Lesson 3 Lab Experiment (s)

Splitting Hairs - How Fibers are Spliced and Connected to Equipment

 
Home       These is the lab experiment for Lesson 5.  Please conduct these experiments under direct supervision of an adult including a parent or teacher. 



Experiment #1 - Splicing Two Fibers
Objective: Observe difficlty in manual alignment of optical fibers



Required Materials:
1. Optical Fiber from Fiber Guru
2. USB or Standard Microscope
3. Superglue or equiv.

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.  For 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).

Using the microscope, align the ends of two fibers, then use superglue to bond the ends together.  Try your best to keep the fibers aligned as much as possible so that the outside of the glass has no bumps.  If you fail, merely clip off the ends and repeat the preparation above.





Optical Fibers


This excersize is intended to expose students to the difficlty in working with the small optical fibers.  Even with the advanced technology of today, splicing of optical fibers is still an acquired skill that improves with experience.

The other thing to stress with students is the fiber Coating is 250 microns in diameter (µm micrometers, or one millionth of a meter), the Cladding  (glass fiber with coating removed) is 125µm in diameter, and the fiber Core is 9µm in diameter. 

Therefore, they can clearly see the Cladding under the microscope, but we really only use the 9µm Core.  Ask them if they can use a needle and locate the exact center of the optical fiber?  The answer is that if the fiber were magnified enough, this is possible, but have them try with zero magnification.  In fact, its impossible.

A reminder that the Core and Cladding are the same glass, so you cannot "strip" the cladding from the Core.  The Core is merely a different refractive index from the Cladding as described in Lesson 1.

Single Mode Fiber

 


This concludes the experiments for Chapter 3- Splitting Hairs - How Fiber are Spliced and Connected to Equipment

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!


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