National Engineer Week Fiber Optics

Imagine This? glass fiber the size of a human hair could carry all the telephone conversations made nationwide during the year's peak calling period on Mother's Day. 4 oz optical fiber could carry as much information as 33 tons copper wire. 10 percent of the original light entering a 30 mile fiber optic line is still visible at the end

WHAT IS FIBER OPTICS? made of glass (and sometimes plastic) inner core of doped silica (glass) material.   surrounded by a cladding of pure silica (glass) which keeps the light signal within the core.  Together the layers form the light tunnel.  A coating is applied over the cladding providing protection and allowing fiber to be handled without damage.

HOW DOES FIBER OPTICS WORK? A transmitter (light source), such as a laser or light emitting diode (LED) at one end of the fiber initiates on/off light pulses.   A receiver (light detector) at the other end converts the light pulses back into electrical signals, representing the "bits" of information.  At least two fibers are needed to transmit and receive data.  Transmission occurs only in the core of the fiber.

ADVANTAGES OF FIBER OPTICS Immune to EMI/RFI Noise No Crosstalk Between Fibers More Lightweight than Copper Wire High Operating Bandwidth Low Attenuation (loss) Increased Transmission Security Complete Electrical Isolation Immune to Lightning/Surge Currents Wide Range of Operating Temperatures No Sparks No Electrical Ground Loops Will not corrode Unaffected by most chemicals

A SHORT HISTORY OF FIBER OPTICS Circa 2500 B.C.: Earliest known glass Roman Times: Glass is drawn into fibers French engineer Claude Chappe invented the "optical telegraph" in the 1790s In the 1840s, Swiss physicist Daniel Collodon and French physicist Jacques Babinet showed that light could be guided along jets of water for fountain displays Alexander Graham Bell patented an optical telephone system, which he called the Photophone, in 1880 An English inventor, Sir Charles Vernon Boys, invented the first glass fibers in 1887.. American and English inventors developed clad optical fibers in the 1950s laser developed in 1960. Scientists at Corning Incorporated broke the 20 decibel barrier in 1970. Robert Maurer, Donald Keck, and Peter Schultz, developed a "low-loss" optical fiber with an attenuation of 17. Fujitsu, NTT Labs, and Bell Labs all report sending one trillion bits per second through single optical fibers in separate experiments using different techniques. February 1996:

Optical Transmitters The basic optical transmitter converts electrical input signals into modulated light for transmission over an optical fiber

How Long Would it Take? Modem Speed Picture (20Mb) Movie 28.8Kb 97 (Minutes) Movie (4.7Gb) 28.8Kb 97 16.2 days 56.6Kb 49 8.1 days ISDN 128Kb 22 3.6 days DSL 512Kb 5 22 Hours Cable 1.5Mb 2 7.2 Hours

Fiber Optics Demonstrations

Bar Codes With a black magic marker, draw several parallel lines (resembling a typical UPC bar code) on a white piece of paper. Slowly scan the laser beam over the bar code and allow the students to observe the change in beam intensity as the laser scans from the dark to the light areas. (You may have to pass the laser and the paper around to the students.) For fun, have the students make up a variety of different patterns of light and dark areas and assign these "bar codes" to different objects (or words). Split the group up into groups. Have one group of students send the codes via fiber optic and the other group receive and decipher the codes. (This works well with the long single strand fibers.) Have a student scan the laser beam over the bar codes at a slow but steady pace. In addition, another student should move the end of the fiber optic along with the beam spot just above the surface of the paper such that the light scattered off the paper is caught by the tip of the fiber optic. The students should avoid having the fiber optic directly in the laser beam path since it is the scattered light that contains the bar code information. (The students may need to practice this a little.) The students at the other end of the fiber optic should decipher the light and dark patterns and assign the pattern to the correct objects. The students may be interested to know that CD players work on a similar principle. A laser beam is scattered off the surface of a CD and translated by a computer chip into various sounds.

Transmission Order per Team (4- 6 Students per Team) Team A LION,BUILDING,BOOKS,WASHINGTON Team B WASHINGTON,LION,BOOKS BUILDING Team C BOOKS,WASHINGTON, LION,BUILDING Team D BUILDING, LION,WASHINGTON,BOOKS

Materials Needed per Team Bar Code Experiment 1 Fiber optic cable > 6ft 2 pen flash lights 4 pictures (bar coded) Black Marker Blank white paper sheets 2 Sheets black construction paper tape

Think about: Bar Code Experiment How are you going to indicate the start of a new picture? How are you going to know if the team did not get picture correctly? How do you know to resend picture? How fast are you going to send the black & white bars of the picture