Final Report

LIGHT PEAK TECHNOLOGY

SEMINAR REPORT

Submitted in the partial fulfillment of the award of the degree

of

Bachelor of Technology in

Electronics and Communication Engineering of

Cochin University of Science and Technology

GEORGE RAHUL PAUL

OCTOBER 2011

Department of Electronics & Communication Engineering

College of Engineering, Chengannur-689121

Phone: (0479) 2454125, 2451424 Fax: (0479) 2451424


SEMINAR REPORT

Submitted in the partial fulfillment of the award of the degree

of

Bachelor of Technology in

Electronics and Communication Engineering of

Cochin University of Science and Technology

GEORGE RAHUL PAUL

OCTOBER 2011

Department of Electronics & Communication Engineering

College of Engineering, Chengannur-689121

Phone: (0479) 2454125, 2451424 Fax: (0479) 2451424

COLLEGE OF ENGINEERING, CHENGANNUR

KERALA

DEPARTMENT OF ELECTRONICS AND COMMUNICATION

ENGINEERING

CERTIFICATE

This is to certify that the seminar entitled


Submitted by,

George Rahul Paul

is a bonafide record of the work done by him

Head of the Department Co-ordinator

ACKNOWLEDGEMENT

First and foremost I would like to thank GOD ALMIGHTY for giving me the strength and

confidence to see this seminar through and make it a reality.

With immense gratitude, I acknowledge all those who contributed with their valuable

suggestions and timely assistance towards the completion of this seminar.

I am grateful to Prof. Dr. V.P. Devassia, Principal, College of Engineering, Chengannur, for

providing me the best facilities and atmosphere for the development and presentation of my

seminar.

I thank Prof. V.P. Jyothiraj, Head of the Department, Department of Electronics Engineering,

for his encouragement and support.

I am indebted to Mr. Manoj Kumar P, Assistant Professor in Electronics and Communication

Engineering, Mrs. Laghima P.M, Assistant Professor in Electronics and Communication

Engineering, and Mr. Ayoob Khan T.E Associate Professor in Electronics and Communication

Engineering, for their valuable suggestion and ideas without which this seminar would have been

a tough task.

A sincere word of thanks to all my friends and family members for their support and prayers

offered which were inevitable for the successful completion of the seminar.

ABSTRACT

Light Peak is Intel's code-name for a new high-speed optical cable technology designed

to connect electronic devices to each other in a peripheral bus. Light Peak delivers high

bandwidth starting at 10Gb/s with the potential ability to scale to 100Gb/s over the next

decade.At 10Gb/s, you could transfer a full-length Blu-Ray movie in less than 30 seconds.

It is intended as a single universal replacement for current buses such as SCSI, SATA,

USB, FireWire, PCI Express and HDMI. In comparison to these buses, Light Peak is much

faster, longer ranged, smaller, and more flexible in terms of protocol support. Light Peak also has

the ability to run multiple protocols simultaneously over a single cable, enabling the technology

to connect devices such as peripherals, displays, disk drives, docking stations, and more.

Light peak was developed by Intel and brought to market with technical collaboration

from Apple Inc. In late February 2011, Apple introduced its Mac Book Pro laptop computers

with light peak technology and announced its commercial name as Thunderbolt. It can be added

to existing products with relative ease.

CONTENTS

1. INTRODUCTION ……………………………………………….…………………..1

2. LIGHT PEAK TECHNOLOGY ………………………………...……………….3

3. TODAYS CHALLENGES……………………………………..…………………..6

4. LIGHT PEAK V/S USB 3.0 ………………………………………….……………9

5. DATA TRANSFER SPEED COMPARISION………………….……………11

6. COMPONENT OVERVIEW...……………………………………….…………..13

6.1 Fiber Optics Cable ……………..………………….………………..…………15

6.2 Optical Module ………………………………………..………..…….………..16

6.2.1 VCSEL …………………………………….……….…….….……….16

6.2.2 Optical Modulator ………………………………….…...…………..17

6.3 Controller Chip ………………………………………….…………….……....19

7. LIGHT PEAK TECHNOLOGY OVERVIEW .………...…….….…………20

7.1 Light Peak Protocol Architecture ...….………….…….…….………………..21

8. ADVANTAGE……………………………………….………….…………..………..23

9. CONCLUSION…………………………………………………..………….…….…25

10. REFERENCES………………………………….…………….…….…..……….....28

College of Engineering Chengannur

1. INTRODUCTION

2 Light Peak Technology


1. INTRODUCTION

The present era is the era of connectivity. Think of any sort of information, and it can be

transferred to us within question of a little time; be it audio information, video information or

any other form of data.

