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The study of lightwave communications is both interesting and relevant to high school students. Most students are interested in CD players, digital tapes, telephones, and other forms of modern communication. This unit is designed to provide students with both the historical and theoretical background information necessary to understand the fundamentals of lightwave communication (see student objectives, p. 2-1). The most important component of this unit is the set of student lab investigations. Starting with simple components, students will build a number of devices that will allow them to understand the mysteries of modern lightwave communications systems.

The study of lightwave communications is both interesting and relevant to high school students. Most students are interested in CD players, digital tapes, telephones, and other forms of modern communication. This unit is designed to provide students with both the historical and theoretical background information necessary to understand the fundamentals of lightwave communication (see student objectives, p. 2-1). The most important component of this unit is the set of student lab investigations. Starting with simple components, students will build a number of devices that will allow them to understand the mysteries of modern lightwave communications systems.

Much of this booklet is based on the work done at the Rutgers National Leadership Institutes for Physics Teachers. The summer institutes allowed high school teachers to learn directly from research physicists from AT&T, Bell Labs, BELLCORE, etc. As a result of these collaborations, various teaching “modules” were developed, including one on “LIGHTWAVE COMMUNICATIONS.” The summer workshops were co-directed by Dr. George Pallrand (Rutgers) and Dr. Sidney Millman, retired director of AT&T Labs. The success of the program was largely due to their personal interest, energy, and unbounded enthusiasm.

This booklet is not intended as a textbook, but rather as a resource and workshop guide. A brief history and a theoretical framework for understanding lightwave communications, student activities, and demonstrations are included. Because much of the technology is relatively new and not included in most textbooks, Sections 3 and 5 should be copied and distributed to students.

The philosophy of this workshop is that students should have a maximum of hands-on learning, and that the equipment should be as simple (and inexpensive) as possible while still working reliably. Additionally, connections need to be made between the simple materials and the complex modern technology of lightwave communications. The physics should be UNCOVERED rather than covered! Teachers and students will find that this unit ties together the topics of sound, light, electric circuits, electromagnetic interactions, and digital communications.

This manual is designed to show you how to run a full day workshop for teachers. When used with your classes, you will find enough material for 6 or 7 class periods. Even though you will need a lot of materials for this workshop, most of the materials can probably be found in your storage area. All are inexpensive and all of the materials can be re-used.

With proper planning, you will have a great workshop!

  • — 1.

    Ask a fellow teacher(s) to help you organize and assist at the workshop. Try to have at least one teacher for each 15 participants.

  • — 2.

    Reserve a room large enough for your anticipated audience.

  • — 3.

    Require a deposit from participants at least three weeks before the scheduled event so that you can order enough materials. Give them a deadline and expect almost everyone to wait until the deadline. Remember that your costs will include shipping and handling. Also include the cost of lunch in the workshop.

  • — 4.

    Order the materials. When ordering by phone, confirm that all needed items are IN STOCK. Order 10% more than needed to cover possible breakage or faulty components. Ask for a guaranteed delivery date.

  • — 5.

    Cut and drill the plastic sheet needed for the bias circuits. Cut and drill a few extras and build a few circuits to use as models for the participants.

  • — 6.

    Solder the telephone microphones to the wires. This is a time-consuming process due to the large heat sink of the microphone.

  • — 7.

    Inventory the materials as they arrive. Use clear, sealable plastic bags to pack the components for each participant.

  • — 8.

    Mail a map to all participants. Include a building map, room number, and recommended parking areas. Include the day’s agenda and your home and work phone numbers.

  • — 9.

    Make arrangements for coffee, tea, and donuts and also a simple, but elegant lunch. It is much preferred to eat near the workshop site.

  • — 10.

    Review this checklist! Time is running out. Try to remain calm. If you have faithfully kept to these timelines you will be ready!

  • — 11.

    Make sure that all hand tools, wires, glue guns, etc. will be available for workshop.

