgandhi, Dept of ECE, boyapatirajivgandhi@gmail.com,**L.Hemasundar, Dept of ECE, lhemasundar@gmail.com

YOGANANDA INSTITUTE OF TECHNOLOGY AND SCIENCE

ABSTRACT-- Silicon photonics is rapidly

gaining importance as generic technology platforms

for a wide range of applications in telecom,

datacom, interconnect and sensing. It allows

implementing photonic functions in or above silicon

through the use of wafer-scale technologies

normally used for advanced CMOS-processing. In

recent years there has been a plethora of

breakthroughs in this field, including the

demonstration of ultra-compact passive optical

functions, high speed optical modulators and

detectors, silicon lasers, all-optical signal processing

functions

After dominating the electronics industry

for decades, silicon is on the verge of becoming the

material of choice for the photonics industry: the

traditional stronghold of III-V semiconductors.

Stimulated by a series of recent breakthroughs and

propelled by increasing investments by

governments and the private sector, silicon

photonics is now the most active discipline within

the field of integrated optics.

This paper provides an overview of the

state of the art in silicon photonics and outlines

challenges that must be overcome before large-

scale commercialization can occur. In particular,

for realization of integration with CMOS very large

scale integration (VLSI), silicon photonics must be

compatible with the economics of silicon

manufacturing and must operate within thermal

constraints of VLSI chips. The impact of silicon

photonics will reach beyond optical

communication-its traditionally anticipated

application. Silicon has excellent linear and

nonlinear optical properties in the midwave

infrared (IR) spectrum. These properties, along

with silicon's excellent thermal conductivity and

optical damage threshold, open up the possibility

for a new class of mid-IR photonic devices

KEYWORDS: Photonics, CMOS-Processing,

Optical, Silicon lasers, VLSI

WHAT IS SILICON PHOTONICS

AND WHY?

Silicon photonics is the study and

application of photonic systems which use silicon

as an optical medium. The silicon is usually

patterned with sub-micrometer precision, into

micro photonic components. These operate in the

infrared, most commonly at the 1.55 micrometer

wavelength used by most fiber optic

telecommunication systems. The silicon typically

lies on top of a layer of silica in what (by analogy

with a similar construction in microelectronics) is

known as silicon on insulator (SOI).

Silicon photonic devices can be made

using existing semiconductor fabrication

techniques, and because silicon is already used as

the substrate for most integrated circuits, it is

possible to create hybrid devices in which the

optical and electronic components are integrated

onto a single microchip. Consequently, silicon

photonics is being actively researched keeping on

track with “Moore's Law”, by using optical

interconnects to provide faster data transfer both

between and within microchips. Fiber optics has a

lot to offer in the speed of data transmission.

CMOS manufacturing processes have a lot to offer

in making things smaller, cheaper, and faster. It

would only make sense that putting these two

things together would be advantageous

IMPLEMENTATION OF SILICON

PHOTONICS:

Silicon Photonic gives the idea to build

all the components for optical circuits with the

CMOS manufacturing processes and eliminate the

bottleneck. Extend the optical communication path

inside the computer, inside any electronic devices

in the path, perhaps even all the way into the

microprocessor and memory chips themselves.

It would be appropriate to assume that

once all components are in place the intelligence

needed to drive an optical circuit can be derived

from the larger, more costly brethren from which

this new technology hails the first steps addressed

were the light guides and modulation. Silicon has

the characteristic of being transparent to

wavelengths of light in the optical transmission

range. By using Si as the medium and constructing

surfaces around it, a ‘wave guide’ can be produced

to channel light through a semiconductor circuit.

Coupling these wave guides with micro circuitry to

perform the modulation functions was successfully

started in the early 2000’s). Today Si-based

modulators are performing at 10Gbps speeds.

How does it work?

Digging into the science behind the

Silicon Photonics Link, Intel's solution comprises

of two key components; the transmitter and

receiver chips.

The transmitter chip, depicted above, is

built on the foundations of the Hybrid Silicon

Laser. Created in collaboration with the University

of California, Santa Barbara, the Hybrid Silicon

Laser - itself built by bonding Indium Phosphide

and Silicon through a low-temperature plasma-

enhanced oxidation process - is able to channel the

light-emitting capabilities of Indium Phosphide

through silicon waveguides.

Using four Hybrid Lasers on a single

transmitter, each of which generates four different

wavelengths in four different colors, the chip sends

the data to four high-speed 12.5Gbps optical

modulators that then couple the four channels onto

a single 50Gbps optical fibre.

Intel Contribution:

Mario Paniccia, Intel Fellow and Director

Photonics Technology Lab at Intel, which has been

a leading player in the integration of electronic and

photonic technologies on silicon

Intel has reached an important

milestone in its quest to bring Silicon Photonics to

the mainstream by creating the world's first silicon-

based optical data connection with integrated

lasers.

