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         Optical                 Jonathon
Technologies and                 Hodgkins,
    there uses in                Romanelli
         Team: Sherwood Forest
       The concept of optical computing is a relatively new one, and is still being investigated

and explored. Being on the forefront of the technological world, optical computing is a complex

and involved field of study. This paper will cover what optical technologies are as well as a look

into how they may be used by the United States Department of Homeland Security.

Optical computing

       Optical computing, or the use of an optical device/phenomenon to perform information

processing and computations, is relatively new technology. Optical computing is the use of

photons to transmit information in the place of electrons, a much more efficient and powerful

method. Optical computing has many advantages over typical computing such as:

      “Photons move much quicker than electrons, they move at the speed of light, so they can

       transmit data much quicker.

      Photon processors can perform multiple operations simultaneously much more


      Photon processors are compact, lightweight, and easy to manufacture.

      Optical bandwidth exceeds that of electronic computing.

      Optical computers would be able to retain more functionality while getting smaller, so a

       smaller electronic computer of the same size as an optical computer would be less


      The functional equivalent to electronic transistors for optics would be transphasors,

       which can handle multiple incoming signals at the same time unlike its counterpart.
        Photons also have the ability to cross each other’s paths and pass through one another

         without disrupting the information contained within the message, whereas electrons

         would lose everything”. (Alan Leewllyn Bivera)

         Early research into optical signal processing resulted from attempts to process large

amounts of data from radar systems. However, results from such research were rudimentary in

nature, and it wasn’t until 1960 with the advent of the laser that optical computing stumbled


History of Light Based Technology

         Optical computing is the practice of using the power of light as opposed to simple

electricity to power a computer. Regular computers that are electron based put out heat as they

work harder and process more information, however optical computers use photons which, in

theory, can process the same amount of information, yet without producing anywhere near as

much heat.

         Optical technologies have a long history, and the basics of which began around 1870.

John Tyndall, an English, natural philosopher, bent light around a stream of water, thus proving

that light can be redirected. Below is an image of John Tyndall's experiment.
        “While several theories and proposals were made in the following decades, the next

major event in optical technology was in 1960 when Theodore Maiman operated the first laser at

Hughes Research Laboratory. While the technology was progressing through the decades, one of

the most impressive leaps was the U.S. Air Force’s replacement of 302 copper wires which

weighed 40 kg with fiber optic wires that weighed 1.7 kg. In the 1970’s and 1980’s telephone

companies began using optical fibers to great effect.” (Optical Communication - Optical Fibres,


        In 2002, optical encryption (optical cryptography) was proclaimed to be on of ten

technologies that would change the world by Newsweek and the MIT Technology Review. The

ability to detect tampering with a fiber optic cable transmitting data is very important due to the

ease at which an attacker can intercept the information. Disturbances in the photons’ movements

are what are detected and thus if a message has been sent containing an encryption key the

sender will know if he/she needs to change the encryption key. If an intrusion isn’t detected

he/she can be confident in the knowledge that the encryption key was not intercepted and that it

can continue to encrypt future documents.

Optical Communication

        For you to understand Optical communication you must first understand how it began

and how has it changed over so many years. The use of light to send messages is not new. Fires

were used for signaling in biblical times, smoke signals have been used for thousands of years

and flashing lights have been used to communicate between warships at sea since the days of

Lord Nelson.
       “The idea of using glass fibre to carry an optical communications signal originated with,

Alexander Graham Bell. However this idea had to wait some 80 years for better glasses and low-

cost electronics for it to become useful in practical situations.

       Development of fibres and devices for optical communications began in the early 1960s

and continues strongly today. But the real change came in the 1980s. During this decade optical

communication in public communication networks developed from the status of a curiosity into

being the dominant technology.” (Dutton, H)

       In any kind of computer communication, information must be transformed into binary so

that a computer can understand it. Optical communications and encryption operates in this

manner as well, however by way of photons instead of electrons. Information encrypted by using

an optical method takes those 1’s and 0’s and makes them O’s and _’s (or absences) representing

the presence of a photon or the absence of one. Since photons are subject to the effects of

quantum forces, local electromagnetic fields found in the fiber-optic cable can interfere with the

transmission of clear data. This and other quantum disruptions can be used to help prevent

possible eavesdroppers from understanding or decrypting the data.

       Optical communications, the use of photons to transmit information is already extremely

secure due to the characteristics of optical fibers. The size of some optical fibers is no more than

that of a human hair, yet extremely durable and strong. These fibers are also incredibly light

especially in comparison to their counterparts, copper wires. Made from superheated silicon

sand, the fiber is actually a combination of a glass core and a plastic outer shell. Although the

fiber itself produces a small electromagnetic field, it does shield the photons from outside

quantum interferences. “The cables have a loss of data during transmission rate of about .01
dB/km or decibels per kilometer, which is incredibly low. Finally, due to the nature of the

materials used to make the cables, they are extremely affordable.” (Stamatios Kartalopoulos)

                                       Optical transmission

The basic components of an optical communication system

      “A serial bit stream in electrical form is presented to a modulator, which encodes the data

       appropriately for fibre transmission.