  • — 12.

    Have your host personally ask the school’s principal to stop by and either say a few words of welcome or just to see what you are doing.

  • — 13.

    Call a local newspaper to tell them about your workshop. Briefly describe the purpose and the scope of the workshop. Invite them to send a reporter and photographer for the afternoon session. Most of the construction should be completed by then.

  • — 14.

    Call to confirm your luncheon arrangements.

  • — 15.

    Bring all of your materials to the workshop sight (if possible) and meet with your co-presenter, host, helpers, etc.

  • — 16.

    Verify that you will have a working oscilloscope, laser, overhead projector, etc.

  • — 17.

    Carefully unpack all of the materials. Make sure that all hand tools are available, including soldering irons (with solder and wet sponges), glue guns (with glue sticks), wire strippers, etc.

  • — 18.

    Put up welcome signs and arrows at the outer entrance doors.

  • — 19.

    Enjoy a restful night’s sleep.

  • — 20.

    Arrive one hour early to meet with your host, put out the coffee and donuts, etc.

  • — 21.

    Locate the nearest restrooms and have the custodian unlock them.

  • — 22.

    Put out a few of already completed reflection photophones and bias circuits as models for the participants.

  • — 23.

    Plug in the oscilloscopes, lasers, overhead projectors, where they will be used.

  • — 24.

    Arrange your demonstrations on a front table safely out of the traffic path.

  • — 25.

    Have participants check in as they arrive and wear a name tag!

8:30 Sign in, donuts and coffee 
8:45 Distribution of workshop manuals and material packets 
9:00 Welcome and overview of workshop goals 
9:15 Display of solar cell, amplifier/speaker, reflection photophone, and cheap speaker 
9:20 Build and test—solar cell, reflection photophone, and cheap speaker 
9:50 Break to ask questions, discuss problems, etc. 
10:00 Display of bias circuit and demonstrations using it 
10:10 Build and Test the Bias Circuit 
11:00 Break to ask questions, discuss problems, etc. 
11:15 Demonstrations of response of “grain of wheat” lamp vs. LED on an oscilloscope, AM modulation of microwaves 
11:30 LUNCH BREAK 
12:30 Demonstration of internal reflection, electrical interference by spark source, etc. 
12:45 Discussion of attenuation, sample problems 
1:00 Cutting and testing the optical fibers 
1:15 Analog and digital signal theory and worksheets. Shannon’s theory, Nyquist’s theory, the need for more bits and more bandwidth 
1:30 Analog-to-digital and digital-to-analog game 
2:00 Demonstration and discussion of channel changer signal with solar cell and oscilloscope 
2:10 Other methods of digital modulation (CD, bar codes, etc.) 
2:30 How to “fit the materials into existing curriculum” 
2:45 Clean up and open laboratory (for those who want to play more!) 
8:30 Sign in, donuts and coffee 
8:45 Distribution of workshop manuals and material packets 
9:00 Welcome and overview of workshop goals 
9:15 Display of solar cell, amplifier/speaker, reflection photophone, and cheap speaker 
9:20 Build and test—solar cell, reflection photophone, and cheap speaker 
9:50 Break to ask questions, discuss problems, etc. 
10:00 Display of bias circuit and demonstrations using it 
10:10 Build and Test the Bias Circuit 
11:00 Break to ask questions, discuss problems, etc. 
11:15 Demonstrations of response of “grain of wheat” lamp vs. LED on an oscilloscope, AM modulation of microwaves 
11:30 LUNCH BREAK 
12:30 Demonstration of internal reflection, electrical interference by spark source, etc. 
12:45 Discussion of attenuation, sample problems 
1:00 Cutting and testing the optical fibers 
1:15 Analog and digital signal theory and worksheets. Shannon’s theory, Nyquist’s theory, the need for more bits and more bandwidth 
1:30 Analog-to-digital and digital-to-analog game 
2:00 Demonstration and discussion of channel changer signal with solar cell and oscilloscope 
2:10 Other methods of digital modulation (CD, bar codes, etc.) 
2:30 How to “fit the materials into existing curriculum” 
2:45 Clean up and open laboratory (for those who want to play more!) 