The connection, dubbed the Intel 50G

Silicon Photonics Link, can move data at a rate of

50 billion bits per second (50Gbps) and is being

positioned as the next-generation successor to

today's widespread copper cables.

Building on the breakthroughs of recent

years, the 50G Link consists of a silicon transmitter

and a receiver chip; both of which utilize previous

Intel innovations including the 2006 Hybrid Silicon

Laser and high-speed optical modulators and photo

detectors from 2007.

Bringing the building blocks together, the 50G

Link - described at this stage as merely a "concept

vehicle" - is able to provide ultra-high-speed data

transfers on fibre cables that are typically thinner

than a human hair.

Commenting on the announcement, Intel's

director of the Photonics Technology Lab Dr.

Mario Paniccia states that Silicon Photonics is "not

a technology that we [Intel] think is 10 years out",

adding that he expects to see commercialization in

three-to-five years.

What does the future hold?

Intel's vision of the future is one in

which optical connections replace today's copper

cables. The implications of such a change are

obvious for data centres and servers, but Silicon

Photonics could revolutionize computing in

numerous other ways.

Despite admitting that it's currently

very difficult for optical links to replace copper

traces over short distances (less than six inches),

Intel's keen to point out that Silicon Photonics

could one day change the way in which everyday

computers such as notebooks are designed and

created.

Silicon Photonics is the next generation,

and, priced in the "same ball-park" as Light peak, is

expected to go way beyond the 50Gbps being

prototyped today. Scaling up, Intel predicts that the

speed of each optical modular will rise

exponentially, and there's nothing stopping the

technology from growing wider through the

addition of more Hybrid Silicon Lasers to each

chip.

If Intel's ambition of a Terabit link does

come to fruition, you could be backing up your

entire PC in under a second. Once received by

Intel's receiver chip, a demultiplexer splits up the

four wavelengths into their four original

channels/colours, and silicon germanium photo

detectors then convert the signal back to electrons

and electrical data.

APPLICATIONS:

Future progress in computer technology

is becoming increasingly dependent on ultra-fast

data transfer between and within microchips .Some

applications of silicon photonics in this field are

High speed optical interconnects which is seen as a

promising way forward, due to the ability to

integrate electronic and optical components on the

same silicon chip Another application of silicon

photonics is in signal routers for optical

communication Silicon micro photonics can

potentially increase the Internet's bandwidth

capacity by providing micro-scale, ultra low power

devices

ADVANTAGES OVER OTHER

COMMUNICATIONS:

Silicon micro photonics can potentially

increase the Internet's bandwidth capacity by

providing micro-scale, ultra low power devices.

Furthermore, the power consumption of datacenters

may be significantly reduced

There is no doubt about the economic

and technical advantages of silicon and it was

inevitable that silicon would be employed wherever

optic fiber is deployed. Predictably, with the rise in

Internet and data transmission, the need for higher

speed, broader bands, and lower cost matches all

four of the material benefits provided by silicon:

Photonic: wide band infrared

transparency,

Electronic: low noise, high speed

integrated circuits,

Thermal: high heat conductance, and

Structural: rugged 3-dimensional

platforms and packages

FUTURE CHALLENGES:

The future ahead is Silicon Integrated

Nanophotonics which is to develop a technology

for on-chip integration of ultra-compact

nanophotonic circuits for manipulating the light

signals, similar to the way electrical signals are

manipulated in computer chips. Nan scale silicon

photonics circuits are being developed to enable the

integration of complete optical systems on a

monolithic semiconductor chip that would

eventually allow to overcome severe constraints of

today’s mostly copper I/O interconnects.

CONCLUSION:

Although research in the area of planar

optics in silicon has been underway for several

decades, recent efforts at Intel Corporation have

provided better understanding of the capabilities of

such devices as silicon modulators, ECLs and SiGe

detectors. Incorporating silicon in an ECL opens a

path towards hybrid silicon photonic integration, or

even a Silicon Optical Bench (SiOB) platform for

silicon photonics.

Silicon modulators operating at 2.5

GHz have demonstrated two orders of magnitude

improvement over other known si-based

modulators, with theoretical modeling indicating

performance capabilities beyond 10 GHz.

REFERENCES:

http://en.wikipedia.org/wiki/

Silicon_photonics

http://blogs.intel.com/intellabs/

2010/07/23/50g-link/?

wapkw=silicon+photonics+link

Optical Fiber Telecommunications: Components and Subsystems by Ivan P. Kaminow, Tingye Li, Alan E. Willner

http://books.google.co.in/books? id=NVmnuGREwj4C&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

http://silicon-photonics.ief.u-psud.fr/

http://optics.org/indepth/3/2/4

http://www.trustedreviews.com/news/ Silicon-Photonics-The-Next-Step

http://www-03.ibm.com/press/us/en/ pressrelease/39641.wss

http://www.eetimes.com/design/eda- design/4402970/Silicon-photonics-ushers-in-100G-networks