      A light source (laser or Light Emitting Diode - LED) is driven by the modulator and the

       light focused into the fibre.

      The light travels down the fibre (during which time it may experience dispersion and loss

       of strength).

      At the receiver end the light is fed to a detector and converted to electrical form.

      The signal is then amplified and fed to another detector, which isolates the individual

       state changes and their timing. It then decodes the sequence of state changes and

       reconstructs the original bit stream.
        The timed bit stream so received may then be fed to a using device.” (Stamatios


         This transmission shows the light source (laser or Light Emitting Diode -LED) travels

down the fibre glass tube. During that state the light sensor (Detector) decodes the sequence and

reconstructs the original part of the bit stream.

Optical Encryption

         Encryption is the practice of converting regular data or plain text into a set of data called

cipher text which cannot be interpreted by anyone other than those who have access to the key

which encrypted the data originally. Optical encryption is the practice encrypting and decrypting

data via the use of light, hence the term “Optical.” This change from normal encryption is

extremely beneficial primarily in the sense of speed. Typical electronic encryption moves at a

speed of 10G bps (bits per second) whereas optical technologies are moving at 40G bps speeds in

an applied setting and 100G bps in the lab. (http://www.pcworld.com, optical encryption called capable of 100G bps)
       In optical encryption a beam of light is passed through a phase mask which contains

encrypted data, followed by a phase mask with the encryption key in it, and then finally through

a set of lenses. This is an image of how the process ends as the information has already been

encrypted and is now being decrypted.

Phase 1:

       The information that is to be transmitted must first be electronically scrambled and then

used to create an encrypting phase mask that can send the data safely. The decrypting phase

mask is simply the opposite of the encrypting mask. “The light can be monochromatic, one

wavelength, or multi chromatic, multiple wavelengths, depending on how secret the information

is and how complex the sender desires it to be.” (Jesper Gluckstad)

Phase 2:

          “In the image above, the light is first passing through the encrypted phase mask that

contains the algorithm that protected the data through its transit along optical cables. The

encryption key is found within its construction. This phase mask can either be one that has a set

pattern of areas on it that have a defined thickness or it could be a shifting phase mask with areas

that change in thickness depending on the wavelengths of light being used. In this particular

situation, the phase masks are shifting.” (Jesper Gluckstad)

Phase 3

          In the next step, the encrypted light beam passes through the decryption phase mask

which, like the previous encryption mask, can be either of a fixed thickness or a shifting

thickness. This mask decrypts the image finally but the receiver still cannot view it perfectly.

“This experiment was simply to view the process of encryption and decryption as opposed to

being concerned with serious safe transmission of data. If that were the case, the decryption
process would occur after the last lens.” (Jesper Gluckstad)

Phase 4

          Next the light passes through an aperture that determines the direction in which the beam

of light should continue moving. This simply ensures that the light does not stray in any

undesirable angle, thus missing the final steps of the process and failing to display the

information. It guides the light into the lenses.

Phase 5

       The light finally continues on into a lens which magnifies it and displays it in its final

unencrypted form.

       What has just been described is only a basic level of how optical encryptions actually

work. “Other methods have been researched involving multiple levels of phase shifts as well as

multiple levels of encryption and decryption masks. Just as in normal encryption methods,

optical encryption has multiple levels of complexity.” (Jesper Gluckstad)


       The process described above is only one version of to encrypt light beams. One of the

other methods used is a multiphase encryption method where multiple light frequencies are

encrypted and sent through similarly adapted phase masks so that the frequencies can be

decrypted. Phase masks are directly related to the light that is being passed through them so

without the corresponding mask, the light beam cannot be decrypted. This process is further

complicated by the option of using an alternative phase shift mask, a type of phase mask that

changes its thickness and thinness which affects the light beam’s output.
       “A passive optical encoder, a dime sized piece of technology, varies frequencies of light

pulses entering a network. By doing this, anyone who tapped into the network would be unable

to even see any of the pulses of light that represent 1’s and the absences of light which represent

0’s. This would be key if the security of the information was in jeopardy.” (Optical Encryption)

The Optical Fourier Transform

       “The simplest way to understand the principles of the Fourier transform is to understand

that a simple lens can perform a Fourier transform in real time. By placing an image, for

example a slide transparency, at the focal length of the lens, and illuminate that slide with a

coherent light, like a collimated laser beam. At the other focus of the lens place a frosted glass

screen. The lens will automatically perform a Fourier transform on the input image, and project

it onto the frosted glass screen. Each point on the input image radiates an expanding cone of

rays toward the lens, but since the image is at the focus of the lens, those rays will be refracted

into a parallel beam that illuminates the entire image at the ground-glass screen.” (Lehar, S.)

Simply stated every point of the input image is spread uniformly over the Fourier image, where

constructive and destructive interferences will automatically produce the proper Fourier

       Conversely, parallel rays from the entire input image are focused onto the single central

point of the Fourier image, where it defines the central DC (zero frequency) term by the average

brightness of the input image.

       The optical Fourier transform automatically operates in the reverse direction also, where

it performs an inverse Fourier transform, converting the Fourier representation back into a spatial

brightness image. “Mathematically the forward and inverse transform are identical except for a

minus sign that reverses the direction of the computation.” (Lehar, S.)