NOTE - this list will only include USEFUL REFERENCES!!

Magazine Articles

Nosov
,
Antoly
.
The Talking Wave of the Future
,
QUANTUM
,
Nov./Dec.
1992
, pp.
12
17
Nosov
,
Yury R.
,
Lightning in a Crystal
,
QUANTUM
,
Nov./Dec.
1990
, p
12
ff.

Books

Fiber Optics: Communications, Experiments, and Projects
,
Waldo T.
Boyd
, (
Howard W. Sams & Co
,
Indianapolis
,
1982
) Describes optical fibers and communication systems, and includes many projects to communication over fiber optics using both amplitude and pulse-code modulation.
Light Emitting Diodes
,
Forest M.
Mims
, III
, (
Howard W. Sams & Co.
,
Indianapolis
,
1973
) Detailed description of theory, practice, and applications of LEDs and semiconductor light detectors.
LED Circuits and Projects
,
Forest M.
Mims
, III
, (
Howard W. Sams & Co.
,
Indianapolis
,
1973
) Companion to the preceding book. Limited description of LEDs with emphasis on applications.
The Way Things Work
,
David
Macauley
. Numerous references to speakers, lasers, telephones, digital coding, CD’s, TDM (time domain multiplexing), etc.
Telecommunications
,
John
Allen
(
MacMillan Education, Ltd.
,
London
,
1991
) This exceptional resource explains theory and technology of the telephone, radio, satellite systems, and fiber optics.

Textbook References

Modern Physics
,
John E.
Williams
,
Frederick E.
Trinklein
,
H. Clark
Metcalfe
, (
Holt, Rinehart, and Winston
,
New York
,
1984
)
Sound: Chapter 11. Especially pp. 252-256
Light: Chapter 12. Especially pp. 280-300. Total internal reflection, p 338,
Electric circuits: Chapter 17
Electronic devices: Chapter 22. Especially 565-576
Physics: Principles and Problems
,
Paul W.
Zitzewitz
,
Mark
Davids
, and
Robert F.
Neff
(
Glencoe, Westerville OH
,
1995
)
Sound: Chapter 15 Especially pp. 306-314
Light: Chapter 16. Total internal reflection, pp. 356-358
Electric circuits: Chapters 22 and 23. Voltage divider, p 472; diode current, p 466.
Electronic devices: Chapter 29
Conceptual Physics
,
Paul
Hewitt
, 5th Ed. (
Little, Brown Publishers
)

Numerous references to sound, laser discs, am, fm, light

The following list is organized by the device for which the materials are required. The estimated cost for a complete set of materials for one station is $45, based on quantity discounts listed in the most recent catalogs. The quantities shown are those required for a laboratory of 10 stations or a workshop serving 10 teachers. Consult the appendices of Section 3 for alternative methods of constructing the photophone.