Now talking about transferring data between our computer and the other peripherals, the

first and foremost standard comes to our mind is Universal Serial Bus (USB). It is a medium

speed serial data addressable bus system which carry large amount of data to a relatively short

distance (up to 5m).The present version USB 3.0 promises to provide theoretical speed of up to

5Gbps.

But Intel has unveiled a new interoperable standard called LIGHT PEAK which can

transfer data between computers and the peripherals at the speed of 10Gbps in both the directions

with maximum range of 100m (much higher than USB or any other standard) and has potential

to scale its speed high up to 100Gbps in near future.

Light Peak is the code name for a new high-speed optical cable technology designed to

connect electronic devices to each other.

Light Peak is basically an optical cable interface designed to connect devices in peripheral

bus. It is being developed as a single universal replacement for the current buses such as SCSI,

SATA, USB, FireWire, PCI Express, and HDMI etc in an attempt to reduce the proliferation of

ports on computers.

Fiber-optic cabling is not new, but Intel executives believe Light Peak will make it cheap

enough and small enough to be incorporated into consumer electronics at a price point that

consumers and manufacturers will accept.

Thus with light peak, the bandwidth would tremendously increase, multiple protocols could

be run over single longer and thinner cable.

The prototype system featured two motherboard controllers that both supported two

bidirectional buses at the same time, wired to four external connectors. Each pair of optical

cables from the controllers is led to a connector, where power is added through separate wiring.

The physical connector used on the prototype system looks similar to the existing USB or

FireWire connectors.

Intel has stated that Light Peak has the performance to drive everything from storage to

displays to networking, and it can maintain those speeds over 100 meter runs.


2. LIGHT PEAK TECHNOLOGY



2. LIGHT PEAK TECHNOLOGY

Optical networking technologies have been over the last two decades reshaping the entire

telecom infrastructure networks around the world and as network bandwidth requirements

increase, optical communication and networking technologies have been moving from their

telecom origin into the enterprise and Light Peak is one of its successful outcome.

It is basically a new high-speed optical cable technology designed to connect electronic

devices to each other .It also support multiple protocols simultaneously with the bidirectional

speed of about 10Gbps (can scale up to about 100Gbps). In comparison to other bus standards

like SATA and HDMI, it is much faster, smaller, longer ranged, and more flexible in terms of

protocol support.

Thus it basically provides a standard low cost high bandwidth optical-based interconnect, it

supports multiple existing I/O protocols and smooth transition between them, it supports wide

range of devices (handhelds, PCs, workstations etc.) ,connect to many devices with the same

cable, or to combo devices, have smaller connectors and longer (up to 100m on single cable),

thinner and economical.

Light peak consist of a controller chip and optical module that would be included in

platform to support this technology. The optical module performs the task of conversion of

electricity to light conversion and vice versa, using miniature lasers and photo detectors. This

transceiver can send two channels of information over an optical cable, necessary, since pc needs

at least two ports. The controller chip provides protocol switching to support multiple protocols

over single cable.

The Light Peak cable contains a pair of optical fibers that are used for upstream and

downstream traffic to provide speed of about 10Gbps in both the directions and power is added

through separate wiring.

It was developed as a way to reduce proliferation of number of ports on the modern

computer. Earlier USB was developed for the same purpose and performed very well in this

direction but increased bandwidth demand and high performance has led to development of new

more efficient technologies.

Combining the high bandwidth of optical fiber with Intel’s practice to multiplex multiple

protocols over a single fiber, optical technology may change the landscape of IO system design



in the future. It’s possible that most of the legacy IO protocols can be tunneled by optical capable

protocols, so some of the legacy IO interfaces can be converged to one single optical interface,

significantly simplifying the form factor design of computers. This change in IO system will

definitely affect the design of systems.

