Thursday, October 14, 2010
What's Inside a Fiber Optic Cable? Project
When we moved to Teaneck two years ago (this post has been a long time coming) we had FiOS installed. One of the many things that went wrong that day was them bringing too short of a fiber optic cable, requiring them to cut off the one they started to install. I snagged a piece of the removed and discarded cable and this naturally led to the:
What's inside a Fiber Optic Cable Project!
The outside of the cable consists of this stiff, hard and smooth black plastic (polyethylene) casing:
product page here, along with a spec sheet [pdf]. The outer casing provides a strong outer protective layer. This is what the cable looks like in cross-section (fingers add some scale):
Kevlar cables. This stiffens the cable and, by sandwiching the actual fiber in between the two Kevlar things, decreases the likelihood of something damaging the optical fiber.
The next thing in is a soft opaque tube filled with a gooey gel type stuff. This is called a "buffer" and serves as an additional layer of protection for the optical fiber inside.
Well, sort of. First you have the "cladding" -- the blue line in the picture.
index of refraction than the "core" optical fiber, helps the light reflect back into the fiber. Finally, then, after the plastic, the Kevlar, the buffer, the cladding [the frog, the lights, the armor], we get what's all the way inside the fiber optic cable: The optical fiber itself:
functioning micrometer (or SEM) at home, so I'm not sure how thick the fiber (or fiber+cladding) actually is, but I'd estimate on the order of 100μm [about a hair's thickness]. I could probably compare from the scale of an easier-to-measure thing, but I'm too lazy. Readers: feel free. Anyway, from the spec sheet, that seems about right, too.
And, for the record (lest you think my lack of micrometer at home lowers my scientist "cred"), the microscope images were taken on my dining room table: