Lesson 1 Lab Experiment (s)

A Pile of Sand Becomes a Strand of Glass

 
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These are the lab experiments for Lesson 1.  Please conduct these experiments under direct supervision of an adult including a parent or teacher. 

Experiment #1 - Compare my hair (to an optical fiber under microscope)  Great fun for classroom setting

Experiment #2 - Emulate process for manufacture of optical fibers - HOME VERSION

Experiment #3 - Emulate process for manufacture of optical fibers - HIGH SCHOOL/COLLEGE LAB VERSION

Experiment #4 - Create model of Fiber Preform, Single Mode and Multi-Mode fibers


Don't forget you can order a sample fiber from a real telephone cable for use in some experiments by clicking the ORDER FIBER button on the top right of the Home page.  Prices from $1.00 per fiber.  Great way to earn extra credits in your next Technical Presentation, Science Fair or Merit Badge!




Experiment #1 - Compare my hair (to an optical fiber under microscope)
Objective: determine the size difference between an optical fiber and the human hair

Required materials:
1. USB or standard microscope
2. variety of human hairs
3. carrier-grade 125µm optical fiber (can be ordered here)

In this excersize we will compare the size of an optical fiber to a variety of human hairs.  While we often compare the size of optical fiber to human hair, the fiber is actually slightly larger in size.  The challenge in this excersize is to determine if there is a significant difference in the size of a hairs of different types as shown in the chart below the photo.

If you do not have a microscope for comparisons, a low-cost solution is a USB microscope that can be used with a laptop or desktop PC.  Just perform an Amazon search for USB Microscope and several adequate models are in the $20.00 range.  Many can be used either with a PC or iPhone. etc.  The unit we used in the photo below has a range of 50x to 1000x magnification.

To compare the optical fiber you purchased from Fiber Guru, the outer polymer coating must be removed, as the actual glass fiber is much smaller than the coated fiber.  To remove the coating, soak the very end of the fiber in nail polish remover (acetone-based).  After about 10 minutes, the outer coating can be easily wiped away with a tissue. 

Alternatively, use a pair of scissors to carefully scrape the coating from the fiber.  Note, this takes some practice but is doable.  Form a "V" with the scissor blades, then put the end of the fiber into the V and exert slight pressure (make the V smaller) while pulling the fiber away from the scissors.  Too much pressure will sever the fiber, so be gentle but firm.  The fiber below was stripped using scissors.

For best results, use scissors to trim the exposed fiber to about 1/4 inch (from the coating).

IMPORTANT NOTE: Once the coating has been removed, the glass fiber is now unprotected from abrations.  Even the pores of your skin will act like sandpaper to the fragile fiber, so try not to touch the glass with anything but a tissue.  If you abraid the fiber (scratch it), a piece will break off when bent, and the sliver can fall into your lap, easily piercing your skin.  This is very similar to working with fiberglass insulation where small slivers of glass cause your skin to itch and become irritated.  When removing coatings, make sure you are in a standing postions so any broken pieces fall harmlessly to the floor.

Also: once the coating has been removed from the fiber and you are finished with experiments, cover the end of the fiber with tape to protect the glass from breakage.




Optical Fiber (left) Compared to Human Hair (right)



NOTE: Never forcibly remove hairs from yourself or anyone else.  Sample hairs can be retrieved from hair brushes, clothes, etc.  Respect each others right to privacy and let each person present their own hair for comparison.

The goal here is to allow every student the opportunity to compare their own hair to the fiber, recording the results in a chart similar to below.  Use your imagination to compare as many types as possible, including a variety of colors and ethnicity, hair that was washed the same day or perhaps unwashed for several days, hairs from various animals, etc.

While the primary objective is comparing hair sizes to the optical fiber, a secondary discussion is why there are size differences between hairs of differing colors, etc.  Human hairs range from 40 microns to 120 microns (µm....micrometers, or one millionth of a meter), but what types of hairs vary the most from the average of 99µm?  This is for you and your students to discover.



Hair Type

Larger

Than

Fiber

Smaller

Than

Fiber

Same

Size As

Fiber

Black

 

 

 

Red

 

 

 

Blond

 

 

 

Brown

 

 

 

Clean

 

 

 

Dirty

 

 

 

Natural

 

 

 

Dyed

 

 

 

Dog

 

 

 

Cat

 

 

 

Horse

 

 

 

Old

 

 

 

Baby

 

 

 

 
Chart of Hair Types


Have fun with this experiement, as the goal is to awaken a curiosity the requires additional study.  Make sure students respect each other's personal space when gathering hairs for comparison.....this excercize should be fun for everyone.











Experiment #2 - Emulate process for manufacture of optical fibers - HOME VERSION
Objective: demonstrate actual drawing of optical fiber from optical preform in manufacturing process

Required materials:
1. Cheesy Casserole or pizza
2. Food thermometer
3. Oven mitts
4. Safety glasses
5. long-handled wooden spoon

As the casserole or pizza is presented for a meal, use oven mitts and safety glasses for protection to measure the temperature of the dish with a food thermometer (NOTE- you must use a food thermometer, do NOT use a thermometer intended for use on humans).  Record the temperature of the dish as it is being served.

Using the oven mitts and safety glasses for protection, use the long-handled wood spoon to dip as deep as possible into the dish, extracting the spoon slowly to engage strings of cheese from the dish as shown below.  (For the record, this is a pizza from Giordano's Pizza in Chicago - THE best Chicago deep-dish pizza!  We highly recommend this product for the experiment!)



Stringy Cheese


Use the long-handled wooden spoon to "draw" cheese from the dish for as long as possible.  Do not break the cheese, just keep reeling it onto the wooden spoon for as long as it allows.  When the dish cools to the point it no longer yields a string of cheese, measure the dish temperature again and record the results.

Once you have drawn as much fiber from the dish as possible, unreel the string of cheese from the wooden spoon and measure the total length.

This experiment has three elements:

1. determine the temperature when the dish produces a string of cheese
2. determine the temperature when the dish no longer yeilds a string of cheese
3. determine the length of cheese that can be drawn from the dish before it becomes too cool to string

Conclusion:
The cheesy dish can be a source of string cheese when the temperature is between xxx and xxx degrees (you fill in the xxx).  If the dish is too hot, the cheese is molten (liquid) and does not string well, and if the dish is too cool the string becomes a solid and will not string at all.

This is the same principle with the manufacture of optical fibers.  If the Fiber Preform is not heated to precision temperatures, the preform will not yield a consistant string of fiber.

NOTE- if you compare temperatures across the country, the melting points will vary based on elevation and humidity.  We welcome the results of your experiment at feedback@fiber.guru.  Be sure to include the temperatures and lengths of cheese attained.  Longest continuous lengths will be on our Wall of Fame.








Experiment #2 - Emulate process for manufacture of optical fibers - HIGH SCHOOL/COLLEGE LAB VERSION
Objective: demonstrate actual drawing of optical fiber from optical preform in manufacturing process

Required materials:
1. Several types of cheese
2. Food thermometer
3. Oven mitts or equiv
4. Safety glasses
5. Bunson burner or non-flame heat source
6. Take-up spool


NOTE - this experiment is intended ONLY for a controlled,  laboratory environment with appropriate personal and fire-safety equipment.  If you are not in such a location, use the HOME edition of this experiment.

In this experiment we will be rating the ability of various types of cheese to produce an unlimited quantity of string cheese.  The basic setup can be vertical or horizontal orientation, and the string drawn upward or downward depending on your lab setup.  Below is a suggested setup.


Suggested Lab Setup


Using a holder apparatus, situate the block or cylinder of cheese in such a way as to allow a consistant temperature at the corner or end of the cheese.  It is critical that the appropriate level of heat be applied in a consistant manner so as to maintain the perfect temperature to yield a constant string of cheese.