Fig. 2.1 Abstract model of the optical-enabled system

There are four main components in this figure, the IO devices, the IO controller which

connects to the IO devices through optical fiber, the processing unit and the interconnection

between the IO controller and the processing unit, whatever it can be implemented as.

Mobile and handheld devices are two fast growing market segments which attract interests

from processor vendors. For mobile and handheld devices, user interface and IO are two

important factors besides computing power that affect end users purchase decision .Taking

power into account, it’s possible that more carefully tuned IO workload offloading engines will

be integrated into the IO controller, saving the power to move the data from IO a long way to the

system memory. It makes no sense to have a high throughput IO system with insufficient

processing power or overloaded interconnections between IO system and the processor. The

ultimate goal of system architects is to make a balanced and efficient system, on both power and

cost grounds

.


3. TODAYS CHALLENGES



3. TODAYS CHALLENGES

In the coming future, people would be using more and more electrical devices such as HD

devices, MIDs and many more and user experience would depend on the huge volume of data

capturing, transfer, storage, and reconstruction. But existing electrical cable technology is

approaching the practical limit for higher bandwidth and longer distance, due to the signal

degradation caused by electro-magnetic interference (EMI) and signal integrity issues. Higher

bandwidth can be achieved by sending the signals down with more wires, but apparently this

approach increases cost, power and difficulty of PCB layout, which explains why serial links

such as SATA, SAS, and USB are becoming the mainstream. However optical communications

do not create EMI by using photonics rather than electrons, thus allowing higher bandwidth and

longer distances. Besides, optical technology also allows for small form factors and longer,

thinner cables.

The USB connectors on the smaller devices like mobile phones have to use mini-USB or

micro-USB to save on the space taken up by the wiring and electricity through wire creates

electric field interference, but light do not create EMI since it rely over photonics. Optical

connecters can carry extremely narrow beams of light and fiber can be thinner because more

streams can pass through glass or plastic passages. Each fiber is only 125 microns wide, the

width of a human hair.

In the present scenario, the devices are getting smaller, thinner, and lighter but present

connecting standards seems to hinder in their performance being to thicker and stiffer. So

vendors turn over to new technologies providing much better performance and Light Peak seems

to be a providing a good solution.

Different protocols demands for different connectors leading to too many connectors and

cables. But in Light Peak there is the Light Peak protocol and the native protocols such as PCI

Express, Display Port, USB or whatever might be running on it. The native protocols run

basically on top of the Light Peak protocol. But the Light Peak protocol defines the speed. The

protocol is running at 10 gigabits per second. So, if the native protocols that are running on top

of it are also running at 10 gigabits per second, or something close to that, then the effective

bandwidth for a device on the other end would be equivalent to that 10Gbps.



Fig 3.1 Different interconnects

Thus, it can be said that presently we demand for the devices and technologies that provides

much higher bandwidth , more flexible designs, thinner form factor and new and better usage

models and much simpler and easier in terms of connectivity’s.

It’s possible that most of the legacy IO protocols can be tunneled by optical-capable

protocols, so some of the legacy IO interfaces can be converged to one single optical interface,

significantly simplifying the form factor design of computers. This change in IO system will

definitely affect the design of systems. It makes no sense to have a high throughput IO system

with insufficient processing power or overloaded interconnections between IO system and the

processor. Ultimately the main aim is to build an efficient and balanced system.

Thus Light Peak seems to be providing a good solution to the problems existing with the

copper connectors and provides a good platform for the high performance system.


4. LIGHT PEAK VS USB 3.0



4. LIGHT PEAK V/S USB 3.0

USB 3.0

1. It is an electrical cable technology

which transmits data using electricity

which put limitation on speed and

length.

2. It consists of 9 copper wires for

transfer of data between the PC and the

peripherals.

3. Theoretically it can provide maximum

speed of 5Gbps which on practical

grounds get restricted to about 3Gbps.

4. It supports only USB protocol.

5. The maximum allowable cable length

for USB 3.0 is only about nine meters

LIGHT PEAK

1. It is an optical cable technology which

relies over light to transmit data thus

providing much better speed and

length.

2. It consists of 4 optical fibers for both

upstream and downstream traffic

simultaneously.

3. Initial proposed speed for Light Peak

(LPK) [10] starts at 10Gbps and has

future potential to scale up to

100Gbps.).

