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An Optical Signal Processing View

              Terry Turpin
    Chief Scientist Essex Corporation
• The ―The Universe‖ is analog
• Human technology is still mostly analog
   – (did you ever see a digital bicycle)
• Digital has dominated the information processing and
  communications world for more than three decades
• Analog processing has been ignored by educational
• There are at least two generations of scientists and engineers
  that have never learned analog processing or communications
• Analog optical processing in the past as been a small but
  persistent exception
• Optical communications and analog optical processing are
  merging the same way that digital processing and digital
  communications did in the past
Processing Overload
World of Analog Signals

                   Spectrum      A
                   Fiber Optic   to Digital Stream
                   Microwave     D
                   Land Lines

                   Radio 3,488 Tbs               17,905,340 Tbs!!
                   Television 68,955 Tbs           (2002 Data!)
                   Telephone 17,300,000 Tbs
                   Internet 532,897 Tbs
The Information Superiority Problem
    So much information…
             so little time to process it
    Processing power is the key to
    superiority in a world market

                           Summary of electronic information flows of
                             new information in 2002 in terabytes
                            … 17.7 exabytes each year, and growing
“Era of Tera”*
          … a Digital Perspective

                         *Pat Gelsinger, CTO Intel
                          (Keynote address at Intel Developer Forum Feb 2004)
Digital Dilemma over Power
    “Power density is increasing at a rate that implies that
  tens of thousands of watts per centimeter (w/cm2) will be
   needed to scale the performance of Pentium processor
   architecture over the next several years. But that would
      produce more heat than the surface of the Sun…”*

                                       *Pat Gelsinger, CTO Intel
                                        (Keynote address at Intel Developer Forum Feb 2004)
… Begins the Age of Optical


                                     Optical Processors

Analog Optical Processors excel at
 - Images
 - Signals
 - Correlations                       *Pat Gelsinger, CTO Intel
                                       (Keynote address at Intel Developer Forum Feb 2004)

                                        References to Optical Processors added by Essex Corp.
Analog Optical Processing Overview

                   Optical Processing
                  Today       Future     Measured By

      Faster      Yes          Yes          TIPS

      Cheaper   Sometimes      Yes         Bytes/$

      Cooler     Always       Always      Watts/cm2

      Better    Sometimes    Sometimes
An Unclassified Success in
Size, Weight and Power

• Acousto-Optic Spectrometer AOS launched late
  1998 on SWAS for a 2 year mission
• 4 channel 1400 point Fourier transform in real
  time on a 1.4 GHz analog signal
• Compute power is 500 Gigaflops (Sustained) for
  12 Watts electrical power
• Analog input eliminated the need for high speed
  A/D converters
• Mission to study the chemical composition of
  interstellar clouds
• SWAS would be impossible without the AOS
  optical computer
Optical Processor/Computer?

        … a machine
        that performs
   mathematical functions
    with light rather than

 Functions most frequently used
   •Fourier Transform
   •Correlation (pattern detection)
   •Data distribution and replication
Why go to Analog Optical Processors?

   • Speed
   • Reduced size and power consumption
   • OEO Overhead & Cost are Excessive
        (optical - electrical - optical)

   • Natural Fit: Optical Processing for
                    - Optical Communications
                    - Images
                    - Signals
                    - Correlations

   • Typical improvement is a factor of 50000
Information on Light

• Information is carried by the complex-valued
  property of light (spatial frequency, amplitude
  and phase)
• When an information-carrying beam is passed
  through a special lens or coating, or interfered
  with another reference beam, light performs
  mathematical functions
Massive Parallelism
• Operates simultaneously on an entire wave
  front and more than one variable — e.g.,
  direction, amplitude and phase
• Digital systems are serial in nature
• Example: A lens simultaneously acts on the
  entire light beam
Computational Set

• Analog optics can perform mathematical
   –   add
   –   copy
   –   multiply
   –   Fourier transforms
   –   correlation
   –   convolution
• Operates on one- and two-dimensional arrays of
  numbers in parallel
• A single analog optical computer ―instruction‖
  might require thousands or millions of individual
  instructions for a conventional computer
Analog Optical Computing
   Combines the best of both worlds:
   precision of electronics with
   massive computational power of light.

   Optical                            Smaller,
                                      Lower Power,
                                      Lighter Computers
                   12 inches square

                                Vs.          Supercomputer power where
                                             it can’t go now.
                                             • Head of a missile
   Many Parallel                             • UAV
    Electronic                               • Mobile ICBM Defenders
                                             • Satellites
    Cutting Edge Elements
•Photonic Crystals
•Non-Linear Materials
                                         New Components
•Silicon Germanium
•III-V & II-VI Materials Systems   •Optical Fiber
                                   •Optical Amplifiers
                                   •Optical Correlators
                                   •Optical Signal Processors
     •Photon Echo
     •Optical Tap Delay
Example: Analog Optical Encryption

   • Digital Encryption
      –   ATM at 10Gbps soon
      –   No 40 Gbps on horizon
      –   Protocol specific
      –   Cost increases linearly with number of signals on a
   • Analog Encryption
      – 5000 Gbps on horizon (ESSEX Eclipse Module)
      – Potential for multi-band encryption (L,C, and S)
      – Protocol agnostic
      – Cost is market driven and grows slowly with
        capacity on a fiber
      – 100 Teraflops for less than 10 Watts of electrical
Hyperfine Analog Optical Encryptor
                            Point A                                                    Phase Key
      X Gbps Device                                                                    Computer

                                               Hyperfine Device
                                                                  Sub-channels         Reflective Phase

                                                                                       Modulator Array


                          X Gbps

    C Band Comms Device                                                                 Analog Encoding
    Phase Key
                              Point B
    Computer                                            X Gbps
                                                                                   X Gbps Device
                                     Hyperfine Device


Reflective Phase


Modulator Array

Analog Decoding
     ―key‖                                                                       C Band Comms Device
How Does it Work?

                    Scrambled Photons


                        Simulated Data
    Terabit Security – Cost


*Assumes that aggregate bandwidths           ** Estimated costs are based on a multiplexed
 above 10 Gbps will be encrypted using         optical signal with aggregate bandwidth as
 multiple 10 Gbps encryptor pairs – 1 pair     indicated, and single optical encryptor pair per
 per wavelength                                optical link
Additional Advantages
• Analog optical processing provides an alternate
  approach to thinking about problems
• This alternate approach often leads to solutions
  that are radically different and sometimes better
• For example, to implement continuous scale
  change and Fourier transforms on data that has
  not been sampled or digitized
• Enable solutions to problems that are thought to
  be too complex to solve economically
• In supercomputing applications the improvement
  is about a factor of 50000
• Analog is faster, cheaper and better
• Examples are
   – Separating signal channels in frequency
   – Optical Encryption
   – Optical Communications
   – Optical Signal Processing
• Analog is a key technology
• Analog optical technology will force analog electronics
  because of the A/D conversion limitation
• In optical communications, analog encryption and
  wavelength routing will provide growth at low cost per

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