This experiment has several elements:
1. What type of cheese yields the longest and most consistant string?
2. What is the optimum temperature for each type of cheese to achieve #1 above?
3. What is the longest continuous string of cheese you have "drawn" in this experiment?
4. What mechanism was used to drive the take-up spool at the appropriate speed to achieve optimal yeild?

Conclusion:
The cheese can be a source of string cheese when the temperature is between xxx and xxx degrees (you fill in the xxx).  If the temperature is too hot, the cheese is molten (liquid) and does not string well, and if too cool the cheese remains becomes a solid and will not string at all.

This is the same principle with the manufacture of optical fibers.  If the Fiber Preform is not heated to precision temperatures and appropriate tension from the take-up reel, the preform will not yield a consistant string of fiber.

Please consider this a challenge to teachers and professors to have your students design and construct an apparatus to achieve the desired results.  The drawing above is only to serve as an example.  A better method may be simmering cheese in a pan, etc.  The goal remains the same - draw the longest continuous string of cheese from the source.  Can your team rule the nation in longest continuous string of cheese?

Send your results to feedback@fiber.guru.  Top lengths will appear on our Wall of Fame.













Experiment #4 - Create model of Fiber Preform, Single Mode and Multi-Mode fibers
Objective: create a large scale replication of preforms and fibers

Required Materials:
1. empty paper towel tube
2. long piece of uncooked spaghetti
3. 1/2 inch wooden dowel rod (approx 20 inches in length)
4. aluminum foil
5. Saran™ wrap
6. small, black trash bags
7. clear tape
8. scissors
9. 10 feet of clear fishing line
10 one dime





Create Fiber Preform Model
Demonstrates the actual manufacturing process for optical fibers
This will be your science fair winner


Use scissors to cut several slits into one end of the empty paper towel tube (use care not to cut yourself), then form the end of the tube into a pointed end as shown below leaving a small hole at the very bottom.  Secure the end with tape.

Empty Paper Towel Tube Slit Tube End Form Pointed End


Wrap the tube with aluminum foil with the shiniest side facing outward as shown below.


Cover Tube With Aluminum Foil Compress Foil At Pointed End


The covered tube represents the Fiber Preform as it is ready to be placed into the Drawing Tower.  Next we will add the fishing line to simulate the actual manufacturing process.

Insert Fishing Line Fiber Extends Out Pointed End


Using the fishing line, snake the line up from the bottom until you can grasp the end at the opposite end of the tube.  Pull all the line up through the pointed end, leaving a few inches outside the tube opening.

Secure a dime to the end of the fishing line and pull the slack from the opposite end so that the dime is touching the pointed end.

Coil the remaining fishing line into the wide opening at the opposite end of the tube.  When lifting the tube, be sure to hold the dime against the pointed end of the tube.

Excess Fishing Line in Large End Dime Connected to Line




Completed Fiber Preform Model



Once the Fiber Preform Model is completed as shown above we are ready to demonstrate the process for manufacturing optical fibers.  While holding the dime to the pointed tip of the model, have a student hold the model upright at chest level with pointed end facing the floor, then let go of the dime.  If the fishing line was loosly coiled indside the tube, the dime will plummet to the floor, drawing the fishing line along behind.

This is exactly as it happens when a real Fiber Preform is in the Drawing Tower, the tip is heated until a gob of glass builds at the tip and when it reaches a critical mass, it breaks free from the preform, sailing downward in the drawing tower while trailing a sting of optical fiber in its wake.

This model can be mounted onto a posterboard, and demonstrated many times.  Just pull the fishing line back up through the tube and drop the dime repeatedly.  You could even fashion red crepe paper onto pipe cleaners to simulate the heat applied to both sides of the the tip of the perform and an empty spool from sewing thread fastened at the bottom to simulate a take-up reel.

This model is sure to be a winner at science fairs.  Please send us photos of your own models at feedback@fiber.guru.










Create Model of Single Mode and Multi-Mode Optical Fibers
Demonstrates the actual core diameters for optical fibers
This will be your science fair winner




Single Mode Fiber Model
The single mode fiber model requires patience, as you have to be very careful not to break the spaghetti.  Use care.