Quantity Catalog Number Description Source Unit Cost Total Cost 
1) Commercial Speaker 
10 each 253-4130 3”, 8-Ω speaker 1.83 18.30 
2) Homemade Speaker 
10 each  5” foam or aluminum plate local   
1 roll L3-616 32 gauge magnet wire EDL 2.95 2.95 
10 each CB-60 block magnet TMS1 0.90 9.00 
  OR    
10 each 78293C block magnet CENCO 4.95 49.50 
3) Lightwave Receiver 
10 each 39810 solar cell 4.35 43.50 
10 each 277-1008 miniamp (amplifier/ speaker) RS 10.76 107.60 
10 each  9-V battery (for miniamp) local 0.60 6.00 
10 each  9-V battery (for miniamp) local 0.60 6.00 
1 roll2 515-2100-12-01 24 gauge wire (red) 3.94 3.94 
1 roll2 515-2100-12-03 24 gauge wire (black) 3.94 3.94 
20 each 42-2421 miniplug with clips (need 2) RS 2.39 47.80 
1 Note: TMS is The Magnet Store, call 1-800-222-7846 
2 Note: This is enough wire for 20 setups 
4) Reflection Photophone 
10 each  balloons local   
10 each  2” length of 3”-diam PVC pipe local   
10 each  l” square of mirror film local   
1 each3  2’ x 4’ x 1/8” clear plastic (cut into 4” x 8” pieces) local or pp  10.00 
3 Note: This is enough Plexiglas for 144 setups. See PP on page 1-12 for source of pre-cut and drilled plates. 
Quantity Catalog Number Description Source Unit Cost Total Cost 
5) Photophone 
10 each 31VC205 500-W linear pot 0.85 8.50 
40 each TE1447-57 alligator clip (need 4) EDL 0.52 20.80 
3 pks. 274-415 control knob RS 1.69 5.17 
10 each 12BC144 battery snap 0.30 3.00 
10 each 534-079 battery holder 0.20 2.00 
10 each  9-V battery (for photophone) local 0.60 6.00 
10 each 271-1313 220-W resistor RS 0.10 1.00 
40 each 517-SJ-5514BK rubber bumper (need 4) 0.38 15.20 
20 each 11-554 2-56 screw EDL 0.037 0.74 
20 each 11-100 2-56 nut EDL 0.019 0.38 
10 each 35LS026 2V, 60 mA grain of wheat lamp 0.37 3.70 
10 each 276-087 2000 med LED RS 1.79 17.90 
1 each 515-1356-12-90 24 gauge speaker wire 6.30 6.30 
6) Transmitter 
10 each ITT-7555-101 telephone microphone 2.01 20.10 
10 each 12-202 AM radio RS 6.26 62.60 
20 each  1.5-V AA battery (need 2) local 1.50 30.00 
7) Optical Fiber 
10 each4 C2539 4’ length of optical fiber 8.40 84.00 
4 Note: For workshops with over 25 teachers, you should consider buying the 200 foot roll and selling the extra at cost. 
8) Miscellaneous 
Small and large sellable plastic bags for pre-packing components, candles, matches, clay, 2-liter bottle, and non-dairy creamer (to show light path in water). 
Quantity Catalog Number Description Source Unit Cost Total Cost 
1) Commercial Speaker 
10 each 253-4130 3”, 8-Ω speaker 1.83 18.30 
2) Homemade Speaker 
10 each  5” foam or aluminum plate local   
1 roll L3-616 32 gauge magnet wire EDL 2.95 2.95 
10 each CB-60 block magnet TMS1 0.90 9.00 
  OR    
10 each 78293C block magnet CENCO 4.95 49.50 
3) Lightwave Receiver 
10 each 39810 solar cell 4.35 43.50 
10 each 277-1008 miniamp (amplifier/ speaker) RS 10.76 107.60 
10 each  9-V battery (for miniamp) local 0.60 6.00 
10 each  9-V battery (for miniamp) local 0.60 6.00 
1 roll2 515-2100-12-01 24 gauge wire (red) 3.94 3.94 
1 roll2 515-2100-12-03 24 gauge wire (black) 3.94 3.94 
20 each 42-2421 miniplug with clips (need 2) RS 2.39 47.80 
1 Note: TMS is The Magnet Store, call 1-800-222-7846 
2 Note: This is enough wire for 20 setups 
4) Reflection Photophone 
10 each  balloons local   
10 each  2” length of 3”-diam PVC pipe local   
10 each  l” square of mirror film local   
1 each3  2’ x 4’ x 1/8” clear plastic (cut into 4” x 8” pieces) local or pp  10.00 
3 Note: This is enough Plexiglas for 144 setups. See PP on page 1-12 for source of pre-cut and drilled plates. 
Quantity Catalog Number Description Source Unit Cost Total Cost 
5) Photophone 
10 each 31VC205 500-W linear pot 0.85 8.50 
40 each TE1447-57 alligator clip (need 4) EDL 0.52 20.80 
3 pks. 274-415 control knob RS 1.69 5.17 
10 each 12BC144 battery snap 0.30 3.00 
10 each 534-079 battery holder 0.20 2.00 
10 each  9-V battery (for photophone) local 0.60 6.00 
10 each 271-1313 220-W resistor RS 0.10 1.00 
40 each 517-SJ-5514BK rubber bumper (need 4) 0.38 15.20 
20 each 11-554 2-56 screw EDL 0.037 0.74 
20 each 11-100 2-56 nut EDL 0.019 0.38 
10 each 35LS026 2V, 60 mA grain of wheat lamp 0.37 3.70 
10 each 276-087 2000 med LED RS 1.79 17.90 
1 each 515-1356-12-90 24 gauge speaker wire 6.30 6.30 
6) Transmitter 
10 each ITT-7555-101 telephone microphone 2.01 20.10 
10 each 12-202 AM radio RS 6.26 62.60 
20 each  1.5-V AA battery (need 2) local 1.50 30.00 
7) Optical Fiber 
10 each4 C2539 4’ length of optical fiber 8.40 84.00 
4 Note: For workshops with over 25 teachers, you should consider buying the 200 foot roll and selling the extra at cost. 
8) Miscellaneous 
Small and large sellable plastic bags for pre-packing components, candles, matches, clay, 2-liter bottle, and non-dairy creamer (to show light path in water). 