4. It is a Universal connector supporting

multiple existing protocols.

5. The maximum allowable cable length

is about 100 meters and can be even

extended more.


5. DATA TRANSFER SPEED COMPARISON



5. DATA TRANSFER SPEED COMPARISION

How does Light Peak compare to the latest technologies? The slowest is wireless. HDMI

version 1.3 and higher will transfer at 10.2 Gbps, while Display Port can go up to 10.8 Gbps.

These are slightly better than Light Peak, but they are mostly designed for video. No one is

pushing the data transfer rates of these protocols.

Fig 5.1 The chart shows how Light Peak compares to all of these other protocols.


6. COMPONENT OVERVIEW



6. COMPONENT OVERVIEW

Light Peak consists of a controller chip and an optical module that would be included in

platforms supporting this technology. The optical module performs the conversion from

electricity to light and vice versa, using miniature lasers (VCSELs) and photo detectors. Intel is

planning to supply the controller chip, and is working with other component manufacturers to

deliver all the Light Peak components.

The main components are:

1. Fiber optics cable

2. Optical module

3. Controller chip

Fig 6.1 Prototype view of components of light peak controller



6.1 Fiber Optics Cable

The fiber used here is a silica-based optical fiber structure which consists of a cladding

layer with a lower refractive index than the fiber core it surrounds. This refractive index

difference causes a total internal reflection, which guides the propagating light through the fiber

core with an attenuation less than 20 dB/km necessary threshold to make fiber optics a viable

transmission technology.

The fiber is coated with a thin primary coating to protect the inner glass fiber from

environmental hazards. Light Peak is based on Laser-optimized Multi-mode fiber (LOMF). By

laser optimized it just means that the fiber was designed to be used with lasers, and in the case of

MMF, typically VCSELs. The internal diameter of each Light Peak fiber is 62.5 microns (around

half the size of a human hair, but thicker than the fiber used in telecoms). The beam expander

molded into the lens expands that to 700 microns, so that dusts usually around 100 microns may

interrupt the beam partially but the connection will still work. The beam expander also

compensates for distortion or movement in the connector after been used for a while. Light Peak

fiber has a 3-micron coating to prevent cracking, it can be bent to a radius of 3mm and it won't

break. It is mixed with copper wires for power and fiber optic cables for data.

Fig 6.2 Light peak optical cable



6.2 Optical Module

The optical module does the function of converting optical signals into electrical signals

and vice versa. This module contains an array of VCSEL (vertical cavity surface emitting laser).

Fig 6.3 Schematic diagram of Optical module

This consists of:

1. VCSEL (light source)

2. Optical modulator

3. PIN diode(light detector)

6.2.1 VCSEL

VCSELs are semiconductor lasers, more specifically laser diodes with a monolithic laser

resonator, where the emitted light leaves the device in a direction perpendicular to the chip

surface. The laser resonator consists of two distributed Bragg reflector (DBR) mirrors parallel to

the wafer surface with an active region consisting of one or more quantum wells for the laser

light generation in between. The planar DBR-mirrors consist of layers with alternating high and

low refractive indices. Each layer has a thickness of a quarter of the laser wavelength in the

material, yielding intensity reflectivity above 99%.



VCSELs has low-cost potential because the devices are completed and tested at the wafer

level for material quality and processing purposes and a matrix VCSEL is capable of delivering

high power( up to few watts).

Light Peak Technology VCSELs have low threshold current value, low temperature

sensitivity, high transmission speed, high fiber coupling efficiency and circular and low

divergence output beam as compared to edge emitters.

VCSELs for wavelengths from 650 nm to 1300 nm are typically based on gallium arsenide

(GaAs) wafers with DBRs formed from GaAs and aluminium gallium arsenide (AlxGa(1-x)As).

The current is confined in an oxide VCSEL by oxidizing the material around the aperture

of the VCSEL. As a result in the oxide VCSEL, the current path is confined by the ion implant

and the oxide aperture. The wavelength of VCSELs may be tuned, within the gain band of the

active region, by adjusting the thickness of the reflector layers.

6.2.2 Optical modulator

In optical networks, binary digital modulation is typically used, namely on (light on) and

off (no light) to transmit data. These semiconductor laser devices generate output light intensity

which is proportional to the current applied to them, therefore making them suitable for

modulation to transmit data.

