Optical Interconnects

Presented by :Manar Ahmed Abdel Galil

Historical Overview

• The beginning Bell Labs 1980sRemember : Bell Labs Transistor , LASER , Information theory , UNIX , C programming , C ++

• Induced by Optical fibers Optical computing research efforts (as a byproduct)

What is an optical interconnect ?

• Fixed connections (independent of inputs) Interconnect • Reconfigurable connections (based on a control

signal) Switch

Why optical interconnects?

• Density : higher density with less cross talk and losses .• Bandwidth : higher BW compared to electrical

interconnects .For electrical :

(bits/sec without overlap)

“R” limits rise and fall time of signals limits data rateFor optical : governed by other physical effects transport data more accurately at high speeds

Why optical interconnects? (cont’d)

• Delay : photons are faster ! For electrical : fanout propagation delay For optical : velocity of light is constant ! (independent of fanout )

Why optical interconnects? (cont’d)

• Power : For electrical : To avoid reflections matched impedance spend more power For optical :To avoid reflections just use an antireflection coating !

Why optical interconnects? (cont’d)

• Attenuation and complexity of the design : For electrical : • Copper wiring high attenuation at high data rates require extra repeaters/amplifiers /signal conditioners Complicated system and more power consumption For optical :• Less attenuation and high accuracy for high data rates and

long distances

Why optical interconnects? (cont’d)

• 80 % of the microprocessor power is consumed by sending data over the wires (interconnects) !!!

• Solve bottlenecks in electronic computers (e.g. moving data memory to CPU )• Handle the flood of information from optical

fibers (stretching to future homes)• Keep up with the internet’s exploding need for

bandwidth (carry , route and process data at light speed)

What professors say

"The trend is to make light do as many things as possible . You may not replace electronics completely, but you want to make light do as much as you can.“John D. Joannopoulos (MIT)

What professors say (cont’d)“There’s not a breakthrough needed to do this , But we have a lot of research to do.” David Miller (Stanford)

“When fiber-to-the-home happens, you will want fiber-to-the-processor-based systems in your home to look at real-time holograms of the grandkids.” Anthony F. J. Levi (Univ. of Southern California)

Optical interconnects in industry

• Intel : Silicon photonics R&D department .- The World’s First Intel based Optical Server - First GHz Silicon Modulator - First

Continuous Silicon Laser . . . and the list continues

• Intel and Facebook : Collaborate on Future Data Center using silicon photonics

• IBM (Big Blue): Thomas J. Watson Research Center - Research for servers, data centers and supercomputers .- Developing promising technologies such as optical PCBs , ultra-small CMOS optical

transceivers with very low power consumption .

- CISCO: optical networking - Acquisition of “Lightwire” (a company for innovative optical interconnect technology)

to build Next-Generation Internet.

Types of optical interconnects

Optical waveguides Free-space refractive and diffractive components (mirrors , lenses , prisms .. )

Examples of optical interconnects

Photonic crystals as a medium

• Semiconductors Electron

s

• Photonic crystals Photons Excellent medium for controlling the flow of light

Challenges

• Unlike electricity, light is hard to steer through very small spaces we need new ways to direct light through tight confines

( nano photonics research )• Technology for mass production • Automation for sophisticated and

large scale circuit design

The Leap Of Faith

The motivation for the jump

• Remember optical fiber technology revolutionized the way people communicate, live and work.

• Remember the era of the “BIG DATA” , the “Internet of Things” and “cloud service data centers“ is coming .

• New smart devices and wide spread sensors will challenge the capacity of the current local area networks .• No more heating up of laptops

Attempts to cross the technology barrier (Automation trials)

• Stanford engineers invented an inverse design algorithm.

The engineers

specify what they want the optical

circuit to do

Using standard industrial

processes to transfer the pattern onto

a slice of silicon

The software provides the

details of how to fabricate a

silicon structure to perform the

task.

The Killer App concept

• PCs revolution • Internet revolution : the .com bubble • Optical interconnects killer app ??

Papers to read • “ Optical interconnects to electronic chips “(David Miller) , 2010• “ Rationale and Challenges for Optical Interconnects to Electronic

Chips “ (David Miller) , 2000• “ First demonstration of high density optical interconnects

integrated with lasers, optical modulators, and photodetectors on single silicon substrate “ , 2011

• “ Optical interconnects to silicon “ (David Miller) , 2000• Intel research papers • IBM research papers

Don’t forget to make the jump :)