       Since the advent of computers there has been a vast dissemination of information, some

of which needs to be kept private, some of which does not. Plaintext is the name given to

information that is to be put into secret form. The information may be hidden in two basic ways.

The methods of steganography conceal the very existence of the secret information. When

steganography is applied to electrical communications it is called transmission security.

       The methods of cryptography, on the other hand, do not conceal the presence of secret

information but render it unintelligible to outsiders by various transformations of the plaintext.

“The cryptologist is the entity that performs cryptography. The stegator is the entity that

performs steganography. The cryptanalyst is the entity that tries to break the cryptographic code
or find the steganographic information. A cryptanalyst is more commonly known as a hacker.”

(Olszewski, M., & Katarzyna Chalasinka-Macukow)

        Steganography is the science of hiding data in otherwise plain text or images. It is a

method by which a message can be disguised by making it appear to be something else. “It

derives from two Greek words Stego- means roof, or cover and -graphy means to write.

In modern times, steganography techniques include invisible inks, microdots (used by modern

HP and Xerox color laser printers where tiny yellow dots containing printer serial number, date

and time stamp, are added to each page), and digital watermarks.”( Olszewski, M., & Katarzyna

Chalasinka-Macukow) Whereas Optical encryption uses light, hence the term “Optical.”

        This table will list the main differences between Optical encryption and Steganography


Category                Optical encryption                       Steganography

transportation transport via optical fiber (uses light) transport via cables (electric current)

speed                   40G bps                                  10G bps

cypher text     The data looks like white noise          looks the same as plain text

                                                         least significant bit (LSB) insertion

Applicable Uses for Homeland Security

        The need to keep information secure during transit is very important especially when that

information is vital to national security. The Department of Homeland Security deals with secret,

and top-secret classified documents on a daily basis and the transmission of such information
must be secure if it is to stay out of unfriendly hands. Transmitting information across the

Internet can be extremely dangerous with career cybercriminals, unfriendly nation states, and

simple mischievous hackers out to make a name for themselves all loving to intercept a top

secret package going from a Homeland server to a Department of Defense (DOD) server.

       Using a series of fibre optic cable networks, the Department of Homeland Security could

not only transmit its information safely around the country but also know when a part of the

network has been tampered with. The safe transmission of information is assured, and a series of

response teams could easily be assembled at key locations to thwart any attempts to sabotage the


       The optical portion of this technology infers that the information covers long distances in

a very short amount of time. Because of this aspect of the optical technology, more information

can be sent over a shorter period of time. The lightweight aspect of optical technologies makes

for a bright future in portable computers. The laptops we have now could easily be shrunk to the

size of a net book and still hold all of the processing power.

       The switch from electron based computing to photon based computing will create an

even wider technological gap between the U.S. and anyone else.

       As far as optical encryption is concerned, by using a particular phase mask, the sender

ensures that the information can only be decrypted by someone who has an intimate knowledge

of how the information was encrypted in the first place. This almost entirely rules out the

possibility of an outsider attacking the data as he/she would have to know the properties of the

encryption mask that originally encoded the information.

       The benefits that optical technologies pose for Homeland security are numerous and

could be very effectively implemented for the safety of our nation.

       In conclusion, optical technologies pose the next big leap in computing. They’ve already

begun to be implemented but mainstream adaptation will take time. The primary advantages to

optical technologies are their weight and speed. As processors get smaller and smaller, a portable

device of incredible power on a person at all times is a very plausible concept. Having the power

of a desktop at one’s fingertips constantly will make life much easier.

       The Department of Homeland Security (DOH) is the agency that the population of the

United States entrusts to protect it. The incredible computing advantages would speed up

communication and transmission of information to new heights. The DOH’s efficiency would be

multiplied not to mention all the other government agencies that collaborate with it.

       We should all hope that optical technologies become main stream as quickly as possible.
                                        Work Cited

1. Dutton, H. (, November 15). IBM Redbooks. Red Books. Retrieved December 5, 2010, from


2. Jesper Gluckstad. (, October 1). Programmable Phase Optics. Programable Phase Optics.

    Retrieved December 5, 2010, from http://www.ppo.dk/Research-OC.html

3. Lehar, S. (, November 17). An Intuitive Explanation of Fourier Theory. An Intuitive Explanation of

    Fourier Theory. Retrieved December 5, 2010, from


4. Stamatios Kartalopoulos. (, November 12). Is optical quantum cryptography the ‘Holy Grail’ of

    secure communication? | SPIE Newsroom: SPIE. SPIE. Retrieved December 5, 2010, from


5. Alan Leewllyn Bivera. (, October 24). Optical Computing. Retrieved December 5, 2010, from


6. Optical Encryption Called Capable of 100G Bps - PCWorld Business Center. (, October 25).

    PC world. Retrieved December 5, 2010, from



7. Olszewski, M., & Katarzyna Chalasinka-Macukow. (, November 22). . . NET user ℡. Opera.

    Retrieved December 5, 2010, from http://www.opera2015.org/home.asp