Modulation schemes can be divided into two main categories: a direct and an external

modulation.

In a direct modulation scheme, modulation of the input current to the semiconductor laser

directly modulates its output optical signal since the output optical power is proportional to the

drive current.

In an external modulation scheme, the semiconductor laser is operating in a Continuous-

Wave (CW) mode at a fixed operating point. An electrical drive signal is applied to an optical

modulator, which is external to the laser. Consequently, the applied drive signal modulates the

laser output light on and off without affecting the laser operation.



Fig 6.4 Block diagram of a typical external modulator

Typical external modulator consists of an optical splitter a material called lithium

niiabate(LiNbO3)-whose refractive index varies with the applied electric field and an optical

combiner. The input light enters the external modulator via the input fiber. The light is first splits

into two fibers using an optical splitter. The top fiber path travels through a length of LiNbO3

crystal. The light in the bottom fiber experiences a fixed delay. After the light travels through the

lithium niobate crystal and the fixed length of fiber, an optical combiner merges the two fiber

paths. The light travels through identical path legs .By applying an electric field to the material,

its refractive index changes. If the time delay through the fixed fiber and the LiNbO3 crystal is

equal, the light will be in phase when it reaches the output optical combiner. Due to the nature of

light, since the light in both legs are in phase, they will constructively add to form the maximum

possible output .The refractive index and the speed of light change as the applied voltage

changes. When the speed changes enough to delay the light by half of one wavelength, the light

will add destructively, yielding a minimum possible output



6.3 Controller Chip

The heart of Light Peak is an Intel-designed controller chip that handles the protocols,

along with an optical module that converts electrical signals to photons and vice versa.

Basic implementation unit of Light Peak Controller contains, firstly a Cross bar switching

unit which switches the various protocols from LPK to their respective protocol adapter.

Secondly LPK Ports and Protocol Adapter ports which connect down to PC using any standard

and diverging it their respective protocol through protocol adapter.

The Host controller is typically multi protocol and has multiple ports with a software

interface unit and is optimized for host side implementation whereas the peripheral controller

could be single port and single protocol-based and is optimized for particular usage.

This is because of this controller chip that different protocols get identified and transmitted

correctly. API (Application programming interface) helps to determine the different protocols. It

places the FIS (Flag Identification Symbol) packets in the memory, the controller access these

packets from the memory and send these packets to the destination over the optical link.

The multi-protocol capability the controller implements is an innovative new technology

that will enable new usage models like flexible system designs and thinner form factors, media

creation and connectivity, faster media transfer and cable simplification.

Fig 6.5 Light peak controller schematic


7. LIGHT PEAK TECHNOLOGY OVERVIEW



7. LIGHT PEAK TECHNOLOGY OVERVIEW

Light Peak Technology is an optical cable technology that consists of an optical module

and controller chip which allows multiple protocols to run over the single cable. From the

technical point of view, Intel’s Light Peak Technology can be overviewed as:

1. Light peak protocol

2. Light Peak controller

3. Light peak platforms

7.1 Light peak protocol architecture

Simplified views of protocol Light Peak Networks use a similar idea of packet switching.

Light peak technology uses packet switch multiplexing for packetize data to transfer, multiplex it

onto the wire and to allow packets from different connections share the same link.

Each packet is composed by the payload (the data we want to transmit) and a header. The

header contains information useful for transmission, such as:

1. Source (sender’s) address

2. Destination (recipient’s) address

3. Packet size

4. Sequence number

5. Error checking information



Fig 7.1 Simplified view of protocol

.

All the IO devices may have their native protocols but when using Light Peak they all run

over Light Peak protocol. That is they uses their individual protocol for data transfer but their

speed is defined by light peak.

Also it uses Virtual Wire Semantics thus performs high level of isolation between

high level protocols (QoS).

It provides cheap switching and establishes all routing at the setup only.


8. ADVANTAGE



8. ADVANTAGES

The light peak optical modules are physically much smaller than those of telecom grade.