Lay the long piece of uncooked spaghetti onto a flat surface.  Hold a length of aluminum foil near the spaghetti, cutting the foil three inches shorter than the length of the spaghetti.  Lay the cut foil shiniest side up and place the spaghetti one inch in from one end. Carefull wrap the aluminum foil around the spaghetti as shown below.  This will not require very much foil, don't ovedo it.  Three wraps is enough.  Do NOT tape the aluminum foil to the spaghetti.


Spaghetti Wrapped in Aluminum Foil


Using the Saran™ wrap, wrap the spaghetti and aluminum foil until the Saran™ wrap is approx 15 times the size of the spaghetti (not critical to be exact).  Again, be patient and slow so as not to break the shaghetti.


Spaghetti Wrapped in Aluminum Foil and Saran™ wrap


Once the Saran™ wrap layer is of sufficient size, use tape to secure if required.  Next step is to use small black trash bags (or equiv of your choosing) to wrap another layer which should be approximately the same thickness as the Saran™ wrap.

Spaghetti Wrapped in Aluminum Foil, Saran™ wrap and Trash Bag
(sorry, this shows the dowel rod instead of the spaghetti)



Once the trash bag layer is completed, the model is nearly finished as shown below.


Completed Single Mode Fiber Model



Once the model is completed, carefully pull the spaghetti toward you to remove it from the model.  If you did not break the spaghetti during the construction process, the very center of our model will pass light.  If by chance you did break the spaghetti, do not fret, use another unbroken piece of spaghetti to gently nudge out any broken pieces.


Model With Spaghetti Removed


For Single Mode fibers, the diameter of the Core is 9 microns (µm), the diameter of the Cladding is 125µm, and the diameter of the Coating is 250µm.  The constructed model shows how small the core is on a single mode fiber.  The aluminum center represents the fiber CORE and the Saran™ wrap represents the Cladding.  The trash bag represnts the polymer coating that is applied to the fiber during the manufacturing process.  In reality, the fiber Core is not hollow, just glass of a differnt refractive index form the Cladding.

Next we'll repeat these steps to create a multi-mode fiber model.



Multi-Mode Fiber Model

The process for creating a model of Multi-Mode Fiber is exactly the same as with the Single Mode Fiber we constructed earlier, except we will use a 1/2 inch wodden dowel rod in place of the Spaghetti.  Wrap the dowel rod as shown with shiniest side toward dowel rod.  Do NOT tape the aluminum foil to the dowel rod.

Model With 1/2 Inch Dowel Rod



Once aluminum fiol wrap is completed, wrap with Saran™ wrap until layer is approx. twice the size of the dowel rod.

Model With 1/2 Inch Dowel Rod and Saran™ wrap


Once the Saran™ wrap layer is completed, wrap the model with the trash bag (or coating of your choice) until it is approx the same outside diameter as the single mode model we created earlier.

Model With 1/2 Inch Dowel Rod and Saran™ wrap and Trash Bag


Once the model is completed, carefully extract the dowel rod by pulling towards you.  You may have to gently twist the dowel rod.

Completed Model With 1/2 Inch Dowel Rod Removed


For Multi-Mode fibers, the diameter of the Core is 62.5 microns (µm), the diameter of the Cladding is 125µm, and the diameter of the Coating is 250µm.  The constructed model shows how large the core is on a multi-mode fiber as compaed with the single mode model we created earlier.


Conclusion
Multi-Mode fibers are used only for short distances like campus or inner building needs.  Since the distances are short, lower coast LED light sources may be used with the large core diameter.

Single Mode fibers are used for longer distance communications that require the power of a laser.  Single Mode fibers have very small diameter cores to accomodate the wavelengths of laser transmitters.


Completed Models for Fiber Preform, Single Mode and Multi-Mode Fibers


Once these models are created, use them in scinece fairs for winning results.  Please send us photos of your own models and science fair submissions at feedback@fiber.guru.







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