To build all of the equipment and show all of the demonstrations, you should have the following equipment and tools:

laser, overhead projector, slide projector, oscilloscope, multimeter, TV remote control unit, audio oscillator (10 Hz - 10 kHz), radio-frequency (RF) generator, and microwave generator with receiver.

For each 10 participants, you should also have

1 roll of duct tape, 2 soldering irons with solder, sandpaper, 2 hot-melt glue guns with glue sticks, 2 small standard screwdrivers, 2 Phillips screwdrivers, 2 pliers, 2 wire strippers, 1 flashlight, sandpaper, clay, matches, dry cream, 2-liter soda bottle.

RS = Radio Shack PP = Precision Plastics E = Edmund Scientific 
EDL = Edlie M = Mouser Electronics G = Graybar Electric 
RS = Radio Shack PP = Precision Plastics E = Edmund Scientific 
EDL = Edlie M = Mouser Electronics G = Graybar Electric 

Precision Plastics

400 Comstock Ave., Suite 4

Winter Park, FL 32789

(407) 644-2991

 

Edmund Scientific

101 E. Glouster Pike

Barrington, NJ 08007-1380

(609) 573-6270

 

Mouser Electronics

2401 Highway 287 North

Mansfield, TX 76063-4827

(800) 346-6873

 

Edlie Electronics

2700 Hempstead Pike

Levittown LI, NY 11756-1443

(800) 645-4722

 

Graybar Electric

2325 Featherstone

Auburn Hills, MI 48326

(313) 373-3100

 

The Magnet Store

6073 N.W. 167th Street

Miami, FL 33015

(800) 222-7846

 

Precision Plastics

400 Comstock Ave., Suite 4

Winter Park, FL 32789

(407) 644-2991

 

Edmund Scientific

101 E. Glouster Pike

Barrington, NJ 08007-1380

(609) 573-6270

 

Mouser Electronics

2401 Highway 287 North

Mansfield, TX 76063-4827

(800) 346-6873

 

Edlie Electronics

2700 Hempstead Pike

Levittown LI, NY 11756-1443

(800) 645-4722

 

Graybar Electric

2325 Featherstone

Auburn Hills, MI 48326

(313) 373-3100

 

The Magnet Store

6073 N.W. 167th Street

Miami, FL 33015

(800) 222-7846

 
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