Photon2 InternshipPENN STATE UNIVERSITY

Materials Research Lab

June 2005

Paul Longwell

Dr. Venkatraman GopalanCooperating Faculty

Topic:Fiber Optic Communication

Focus – Signal Modulation

(Encoding Information to be Sent)

Fiber Optic CommunicationBegins With Laser Light

The light is produced by a tiny diode.

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Fiber Optic CommunicationInformation (Voice, Websites, Etc) is

Encoded into Pulses.

First, a laser beam is split into two identical beams.

How?

Fiber Optic CommunicationInformation is Encoded into Pulses

Each beam travels an identical path and then they are recombined, but….

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Fiber Optic CommunicationInformation is Encoded into Pulses

…one beam must pass through an ELECTRO-OPTIC crystal.

Fiber Optic CommunicationInformation is Encoded into Pulses

When an electronic signal is delivered to the crystal, the light wave shifts.

Many layers in a thin device!

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Fiber Optic CommunicationInformation is Encoded into Pulses

When the light waves recombine, the result is ON (pulse) or OFF (no pulse)

The ON and OFF signals carry the code of information!

Identical Waves

One Shifted Wave

ON

OFF

Fiber Optic CommunicationTo study the splitting and recombining of a

laser beam, I tried it!

Mach-Zehnder

Inteferometer

Fiber Optic CommunicationRecombining the Beams Perfectly is

Challenging!

Good

GoodBad

Bad

Fiber Optic Communication“Perfectly” Aligned!

Good

Good

Fringes Seen On the White

Paper

Fiber Optic CommunicationHow do the laser pulses carry the information

from one place to another?

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Fiber Optic Communication

Fiber optic cables contain several layers:

Fiber Optic Communication

Total Internal Reflection allows the light to remain in the fiber optic cable as it travels.

Fiber Optic Communication

After the light has traveled through the cable, the initial encoding process is essentially reversed

and the information is delivered.

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Other Internship Images

A diffraction grating used in laser experiments

Other Internship Images

Other Internship Images

Thank YouDr. Venkatraman Gopalan

Sava Denev

Lili Tian

Aravind Vasudevarao