The optical modules are designed to be much lower cost and higher performance. Light Peak can

send and receive data at 10 billion bits per second. The thin optical fiber will enable Light

Peak to transfer data over very thin, flexible cables. Unlike electrical cables, Light Peak do

not faces the problem of EMI, thus can be used up to 100m.Light Peak also has the ability to

run multiple protocols simultaneously over a single cable, enabling the technology to connect

devices such as docking stations, displays, disk drives, and more. The data transfer is

bidirectional in nature thus enabling devices to transfer simultaneously.

Quality of service implementation . No Operating System (OS) changes required. It also

supports another feature known as ³Hot-swapping´ which means the PC needs not be shut down

and restarted to attach or remove a peripheral.

Economies of scale from a single optical solution. Enables I/O performance for the next

generation Allows for balanced platform, with external I/O keeping up with most platform

inter connects.

Up to 100 meters on an optical-only cable. Each fiber is only 125 microns wide,

the width of a human hair. Supports multiple existing I/O protocols over a single cable and

smooth transition for today’s existing electrical I/O protocols. Can connect to more devices

with the same cable, or to combo devices such as docking stations.


9. CONCLUSION



9. CONCLUSION

Light Peak is a high-speed, multi-protocol interconnect for innovative and emerging client

usage models, that complements other existing interconnects

Light Peak is the name for a new high-speed optical cable technology designed to connect

electronic devices to each other. Light Peak delivers high bandwidth starting at 10Gb/s with the

potential ability to scale to 100Gb/s over the next decade. At 10Gb/s, we can transfer a full-

length Blu-Ray movie in less than 30 seconds. Light peak allows for smaller connectors and

longer, thinner, and more flexible cables than currently possible. Light Peak also has the ability

to run multiple protocols simultaneously over a single cable, enabling the technology to connect

devices such as peripherals, displays, disk drives, docking stations, and more.

Intel is working with the optical component manufacturers to make Light Peak components

ready to ship in this year, and will work with the industry to determine the best way to make this

new technology a standard to accelerate its adoption on a plethora of devices including PCs,

handheld devices, workstations, consumer electronic devices and more. Light Peak is

complementary to existing I/O technologies, as it enables them to run together on a single cable

at higher speeds.

At the present time, Intel has conducted three successful public demonstrations of the Light

Peak technology and confirmed that the first Light Peak-enabled PCs should begin shipping

soon.

The goal of this new developing technology is to build a high-bandwidth, fault-resilient,

low-cost network that can deliver performance isolation across applications. The basic approach

to achieve this target is to integrate low-radix switches into server platform and interconnect

severs directly using multipath topologies. Thus if the question WHY LIGHT PEAK?? arises,

then the answer would be because it is cheaper as it incorporates cheaper switching components,



provide better bandwidth allocation and performance isolation, uses flexible topologies, integrate

multiple protocol devices on to one cable.

Intel CEO Paul Otellini called Light Peak the I/O performance and connection for the next

generation,´ and confirmed that both Nokia and Sony have publicly announced their support.

Victor Krutul, director of Intel’s optical development team and founder of the Light Peak

program, is even more effusive, calling Light Peak ³the biggest thing to happen to the optical

industry ever, or at least since the creation of the laser.´


10. REFERENCES



10. REFERENCES

[1] Sreenivas Addagatla, Mark Shaw, Suyash Sinha and Prashant Chandra, Ameya S.Varde,

Michael Grinkrug , “Direct Network Prototype Leveraging Light Peak Technology” , 18th

IEEE Symposium on High Performance Interconnects,2010

[2] Jason Ziller and Victor Krutul , “A New Optical Technology-Light Peak” Intel

Technology Journal, Volume 8

[3] Wooten, E. L., “A Review of Lithium Niobate Modulators for Fiber-Optic

Communications Systems”

[4] http:// en.wikipedia.org/wiki/Light_Peak

[5] http://en.wikipedia.org/wiki/Light_Peak

[6] http://news.cnet.com/8301-13924_3- 20025559-64.html

[7] http://www.lightpeakinfo.com

[8] http://www.technewsworld.com/story/68231.html

[9] http://optics.or g/indepth/1/3/6

[10] http://arstechnica.com/apple/news/2009/09/apple- inspiration-behind- light-peak-optical-

[11] http://www.lightwaveonline.com/about-us/lightwave-current-issue/Intel-plots-Light-

[12] http://Peak- interconnect-revolution.html

Documents

Final Report